FIELD OF THE INVENTION

The present invention relates to surface modified coal compositions. The compositions of the invention could find use, for example, to mitigate ammonia emissions and reduce odours from animal (or intensive livestock) wastes by adsorbing ammonia and/or ammonium ions. The present invention also relates to methods of manufacturing surface modified coal compositions, and methods of using the same.

BACKGROUND OF THE INVENTION

Ammonia (NH3) and ammonium ion (NH4 ⁺ ) occurring in wastes from animals (for example faecal matter, urine, and admixtures of faecal matter and urine), is a significant issue, especially on farms where animals live in close quarters. The emissions from such waste are not just an odorous problem, in the case of ammonia, they also contribute to eutrophication and acidification of ecosystems, in the case of ammonium ion, and may cause contamination of ground waters and soils.

Furthermore, ammonia may react with or adsorb onto other air pollutants to form particulate matter (PM), which poses additional risks to human health. Ammonia is also an indirect greenhouse gas as up to 5% ammonia deposited on the land surface will be converted to nitrous oxide which is a potent greenhouse gas. Agricultural industries, especially intensive livestock operations, are the largest global sources of anthropogenic ammonia (-68%), and this is projected to keep increasing (Behera et ai, Environ. Sci. and Pollut. R. 20 (2013) 8092). Ammonia volatilization from animal manure begins immediately after urine and feces are excreted. Animal feedlots are one such hotspot of ammonia and/or ammonium ion emissions from which about 60% of total excreta N is lost from manure. Animal health is also greatly affected by build-up of ammonia and/or ammonium ion, especially in confined spaces, resulting in decreased productivity.

A large number of strategies for reducing the production of ammonia and/or ammonium ions from animals, or the build-up of ammonia and/or ammonium ions from animal waste have been described, including: diet modification to decrease ammonia and/or ammonium ion production; air modification, including use of fans, spraying housing and/or exhaust air with chemicals that react with ammonia, use of electrostatic fields to decrease aerial dust and ammonia, or use of vegetation barriers to adsorb ammonia; and manure modification, including covering manure pits with oil and/or treating the manure with microbes, alkali solutions, or other chemicals, or sub-surface field injection of manure.

One particularly interesting approach to lowering the amount of ammonia is use of litter or bedding material amendments, whereby the litter or bedding is treated with microbes or chemicals to lower the amount of ammonia. The chemicals described in the literature include aluminium chloride, aluminium sulfate, ferric sulfate, hydrated lime (calcium hydroxide), sodium bisulfate, sulfuric acid, zeolites, humate material, and urease inhibitors. However, these amendments have not been widely adopted by the agricultural industry, due to a number of factors including cost, short duration of action, and/or difficulties related to implementation.

Activated carbon materials are effective at adsorbing molecules such as odours, due to their high porosity and high surface area, and can be prepared from a variety of carbonaceous precursors, as discussed below. However, activated carbon materials usually exhibit nonpolar surfaces which decreases their capability to interact with polar gases (e.g., ammonia). For example, Rodrigues etal. (Bioresour. Technol. 98 (2007) 523) reported that the ammonia adsorption capacity of a commercial coconut shell activated carbon was 0.6 to 1.8 mg/g at 40°C under an ammonia concentration range of 600-2400 ppm.

Gongalves et al. (Environ. Sci. Technol. 45 (2011) 10605) investigated an activated carbon which was further modified with nitric acid solution. It was found that the ammonia adsorption capacity increased from 4.7 to 17.5 mg/g in dry air and increased from 5.3 to 20.1 mg/g in the presence of 70% moisture in air containing 1000 ppm of ammonia at 23°C. The amount of ammonia adsorbed varied highly depending on the modification process.

Further surface modifications are usually needed to tailor the porous structure and surface chemistry to enhance ammonia adsorption. For example, Mochizuki et at. (Fuel Process. Technol. 144 (2016) 164) studied ammonia adsorption behaviour of activated carbon prepared from petcoke with potassium hydroxide (KOH) chemical activation. Results showed that the ammonia adsorption capacity of 600°C activated carbon (KOH/petcoke ratio = 6:1) was 52.7 mg/g at 30°C with ammonia partial pressure of 0.2 kPa.

Although some modified activated carbons efficiently adsorb ammonia, their widespread use is still hindered by the high costs and complexities in the activation and modification processes.

The present inventors have recently reported that coal, in the form of lignite, added as an amendment to the bedding of cattle pens effectively decreased daily ammonia emissions by at least 60% (Chen et ai, Scientific Reports, 5 (2015) 16689).

There are four types of coal, known as lignite, sub-bituminous coal, bituminous coal and anthracite, which are distributed unevenly across the world. Lignite (also known as brown coal) and sub-bituminous coal are classified as low rank coals as they have a lower carbon content than higher rank coals. Lignite accounts for about 17% and sub- bituminous coal accounts for about 30% of world reserves (www.worldcoal.org).

Victoria is the only state in Australia where lignite is mined, much of it in the Latrobe Valley in eastern Victoria. On the other hand, about 57% of cattle in feedlots are in the state of Queensland. The transport cost to deliver lignite from Victoria to Queensland (or any other part of the world) represents just one hurdle to its implementation as a bedding amendment to lower the amount of ammonia and/or ammonium ion. Bituminous coal (BC, also known as black coal) on the other hand is mined all around the world and accounts for 52% of world coal reserves. Bituminous coal and anthracite (which accounts for about 1% of world coal reserves) are higher rank coals as they contain a higher carbon content. Due to their greater availability, sub-bituminous coal and bituminous coal would be promising alternatives to lignite for the mitigation of ammonia emissions from animal waste, such as from livestock operations. Coal tailings are a waste material from coal mining and are also available as a starting material for activated coal as described below.

There is a need for ammonia/ammonium ion lowering strategies that mitigate at least one of the problems outlined above, for example, being effective, low-cost, non-toxic to animals and/or humans, or environmentally benign.

The present invention is predicated at least in part on the discovery of an activated coal composition suitable for lowering ammonia and/or ammonium ion, such as from animal waste, which may at least provide an alternative to the solutions presently available.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a method of activating a coal composition, comprising: (a) providing finely divided coal; and (b) heating the finely divided coal, under aerobic conditions, to provide the activated coal composition, wherein the aerobic conditions at step (b) comprise subjecting the finely divided coal to a stream of air, wherein the stream of air has a flow rate of between about 20 mL/min and 60 mL/min per 10 g sample of finely divided coal.

In another aspect, the present invention provides an activated coal composition, wherein a pH of the composition is less than about pH 6.5, when a mixture of coal and water is measured at a ratio of 1 : 10.

In another aspect, the present invention provides a method of activating a coal composition, comprising: (a) providing finely divided coal; and (b) heating the finely divided coal, under aerobic conditions, to provide the activated coal composition, wherein the activated coal composition has an adsorption capacity of ammonia of between about 30 mg/g and about 90 mg/g.

Other aspects of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention, taken in conjunction with the accompanying figures.

FIGURES

Figure 1 shows TGA curve for pyrolysis of an original lignite sample (without any drying or activation) using an argon gas flow rate of 20 mL/min and ramped heating rate of 20°C/min.

Figure 2 shows the derivative of TGA (DTG) for original (red) and dewatered lignite at 200°C (black).

Figure 3 shows the TG curve for pyrolysis of original (black) and dewatered at 200°C (red) lignite samples with an argon gas flow rate of 20 mL/min and at heating ramp rate of 20°C/min. The water content was obtained using weight loss at 105°C based on dry lignite.

Figure 4 shows FTIR spectra for original lignite (black line) and activated lignite at 200°C (red line). Figure 5 shows FTIR spectra for initial BC (black line) and activated BC at 300°C (red line).

Figure 6 shows changes in pH of activated lignite (via aerobic and thermal treatment) as a function of treatment temperature.

Figure 7 shows changes in pH of activated BC (via aerobic and thermal treatment) as a function of treatment temperature.

Figure 8 shows helium ion microscopy (HIM) images (a) - (c) of original lignite samples (non-activated) at multiple scales and (d) activated lignite following aerobic thermal treatment at 200°C at the same scale as (c).

Figure 9 shows helium ion microscopy (HIM) images of (a) original bituminous coal samples (non-activated) at two different scales and (b) activated bituminous coal following aerobic thermal treatment at 300°C at two different scales.

Figure 10 shows XPS spectra of electrons from the 1s orbital of carbon atoms (C1s) in (a) non-activated lignite and (b) activated lignite.

Figure 11 shows (a) XPS survey spectra and (b) high-resolution C 1s XPS spectra of non-activated BC in comparison to BC300 (BC activated at 300°C).

Figure 12 shows ammonia adsorption on non-activated and activated lignite samples. Gas phase ammonia isothermal adsorption is shown, in 30% NH ₃ balanced by moist air.

Figure 13 shows ammonia adsorption on non-activated and activated lignite samples. NH ₃ -TPD-MS profile is shown, with 10% NH ₃ balanced with 90% He (in the absence of moisture).

Figure 14 shows ammonia adsorption capacities at 25°C for non-activated and activated BC as a function of time.

Figure 15 shows ammonia adsorption capacities at 25°C for non-activated and activated BC as a function of activation temperature. Figure 16 shows ammonia adsorption capacity of BC as a function of (a) total amount of acidic functional groups; the amount of (b) carboxylic functional groups, (c) lactone functional groups, and (d) phenolic functional groups.

Figure 17 shows a comparison of aqueous ammonium ion adsorption on lignite samples heated in air at 200°C, versus heating under nitrogen at 200°C.

Figure 18 shows ammonium ion adsorption on non-activated and activated lignite samples, using aqueous phase ammonium ion adsorption.

Figure 19 shows ammonium ion adsorption capacity of lignite as a function of (a) hydroxyl functional groups; the amount of (b) carboxylic functional groups, (c) lactone functional groups, and (d) total amount of acidic functional groups.

Figure 20 shows (a) Langmuir and (b) Freundlich adsorption isotherms for adsorption of ammonium ion onto non-activated BC and BC300 (activated at 300°C).

Figure 21 shows risk of spontaneous combustion for non-activated (70°C dried, black) and activated lignite (red): (a) TG curve of lignite samples with air flow rate of 20 mL/min and at heating rate of 20°C/min, (b) linear fitting for calculation of apparent activation energy of combustion for lignite samples.

Figure 22 shows cumulative ammonia emission from cattle manure with 30% best performing activated lignite and activated bituminous coal (black coal) materials.

Figure 23 shows cumulative ammonia emission from poultry manure with 20% best performing activated lignite and activated bituminous coal (black coal) materials.

Figure 24 shows changes in pH of activated coal tailings (via aerobic and thermal treatment) as a function of treatment temperature.

Figure 25 shows changes in pH of activated lignite (via aerobic and thermal treatment) as a function of treatment time.

Figure 26 shows ammonia adsorption capacities at 25°C for activated coal tailings as a function of activation temperature. Figure 27 shows ammonia adsorption capacities at 25°C for activated coal tailings as a function of activation time.

Figure 28 shows ammonia adsorption capacity of coal tailings as a function of total amount of acidic functional groups.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method of activating a coal composition, activated coal compositions, and uses of activated coal compositions for adsorbing ammonia and/or ammonium ion, such as may be present in the faeces, urine, and manure of animals. It has been found that activated coal provides a superior ammonia and/or ammonium ion adsorbing ability compared to non-activated coal. The composition of the present invention is derived from cheap and readily available materials, and provides an alternative use of coal compared to conventional burning for production of energy.

One factor related to transport cost is the weight of any coal composition being used to lower amounts of ammonia and/or ammonium ion from animal waste. Coal has a moisture content which will contribute to its mass, with lignite having as much as 75% moisture content and anthracite typically having a moisture content of less than 15%.

Various dewatering processes have been developed for the drying of lignite, which can be classified mainly as evaporative drying (hot air, combustion gases, superheated steam) and non-evaporative drying (hydrothermal, mechanical, hot water). Although many of the non-evaporative drying technologies usually generate significantly upgraded products, their utilization by industry in the near future will be limited due to their complexity, high operating temperature and pressure, and high cost. Some methods, such as hydrothermal dewatering (HTD), also increases the risk of spontaneous combustion of lignite. In addition, decreasing the water content of lignite tends to suppress ammonia adsorption.

Advantageously, the present invention may provide a dewatering protocol for coal that has a reduced risk of spontaneous combustion. Furthermore, the resulting activated coal product has a significant capacity to adsorb both aqueous phase NH ₄ ⁺ and gas phase NH ₃ . Definitions

In this specification a number of terms are used which are well known to a skilled addressee. Nevertheless, for the purposes of clarity a number of terms will be defined. As used herein, the term “activate”, and related terms such as “activated” and

“activating”, means that the surface of a coal composition has been modified compared to a non-activated coal composition.

The modification is as described in the claims, and requires the application of heat under aerobic conditions. Coal by its nature is formed from organic material that has been deposited, then subsequently subjected to temperature and pressure for a long period of time. The composition of coal will vary from sample to sample, dependent upon the material from which it is formed and the conditions under which it has been subjected to. Generally, coal will be comprised mostly of hydrocarbons, typically aromatic hydrocarbons, with functional groups which will include oxygen-containing functional groups such as hydroxy, lactones, and carboxylates such as carboxylic acids. When a phenyl group is hydroxylated this is known as a phenol. Coals may also contain sulfur-containing compounds, and the sulfur content of coal can sometimes be high. Without wishing to be bound by theory, activation of coal is believed to increase the number of surface functional groups which contain oxygen, via oxidation, which in turn increases the amount of ammonia and/or ammonium ion that can get adsorbed onto the surface. One mechanism that adsorption may occur is by deprotonation of a surface group by an ammonia molecule, acting as a base, resulting in an ammonium cation which will have as anion the corresponding deprotonated functional group. Another possible mechanism is that ammonia may act as a nucleophile, such as on a lactone group. The lactone ring will react with an ammonia molecule to produce an amide. Regardless of the mechanism, increasing the number of oxygen-containing functional groups results in increased capacity to adsorb ammonia and/or ammonium ion onto the surface of the activated coal composition. Sulfur compounds can also react with ammonia and/or ammonium ion and produce stable compounds, for example, ammonium sulfates. The term “non-activated” and related terms means that the coal composition has not been heated or subjected to aerobic conditions as described herein. As used herein, the term “coal composition” is intended to mean a coal-derived material. As noted above, coal can be classified into four different types: lignite (brown coal), sub-bituminous coal, bituminous coal (black coal), and anthracite. The coal composition may also be derived from coal tailings. The lower rank coals have higher water content and lower carbon content than the higher rank coals.

As used herein, the term “crush”, and related terms such as “crushed” and “crushing”, means to break up a large piece of coal into smaller pieces by application of pressure between, for example, two jaws of a crushing machine. It will be appreciated by one of skill in the art that it does not matter how the smaller pieces are obtained, or which type of machine is used to do so. For example, the coal stock could be broken into smaller particles by agitation or by tumbling. Typically, a machine such as a jaw crusher will be used to break the coal into the desired particle size.

As used herein, the term “finely divided” means that the coal has been broken up into very small particles. Small particles may be separated from larger particles, for example by passing through a sieve or mesh, or any other means known to one of skill in the art, such as centrifugation or classification.

As used herein, the term “stream of air” means a quantity of air which is forced over the coal at a rate, which is typically measured in millilitres per min. Air is a mixture of gases comprising mostly of nitrogen (about 78%) and oxygen (about 21%), with the remainder being argon, carbon dioxide, and a range of other gases. As the activation depends upon oxidation of the coal, one of skill in the art will appreciate that the oxygen content of the air used to activate the coal can be varied, and activation will still occur. For example, the stream of air can contain 1% oxygen, or less, and oxidation will still occur. The stream of air may contain 100% oxygen, which will also cause oxidation. The main determinant for the composition of air used, provided it contains some oxygen, will be cost, with unadulterated air being the most cost-effective.

As used herein, the term “dry”, and related terms such as “dried” and “drying”, means to remove most of the water, for example, to have a water content of coal of between 0 and 10% water. It is not intended to mean that all water is removed, as this may be very difficult to achieve with some substances which are able to hold onto water very tightly. In relation to the invention, drying simply means to remove the bulk of the water, for example, to reduce the amount of agglomeration once coal is crushed into powder.

As used herein, the term “catalyst” means a substance which reduces the amount of energy and range of temperatures required for a reaction to take place, compared to if no catalyst was used. The catalyst used in the present invention may be a metal oxide, such as titanium dioxide or other reducible metal oxides, which decreases the temperature at which activation of the coal surface occurs.

As used herein, the term “animal enclosure” means an area where animals are confined. The enclosure may be covered with a roof or it may be open, and may be for example a fenced-off paddock, a milking barn, a feedlot, a shed, a barn, or any combination thereof. It may be a multi-storey barn, as may be used for large poultry farms.

As used herein, the term “animal waste” means faeces and/or urine from animals. Furthermore, manure is a generic term for an admixture of faecal and urine materials in a range of ratios. The animal may be any animal that will spend a portion of time in an enclosure, such as chickens, turkeys, ducks, geese, rabbits, cats, dogs, sheep, goats, kangaroos, buffalo, cows, cattle, or any other domesticated animal. The animal may be the type of animal kept in a zoo. Typically, the animal will be a farm animal.

Thus in one aspect, the present invention provides a method of activating a coal composition, comprising providing a finely divided coal; and heating the finely divided coal, under aerobic conditions, to provide the activated coal composition, wherein the aerobic conditions comprises subjecting the finely divided coal to a stream of air, wherein the stream of air has a flow rate of between about 20 mL/min and 60 mL/min per 10 g sample of finely divided coal.

The method of the present invention allows the number of oxygen-containing functional groups on the surface of the coal to be increased, compared to non-activated coal, which increases the amount of ammonia and/or ammonium ion that can be adsorbed onto the surface of the coal composition.

Without wishing to be bound by theory, it is believed that the number of oxygen- containing functional groups is increased due to oxidation. The amount of oxidation that takes place on the surface of the coal composition will be related to the amount of oxygen that the coal surface is exposed to, the temperature at which the oxygen is reacted with the coal, any light that may be present, the pressure, and the presence of any catalyst that may accelerate the oxidation. The amount of oxygen that the coal surface is exposed to is related to the flow rate of the stream of air. The ability of the coal composition to adsorb ammonia and/or ammonium ion is related to the extent of oxidation on the surface of the coal. There will be an infinite number of variations on the reaction conditions (flow rate of the stream of air, amount of oxygen in the air, temperature, pressure, catalysts, and light present) that maximise the extent of oxidation and minimise the extent of degradation. Such degradation may be caused, for example, by decarboxylation. It is not the intent of the inventors to limit the invention by the various embodiments and examples, and combination of conditions listed herein. What is most important is that the oxidation of the coal surface is carried out under conditions that maximise oxidation and minimise degradation of oxidation products.

The stream of air may have a flow rate of between about 1 mL/min and 100 mL/min, for a 10 g sample of finely divided coal, for example between about 1 mL/min and 90 mL/min, or between about 1 mL/min and 80 mL/min, or between about 1 mL/min and 70 mL/min, or between about 1 mL/min and 60 mL/min, or between about 1 mL/min and 50 mL/min, or between about 1 mL/min and 40 mL/min, or between about 10 mL/min and 100 mL/min, or between about 20 mL/min and 100 mL/min, or between about 30 mL/min and 100 mL/min, or between about 40 mL/min and 100 mL/min. In some embodiments the flow rate of air may be between about 20 mL/min and 60 mL/min per 10 g sample of finely divided coal. The flow rate may be selected from the group consisting of about 1 mL/min, about 10 mL/min, about 20 mL/min, about 30 mL/min, about 40 mL/min, about 50 mL/min, about 60 mL/min, about 70 mL/min, about 80 mL/min, about 90 mL/min, and about 100 mL/min per 10 g sample of finely divided coal. In certain embodiments the flow rate of air is about 40 mL/min per 10 g sample of finely divided coal.

The activation of the coal composition of the present invention may take place at any pressure, except for under a complete vacuum. As one of skill in the art will appreciate, conducting the activation at higher pressure may accelerate the oxidation reactions occurring at the surface of the coal compared with at lower pressures. Thus the activation may be conducted at a pressure lower than atmospheric pressure. As one of skill in the art will appreciate, aside from a complete vacuum a low pressure environment does not exclude the presence of molecules such as oxygen. The activation may be conducted at a pressure higher than atmospheric pressure. In preferred embodiments the activation is conducted at atmospheric pressure.

The heating of the coal composition of the present invention, during the activation step, may take place for any period of time sufficient to maximise the amount of oxidation of the surface functional groups whilst minimising the amount of degradation. It is not the intention of the present inventors to limit the invention by specifying a period of time that the heating takes place, as the amount of time required will depend on a number of other factors such as composition of the stream of air, pressure, temperature and/or light, the presence of any catalysts, the amount of water present, and the composition of the coal used, as will be appreciated by one of skill in the art. As such, the heating may take place for a period of time between about 1 hour and about 10 hours, for example between about 1 hour and 9 hours, or between about 1 hour and 8 hours, or between about 1 hour and 7 hours, or between about 1 hour and 6 hours, or between about 1 hour and 5 hours, or between about 2 hours and 10 hours, or between about 3 hours and 10 hours, or between about 4 hours and 10 hours, or between about 5 hours and 10 hours. The heating may take place for a period of time selected from the group consisting of about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, and about 10 hours. In some embodiments the heating is carried out for about 5 hours.

The coal composition is derived from a coal stock. A coal stock is simply coal that has been excavated from the ground, and may or may not have been washed prior to being transported to the processing equipment where activation takes place. For example, it may be coal washings or tailings from a spoil heap, such as may be generated as part of a mining remediation practice. It is not the intention of the inventors to limit the invention to any one particular type of coal stock, as all coal stocks are derived from organic material and, aside from the differences in starting organic material, differ only in the water content and the amount of heat, pressure and time that each type of coal has been subjected to. Accordingly, in one embodiment, the coal stock is lignite. In another embodiment, the coal stock is sub-bituminous coal. In another embodiment, the coal stock is bituminous coal. In another embodiment, the coal stock is anthracite. In another embodiment, the coal stock is a combination of lignite and sub-bituminous coal. In another embodiment, the coal stock is a combination of sub-bituminous coal and bituminous coal. In another embodiment, the coal stock is a combination of bituminous coal and anthracite. In another embodiment, the coal stock is a combination of lignite and bituminous coal. In another embodiment, the coal stock is a combination of lignite and anthracite. In another embodiment, the coal stock is a combination of sub-bituminous coal and anthracite. In another embodiment, the coal stock is a combination of any three selected from the group consisting of lignite, sub-bituminous coal, bituminous coal, and anthracite. In another embodiment, the coal stock is a mixture of lignite, sub-bituminous coal, bituminous coal, and anthracite.

In some embodiments, particularly where the coal stock contains significant water, the coal stock may be dried prior to crushing. Where the particle size is already small, there may not be a need for drying prior to crushing. For example, lignite may be subject to drying to remove at least a portion of water before it is subjected to the method of the invention. On the other hand, coal compositions with low water content, such as bituminous coal, may not be subject to a drying step, or may only require a less vigorous drying step, such as heating at a lower temperature and/or for a lesser time. Drying of the coal stock prior to crushing may be carried out by any number of means known in the art, such as by heating, either under a vacuum, at atmospheric pressure, or at higher than atmospheric pressure. If heated at atmospheric pressure it will be appreciated that a higher temperature will be required, compared with heating under a vacuum. Higher temperatures also require higher costs. It is not the intention of the present inventors to limit the invention by heating the coal stock, prior to crushing, at any one particular temperature, as water may be removed by heating at any temperature depending upon the time allowed and the pressure (or vacuum) that the heat is applied at. In some embodiments, drying the coal stock prior to crushing may be carried out by heating at a temperature of between about 20°C and about 110°C, for example between about 20°C and about 100°C, or between about 20°C and about 90°C, or between about 20°C and about 80°C, or between about 20°C and about 70°C, or between about 30°C and about 110°C, or between about 40°C and about 110°C, or between about 50°C and about 110°C, or between about 60°C and about 110°C, or between about 70°C and about 110°C. The drying may be carried out by heating at a temperature selected from the group consisting of about 20°C, about 30°C, about 40°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, and about 110°C. In some embodiments, the drying is carried out by heating a coal stock, prior to crushing, at a temperature of about 70°C. As mentioned above, the heating temperature will also depend on the amount of time that the heating is carried out. In some embodiments, the heating is carried out for a period of time between about 1 hour and about 24 hours, for example between about 1 hour and about 23 hours, or between about 1 hour and about 22 hours, or between about 1 hour and about 21 hours, or between about 1 hour and about 20 hours, or between about 1 hour and about 19 hours, or between about 1 hour and about 18 hours, or between about 1 hour and about 17 hours, or between about 1 hour and about 16 hours, or between about 1 hour and about 15 hours, or between about 1 hour and about 14 hours, or between about 1 hour and about 13 hours, or between about 1 hour and about 12 hours, or between about 1 hour and about 11 hours, or between about 1 hour and about 10 hours, or between about 1 hour and about 9 hours, or between about 1 hour and about 8 hours, or between about 1 hour and about 7 hours, or between about 1 hour and about 6 hours, or between about 1 hour and about 5 hours, or between about 2 hours and about 24 hours, or between about 3 hours and about 24 hours, or between about 4 hours and about 24 hours, or between about 5 hours and about 24 hours. In some embodiments, the heating, prior to crushing of the coal stock, may take place for a period of time selected from the group consisting of about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, about 11 hours, about 12 hours, about 13 hours, about 14 hours, about 15 hours, about 16 hours, about 17 hours, about 18 hours, about 19 hours, about 20 hours, about 21 hours, about 22 hours, about 23 hours, and about 24 hours. In some embodiments, the heating, prior to crushing of the coal stock, may take place for a period of time of about 5 hours.

In embodiments where the coal stock is provided in chunks or lumps, the coal will require crushing to provide smaller particles. In some embodiments, for example, coal tailings, the coal stock may be obtained in particulate form or finely divided form and no crushing would be required. In embodiments where the coal is provided in non particulate form, crushing will be required to obtain a desirable particle size. As one of skill in the art will appreciate, the smaller the particle size is, the greater will be the surface area. Accordingly, smaller particle sizes will have a greater capacity for adsorbing ammonia and/or ammonium ion. However, the provision of finer particles will come at a cost of energy and/or time, and may require the use of specialised equipment. In addition, the use of particles of size smaller than about 10 pm may present a hazard to human health. Particulate matter with a diameter between 2.5 pm and 10 pm are categorised as PMio, and are a hazard due to their airborne and therefore inhalable nature. It is not the intention of the present inventors to provide PMio particles, which may pose a hazard to the animals and/or the humans involved in administration of the activated coal composition of the present invention. The provision of particles of a certain size range is well within the skill of one in the art. An example might be particles of size greater than about 50 pm and less than about 5 mm, or greater than about 1 mm and less than about 2 mm, or greater than about 100 pm and less than about 1 mm. It is also well within the skill of one in the art to provide particles with an average size of, for example, 100 pm, or 1 mm, or 2 mm. It is not the intention of the inventors to limit the invention to particles of a certain size or size range, as any small size will work, insofar as the particle size does not cause a hazard to human and/or animal health. In some embodiments, the finely divided coal has a minimum particle size of greater than about 50 pm. In these embodiments, the maximum particle size may be less than about 5 mm, or less than about 4 mm, or less than about 3 mm, or less than about 2 mm, or less than about 1 mm, or less than about 900 pm, or less than about 800 pm, or less than about 700 pm, or less than about 600 pm, or less than about 500 pm, or less than about 400 pm, or less than about 300 pm, or less than about 200 pm, or less than about 100 pm. As one of skill in the art will appreciate, the size range selected will depend upon the classification method and/or equipment used. If a mesh is used to classify the particles, the size of the holes will depend on the width of the wire used to make the mesh and the spacing between adjacent wires.

A typical standard mesh is US mesh. For US mesh 10, 20, 30, 40, 50, 60, 100, 270, and 325 the size of particles that can pass through are about 2.00 mm, 850 pm, 600 pm, 425 pm, 300 pm, 250 pm, 150 pm, 53 pm, and 44 pm, respectively. In a preferred embodiment, for example when lignite is the coal stock, the finely divided coal has a particle size of between about 50 pm and about 5 mm, for example between about 50 pm and about 2 mm. In another preferred embodiment, for example when bituminous coal is the coal stock, the finely divided coal has a particle size of between about 50 pm and about 500 pm, for example between about 50 pm and about 246 pm.

The heating of finely divided coal, under aerobic conditions, may be carried out at any ramp rate that maximises the amount of oxidation on the surface of a coal and minimises the amount of degradation. The coal may not be subjected to a ramp rate at all, for example if the finely divided coal at room temperature is inserted into an oven at the desired temperature of, for example, 200°C or 300°C. If a heating ramp rate is used, the heating ramp rate may vary between about 1°C/min and about 100°C/min, for example between about 1°C/min and about 90°C/min, or between about 1°C/min and about 80°C/min, or between about 1°C/min and about 70°C/min, or between about 1°C/min and about 60°C/min, or between about 1°C/min and about 50°C/min, or between about 1°C/min and about 40°C/min, or between about 1°C/min and about 30°C/min, or between about 1°C/min and about 20°C/min, or between about 1 ⁰ C/min and about 10°C/min. The heating ramp rate may be selected from the group consisting of about 1°C/min, about 2°C/min, about 3°C/min, about 4°C/min, about 5°C/min, about 6°C/min, about 7°C/min, about 8°C/min, about 9°C/min, about 10°C/min, about 11°C/min, about 12°C/min, about 13°C/min, about 14°C/min, about 15°C/min, about 16°C/min, about 17°C/min, about 18°C/min, about 19°C/min, about 20°C/min, about 30°C/min, about 40°C/min, about 50°C/min, about 60°C/min, about 70°C/min, about 80°C/min, about 90°C/min, and about 100°C/min. In some embodiments, the finely divided coal is heated at a ramp rate of about 10°C/min. The starting temperature, ramp rate and target temperature will determine the amount of time taken to reach the target temperature.

The heating of finely divided coal, under aerobic conditions, may be carried out at a temperature between about 100°C and about 400°C. For example, if the coal stock is lignite, the activation of the finely divided coal may take place by heating, under aerobic conditions, at a temperature of between about 100°C and about 300°C, or between about 100°C and about 290°C, or between about 100°C and about 280°C, or between about 100°C and about 270°C, or between about 100°C and about 260°C, or between about 100°C and about 250°C, or between about 110°C and about 300°C, or between about 120°C and about 300°C, or between about 130°C and about 300°C, or between about 140°C and about 300°C, or between about 150°C and about 300°C.

The heating may be carried out at a temperature selected from the group consisting of about 150°C, about 160°C, about 170°C, about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, and about 250°C. In some embodiments, wherein the coal stock is lignite, the heating is carried out, under aerobic conditions, at a temperature of between about 150°C and between about 250°C, for example about 200°C. If the coal stock is bituminous coal, the activation of the finely divided coal may take place by heating, under aerobic conditions, at a temperature of between about 200°C and about 400°C, or between about 200°C and about 390°C, or between about 200°C and about 380°C, or between about 200°C and about 370°C, or between about 200°C and about 360°C, or between about 200°C and about 350°C, or between about 210°C and about 400°C, or between about 220°C and about 400°C, or between about 230°C and about 400°C, or between about 240°C and about 400°C, or between about 250°C and about 400°C. The heating may be carried out at a temperature selected from the group consisting of about 250°C, about 260°C, about 270°C, about 280°C, about 290°C, about 300°C, about 310°C, about 320°C, about 330°C, about 340°C, about 350°C, about 360°C, about 370°C, about 380°C, about 390°C, and about 400°C. In one embodiment, wherein the coal stock is bituminous coal, the heating is carried out, under aerobic conditions, at a temperature of between about 250°C about 400°C, for example about 300°C. In another embodiment, wherein the coal stock is bituminous coal, the heating is carried out, under aerobic conditions, at a temperature of between about 250°C about 400°C, for example about 350°C. The temperature at which the heating is carried out at can be readily determined by one of skill in the art, for example by monitoring the pH of the finely divided coal at various target temperatures. The pH of the composition will reach a minimum when the amount of oxidation of the surface functional groups is maximised, whilst the amount of degradation is minimised. A typical pH minimum may be less than about pH 7.0, for example about 6.5, and especially less than about pH 5.0, when a mixture of the finely divided coal and water is measured at a ratio of 1:10 (mass in grams:volume in millilitres).

The finely divided coal may be pre-treated, prior to heating under aerobic conditions, with a catalyst. The aim of the catalyst is to accelerate the oxidation reactions occurring on the surface of the finely divided coal so that the temperature that the finely divided coal is heated to, to cause activation, is less than it would be without the use of a catalyst. The catalyst may be any one catalyst described in the art, such as metal oxides, or any combination thereof. Typical catalysts include cerium oxide, iron oxide, magnesium oxide, manganese oxide, molybdenum oxide, tungsten oxide, vanadium oxide, zinc oxide, titanium dioxide, cobalt titanium oxide, nickel titanium oxide, and other reducible metal oxides which are well known in the art, as well as complex solids such as barium titanate and lanthanum cobaltite. Of commercial importance will be the cost and/or effectiveness of the catalyst. In this regard, iron oxide, manganese oxide, and titanium dioxide are preferred catalysts for pre-treating finely divided coal, with titanium dioxide being particularly preferred in some embodiments. In some embodiments, the coal composition that may benefit from the presence of a catalyst are the higher rank coals, such as bituminous coal and anthracite.

The amount of catalyst used is not intended to be limited, and any amount that effects activation of the coal, at a decreased temperature compared to when no catalyst is present, may be used. For example, the amount of catalyst may vary from 0.01 wt% to 10 wt%, based on the dry weight of coal. The catalyst may be added to the coal prior to crushing to a finely divided coal, during crushing, or after crushing. The catalyst may be mixed with the coal with or without water or other dispersing liquid to ensure even distribution of the catalyst, prior to the activation procedure. The skilled artisan will appreciate that different catalysts may require different loadings, such that a coal sample requiring 1 wt% titanium dioxide may require more or less than 1 wt% of iron oxide, or manganese oxide, or a mixture thereof, depending upon the particular activity of the catalyst and/or the chemical make-up of the coal. As stated above, the amount of catalyst may be between about 0.01 wt% and about 10 wt%, such as between about 0.01 wt % and about 9 wt%, between about 0.01 wt % and about 8 wt%, between about 0.01 wt % and about 7 wt%, between about 0.05 wt % and about 6 wt%, between about 0.05 wt % and about 5 wt%, between about 0.05 wt % and about 4 wt%, between about 0.1 wt % and about 3 wt%, or between about 0.1 wt % and about 2 wt%. In one embodiment, wherein the catalyst is titanium dioxide, the amount of catalyst used is about 1 wt%. As noted above, any combination of catalyst may be used in the amounts recited above, and the ultimate combination used will be readily discerned by trial and error by one of skill in the art.

In another aspect, the present invention provides an activated coal composition, produced by: crushing a coal stock, if required, to provide a finely divided coal; and heating the finely divided coal under aerobic conditions, to provide the activated coal composition, wherein the aerobic conditions comprises subjecting the finely divided coal to a stream of air, wherein the stream of air has a flow rate of between about 20 mL/min and 60 mL/min per 10 g sample of finely divided coal. In some embodiments, the stream of air has a flow rate of about 40 mL/min per 10 g sample of finely divided coal.

The activated coal composition of the present invention advantageously has a high total content of oxygen-containing functional groups, compared to non-activated coal compositions. In accordance with the spirit of the invention, the activated coal composition of the present invention has a maximised total content of oxygen- containing functional groups, compared to non-activated coal compositions, with a minimised amount of degradation of oxygen-containing functional groups. Oxygen- containing functional groups on the surface of the coal are typically hydroxyl (or phenol), carboxyl/carboxylic acid, and lactone. The sum of the content of each of these oxygen-containing functional groups provides the total content of oxygen- containing functional groups.

For low rank coals, such as lignite and sub-bituminous coal, the total content of oxygen-containing functional groups is between about 3.30 mmol/g and about 4.30 mmol/g, for example between about 3.30 mmol/g and about 4.20 mmol/g, or between about 3.30 mmol/g and about 4.10 mmol/g, or between about 3.30 mmol/g and about 4.00 mmol/g, or between about 3.30 mmol/g and about 3.90 mmol/g, or between about 3.30 mmol/g and about 3.80 mmol/g, or between about 3.35 mmol/g and about 4.30 mmol/g, or between about 3.40 mmol/g and about 4.30 mmol/g, or between about 3.45 mmol/g and about 4.30 mmol/g, or between about 3.50 mmol/g and about 4.30 mmol/g, or between about 3.55 mmol/g and about 4.30 mmol/g, or between about 3.60 mmol/g and about 4.30 mmol/g, or between about 3.65 mmol/g and about 4.30 mmol/g, or between about 3.70 mmol/g and about 4.30 mmol/g, or between about 3.75 mmol/g and about 4.30 mmol/g. The total content of oxygen-containing functional groups, wherein the coal stock is lignite, may be selected from the group consisting of about 3.30 mmol/g, about 3.40 mmol/g, about 3.50 mmol/g, about 3.60 mmol/g, about 3.70 mmol/g, about 3.80 mmol/g, about 3.90 mmol/g, about 4.00 mmol/g, about 4.10 mmol/g, about 4.20 mmol/g, and about 4.30 mmol/g. In one preferred embodiment, wherein the coal stock is lignite, the total content of oxygen-containing functional groups after activation is between about 3.50 mmol/g and about 4.00 mmol/g, for example, about 3.78 mmol/g.

For higher rank coals, such as bituminous coal and anthracite, the total content of oxygen-containing functional groups is between about 1.75 mmol/g and about 2.75 mmol/g, for example between about 1.75 mmol/g and about 2.65 mmol/g, or between about 1.75 mmol/g and about 2.55 mmol/g, or between about 1.75 mmol/g and about 2.45 mmol/g, or between about 1.75 mmol/g and about 2.35 mmol/g, or between about 1.75 mmol/g and about 2.25 mmol/g, or between about 1.85 mmol/g and about 2.75 mmol/g, or between about 1.95 mmol/g and about 2.75 mmol/g, or between about 2.05 mmol/g and about 2.75 mmol/g, or between about 2.15 mmol/g and about 2.75 mmol/g, or between about 2.25 mmol/g and about 2.75 mmol/g. The total content of oxygen-containing functional groups, wherein the coal stock is bituminous coal, may be selected from the group consisting of about 2.00 mmol/g, about 2.05 mmol/g, about 2.10 mmol/g, about 2.15 mmol/g, about 2.20 mmol/g, about 2.25 mmol/g, about 2.30 mmol/g, and about 2.35 mmol/g. In one preferred embodiment, wherein the coal stock is bituminous coal, the total content of oxygen-containing functional groups is between about 2.00 mmol/g and about 2.50 mmol/g, for example about 2.25 mmol/g.

The activated coal composition according to the present invention will have an acidic pH when a mixture of coal:water is measured at a ratio of 1:10 (mass:volume, for example using 1 g of finely divided coal to 10 mL of water). An acidic pH is a pH that is less than 7. The pH of a mixture of coal and water measured at a ratio of 1 : 10 may be between about pH 3.0 and pH 6.5, for example between about pH 3.5 and pH 6.5, or between about pH 4.0 and pH 6.5, or between about pH 4.5 and pH 6.5, or between about pH 5.0 and pH 6.5, or between about pH 3.5 and pH 6.5, or between about pH 3.5 and pH 6.0, or between about pH 3.5 and pH 5.5, or between about pH 3.5 and pH 5.0. Alternatively, the pH of a mixture of coal and water measured at a ratio of 1 : 10 may be selected from the group consisting of pH 3.0, pH 3.1 , pH 3.2, pH 3.3, pH 3.4, pH 3.5, pH 3.6, pH 3.7, pH 3.8, pH 3.9, pH 4.0, pH 4.1, pH 4.2, pH 4.3, pH 4.4, pH 4.5, pH 4.6, pH 4.7, pH 4.8, pH 4.9, pH 5.0, pH 5.1 , pH 5.2, pH 5.3, pH 5.4, pH 5.5, pH 5.6, pH 5.7, pH 5.8, pH 5.9, and pH 6.0. In some embodiments, the pH of the composition, when a mixture of coal and water is measured at a ratio of 1 :10, is between about 4.0 and about 6.0, such as less than about pH 5.0.

The activated coal composition according to the present invention has a high adsorption capacity for ammonium ion. For example, the adsorption from the aqueous phase of ammonium ion, wherein the coal stock is lignite, may be within a range of between about 2.70 mg/g and about 4.50 mg/g, such as between about 2.80 mg/g and about 4.50 mg/g, or between about 2.90 mg/g and about 4.50 mg/g, or between about 3.00 mg/g and about 4.50 mg/g, or between about 3.10 mg/g and about 4.50 mg/g, or between about 3.20 mg/g and about 4.50 mg/g, or between about 3.30 mg/g and about 4.50 mg/g, or between about 3.40 mg/g and about 4.50 mg/g, or between about 3.50 mg/g and about 4.50 mg/g, or between about 3.60 mg/g and about 4.50 mg/g, or between about 3.70 mg/g and about 4.50 mg/g, or between about 2.70 mg/g and about 4.40 mg/g, or between about 2.70 mg/g and about 4.30 mg/g, or between about 2.70 mg/g and about 4.20 mg/g, or between about 2.70 mg/g and about 4.10 mg/g, or between about 2.70 mg/g and about 4.00 mg/g, or between about 2.70 mg/g and about 3.90 mg/g, or between about 2.70 mg/g and about 3.80 mg/g. The adsorption of ammonium ion, wherein the coal stock is lignite, may be selected from the group consisting of about 2.70 mg/g, about 2.80 mg/g, about 2.90 mg/g, about 3.00 mg/g, about 3.10 mg/g, about 3.20 mg/g, about 3.30 mg/g, about 3.40 mg/g, about 3.50 mg/g, about 3.60 mg/g, 3.70 mg/g, about 3.80 mg/g, about 3.90 mg/g, about 4.00 mg/g, about 4.10 mg/g, about 4.20 mg/g, about 4.30 mg/g, about 4.40 mg/g, and about 4.50 mg/g. In one preferred embodiment, the adsorption of ammonium ion is between about 3.70 mg/g and about 3.80 mg/g, for example about 3.73 mg/g, wherein the coal stock is lignite.

In some embodiments, the activated coal composition has increased oxygenation as evidenced by Fourier transform infrared (FTIR) spectroscopy. For example, when the coal stock is lignite, the activated coal composition exhibits a decreased signal due to C-H between about 2950 cm ^·1 and about 2800 cm ^·1 , such as a decreased signal due to C-H at about 2910 cm ^·1 , when compared to non-activated lignite. The decrease in signal for C-H is accompanied by an increased signal due to C-0 between about 1000 cm ^·1 and about 1200 cm ^·1 , such as an increased signal due to C-0 at about 1152 cm ^·1 and about 1119 crrv ¹ , when compared to non-activated lignite. In one embodiment, wherein the coal stock is lignite, the composition will have a FTIR spectrum substantially as shown in Figure 4 for lignite activated at 200°C. Figure 4 depicts two FTIR spectra, for comparative purposes. One is of non-activated lignite and the other is of lignite activated at 200°C.

When the coal stock is bituminous coal, the activated coal composition exhibits a decreased signal due to C-H between about 2950 cm ^·1 and about 2800 cm ^·1 , such as a decreased signal due to C-H at about 2920 cm ^·1 and about 2850 cm ^·1 , when compared to non-activated bituminous coal. The activated coal composition may also exhibit a decreased signal due to C-H between about 1500 cm ^·1 and about 1400 cm ^·1 , such as a decreased signal due to C-H at about 1444 cm ^·1 , when compared to non-activated bituminous coal. The decrease in signal for C-H may be accompanied by an increased signal due to O-H between about 3600 cm ^·1 and about 3000 cm ^·1 , such as an increased signal due to O-H at around 3430 cm ^·1 , when compared to non-activated bituminous coal. The activated coal composition may also exhibit an increased signal due to C=0 between about 1750 cm ¹ and about 1650 cm ¹ , such as an increased signal due to C=0 at about 1685 cm ¹ , when compared to non-activated bituminous coal. The activated coal composition will exhibit an increased signal due to C-0 between about 1000 cm ¹ and about 1300 cm ¹ , when compared to non-activated bituminous coal. In another embodiment, wherein the coal stock is bituminous coal, the activated coal composition according to the present invention has a FTIR spectrum substantially as shown in Figure 5 for bituminous coal activated at 300°C. Figure 5 depicts two FTIR spectra, for comparative purposes. One is of non-activated bituminous coal and the other is of bituminous coal activated at 300°C.

The activated coal composition according to the present invention has a high capacity for adsorption of ammonia. For example, the composition wherein the coal stock is lignite has an adsorption capacity of ammonia of between about 30 mg/g and about 100 mg/g, or between about 35 mg/g and about 100 mg/g, or between about 40 mg/g and about 100 mg/g, or between about 45 mg/g and about 100 mg/g, or between about 50 mg/g and about 100 mg/g, or between about 55 mg/g and about 100 mg/g, or between about 60 mg/g and about 100 mg/g, or between about 65 mg/g and about 100 mg/g, or between about 70 mg/g and about 100 mg/g, or between about 75 mg/g and about 100 mg/g, or between about 30 mg/g and about 95 mg/g, or between about 30 mg/g and about 90 mg/g, or between about 30 mg/g and about 85 mg/g, or between about 30 mg/g and about 80 mg/g. The adsorption capacity of ammonia, wherein the coal stock is lignite, may be selected from the group consisting of about 50 mg/g, about 55 mg/g, about 60 mg/g, about 65 mg/g, about 70 mg/g, about 75 mg/g, about 80 mg/g, and about 85 mg/g. In one embodiment, wherein the coal stock is lignite, the adsorption capacity of ammonia for the coal composition is between about 60 mg/g and about 90 mg/g, such as about 77 mg/g.

The composition wherein the coal stock is bituminous coal may have an adsorption capacity of ammonia of between about 30 mg/g and about 70 mg/g, or between about 35 mg/g and about 70 mg/g, or between about 40 mg/g and about 70 mg/g, or between about 45 mg/g and about 70 mg/g, or between about 50 mg/g and about 70 mg/g, or between about 30 mg/g and about 65 mg/g, or between about 30 mg/g and about 60 mg/g, or between about 30 mg/g and about 55 mg/g, or between about 30 mg/g and about 50 mg/g, or between about 30 mg/g and about 45 mg/g, or between about 30 mg/g and about 40 mg/g. The adsorption capacity of ammonia, wherein the coal stock is bituminous coal, may be selected from the group consisting of about 30 mg/g, about 35 mg/g, about 40 mg/g, about 45 mg/g, about 50 mg/g, about 55 mg/g, about 60 mg/g, and about 65 mg/g. In one embodiment, wherein the coal stock is bituminous coal, and the activation temperature is about 300°C, the adsorption capacity of ammonia for the coal composition is between about 30 mg/g and about 60 mg/g, such as about 49.7 mg/g. In another embodiment, wherein the coal stock is bituminous coal, and the activation temperature is about 350°C, the adsorption capacity of ammonia for the coal composition is between about 30 mg/g and about 60 mg/g, such as about 42.1 mg/g.

The composition wherein the coal stock is coal tailings may have an adsorption capacity of ammonia of between about 30 mg/g and about 70 mg/g, or between about 35 mg/g and about 70 mg/g, or between about 40 mg/g and about 70 mg/g, or between about 45 mg/g and about 70 mg/g, or between about 50 mg/g and about 70 mg/g, or between about 30 mg/g and about 65 mg/g, or between about 30 mg/g and about 60 mg/g, or between about 30 mg/g and about 55 mg/g, or between about 30 mg/g and about 50 mg/g, or between about 30 mg/g and about 45 mg/g, or between about 30 mg/g and about 40 mg/g. The adsorption capacity of ammonia, wherein the coal stock is coal tailings, may be selected from the group consisting of about 30 mg/g, about 35 mg/g, about 40 mg/g, about 45 mg/g, about 50 mg/g, about 55 mg/g, about 60 mg/g, and about 65 mg/g. In one embodiment, wherein the coal stock is coal tailings, and the activation temperature is about 300°C, the adsorption capacity of ammonia for the coal composition is between about 30 mg/g and about 60 mg/g, such as about 50 to 55 mg/g. In another embodiment, wherein the coal stock is coal tailings, and the activation temperature is about 300°C, the adsorption capacity of ammonia for the coal composition is between about 30 mg/g and about 60 mg/g, such as about 50 to 55 mg/g.

The activated coal composition according to the present invention has a high absolute ammonium ion adsorption. For example, the composition wherein the coal stock is bituminous coal has an absolute ammonium ion adsorption of between about 0.50 mg/g and about 1.00 mg/g, or between about 0.55 mg/g and about 1.00 mg/g, or between about 0.60 mg/g and about 1.00 mg/g, or between about 0.50 mg/g and about 0.95 mg/g, or between about 0.50 mg/g and about 0.90 mg/g, or between about 0.50 mg/g and about 0.85 mg/g, or between about 0.50 mg/g and about 0.80 mg/g, or between about 0.50 mg/g and about 0.75 mg/g, or between about 0.50 mg/g and about 0.70 mg/g, or between about 0.50 mg/g and about 0.65 mg/g, or between about 0.50 mg/g and about 0.60 mg/g. The absolute ammonium ion adsorption may be selected from the group consisting of about 0.50 mg/g, about 0.55 mg/g, about 0.60 mg/g, about 0.65 mg/g, about 0.70 mg/g, about 0.75 mg/g, about 0.80 mg/g, about 0.85 mg/g, about 0.90 mg/g, about 0.95 mg/g, and about 1.00 mg/g. In one embodiment, wherein the coal stock is bituminous coal, the absolute ammonium adsorption is about 0.69 mg/g. In another embodiment, wherein the coal stock is bituminous coal, the absolute ammonium adsorption is about 0.56 mg/g.

The present invention also provides a method of lowering the amount of ammonia and/or ammonium ion from animal waste, comprising administering to an animal enclosure which comprises the animal waste an effective amount of an activated coal composition as described herein. The enclosure may be covered with a roof or it may be open. Typical animal enclosures may be a fenced-off paddock, a milking barn, a feedlot, a shed, a barn, or any combination thereof. It may be a multi-storey barn, as may be used for large poultry farms. It may be a zoo, or a particular enclosure within a zoo. It is not the intention of the inventors to limit the invention to any particular type of animal enclosure.

The coal composition may be administered to the animal enclosure by any means known in the art, such as by use of a mechanical spreader, shovel, or by hand. The coal composition may be distributed to the animal enclosure at any dose rate that is effective to control the amount of ammonia and/or ammonium ion from the animal waste. Such a dose rate is well within the ability of the skilled person to determine, and will vary for each situation depending upon, amongst other things, the number and type of animal being enclosed, the amount of manure being produced and/or average amount of ammonia and/or ammonium ion produced in a given situation, the weather or housing conditions, and the composition of the coal, for example if activated lignite, activated sub-bituminous coal, activated bituminous coal, or activated anthracite are used, or any combination thereof. For example, the coal composition may be administered at a dose rate within a range of about 0.1 kg/m ² to about 20 kg/m ² , or about 1 kg/m ² to about 20 kg/m ² , or about 2 kg/m ² to about 20 kg/m ² , or about 3 kg/m ² to about 20 kg/m ² , or about 4 kg/m ² to about 20 kg/m ² , or about 5 kg/m ² to about 20 kg/m ² , or about 6 kg/m ² to about 20 kg/m ² , or about 7 kg/m ² to about 20 kg/m ² , or about 8 kg/m ² to about 20 kg/m ² , or about 9 kg/m ² to about 20 kg/m ² , or about 10 kg/m ² to about 20 kg/m ² , or about 11 kg/m ² to about 20 kg/m ² , or about 12 kg/m ² to about 20 kg/m ² , or about 13 kg/m ² to about 20 kg/m ² , or about 14 kg/m ² to about 20 kg/m ² , or about 15 kg/m ² to about 20 kg/m ² , or about 16 kg/m ² to about 20 kg/m ² , or about 17 kg/m ² to about 20 kg/m ² , or about 18 kg/m ² to about 20 kg/m ² , or about 19 kg/m ² to about 20 kg/m ² , or about 0.1 kg/m ² to about 19 kg/m ² , or about 0.1 kg/m ² to about 18 kg/m ² , or about 0.1 kg/m ² to about 17 kg/m ² , or about 0.1 kg/m ² to about 16 kg/m ² , or about 0.1 kg/m ² to about 15 kg/m ² , or about 0.1 kg/m ² to about 14 kg/m ² , or about 0.1 kg/m ² to about 13 kg/m ² , or about 0.1 kg/m ² to about 12 kg/m ² , or about 0.1 kg/m ² to about 11 kg/m ² , or about 0.1 kg/m ² to about 10 kg/m ² , or about 0.1 kg/m ² to about 9 kg/m ² , or about 0.1 kg/m ² to about 8 kg/m ² , or about 0.1 kg/m ² to about 7 kg/m ² , or about 0.1 kg/m ² to about 6 kg/m ² , or about 0.1 kg/m ² to about 5 kg/m ² , or about 0.1 kg/m ² to about 4 kg/m ² , or about 0.1 kg/m ² to about 3 kg/m ² , or about 0.1 kg/m ² to about 2 kg/m ² , or about 0.1 kg/m ² to about 1 kg/m ² . The coal composition may be dosed at a rate selected from the group consisting of about 0.1 kg/m ² , about 1 kg/m ² , about 2 kg/m ² , about 3 kg/m ² , about 4 kg/m ² , about 5 kg/m ² , about 6 kg/m ² , about 7 kg/m ² , about 8 kg/m ² , about 9 kg/m ² , about 10 kg/m ² , about 11 kg/m ² , about 12 kg/m ² , about 13 kg/m ² , about 14 kg/m ² , about 15 kg/m ² , about 16 kg/m ² , about 17 kg/m ² , about 18 kg/m ² , about 19 kg/m ² , and about 20 kg/m ² . As one of skill in the art will appreciate, the greater the quantity of coal composition, the greater will be the amount of ammonia and/or ammonium ion able to be adsorbed.

In another aspect, the present invention provides a use of an activated coal composition as described herein, for lowering the amount of ammonia and/or ammonium ion from animal waste. MATERIALS AND METHODS Coal

Lignite and bituminous coal were used in this study as representative samples of the four types of coal, namely, lignite, sub- bituminous coal, bituminous coal, and anthracite. Coal tailings obtained from mining waste after a coal wash were also used and treated in the same manner as dewatered lignite and bituminous coal. The tailings were obtained from Newcastle University and originated from a black coal mine in Queensland, Australia. The tailings were of a size less than 1 mm and no crushing was required. Lignite was obtained from the Maddingley Mine, Latrobe Valley, Victoria, Australia. The lignite sample was crushed after drying at 70°C overnight, sieved, and only the size fractions smaller than 2 mm were used for this work. Bituminous coal (BC) was obtained from the Late Permian Moranbah Coal Measures, Bowen Basin, Queensland, Australia. The initial BC was ground with a jaw crusher (BB 100, Retsch) and sieved to obtain particle size fractions of less than 246 pm before modification The basic physiochemical properties of the initial BC were analysed and are presented in Table 1, below:

Table 1. Physiochemical properties of non-activated BC. _

Moisture

C ^a N ^a O ^a H ^a Ash ^a pH ^b EC ^b Labile C mS cm- % of total

% % % % % % 1 C

4.3 4.8 8.2

BC 85.69 2.12 8.37 <0.1 0.15 <0.01%

1 3 0 ^a C, N, O, H, ash and moisture content of BC based on the initial weight. ^b pH and EC determined at 1 :10 (coal to water) ratio.

Activation of coal

About 10 g of lignite sample was heated under an air flow of 40 mL/min in a tube furnace (5 cm diameter, 60 cm length) at ramp rate of 10°C/min to reach specific target temperatures (100, 150, 200, 250, 300 and 350°C), and then heated for 5 h at the target temperature to oxidize the lignite. The sample was then allowed to cool to room temperature (RT). Coal tailings were treated in the same manner.

For bituminous coal, activation was carried out in a tube furnace (STF1200, Across International). One wt. % titanium dioxide (T1O2) (Sigma-Aldrich, ³99.5%) and 18.2 Qm Milli-Q water was mixed with coal (coal:water = 1:1.3 mass:volume) to form a coal- Ti0 ₂ -water slurry. The resulting samples were then treated in 40 mL/min air flow at various temperatures (100, 150, 200, 250, 300, 350, 400, 450, 500 and 550°C) for 5 hours. The sample nomenclature assigned is as follows: BC = bituminous coal, followed by the oxidation temperature (°C). For example, the sample BC300 was the bituminous coal modified at 300°C.

Water content

The water content of lignite was determined by thermo-gravimetric analysis (TGA). In a typical experiment about 10 mg samples of original undried lignite was kept initially at room temperature for 1 min and then heated with a ramp rate of 20°C/min from room temperature to 1000°C in a Perkin Elmer TGA8000. An argon (Ar) flow rate of 20 mL/min was used as an inert gas for the pyrolysis study. Oven drying at 105°C overnight was also employed to confirm the results. For both methods:

Water content (%) = (W2 -W3) / (W3 - W1) *100 where W2 = weight of container with lid and sample before drying; W3 = weight of container with lid and sample after drying; and W1 = weight of container with lid.

TGA and DTG

Thermo-gravimetric analysis (TGA) and Derivative Thermogravimetry (DTG) were conducted on a TGA8000 (Perkin Elmer) instrument.

FTIR

Fourier transform infrared (FTIR) spectra were scanned with an Equinox55 spectrometer (Bruker) using KBr pellets of the solid samples. Spectra were collected from 4000 cnr ¹ to 400 cnr ¹ wavenumber range with an accumulation of 128 scans and a resolution of 4 cm ¹ . Specimens of coal samples were prepared by mixing with KBr and then grinding in an agate mortar at an approximate ratio of 1:100 (mass of coakmass of KBr). A hydraulic press at 10 MPa for 5 min was used to press the resulting mixtures to discs of 13 mm in diameter to obtain transparent pellets. The background obtained from the scan of air was automatically subtracted from the sample spectra. All spectra were plotted using the same scale on the transmission axis. pH pH was determined on a water suspension (1:10 mass ratio of coal to water). Before measurement, the suspension was shaken with a reciprocating shaker at 100 rpm at 25°C for 24 h to reach equilibrium. pH was measured with a smartCHEM pH meter (Thermo scientific).

Elemental Analyses

Total carbon (C) and total nitrogen (N) content were measured by a LECO TruMac Elemental Analyzer. Hydrogen (H) content was determined by combustion with a Flash Smart™ Elemental Analyzer (Thermo-Scientific). Labile C (potassium permanganate oxidisable C) was determined by the standard procedure of 6E1 (Rayment et ai, Soil Chemical Methods - Australasia, 2011). Hydrogen (H) content was determined by combustion, and total oxygen (O) content was determined through pyrolysis, using a FlashSmart Elemental Analyzer (Thermo scientific).

Morphology

Helium ion microscopy (HIM) images were performed on a Zeiss Orion NanoFab Scanning HIM. Surface elemental composition

Surface elemental composition and chemical bonds within 10 nm of the coal surface were quantified using X-ray photoelectron spectroscopy (XPS) analysis using a Kratos Axis Ultra XPS system or Kratos Axis ULTRA system (Thermo Scientific) with AI Ka radiation (hv= 1486.6 eV). Data was acquired using a Kratos Axis ULTRA X-ray Photoelectron Spectrometer incorporating a 165 mm hemispherical electron energy analyzer. The incident radiation was monochromatic AI Ka X-rays (1486.6 eV) at 150 W (15 kV, 15 mA). Survey (wide) scans were taken at an analyzer pass energy of 160 eV and multiplex (narrow) high resolution scans at 20 eV. The scanned area was about 0.8 mm x 0.3 mm and the depth was less than 10 nm (volume of approximately 2400 cubic microns). Survey scans were carried out over 1200-0 eV binding energy range with 1.0 eV steps and a dwell time of 100 ms. Binding energies were calibrated by taking the C 1s as 285 eV. XPS Peak 4.1 was used to deconvolve the high-resolution spectra of C 1s, O 1s, and Ti 2p after background subtraction (Nahil et ai, Chem. Eng. J. 184 (2012) 228). Narrow high-resolution scans were run with 0.05 eV steps and 250 ms dwell times. Base pressure in the analysis chamber was 1.0 ^c 10 ⁹ torr and during sample analysis 1.0 ^c 10 ⁸ torr. Desorption

The desorption of NH ₃ as a function of temperature was determined by NH ₃ temperature-programmed desorption coupled with mass spectroscopy (NH ₃ -TPD-MS) on a BELCAT-M system connected to a BELMass (MicrotracBEL) device. Approximately 100 mg of lignite sample was placed over quartz wool in a quartz U- tube (10 mm i.d.) and heated by a stainless-steel capillary. The lignite sample was first dried at 120°C for 2 h and then cooled to 35°C in a flow of argon. The argon was then replaced by a flow containing 10% NH ₃ balanced with 90% helium at a rate of 30 mL/min for 1 h for NH ₃ adsorption. This was then followed by an argon purge for 1.5 h and TPD from 35°C to 300°C at a heating rate of 5°C/min. The effluent was sampled throughout the course of desorption and analyzed by mass spectrometer. The mass values of 17 (NH ₃ ) and 18 (H2O) were monitored.

Surface functional groups Surface functional groups on modified coal samples were quantified using the Boehm titration method. Boehm titration was conducted with an OrionStar pH titrator (Thermo Scientific) using bases of increasing strength, NaHC0 ₃ , Na ₂ C0 ₃ and NaOH, and titration by HCI according to the procedure reported by Boehm (Chemical identification of surface groups, in Advances in Catalysis, Academic Press, 1966, pp. 179-274. Eds D.D. Eley, H. Pines and P.B. Weisz; and Carbon 32 (1994) 759). The amounts of acidic functional groups on the solid surface are measured under the assumption that NaOH neutralizes carboxylic, phenolic and lactone groups; Na ₂ C0 ₃ neutralizes carboxylic and lactone groups; and NaHC0 ₃ neutralizes only carboxylic groups. 1 g of an activated coal sample was placed in 50 ml_ of 0.1 M basic solutions of either NaOH, Na ₂ C0 ₃ or NaHC0 ₃ . The samples were sealed and shaken for 24 h at 100 rpm at

25°C, and then 20 ml_ of each filtrate was pipetted, and the excess of the base titrated with 0.1 N HCI. All the filtrates were degassed with N2 flow for 30 min before titration. The endpoint of the titration was pH = 5.1 for Na ₂ C0 ₃ and NaHC0 ₃ since a medium- strong base was titrated with a strong acid (HCI). In contrast to that, the endpoint for the strong base NaOH and strong acid HCI was pH = 7.0.

Surface area and pore volume

Before adsorption isotherms were obtained, activated coal samples were purged with pure N ₂ overnight at 50°C to remove any contaminants and moisture that may have been present in the samples. The Brunauer-Emmett-Teller surface area (SBET) was evaluated from N ₂ adsorption data at -196°C in p/p° from 0.04 to 0.2. The total pore volumes (V _totai ) were estimated on the basis of the volume adsorbed at p/p° ~ 0.995 using the BJH method. The micropore surface areas (Smicro) and micropore volume (V _micro ) were calculated by the t-plot method. The average pore width (D) derived from the adsorption branches of the isotherms were obtained using the BJH method.

NH ₃ adsorption

Isothermal adsorption of NH ₃ gas by the original (non-activated) and activated coal was investigated by the thermogravimetric method at room temperature using 30% NH ₃ gas balanced with moist air at ambient pressure. Around 1.00 g of sample was put in an OHAUS balance scale (0.0001 g precision), and 20 ml_ of 30% ammonium hydroxide solution (NH ₃ Ή2q) (Sigma-Aldrich) was placed on the balance at the same time. The partial pressure of NH ₃ gas and water vapor above aqua ammonia in the scale balance were calculated to be about 6.21 and 0.51 kPa, respectively (Ham, The Total and Partial Vapor Pressures of Aqueous Ammonia Solutions, 1925). The amount of NH ₃ absorbed on the coal was calculated from the sample weight change recorded by the balance scale. The weight change was recorded every minute. Nanopure™ water was used in all analyses.

NH ₄ ⁺ adsorption

NH ₄ ⁺ adsorption on initial and modified coal was performed by batch experiments at room temperature. The experiments were carried out in plugged 30 ml_ vials containing 0.5 g coal sample and 15 mL NH ₄ CI (33 ~ 2617 mg/L) solution for 24 h. After equilibrium the adsorbents were eliminated by filtering through 0.45 pm. Initial and equilibrium concentrations of NH ₄ ⁺ were determined by a continuous flow analyzer (SFA, Skalar San+). The amount of NH ₄ ⁺ adsorbed by coal was calculated from the decrease in NH ₄ ⁺ concentrations in solution. The quantities of NH ₄ ⁺ adsorbed by samples were calculated from the reduction of NH ₄ ⁺ concentrations in solution. The NH ₄ ⁺ adsorption capacity was calculated with the following equation:

(C ₀ - C _f ) x V q ⁼ - m - where C ₀ (mg/L) is the initial concentration of NH ₄ ⁺ and C _f (mg/L) is the NH4 ⁺ concentration in aqueous phase after adsorption, V the total solution volume (ml_) and m ( g) the amount of sorbent on a dry basis (Maranon et al, J. Hazardous Materials 137, (2006), 1402). NH ₄ ⁺ -N adsorption of lignite samples was performed by batch experiments at 295 K. The experiments were carried out in plugged 30 ml_ vials containing 0.25 g lignite sample and 25 ml_ NH ₄ CI solution. On reaching equilibrium the adsorbents were removed by filtering through a Millipore filter (0.45 pm). Initial and equilibrium concentrations of ammonium ions were determined by SFA. Analytical grade reagents were used for the experiments. Risk of spontaneous combustion

Combustion of coal char is a heterogeneous reaction that was evaluated by a non- isothermal single heating rate method. Under low heating rate conditions, the reaction was treated as a kinetically controlled one, and Arrhenius’ law was used to calculate the combustion rate. TGA data of a single heating rate test was used to calculate kinetic parameters by the Coats-Redfern method, which has also been used by other researchers to obtain kinetic parameters (e.g. Bergstrom etai, Global Change Biology, 12 (2006) 635; and Bouwman et al., Global Biogeochemical Cycles, 16 (2002), 8-1-8- 14). Coal-char combustion is thought to be governed by the first-order Arrhenius law. So the kinetics of reaction is described as: where a is the extent of conversion; f(a) is the hypothetical model of the reaction mechanism; A is the frequency factor, min ^-1 ; E is the apparent activation energy, kJ mol ¹ ; R is the gas constant and equals 8.314 kJ mo K ¹ ; Tis the absolute temperature, K; t is time, min; mo is the initial mass of the sample; m _t is the mass of the sample at time f; and m~ is the final mass of the sample.

When the heating rate (/3=dT/df) is a constant during combustion, Eq. (1) can be transformed into:

In many kinetic studies using TGA, the chemical reaction model is the used. The chemical reaction model is described as: f(cc ) = (1 — a) ⁿ (4) where n is the order of reaction. Normally, the assumption is made that the main burning process is described by first order kinetics. The equation derived for calculating the activation energy value is given as: where E and A can be estimated from the slope and intercept of a plot of In against 1/T. In this method, TGA data at a single heating rate are sufficient for the analysis and kinetic parameters extraction.

EXAMPLES

The present invention will now be more fully described by reference to the following non-limiting Examples. Example 1

A coal sample was analysed by TGA and DTG to determine loss of water upon heating.

The TGA curve of lignite (without any drying) obtained under argon is shown in Fig. 1. There were two major intervals of weight losses as temperature was increased, corresponding to drying (up to around 100°C) and the removal of volatile organic matter (100-600°C). The first stage of lignite heating and drying was characterized by a sharp acceleration of the loss of mass with increasing temperature, marked with a clear DTG peak followed by a decreased reaction rate (Fig. 2). Surprisingly, the weight loss due to pyrolysis of lignite between 100°C and 300°C was only 6.9% (Fig. 1). As such, a temperature range between 100°C and 300°C is expected to be suitable for efficient dewatering of lignite without drastically decreasing the amount of volatile organic matter. Heating lignite at 200°C reduces the water content from 61.6% to 4.2% based on TGA and oven-drying measurements (Fig. 3).

Example 2

Coal samples were analysed by FTIR to evaluate the nature of the surface functional groups. FTIR of original lignite (non-activated) and lignite activated at 200°C are shown in Fig.

4. Original lignite showed bands at 2910 cnr ¹ which can be assigned to asymmetric and symmetric -C-H stretching vibrations in -CH ₃ , =CH ₂ , and -CH ₂ CH ₃ aliphatic groups. Surprisingly, and in contrast to results reported by Wang (Mining Science and Technology 20 (2010) 35), this band almost completely disappeared after aerobic treatment at 200°C using the conditions described herein. Furthermore, the oxidation treatment increased the relative intensity of the broad peak at 1000-1200 cm ^·1 , which can be attributed to functional groups containing C-0 stretching, such as carboxyl, lactone and hydroxyl functional groups. This suggests that a transition of alkyl groups to oxygen-containing functional groups occurs due to the aerobic treatment as described herein.

FTIR of original BC (non-activated) and BC300 (activated at 300°C) are shown in Fig.

5. A very broad band centered at about 3430 cm ^·1 is found for both samples, but is enhanced for the activated BC. This peak is mainly assigned to -OH stretching vibrations in adsorbed water, carboxylic and phenolic groups. The bands at around 2920 and 2850 cm ¹ are found to be weaker in activated BC compared to the non- activated BC, which are attributed to aliphatic C-H vibration of -CH ₃ and -CH ₂ stretching vibrations, respectively. This trend follows that discussed above for lignite. The weak band at about 1444 cm ¹ is ascribed to symmetric aliphatic C-H vibrations of -CH ₂ . The emerging intense band for activated BC at around 1685 cm ¹ (C=0) is attributed to a high density of carboxylic and lactone groups that were generated during aerobic treatment. Finally, several enhanced characteristic peaks were observed between 1000 and 1300 cm ¹ which can be attributed to the C-0 bonds from phenolic, carboxylic, etheric, and ester groups, implying that oxygen-containing surface functionalities are generated. These new bands may not be seen very clearly due to interference with water, adsorbed on the KBr, which made it difficult to distinguish the absorption bands of hydroxyl groups and other groups that contained C-0 bands.

The FTIR spectra provide evidence of oxidative transformation of C-H groups to C- 0/C=0 groups on coal surfaces due to partial and/or full oxidation.

Example 3 pH of a coal/water slurry was analysed as a function of activation temperature.

Lignite samples were activated by heating at temperatures ranging from 100°C to 350°C, under aerobic conditions, as shown in Fig. 6. BC samples were pre-treated with a catalyst (titanium dioxide), then activated by heating at temperatures ranging from 100°C to 550°C, under aerobic conditions, as shown in Fig. 7. Coal tailing samples were activated by heating at temperatures ranging from 100°C to 400°C, under aerobic conditions, as shown in Figure 24.

Non-activated lignite had a pH of around 4.9, whilst non-activated BC had a pH of around 8.2 and the non-activated coal tailings had a pH of around 10. The pH value of coal decreased initially with increasing modification temperature. Surprisingly, both lignite and BC samples were able to reach a minimum pH of around 4.5, indicating similar levels of oxidation despite the difference in activation temperature (200°C for lignite versus 300°C for BC) and composition of the different coals. The coal tailings sample decreased to about 6.5 at a temperature of 250°C. The pH of coal samples increased upon further heating, although the lignite and BCsamples were still acidic pH even after heating well beyond the optimum temperature where the pH was a minimum.

The reduction in pH for coal tailings was also monitored over time as shown in Figure 25. The pH reduced over time showing that the number of acidic groups increased with the aerobic heat treatment over time.

These results suggest that aerobic treatment increased the acidity of the coal surfaces. Heating beyond the optimum temperature resulted in loss of acidic groups and a resulting rise in pH.

Example 4

Elemental analysis was determined to examine the functional groups on activated versus non-activated coals.

Elemental analysis of lignite showed that the total oxygen content increased from 25.9% to 32.4% after treatment at 200°C.

Example 5

Helium ion microscopy (HIM) was used to analyse the surface of activated coals.

HIM images are shown in Fig. 8. As can be seen in Figs 8(a) to 8(c), the original lignite had irregular size and shape distributions, with pores (<1 pm) clearly visible. Activation due to aerobic heating to 200°C resulted in structural changes (compare Figs 8(c) versus 8(d)) such as removal of pore structures to some extent which suggests a reduction in specific surface area. The diminishing pore structures and specific surface areas are expected to suppress oxidation reactions on the coal surface and thus decrease the tendency of spontaneous combustion. The unexpected benefit of reduced risk of spontaneous combustion may originate from structural changes caused by partial oxidation during the dewatering process.

HIM images of non-activated BC and BC300 (activated at 300°C) are shown in Fig. 9.

A smooth external surface was observed for non-activated BC, while wrinkles, holes and destruction of structure were found on the activated BC surfaces. In addition, both samples showed a non-porous structure, which was consistent with the results of surface area and pore volume analyses that no distinguishable difference was observed between the non-activated and activated BC.

Example 6

X-ray photoelectron spectroscopy (XPS) was also undertaken to examine the functional groups on activated versus non-activated coals.

The XPS spectra of electrons from the 1s orbit of carbon atoms (C1s) at lignite surface are presented in Fig. 10. Deconvolution of the curves shows the peaks at various positions indicating the chemical heterogeneity of the surface. The C1s spectrum for original lignite consists of peaks at 285.0, 286.1 , 287.3 and 289.1 eV that can be assigned to C-C, C-O, C=0 and COO groups, respectively. In addition to the presence of these oxygen groups, it was found that the COO group increased from 6.2% to 7.5% after aerobic treatment.

The XPS survey and high resolution XPS spectra for C 1s of non-activated BC and BC300 (activated at 300°C) are displayed in Fig. 11. The spectra contained distinct peaks for C and O for both samples; a weak peak for Ti only exhibited for activated BC confirms the presence of T1O2 catalyst. The relative contents of C and O obtained from XPS reveal a successful functionalization on the surface of the activated BC sample.

As listed in Table 1 (below), after modification, the C content decreased from 91.3 to 61.0 at%, while the O content increase dramatically from 7.0 to 30.2 at%. In addition, the atomic ratios of O 1s/C 1s of activated BC (49.5%) is also much higher than that of the non-activated BC (7.7%). This indicates the formation of a large amount of oxygen- containing functional groups on the BC surface after activation. To better understand the surface chemistry changes during oxidative modification, the high-resolution spectra for C 1s peak of non-activated and activated BC were deconvoluted according to the banding energies. The optimum fitting results for C 1s are illustrated in Fig. 11b. The deconvolution of the C 1s spectra yielded five peaks: peak 1 (285 eV), Sp3 bulk carbon bound to the edge of the graphene sheets; peak 2 (286.1 eV), -C-O-R in alcohol and ether; peak 3 (287.3-287.7 eV), -C=0 in carbonyl, quinines and ketones; peak 4 (289.1-289.5 eV), -COOR in carboxyl and ester groups; and peak 5 (291.0-291.2 eV), carbon in carbonate groups and/or adsorbed CO and CO2. The relative contents of various peaks of non-activated and activated BC are summarized in Table 2:

Table 2. Elemental composition and chemical states of C on non-activated BC and BC300 (activated at 300°C) obtained from XPS analysis. _

O C N Ti O/C C-C C-0 C=0 COO C0 ₃ ² at% at% at% at% % at% at% at% at% at%

Non- activated 7.0 91.3 0.60 - 7.7 85.6 8.1 2.0 1.8 2.4

BC

BC300 30.2 61.0 0.90 2.70 49.5 60.7 16.4 10.7 8.5 3.6 After aerobic treatment, the relative content of the graphitic carbon (peak 1) decreased, while that of the carbon bonded to oxygen-containing functionalities (peaks 2-5) increased. This information confirms the FTIR results that oxidative modification causes surface chemistry changes and generates more oxygen-containing functional groups on BC surfaces.

It is noted that the amount of titanium dioxide added to the coal sample is 1 wt%, but the amount of Ti measured by XPS, as shown in Table 2, above, is 2.7 at% (atomic %). The reason for the discrepancy may be that the XPS analysis measured the elemental composition within 10 nm of the coal’s surface, which is 2.7 at%, whereas 1 wt% T1O2 is the amount added according to the total weight of starting material (coal).

Example 7

To further quantify the concentration of surface oxygen-containing functional groups, the concentration of hydroxyl, lactonic and carboxyl groups, and total oxygen- containing functional groups, as a function of treatment temperature were calculated using Boehm’s method (Chemical identification of surface groups, in Advances in Catalysis, Academic Press, 1966, pp. 179-274. Eds D.D. Eley, H. Pines and P.B. Weisz; and Carbon 32 (1994) 759). Table 3 shows the results for lignite:

Table 3. Concentrations of oxygen-containing functional groups at lignite surfaces, activated at different temperatures under aerobic conditions. bsolut elative

Oxygen-containing function moniu monium

Temperature (mmol/g) sorpti orption

(°C) (mg/g) mg/g) ydroxyl Lactonic Carbo groups groups grou

Origina 1.43 0.85 0.9 2.25 0

100 1.50 0.90 0.8 2.38 0.13

150 1.55 1.05 0.7 2.76 0.52

200 1.75 1.03 1.0 3.73 1.48

250 1.55 0.98 0.9 2.70 0.45

300 1.64 1.03 0.5 2.51 0.26

350 1.44 0.78 0.2 1.22 1.03

Table 3 shows the largest concentration of total oxygen-containing functional groups was obtained by activation at 200°C (3.78 mmol/g), which is 0.6 mmol/g, or 19%, higher than that of the non-activated lignite. However, excessive heating at temperatures above 200°C resulted in a decrease in the total concentration of oxygen- containing functional groups, probably due to thermal decomposition of oxygen- containing groups. In particular, the influence of treatment temperature on the carboxyl group was more marked than the other groups (Table 3), which showed that carboxyl group content drastically decreased with increasing treatment temperature.

Importantly, the increment of ammonium ion adsorption is in accordance with the large increase in total concentrations of oxygen-containing functional groups and decrease in pH, as discussed above. This suggests that optimizing surface oxygen groups on the surface of the coal may maximize the sorption capacity for ammonium ion. Furthermore, tuning the concentrations of different acidic functional groups in a controlled way will allow analysis of the relationships between ammonium ion adsorption and characteristics of coal at a molecular level. To further clarify the surface functionality changes of BC after activation, the Boehm titration method was employed to provide both qualitative and quantitative information of acidic functional groups on the BC surface. Table 3 summarizes the amount of acidic surface functional groups (carboxylic, lactone, and phenolic groups) of BC activated at different temperatures:

Table 4. Concentrations of oxygen-containing functional groups at BC surfaces, activated at different temperatures under aerobic conditions.

Total

Absolute Relative

Temperature Carboxylic Lactone Phenolic ammonium ammonium acidity adsorption adsorption

°C mmol/g mmol/g mmol/g mmol/g mg/g mg/g

Original 0.19 0

200 0.050 <0.01 0.025 0.075 0.31 0.12

250 0.225 0.175 0.425 0.825 0.26 0.07

300 0.600 0.675 0.975 2.250 0.56 0.37

350 0.450 0.375 0.500 1.325 0.69 0.50

400 0.325 0.200 <0.01 0.525 0.57 0.37

450 0.200 0.075 0.250 0.525 0.23 0.04

500 0.125 0.100 0.275 0.500 0.17 0.02

From these results it can be seen that all the densities of carboxylic, lactone, phenolic groups and total acidity increased when the modification temperature increased from 200°C to 300°C. The highest concentration of acidic functional groups (2.25 mmol/g) were obtained for BC300. The presence of surface acidic functional groups is expected to strengthen the polarity of the BC surface and improve its adsorption ability and selectivity to polar alkaline adsorbates such as ammonia. To be specific, ammonia molecules could accept a proton from an acidic functional group and form ammonium ion (NH4 ⁺ ) as the Bronsted acid. This is in close agreement with previous measurements that showed the highest ammonia adsorption capacity (49.7 mg/g) was also obtained on BC300.

The results also show that when the activation temperature was higher than 300°C (e.g. 350°C, 400°C, 450°C and 500°C), the amount of acidic functional groups seems to decrease at the BC surface. One possible reason for the decrease of oxygen surface groups is that they decompose at temperatures above 300°C.

Example 9

Ammonia desorption profile was analysed by evaluation of the temperature programmed desorption (TPD), which describes the effect of acidic functional groups on ammonia adsorption.

Ammonia adsorption in moist air was increased by 28.8% after activation at 200°C (Fig. 12). In the absence of moisture, the NH ₃ -TPD-MS profile (Fig. 13) of the same lignite sample over the temperature range of 30-300°C confirmed the increase in NH ₃ adsorption, which was ~3.1 times greater than that of non-activated lignite, based on integral of the desorption peaks. Furthermore, only one desorption peak was shown at relatively high temperature (~100°C) demonstrating the strong chemical interaction between the lignite surface and adsorbed ammonia. The broad desorption peak indicates the existence of a range of adsorption sites with different bonding strengths.

Fig. 14 shows the ammonia adsorption profiles of activated BC at room temperature in the presence of moisture. The ammonia adsorption capacity was calculated from the weight change of coal samples within 60 min and the results are summarized in Fig.

15. Ammonia adsorption capacity of non-activated BC was only 4.6 mg/g. The adsorption capacity increased greatly after activation up until about 300°C. The optimal adsorption capacity was achieved in BC300, which is 49.7 mg/g, corresponding to a 10.8-fold increase compared with non-activated BC, which is surprising given the high temperatures experienced by the surface groups. It is also worth noting that this adsorption capacity is much higher than that of commercially activated carbon (1.8 mg/g) (Bioresour. Technol. 98 (2007) 886), or modified activated carbon (20.1 mg/g) (Environ. Sci. Technol. 45 (2011) 10605). The adsorption capacity of activated BC300 is close to an activated carbon (52.7 mg/g) prepared from petcoke by potassium hydroxide chemical activation (Fuel Process. Technol. 144 (2016) 164). At this point, it is important to highlight that the activation conditions for BC for ammonia adsorption is a simple one-step process which only requires relatively low temperature without the addition of strongly caustic chemical reagents such as potassium hydroxide. Higher reaction temperatures (350°C, 400°C, 450°C and 500°C) not only increased the energy cost but also resulted in decreased ammonia adsorption compared with the BC activated at 300°C. As described above, partial oxidation is an effective approach to enhance ammonia adsorption capacity of coal with an optimal modification temperature at 300°C for BC.

The ammonia adsorption capacity of coal tailing samples was calculated from the weight change within 60 minutes and the results are summarised in Fig. 26. Ammonia adsorption capacity of non-activated coal tailings was only 2.1 mg/g. The absorption capacity increased greatly after activation up until 300°C. The optimal absorption capacity was about 52.5 mg/g. Ammonia adsorption capacity also increased with coal tailings that were activated for longer periods of time, showing that optimal activation time was between 5 and 7 hours as shown in Figure 27.

To investigate the role of acidic functional groups on ammonia adsorption, total acidity was plotted against ammonia adsorption capacity for activated BC samples (Fig.

16(a)). These data show that the ammonia adsorption capacity of activated BC samples has a linear relationship with the total amount of acidic functional groups. This result suggests that the chemical interactions between ammonia molecules and acidic functional groups are dominant in ammonia adsorption on activated BC. Additionally, the relationships between ammonia adsorption capacity and the amount of each acidic surface functional group (carboxylic, lactone and phenolic) are shown in Figs 16(b), 16(c) and 16(d). The greatest correlation was obtained for carboxylic groups (R ² =

0.96). Furthermore, the slopes of the linearity, k, were observed as follows: carboxylic < lactonic < phenolic.

Similarly, total acidity plotted against ammonia adsorption for coal tailings is shown in Figure 28. These data show that the ammonia adsorption capacity of activated coal tailing samples has a linear relationship with the total amount of acidic functional groups. This result also suggests that the chemical interactions between ammonia molecules and acidic functional groups are dominant in ammonia adsorption on activated coal tailings.

These results reveal the crucial role of the acidic functional groups in the adsorption of ammonia and, more specifically, the important effect of the more acidic functional groups (carboxylic groups) in the adsorption process. Consequently, we concluded that ammonia adsorption, on activated BC, is mainly controlled by the chemical interactions between ammonia molecules and acidic functional groups on the surface, especially for carboxylic groups. Example 10

The effect of aerobic activation on a coal sample (lignite) was evaluated, in relation to ammonium ion adsorption. Lignite, heated under nitrogen gas at 200°C was compared to a lignite sample that had been aerobically activated at 200°C. Ammonium ion adsorption was analysed for the two samples, as shown in Fig. 17.

Although aerobic treatment at 200 °C enhanced NH4+ adsorption, heating of lignite under pure nitrogen gas at 200°C showed low ammonium ion adsorption (0.39 mg/g). Surprisingly, heating lignite at 200°C under aerobic conditions resulted in an ammonium ion adsorption of about 3.75 mg/g, an increase of almost 1000-fold. This suggests that the enhanced adsorption capacities of lignite originate from the oxygen in the stream of air, resulting in increased oxygen-containing adsorption sites.

Fig. 18 shows the ammonium ion adsorption capacity of lignite after treatment at temperatures spanning 100°C to 300°C. The maximum adsorption of ammonium ion by activated lignite, obtained at an activation temperature of 200°C, was 3.73 mg/g. This capacity corresponds to an increase of 66% compared with non-activated lignite (2.25 mg/g). Heating to higher temperatures caused a large decrease in ammonium ion adsorption, down to the original value or even lower (e.g. 1.22 mg/g at 350°C). These results confirm that aerobic activation at 200°C increases both ammonium ion and ammonia gas adsorption.

To further clarify the role of the oxygen-containing functional groups on ammonium ion adsorption, Fig. 19 compares the ammonium ion adsorption and the total concentrations of oxygen-containing functional groups. The linear correlation between adsorbed ammonium ion and the total concentration of acidic groups on the lignite surface was high, R ² = 0.93 (Fig. 19(d)), while other correlations for single groups were much lower (R ² = 0.63 for hydroxyl, R ² = 0.51 for carboxyl, and R ² = 0.60 for lactone). The slope of the linear regression for the total concentration of oxygen groups was close to 1 on a molar basis, suggesting one oxygen group interacts primarily with only one ammonium ion.

This data confirms that surface oxygen-containing groups play a crucial role in ammonium ion adsorption, predominantly by strong chemical bonding between ammonium ion and oxygen-containing groups on the coal (lignite) surface.

Fig. 20 shows the ammonium ion adsorption isotherms for the Langmuir and Freundlich models, respectively. When pH is low, the NH ₃ /NH ₄ ⁺ equilibrium shifts in favour of its ionized form, NH ₄ ⁺ . Thus, adsorption behaviours of ammonium ion onto non-activated BC and BC300 (activated at 300°C) were also evaluated through adsorption isotherms. The ammonium ion adsorbed at equilibrium (Q _e , mg/g) and residual equilibrium ammonium ion concentration in solution (C _e , mg/L) within different initial ammonium ion concentrations at room temperature were fitted to the: Langmuir (Equation (1)) and Freundlich (Equation (2)) model.

The Langmuir isotherm is based on monolayer adsorption onto a surface containing a finite number of homogeneous adsorption sites within the adsorbent. The linear form of the Langmuir equation is: where Q _e is the amount of adsorbate adsorbed at equilibrium per unit mass sorbent (mg/g); C _e is the equilibrium concentration of adsorbate in solution (mg/L); Q _m is the maximum monolayer adsorption capacity (mg/g); K _L is the Langmuir adsorption constant related to the energy of adsorption (L/mg). The maximum adsorption capacity Q _m and Langmuir constant K _L were determined from the slopes and the intercepts of the plots of C _e /Q _e versus C _e .

The Freundlich isotherm is an empirical equation derived by assuming a heterogenous surface (multilayer adsorption). The linear form of the Freundlich equation is: log where K _F is a constant indicative of the adsorption capacity, 1/n is the adsorption intensity and it also known as the heterogeneity factor. Linear plots of log Q _e versus log C _e allow the estimation of K _F and n values from the intercepts and the slope of the plot, respectively. In Table 4, the values of maximum adsorption capacities (Qm), the rate constants KL, KF, 1/n and the regression coefficients, RL2 and RF2, for the Langmuir and Freundlich models, respectively are summarized:

Table 5. Langmuir and Freundlich parameters calculated from the adsorption isotherms for NhV adsorption onto non-activated BC and BC300 (activated at 300°C). _

Langmuir model Freundlich model

Initial BC QM 0.029 098 0.063 027 077

BC300 2.36 0.004 0.97 0.154 0.35 0.99

The data in Table 5 show that the simple Langmuir equation describes the adsorption of ammonium ion on both non-activated BC (RL ² = 0.98) and BC300 (activated at 300°C) (RL ² = 0.97). The maximum adsorption capacity (Q _m ), determined from the Langmuir isotherm, was 2.36 mg/g for BC300, about 6 times more than the non- activated BC (0.41 mg/g). This relatively high adsorption capacity suggests strong electrostatic interaction of attraction between the NhV molecules and binding-sites on the activated BC. On the other hand, a higher correlation coefficient of the Freundlich model was obtained on BC300 (RF ² = 0.99) than non-activated BC (RF ² = 0.77). This suggests that physical adsorption also occurs on the non-activated BC.

In addition, the ammonium ion adsorption on non-activated BC fit both the Langmuir and Freundlich models (Fig. 20). Similar ammonium ion adsorption behaviour has previously been described with biochar (Kizito et ai, Sci. Total Environ. 505 (2015) 102). This behaviour is attributed to the heterogeneous nature of the carbon surfaces. In general, when the Freundlich adsorption constant K _F value increases, the adsorption capacity of the adsorbent for a given adsorbate increases. A higher K _F value for BC300 (0.154) than non-activated BC (0.063) also suggest improved ammonium ion adsorption after activation. Furthermore, Langmuir values of RL (RL = 0.029 and 0.004 for non-activated BC and BC300, respectively) below 1.0 and Freundlich values of 1/n (1/n = 0.27 and 0.35 for non-activated BC and BC300, respectively) between 0 and 1 revealed the favourability of adsorption of ammonium ion onto both non-activated and activated BC. The ammonium ion adsorption studies revealed that activated BC exhibited much higher overall uptake of ammonium ion at equilibrium compared with non-activated BC and that some level of physical adsorption also occurred.

These results confirm that aerobic activation at 200°C (for lignite) or 300°C (for BC) increases both NhV ion and NH ₃ gas adsorption. Example 11

The risk of spontaneous combustion was evaluated by the apparent activation energy (E _a ) of combustion using TG curves in air with a non-isothermal single rate method. As shown in Fig. 21, after aerobic activation of lignite at 200°C the apparent activation energy increased from 34.8 kJ/mol to 37.8 kJ/mol. The activation of coal (lignite) can therefore slightly reduce the risk of spontaneous combustion, which will improve the safety of transportation of activated coal compositions. Example 12

Coal compositions of the present invention were tested for reactive nitrogen adsorption by application to an animal feedlot. The best performing activated lignite (activated at 200°C) and bituminous coal (activated at 300°C) were used. The incubation study used cattle manure from a commercial beef cattle feedlot in NW Victoria, Australia, and measured cumulative ammonia emissions. The results are shown Figs 22 and 23. In Fig. 22, it can be clearly seen that the total cumulative ammonia emission decreased by 47.5% and 40.0% after application of 30% best performing activated lignite and activated bituminous coal (black coal), respectively.

The incubation study was extended to poultry manure where the results are also very positive. As shown in Fig. 23, the total cumulative ammonia emission decreased by 49.2% and 29.8% after application of 20% best performing activated lignite and activated bituminous coal (black coal), respectively.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.