Treatment of processed bauxite

Abstract

A process of treating treated or untreated processed bauxite (12) to form an aggregated product that can be returned to a natural environment. The process comprises subjecting treated or untreated processed bauxite (12) to chemical and / or thermal treatment (14) to reduce pH and / or sodicity to form a treated material (15); and increasing an aggregate size of the treated material (15) in an aggregator system (26) to form the aggregated product.

Description

[0001] Treatment of Processed Bauxite

[0002] Technical Field

[0003] The present disclosure relates to processes and systems for treating processed bauxite.

[0004] Background

[0005] The Bayer process, widely used in alumina refineries, generates a significant amount of processed bauxite, also known as bauxite residue, Bayer residue or less commonly red mud. This by-product presents environmental challenges due to its high alkalinity and large volume. Traditionally, processed bauxite is stored in residue storage areas.

[0006] As environmental regulations become more stringent and the demand for sustainable practices increases, there is a growing need to reduce reliance on residue storage areas and develop alternative methods for managing processed bauxite. The high pH and sodicity of processed bauxite limit options to use it outside residue storage areas in an environmentally friendly manner, necessitating transformation of this by-product into a material that can be safely returned to the natural environment.

[0007] Existing methods for managing processed bauxite often involve containment and storage, which do not address the underlying chemical and physical properties that make it unsuitable for direct environmental application. There is a need for processes that can effectively treat processed bauxite to reduce its pH and sodicity, thereby transforming it into a product that can be used in various environmental applications, such as agriculture, landscaping, land rehabilitation, and mine backfill.

[0008] Summary

[0009] An embodiment provides a process of treating treated or untreated processed bauxite to form an aggregated product that can be returned to a natural environment comprising subjecting treated or untreated processed bauxite to chemical and / or thermal treatment to reduce pH and / or sodicity to form a treated material; and increasing an aggregate size of the treated material to form the aggregated product.

[0010] In an embodiment, the process comprises chemical treatment including neutralisation.

[0011] In an embodiment, the treated material has 5<pH<9, such as 5<pH<8. Neutralisation may include contacting the treated or untreated processed bauxite with a neutralising agent that includes an inorganic acid including H2SO4, H3PO4, HNO3, HCI, an acid derived from contacting the treated or untreated processed bauxite with elemental sulphur, an organic acid including acetic, oxalic, citric, and / or lactic acid, and / or a species capable of reacting with the processed bauxite to reducethe alkalinity of the processed bauxite. The concentration of the acid may range from about 0.1 M to 1.0M, including 0.2M to 0.5M.

[0012] The process may comprise chemical treatment including contacting the treated or untreated processed bauxite with a treatment solution that contains divalent cations to reduce a sodicity of the treated or untreated processed bauxite by displacing sodium cations in the treated or untreated processed bauxite with the divalent cations in the treatment solution.

[0013] In an embodiment, the divalent cations include magnesium ions and calcium ions. In an embodiment, the magnesium ions are derived from a magnesium sulphate. In an embodiment, the calcium ions are derived from gypsum or calcium chloride and / or products formed from subjecting calcite or tri-calcium aluminate to acid. The calcite and / or tri-calcium aluminate may be present in the processed bauxite, for example, prior to any treatment post-exit from the Bayer process. The process may further comprise washing displaced sodium ions with a washing solution. Thermal treatment may include pyrometallurgy, vitrification, calcination or sintering to mineralise soda or make the soda less soluble in the treated material compared to the processed bauxite.

[0014] In an embodiment, the treated material formed by thermal treatment has a pH<11 , EC<4mS / cm and exchangeable sodium percentage <70%, such as pH<10.5, EC<1 mS / cm and ESP~60%. The process may further comprise mixing processed bauxite with the treated material to form a mixed treated material. In an embodiment, the mixed treated material is formed prior to increasing the aggregate size. In an embodiment, the mixed treated material comprises from about 30wt.% to about 70wt.% processed bauxite. Prior to chemical and / or thermal treatment, the treated or untreated processed bauxite may have pH<11 and EC<3mS / cm in a 1 :5 suspension in water.

[0015] The process may further comprise drying the treated material to form a dried treated material prior to increasing the aggregate size. In an embodiment, the dried treated material has a water content of <25wt.%. Increasing an aggregate size of the treated material may include mixing the treated material with a binder to bind treated material together. Mixing the treated material with a binder may include adding water to the treated material to control a water content of the treated material. In an embodiment, the binder includes a lignosulfonate species, starch, guar, an organic polymer and / or an organic species. The binder may be added as a solution and / or a solid. For example, a solid binding agent may include solid organics. In an embodiment, the binder is added up to 5wt.% of the treated material.

[0016] The process may further comprise drying the treated material after aggregation to form the aggregated product. Aggregating may include agglomeration, pelletising and / or briquetting. In anembodiment, the aggregated product has an aggregate size of about 1 mm to about 50 mm. In an embodiment, the aggregated product is one of a liming agent, a water retention agent and / or nutrient retention agent, topsoil fill, and mining pit backfill.

[0017] An embodiment provides an aggregated product that can be formed from the process and can be returned to a natural environment.

[0018] In an embodiment, an aggregated product that can be returned to a natural environment comprises aggregated processed bauxite having a pH<11 , EC<10mS / cm, an exchangeable sodium percentage (ESP) <70%, and a particle size >1 mm. In an embodiment, the aggregated processed bauxite has pH ranging from 5.0 to 7.5, EC <1mS / cm, and ESP<9.5. In an embodiment, the aggregated product has a size ranging from about 1 mm to about 10 mm. In an embodiment, the aggregated product further comprises up to 5wt.% organic matter. In an embodiment, the aggregated processed bauxite has pH ranging from 5.5 to 8.5, EC <1mS / cm, and ESP<9.5. In an embodiment, the aggregated processed bauxite has pH ranging from 8.0 to 10.5, EC <1 OmS / cm, ESP<9.5 and a size ranging from about 1 mm to about 20 mm.

[0019] An embodiment provides a method of treating an environment that may comprise applying the aggregated product to a natural environment.

[0020] An embodiment provides a treatment plant comprising:

[0021] a treatment system configured to subject treated or untreated processed bauxite to chemical and / or thermal treatment to reduce pH and / or sodicity to form a treated material; and an aggregator system configured to increase an aggregate size of the treated material to form an aggregated product that can be returned to a natural environment.

[0022] In an embodiment, the aggregator system includes an agglomerator, pelletiser, pin mixer, briquette former or roll press. In an embodiment, the agglomerator includes a disc or drum agglomerator. The processed bauxite is typically generated in a Bayer plant or Bayer circuit. The treatment plant may further comprise a binding agent mixer in fluid communication with the aggregator system and configured to form a solution that includes a binding agent that is used in the aggregator system to form the aggregated product. The treatment system may include a neutralisation system configured to receive and neutralise treated or untreated processed bauxite by addition of a neutralising agent to form the treated material. The treatment system may include a sodicity reduction system having a source of divalent cations, the sodicity reduction system configured to mix treated or untreated processed bauxite and the divalent cations to reduce a sodicity of the treated or untreated processed bauxite by displacing sodium cations in the treated or untreated processed bauxite with the divalent cations to form the treated material and wastesolution.

[0023] In an embodiment, the sodicity reduction system includes a dewatering system configured to separate treated material from the waste solution, the dewatering system being positioned upstream of the aggregator and configured such that treated material separated by the dewatering system can be received by the aggregator. In an embodiment, the treatment plant further comprises a dryer positioned downstream of the dewatering system and upstream of the aggregator, the dryer configured to at least partially dry the treated material from the dewatering system prior to being received in the aggregator.

[0024] The treatment plant may further comprise a divalent cation mixer configured to receive and mix a source of divalent cations with a solution to form the solution of divalent cations. In an embodiment, the treatment system includes a pyrometallurgy reactor, calciner, vitrification reactor, or sintering reactor. The treatment plant may further comprise a mixer configured to mix the treated material with processed bauxite to form a mixed material, the mixer being positioned upstream of the aggregator such that the mixed material can be passed to the aggregator.

[0025] Brief Description of the Drawings

[0026] Embodiments will now be described, by way of example only, with reference to the accompanying non-limiting drawings, in which:

[0027] Figure 1 illustrates a block diagram of an embodiment of a system for treating processed bauxite; Figure 2 illustrates a block diagram of another embodiment of a system for treating processed bauxite;

[0028] Figure 3 illustrates a block diagram of an embodiment of a treatment system with a neutralisation system;

[0029] Figure 4 illustrates a block diagram of an embodiment of a treatment system with a sodicity reduction system;

[0030] Figure 5 illustrates a block diagram of an embodiment of a treatment system with a thermal treatment system;

[0031] Figure 6 illustrates a block diagram of an embodiment of a treatment system with multiple processing subsystems; and

[0032] Figure 7 illustrates a block diagram of an embodiment of a treatment plant.

[0033] Detailed Description

[0034] The present disclosure provides methods and systems for the treatment of processed bauxite, a byproduct of the Bayer process used in alumina refineries. The processed bauxite, which may be treated or untreated, is subjected to chemical and / or thermal treatment to reduce its pH and / or sodicity, transforming it into a treated material.The term “processed bauxite” as used herein means fresh processed bauxite such as that formed directly from streams or unit operations in the Bayer Process such as a filter press or superthickener underflow following Bayer process digestion with or without additional Bayer reagents and chemical additions (such as lime, flocculants etc). Accordingly, the term “treated processed bauxite” includes processed bauxite that has been treated in some way for example to reduce a water content and / or metal value content of the residue. In this way, the step(s) used to form the “treated processed bauxite” may be considered as defining a pre-conditioning or pretreatment step prior to further processing in one or more embodiments of the disclosure.

[0035] The term “treated material” is the material formed from processing the treated or untreated processed bauxite and is chemically and / or physically altered compared to the treated or untreated processed bauxite.

[0036] This treated material is then subjected to a process to increase its aggregate size, resulting in an aggregated product that can be returned to a natural environment.

[0037] The term “aggregated product” as used herein refers to a product that can act as soil, a soil ameliorant, or a soil-type product. This includes soil fines, soil aggregates, rocks, gravel, and other particulate forms. The resulting aggregated product is designed to be returned to the environment, where it can contribute to soil health, land rehabilitation, nutrient retention, water retention, other ecological functions, or be present as a non-polluting component of the environment.

[0038] The term “natural environment” as used herein refers to any setting or location where the aggregated product can be returned or applied, mimicking or enhancing natural conditions. This includes agricultural fields, paddocks, mine pits, mine site, forests, landscaping areas, and other terrestrial ecosystems. The natural environment encompasses both managed and unmanaged lands where the aggregated product can contribute to soil health, land rehabilitation, nutrient retention, water retention, plant nutrition, crop yields, other ecological functions, or be present as a non-polluting component of the environment. The term is intended to be broad and inclusive, covering a variety of applications where the aggregated product can be beneficially or harmlessly integrated into the environment.

[0039] The processed bauxite presents environmental challenges due to its high alkalinity and volume. The disclosed methods and systems address these challenges by transforming the processed bauxite into a product that is compatible with environmental applications. This transformation involves a series of steps, which may include dealkalisation, neutralisation, sodicity removal,agglomeration, and the addition of organic matter and nutrients.

[0040] The chemical treatment may involve neutralisation using various agents, and the thermal treatment may involve processes such as pyrometallurgy, vitrification, calcination, or sintering. The treated material may also be mixed with processed bauxite to form a mixed treated material.

[0041] The aggregated product may have various properties depending on its intended use. For example, it may be used as a liming agent, a water retention agent, a nutrient retention agent, topsoil fill, or mining pit backfill. The properties of the aggregated product, such as pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), and particle size, can be adjusted to meet the requirements of these different applications.

[0042] The present disclosure may provide methods and systems for transforming processed bauxite into an environmentally compatible product, addressing the challenges associated with the longterm storage, and reuse, of processed bauxite.

[0043] Increasing the aggregate size of the treated material to form an aggregated product can help to enhance its physical properties, such as stability and strength, to facilitate its use in various environmental applications like agriculture, landscaping, land rehabilitation, and mine backfill. The aggregation process also facilitates easier and safer handling, transportation, and application of the treated material.

[0044] The term “increasing an aggregate size” is to be interpreted broadly to include any device, system and / or process that can be used to increase the aggregate size of the treated material. For example, increasing the aggregate size may include applying a liquid to the treated material, such as for dust suppression, and / or subjecting the treated material to an agglomerator system or similar to physically and / or chemically and / or thermally bind particles of the treated material together. Increasing the aggregate size may only apply to a portion of the treated material. For example, spraying to minimise dust generation may only cause a surface layer of the treated material to have an increase in aggregate size thereby forming a veneer of aggregated product. The aggregated product formed from increasing an aggregate size may be discrete aggregate products and / or form a solid material formed from aggregated treated material, such as a ‘cap’ or ‘veneer’ formed for dust suppression.

[0045] The term “agglomerator system” is to be interpreted broadly to include any device or process that imparts contacting and mixing forces to allow ingredients or components to form an agglomerated product. For example, the aggregator system may include an agglomerator such as a disc or drum agglomerator, pelletiser, pin mixer, briquette former and / or roll press. The agglomeratorsystem may also include two or more stages and / or devices arranged in series to form the agglomerated product.

[0046] The combination of chemical and / or thermal treatment followed by aggregation may provide a comprehensive solution to transform processed bauxite into a product that can be safely returned to the natural environment. This process may not only mitigate the environmental challenges posed by processed bauxite residue but may also create a value-added product that can contribute to soil health, nutrient retention, and water retention in various ecosystems.

[0047] The present disclosure also provides a treatment plant comprising a treatment system and an aggregator system. The treatment system is configured to subject the processed bauxite to chemical and / or thermal treatment, and the aggregator system is configured to increase the aggregate size of the treated material.

[0048] A treatment plant 100 is depicted in Figure 7. The treatment plant 100 includes a Bayer plant 101. The Bayer plant 101 has a bauxite source 110, which provides the raw bauxite material. This raw bauxite is fed into a digestor 112, where it is digested to produce processed bauxite and pregnant liquor. The pregnant liquor is then processed in a precipitator 114 to precipitate alumina hydrate. The alumina hydrate is then processed in a calciner 116 to form alumina.

[0049] The treatment plant 100 also includes a system 10 for treating processed bauxite 12. The system 10 comprises a treatment system 14, which subjects the processed bauxite 12 to chemical and / or thermal treatment to reduce pH and / or sod icity, transforming it into a treated material. This treated material is then directed to an aggregator system 26, which increases the aggregate size of the treated material to form an aggregated product that can be returned to a natural environment. The system 10 is described in more detail with reference to Figure 1 to Figure 6.

[0050] Referring now to Figure 1 , the system 10 is illustrated in further detail for treating processed bauxite. The system 10 forms part of a treatment plant. The system 10 includes a processed bauxite input 12 that feeds into a treatment system 14. The treatment system 14 is configured to subject the processed bauxite 12, which may be treated or untreated, to chemical and / or thermal treatment. This treatment reduces the pH, EC and / or sodicity of the processed bauxite 12, transforming it into a treated material 15. Although not shown in the Figures, the treatment system 14 can include tanks, vessels and / or inline mixer and / or various mixing stages and filters.

[0051] In some embodiments, the chemical treatment may involve neutralisation processes, while in other cases, the thermal treatment may involve processes such as pyrometallurgy, vitrification, calcination, or sintering. The specific treatment or combination of treatments applied to theprocessed bauxite 12 may depend on the specific properties of the processed bauxite and the desired properties of the treated material 15.

[0052] System 10 also has a binder system 16 that is configured to provide a binder mixture for use in the aggregation process. The binder system 16 includes a binder water input 18 and a binding agent source 20. These inputs feed into a binder mixer 22, which combines the water and binding agent to form the binder mixture.

[0053] The binder mixture may include various binding agents, such as lignosulfonate species, starch, guar, an organic polymer, and / or an organic species. In some embodiments, the organic polymer may be polyacrylamide (PAM) or polyvinyl alcohol (PVA). The organic species may include agricultural or urban organic byproducts, such as crop residues, sewage sludge, manure, or food organics and green organics (FOGO). Manure may be suitable for agricultural product applications due to its higher nutrient content compared to other organic sources. These organic byproducts may be composted before being added to the binder mixture, to adjust the carbon, nitrogen, phosphorus, and potassium (CNPK) ratios.

[0054] The specific composition of the binder mixture may be adjusted based on the properties of the treated material 15 and the desired properties of the aggregated product. For example, the binder may be added at a concentration of up to 5 wt.% of the treated material. The binder may be added at a concentration up to 4wt.%. The binder may be added at a concentration up to 3wt.%. The binder may be added at a concentration up to 2wt.%. The binder may be added at a concentration up to 1wt.%.

[0055] In some cases, the binder mixture may be added as a solution to the treated material 15. This may involve dissolving the binding agents in water or another suitable solvent before adding them to the treated material 15. The use of a solution can facilitate the even distribution of the binding agents throughout the treated material 15, promoting uniform aggregation.

[0056] The output from the binder mixer 22 is connected to a pump 24. The pump 24 transfers the binder mixture from the binder mixer 22 to an aggregator system 26. In this way, binding mixer 22 is in fluid communication with the aggregator system 26. The aggregator system 26 is configured to increase the aggregate size of the treated material 15. This may be achieved by mixing the treated material 15 with the binder mixture in the aggregator system 26.

[0057] Although the Figures show and refer to the pump 24 as the means for moving the binding mixture 22, this is not required in all embodiments of the binder system 16. For example, in one or more embodiments, processed bauxite 12 is mixed with solid organics, in which case a conveyor maybe used to move the solid organics to the aggregator system 26. In such embodiments, the solid organics may be transported directly to the aggregator system 26 or may alternatively be mixed with water input 18 in the binder mixer 22 before being transported to the aggregator system 26. The solid organics may act as a binding agent.

[0058] In some embodiments, the aggregator system 26 may include a sintering process for agglomeration. Sintering involves heating the treated material 15 and binder mixture to a temperature below their melting point, causing the particles to bond together and form larger aggregates. This process can be used to create aggregates of various sizes, depending on the specific requirements of the aggregated product.

[0059] In other cases, the aggregator system 26 may include a pelletisation process for agglomeration. Pelletisation involves forming the treated material 15 and binder mixture into small, rounded pellets. This process can be used to create aggregates with a uniform size and shape, which may be desirable for certain applications.

[0060] In yet other cases, the aggregator system 26 may include a granulation process for agglomeration. Granulation involves forming the treated material 15 and binder mixture into irregularly shaped granules. This process can be used to create aggregates with a wide range of sizes, which may be desirable for other applications.

[0061] The aggregator system 26 may also form the aggregate product by briquetting.

[0062] A combination of binding, agglomeration, pelletising and / or briquetting may be in the aggregator system 26 to form the aggregated product. Therefore, the aggregator system 26 includes an agglomerator, pelletiser, briquette former and / or roll press. The agglomerator may include a pin mixer, disc agglomerator and / or drum agglomerator. In embodiments where the agglomerator includes multiple devices, the devices may be arranged in series. For example, material may be processed first in a pin mixer than in a disc pelletiser.

[0063] The aggregation system 26 may also include sprayers or similar that can spray a solution on the treated material 15 to cause agglomeration. For example, sprayers may spray the treated material 15 with a veneer of dust-suppression solution that causes fines to aggregate together.

[0064] Afterthe aggregation process, the treated material 15 is transformed into an aggregated product. The aggregated product may have an aggregate size of about 1 mm to about 50 cm, depending on the specific aggregation technique used and the desired properties of the product. The aggregate size may have a value of between about 5 mm and about 40 cm. The aggregate sizemay have a value of between about 10 mm and about 30 cm. The aggregate size may have a value of between about 1 mm and about 50 mm. The aggregate size may have a value of between about 5 mm and about 25 mm. The aggregate size may have a value of between about 10 mm and about 20 mm. The aggregate size may have a value of at least about 1 mm. The aggregate size may have a value of at least about 5 mm. The aggregate size may have a value of at least about 10 mm. The aggregate size may have a value of at least about 20 mm. The aggregate size may have a value of at most about 50 cm. The aggregate size may have a value of at most about 30 cm. The aggregate size may have a value of at most about 10 cm. The aggregate size may have a value of at most about 50 mm. In some embodiments, the aggregated product may be further processed, such as by drying, to achieve the desired properties. For example, drying may help to set the binder to form a more stable aggregate product.

[0065] The system 10 thus provides a flexible and adaptable process for transforming processed bauxite (treated or untreated) into an environmentally compatible product. The specific treatment and aggregation processes used may be adjusted based on the properties of the processed bauxite and the desired properties of the aggregated product.

[0066] Referring to Figure 2, a variation of the treatment system, designated as system 10a, is illustrated. In this embodiment, the system 10a includes an additional input of untreated processed bauxite 28. This untreated processed bauxite 28 is fed directly into a mixer 30, which is configured to combine the untreated processed bauxite 28 with the treated material 15 to form a mixed treated material. This mixing process occurs prior to the step of increasing the aggregate size of the treated material 15. The mixer 30 is positioned upstream of the aggregator system 26, allowing the mixed treated material to be passed directly to the aggregator system 26 for further processing.

[0067] The mixed treated material may comprise from about 30wt.% to about 70wt.% processed bauxite. The specific proportion of processed bauxite in the mixed treated material may be adjusted based on the desired properties of the aggregated product. For example, a higher proportion of processed bauxite may be used to increase the alkalinity of the aggregated product, while a lower proportion may be used to decrease the alkalinity.

[0068] In some cases, mixing the treated material 15 with processed bauxite 28 can help to control the chemical and / or physical properties of the aggregated material. For example, the untreated processed bauxite 28 may contribute additional alkalinity-generating minerals to the mixed treated material, which can be beneficial for certain applications.

[0069] Prior to chemical and / or thermal treatment in the treatment system 14, processed bauxite 12and / or optionally the untreated processed bauxite 28 may have a pH of less than 11 and an EC of less than 3 mS / cm in a 1 :5 suspension in water. These initial properties of the processed bauxite 12 may be adjusted through the chemical and / or thermal treatment processes to achieve the desired properties. Alternatively, or in addition to, the processed bauxite 12 and / or optionally the untreated processed bauxite 28 may be subject to washing, for example to reduce the EC prior to treatment in the treatment system 14.

[0070] The different types of treatments performed in the treatment system will now be described.

[0071] Dealkalisation

[0072] In some embodiments, the treatment system 14 may include a dealkalisation step prior to neutralisation and / or sodicity reduction. Dealkalisation involves the removal of alkalinitygenerating minerals from the processed bauxite via physical separation, avoidance of precipitation, or alteration of precipitate mineralogy. Alkalinity-generating minerals may include tricalcium aluminate, desilication product (DSP), and calcite. Dealkalisation may be performed using various techniques. In some cases, dealkalisation may involve dissolution of desilication product (DSP) with an acid such as sulfuric acid. In other cases, dealkalisation may involve direct electrolytic removal of silicon from liquor. In yet other cases, dealkalisation may involve atmospheric digestion to alter the mineralogy of precipitates formed during processing. Dealkalisation performed prior to neutralisation may reduce or eliminate the need for acid neutralisation in the neutralisation system 40. In this way, dealkalisation may provide a more efficient pathway for reducing the pH and alkalinity of the processed bauxite 12, particularly for processed bauxite with high concentrations of alkalinity-generating minerals. The specific dealkalisation technique used may depend on the properties of the processed bauxite 12 and the desired properties of the treated material 15.

[0073] Neutralisation

[0074] Referring to Figure 3, the treatment system 14 can include a neutralisation system 40. The neutralisation system 40 is configured to receive the processed bauxite 12 and subject it to a neutralisation process that includes contacting the processed bauxite 12 with a neutralising agent 32, typically within a mixing vessel 34. The neutralising agent 32 may include an inorganic acid, such as sulfuric acid (H2SO4), phosphoric acid (H3PO4), nitric acid (HNO3), or hydrochloric acid (HCI). In some cases, the neutralising agent 32 may be derived from contacting the processed bauxite 12 with elemental sulphur to form sulfuric acid in situ. Alternatively, the neutralising agent 32 may include an organic acid, such as acetic acid, oxalic acid, citric acid, or lactic acid. The neutralising agent may also include a species capable of reacting with the processed bauxite 12 to reduce an alkalinity of the processed bauxite 12 thereby forming treated material 15. As an example, gypsum may also be used as a neutralising agent by providing a calcium source toallow for precipitation of calcite thereby reducing an alkalinity of the processed bauxite 12.

[0075] The concentration of the acid in the neutralising agent 32 may range from about 0.1 M to 1 ,0M. In some cases, the concentration may be within the range of 0.2M to 0.5M. The specific concentration used may depend on the properties of the processed bauxite 12 and the desired properties of the treated material 15.

[0076] The neutralisation process reduces the pH of the processed bauxite 12, transforming it into the treated material 15. The treated material 15 may have a pH within the range of 5 to 9. In some cases, the pH may be within the range of 5 to 8. The specific pH range may be selected based on the desired properties of the treated material 15 and the intended use of the aggregated product.

[0077] In some embodiments, the neutralisation system 40 may use carbon dioxide (CO2) as a neutralising agent in place of an acid. In such embodiments, CO2may be bubbled through a solution in the mixing vessel 34.

[0078] In some embodiments, the neutralisation system 40 may use washing station(s) or washing stage(s) to wash processed bauxite 12 to flush out alkalinity and / or salinity to reduce pH and / or EC. For example, filter presses may be used to remove excess spent treatment solution, then flush or wash with fresh water or flushing solution on the presses to displace residual solution.

[0079] Following treatment in the neutralisation system 40, the treated material 15 can then be further processed, such as to reduce sodicity. This is why the end of the arrow representing the treated material 15 has a terminus within the boundary of the box defining the neutralisation system 40.

[0080] The neutralisation system 40 may be configured in various ways to process the processed bauxite 12. In some embodiments, the neutralisation system 40 may use a continuous stirred tank reactor for the neutralisation process. The continuous stirred tank reactor / s provides a constant mixing of the processed bauxite 12 and the neutralising agent 32, ensuring a uniform distribution of reactants throughout the mixture to facilitate the reaction. This configuration may be beneficial for large-scale operations where a continuous flow of processed bauxite 12 needs to be treated.

[0081] In other cases, the neutralisation system 40 may use a batch treatment stirred pressure vessel for the neutralisation process. In this configuration, a batch of processed bauxite 12 is loaded into the pressure vessel and mixed with the neutralising agent 32 under pressure. This method may be advantageous for treating batches of processed bauxite 12 with varying properties, as the pressure and mixing conditions can be adjusted for each batch to achieve optimal neutralisation.In yet other cases, the neutralisation system 40 may use a displacement wash of processed bauxite cake on a pressure filterforthe neutralisation process. In this configuration, the processed bauxite 12 is formed into a cake on a pressure filter, and the neutralising agent 32 is passed through the cake, displacing the alkaline components and reducing the pH of the processed bauxite 12. This method may be advantageous for treating processed bauxite 12 with high solid content, as it allows for efficient neutralisation without the need for extensive mixing or dilution.

[0082] Although not shown in Figure 3, the treated material 15 may pass through a dewatering system and / or dryer downstream of the mixing vessel and prior to introduction into the aggregator system 26. Dewatering the treated material 15 below a threshold value may help to assist aggregation in the aggregation system.

[0083] These configurations of the neutralisation system 40 provide flexibility in the treatment of processed bauxite 12, allowing for the selection of the most suitable treatment condition and / or method based on the specific properties of the processed bauxite 12 and the desired properties of the treated material 15.

[0084] Sodicity reduction

[0085] Referring to Figure 4, the treatment system 14 can include a sodicity reduction system 60. The sodicity reduction system 60 is configured to receive the processed bauxite 12 and subject it to a sodicity reduction process in mixing vessel 62 which includes contacting the processed bauxite 12 with a divalent source 64. The divalent source 64 can include a treatment solution that contains divalent cations. The treatment solution may include solubilised divalent cations or a suspension of species capable of dissolution to form solubilised divalent cations. For example, a solution of gypsum may include undissolved gypsum and calcium and sulfate ions. The divalent cations in the treatment solution displace sodium cations in the processed bauxite 12 to reduce the sodicity of the processed bauxite 12. The result of this process is a treated material 15 with reduced sodicity.

[0086] The treatment solution containing the divalent cations may be prepared in a divalent cation mixer (not shown in Figure 4), which is configured to receive and mix a source of divalent cations with a solution to form the divalent source 64. The divalent source 64 may include magnesium ions and calcium ions. In some cases, the magnesium ions may be derived from a magnesium sulphate, such as gypsum, while the calcium ions may be derived from gypsum or calcium chloride. The anions of the divalent source may include sulfate, chloride, nitrate, hydroxides, and carbonates salts. The divalent source may also include metal oxides. In an embodiment, apreference order for anions may be SO4=CI=NO3>OH>CO3=O based on solubility, water treatment including removal of anions from wash waters, and effect on pH. In an embodiment, soda reduction (and optionally or alternatively neutralisation) may also include dissolving calcium-containing sources in the processed bauxite to displace sodium ions. In some embodiments, monovalent cations such as potassium ions (K+) or ammonium ions (NH4+) may also be used to displace sodium cations in the processed bauxite 12. Potassium and ammonium ions may provide additional benefits such as nutrient value when the aggregated product is intended for agricultural applications.

[0087] The sodicity reduction process takes place within a mixing vessel 62. The mixing vessel 62 provides a controlled environment for the sodicity reduction process, ensuring that the processed bauxite 12 and the treatment solution are thoroughly mixed. This allows for efficient displacement of the sodium cations in the processed bauxite 12 by the divalent cations in the treatment solution. The mixing vessel is depicted generally and may include pumps, stirrers and associated filters and wash systems.

[0088] After the sodicity reduction process in mixing vessel 62, displaced sodium ions may be removed by washing the treated material 15 with a washing solution. This washing process may be performed in the sodicity reduction system 60, such as when the treated material 15 exits the mixing vessel, or in a separate washing system (not shown in Figure 4).

[0089] Following the sodicity reduction and washing processes, the treated material 15, after undergoing the sodicity reduction process in the mixing vessel 62, may still contain some residual moisture. To further reduce the moisture content of the treated material 15, the sodicity reduction system 60 may include a dewatering system 66. The dewatering system 66 is configured to separate the treated material 15 from the waste solution, which may contain displaced sodium ions and other byproducts of the sodicity reduction process. The dewatering system 66 may use various techniques, such as filtration or centrifugation, air or steam blowing or purging to further separate the solid treated material 15 from the liquid waste solution to displace free moisture. In some embodiments, an additive that can act as a dewatering aid may be used during displacement washing. In some cases, the dewatering system 66 may be positioned upstream of the aggregator system 26, allowing the dewatered treated material 15 to be passed directly to the aggregator system 26 for further processing.

[0090] After dewatering, the treated material 15 may still contain some residual moisture. To further reduce the moisture content of the treated material 15, the sodicity reduction system 60 may include a dryer 68. The dryer 68 is configured to receive the dewatered treated material 15 from the dewatering system 66 and to at least partially dry the treated material 15. The dryer 68 mayuse various drying techniques, such as convective drying, conductive drying, or radiant drying, to reduce the moisture content of the treated material 15. The specific drying technique used may depend on the properties of the treated material 15 and the desired properties of the aggregated product.

[0091] In some embodiments, the dryer 68 may be configured to reduce the water content of the treated material 15 to less than 25 wt.%. In other cases, the dryer 68 may be configured to reduce the water content of the treated material 15 to a range of 10-20 wt.%. Dewatering the treated material 15 below a threshold value may help to assist aggregation in the aggregation system, improving aggregation efficiency and the quality of the aggregated product.

[0092] In some embodiments, the sodicity reduction system 60 may be configured to operate as a continuous stirred tank reactor / s or a batch treatment stirred vessel. These configurations provide flexibility in the treatment of the processed bauxite 12, allowing for the selection of the most suitable method based on the specific properties of the processed bauxite 12 and the desired properties of the treated material 15.

[0093] Thermal treatment

[0094] Referring to Figure 5, the treatment system 14 may include a thermal treatment system 80. The thermal treatment system 80 is configured to receive the processed bauxite 12 and subject it to a thermal treatment process which includes heating the processed bauxite 12 in a thermal reactor 82.

[0095] The thermal treatment process may involve various techniques, such as pyrometallurgy, vitrification, calcination, or sintering. Pyrometallurgy involves the use of high temperatures to bring about chemical and physical transformations in the processed bauxite 12. This may include the reduction, roasting, or smelting of the processed bauxite 12 to change its mineralogical makeup and reduce its sodicity. For example, thermal treatment may mineralise soda, volatilise at least some of the soda and / or make the soda less soluble in the treated material 15 compared to the unprocessed or processed processed bauxite 12.

[0096] Vitrification involves the transformation of the processed bauxite 12 into a glass or glass-like substance through the application of heat. Without being bound by theory, it is thought that vitrification encapsulates or binds the soda at least to some degree within the glass matrix, making it less soluble and reducing its availability for later dissolution.

[0097] Calcination involves the heating of the processed bauxite 12 to bring about thermal decomposition, phase transition and / or the removal of volatile substances. This process canconvert the soda in the processed bauxite 12 into other minerals, reducing its solubility and sodicity.

[0098] Sintering involves the heating of the processed bauxite 12 until its particles adhere to each other. This process can change the physical properties of the processed bauxite 12, such as its porosity and aggregate size. Similar to calcination, sintering may also result in thermal decomposition, phase transition and / or the removal of volatile substances to reduce a solubility of soda in the processed bauxite 12.

[0099] The specific thermal treatment technique used may depend on the properties of the processed bauxite 12 and the desired properties of the treated material 15. For example, pyrometallurgy or calcination may be preferred for processed bauxite 12 with high metal content, while vitrification or sintering may be preferred for processed bauxite 12 with high silica content. Thermal treatment may help to encapsulate or bind the soda at least to some degree within the treated processed bauxite, making it less soluble and reducing its availability for dissolution.

[0100] Following treatment in the thermal treatment system 80, the treated material 15 can then be further processed, such as to reduce sodicity and / or neutralise the treated material 15. This is why the end of the arrow representing the treated material 15 has a terminus within the boundary of the box defining the treatment system 14. When thermal treatment, particularly sintering, is used for aggregation, organic matterand nutrients may be added after the thermal treatment step to avoid loss of organic matter through combustion. In such embodiments, the organic matterand nutrient addition step may be performed downstream of the thermal treatment system 80 and may be integrated with the aggregator system 26 or performed as a separate step prior to or after aggregation.

[0101] After the thermal treatment process, the treated material 15 may have a pH of less than 11 , an electrical conductivity (EC) of less than 4 mS / cm, and an exchangeable sodium percentage (ESP) of less than 70%. In an embodiment, the treated material 15 has a pH<10.5, EC<1 mS / cm and ESP~60% following thermal treatment. Generally, processed bauxite that has been subject to thermal treatment has a lower sodicity and lower alkalinity compared to untreated processed bauxite.

[0102] In some embodiments, the thermal treatment system 80 may be configured to operate as a continuous process, with a continuous flow of processed bauxite 12 entering the thermal reactor 82 and a continuous flow of treated material 15 exiting the thermal reactor 82. In other cases, the thermal treatment system 80 may be configured to operate as a batch process, with batches of processed bauxite 12 being loaded into the thermal reactor 82, treated, and then unloaded asbatches of treated material 15. The specific configuration may depend on the properties of the processed bauxite 12, the desired properties of the treated material 15, and the operational requirements of the Bayer plant.

[0103] Combined treatments

[0104] Referring to Figure 6, the treatment system 14 is shown to include a neutralisation system 40, a sodicity reduction system 60, and a thermal treatment system 80. These systems can be used in various combinations to process the processed bauxite 12 and produce the treated material 15 with reduced pH and sodicity. The specific treatment or combination of treatments applied to the processed bauxite 12 may depend on the specific properties of the processed bauxite and the desired properties of the treated material 15.

[0105] The treatment system 14 is flexible and adaptable, allowing for various combinations of the neutralisation system 40, sodicity reduction system 60, and thermal treatment system 80 to be used based on the properties of the processed bauxite 12 and the desired properties of the treated material 15. For example, the processed bauxite 12 may be subjected to neutralisation in the neutralisation system 40, followed by sodicity reduction in the sodicity reduction system 60, and then thermal treatment in the thermal treatment system 80. Alternatively, the processed bauxite 12 may be subjected to thermal treatment first, which may help to neutralize the processed bauxite 12 and reduce or eliminate the need for neutralisation in the neutralisation system 40. The different treatment options are outlined in Table 1.

[0106] Table 1. Treatment options in treatment system 14

[0107]

[0108] N = Neutralisation; SR = Sodicity reduction; TT = Thermal treatment

[0109] It should be appreciated that the order shown in Table 1 is exemplary only and that the properties of the processed bauxite and treatment conditions may remove the need for specific treatment options. For example, thermal treatment may reduce a pH and / or sodicity to eliminate the need for neutralisation and / or sodicity reduction, while in some cases sodicity reduction may negate the need for a specific neutralisation step.Properties of treated material

[0110] The specific chemical and physical properties of the treated material 15 depend upon the processes and conditions used in the treatment system 14. For example, following chemical treatment, the treated material 15 may have a pH less than 11. The pH may be 5<pH<9, such as 5<pH<8. This pH range may be selected based on the desired properties of the treated material 15 and the intended use of the aggregated product. If a lower pH is required, the processed bauxite 12 may be subject to neutralisation in neutralisation system 40.

[0111] Following treatment in the treatment system 14, the treated material 15 may have an electrical conductivity (EC) of less than 4 mS / cm, and an exchangeable sodium percentage (ESP) of less than 70%. These properties may be desirable for certain applications, such as when the aggregated product is intended to be used in environments with specific pH, EC, and ESP requirements.

[0112] In some embodiments, the treated material 15 may be dried to further reduce its moisture content. For example, this drying process may be performed in dryer 68, but may also be performed in a dryer that is separate from the neutralisation system 40, sodicity reduction system 60 and / or the thermal treatment system 80 (not shown in the Figures). Drying the treated material 15 may reduce the water content of the treated material 15 to less than 25 wt.%. In some cases, the water content of the treated material 15 after drying may be within the range of 10-20 wt.%. The specific water content of the treated material 15 after drying may depend on the desired properties of the aggregated product. For example, a lower water content may be desirable for aggregated products intended for use in dry environments, while a higher water content may be desirable for aggregated products intended for use in moist environments. Water content may also be adjusted to control physical and / or mechanical properties of the treated material 15. Drying of the treated material 15 may not be required if its water content is below a threshold value required for aggregating in the aggregator system 26 and / or if the aggregator system 26 includes a drying step to form the aggregated product.

[0113] Aggregate products

[0114] The aggregated product resulting from the treatment and aggregation processes described above may have various properties and applications, depending on the specific treatment and aggregation techniques used. The properties of the treated material 15 are carried across to the aggregated product. In this way, the binder and the aggregation process used in the aggregator system 26 has little effect on the chemical properties (EC, pH, etc.) of the aggregate product. For example, in general terms, the magnitude of the changes to chemical properties from the treatment processes would be much larger than any minor variations introduced by the binding agent. However, in some circumstances, aggregating fines into larger aggregates may slow therelease of any remaining alkalinity or salt in the processed bauxite, so agglomeration may make the processed bauxite appear less alkaline and saline. This effect will generally become enhanced as the aggregates become larger, and where a higher stability option is used. The use of cementitious binders may increase pH in the processed bauxite.

[0115] In the embodiments described herein, the aggregated product may have a particle size of 1 mm or larger, an electrical conductivity (EC) of less than 10 mS / cm, and an exchangeable sodium percentage (ESP) of less than 70%. The specific properties and applications of the aggregated product may be adjusted based on the treatment and aggregation processes used.

[0116] In some embodiments, the aggregated product may comprise aggregated processed bauxite having a pH of less than or equal to 11 , an electrical conductivity (EC) of less than 10 mS / cm, an exchangeable sodium percentage (ESP) of less than 70%, and a particle size of 1 mm or larger. The processed bauxite may be subjected to neutralisation in the neutralisation system 40 to reduce a pH and / or EC before aggregation.

[0117] In some cases, the aggregated processed bauxite may have a pH ranging from 5.0 to 7.5. This pH range may be desirable for certain applications, such as when the aggregated product is intended to be used as topsoil fill. For this application, the aggregated product may have a size ranging from about 1 mm to about 10 mm. The aggregated product may further comprise up to 5wt.% organic matter, which can improve its suitability for use in agricultural or land rehabilitation applications.

[0118] In other cases, the aggregated processed bauxite may have a pH ranging from 5.5 to 8.5. This pH range may be desirable for other applications, such as when the aggregated product is intended to be used as landscaping gravel, rock for pit backfill, or for iron fertiliser applications. For these applications, the aggregated product may have a size ranging from 10 mm to 50 mm for landscaping gravel, and from 10 cm to 50 cm for rock for pit backfill. For iron fertiliser applications, a concentration of soluble iron is generally around 5-10w / v%.

[0119] In yet other cases, the aggregated processed bauxite may have a pH ranging from 8.0 to 10.5. This pH range may be desirable for applications where the aggregated product is intended to be used as a liming agent. The term “liming agent” as used herein is generally understood to mean any number of a class of agents that increase pH of acidic soils, including agricultural lime, minerals processing byproducts, elemental sulfur, soil acidity corrective and so on. The term “liming agent” may also be referred to as a "soil acidity corrector" or "soil acidity modifier".

[0120] The aggregated product may have a size ranging from about 1 mm to about 20 mm when usedto form a liming agent.

[0121] The aggregated product may be applied to a natural environment in various ways, depending on its specific properties and the requirements of the environment. For example, the aggregated product may be spread over the surface of a field or garden to improve the soil quality, or it may be used to fill in a mine pit or other excavation. In some cases, the aggregated product may be mixed with other materials, such as compost or topsoil, before being applied to the natural environment.

[0122] In some embodiments, the aggregated product may be returned to a natural environment, such as a paddock, mine pit, forest, and so on. The specific environment to which the aggregated product is returned may depend on the properties of the aggregated product and the requirements of the environment. For example, an aggregated product with a high nutrient content may be particularly suitable for use in agricultural applications, while an aggregated product with a high aggregate stability and strength may be suitable for use in mine backfill applications.

[0123] The aggregated product resulting from the treatment and aggregation processes may have various properties and applications, as summarised in Table 2.

[0124] Table 2. Overview of aggregate product properties and applications

[0125]

[0126] In the claims that follow and in the preceding description, 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 disclosure.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.

[0127] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present disclosure.

[0128] Examples

[0129] Embodiments will now be described with reference to the following non-limiting examples.

[0130] Example 1 - aggregate for topsoil fill

[0131] Processed bauxite with an initial pH of 10.5 and an EC of 2.8 mS / cm in a 1 :5 suspension in water is subjected to a neutralisation treatment. The processed bauxite is mixed with a 0.3M sulfuric acid solution in a continuous stirred tank reactor for 30 minutes and is then subject to solid / liquid separation to isolate treated material. After neutralisation, the treated material has a pH of 7.2 and an EC of 3.5 mS / cm.

[0132] The treated material may then be subjected to a sodicity reduction treatment. A solution containing 0.1M magnesium sulfate and / or 0.1 M calcium chloride is added to the treated material in a batch treatment stirred vessel. After 1 hour of mixing, the material is washed with deionized water to remove displaced sodium ions. The resulting treated material has an ESP of 45%.

[0133] Following the chemical treatments, the treated material is dried to a water content of 18 wt.% using for example a rotary dryer. The dried treated material is then mixed with 2 wt.% of a lignosulfonate binder solution and fed into a disc agglomerator to form an aggregated product having a particle size range of 2-8 mm.

[0134] Example 2 - aggregate for landscaping gravel

[0135] Processed bauxite with an initial pH of 10.8 and an EC of 3.2 mS / cm in a 1 :5 suspension in water is subjected to a thermal treatment by feeding into a rotary kiln and heated to 800°C for 30 minutes. After thermal treatment, the treated material has a pH of 9.5 and an EC of 2.5 mS / cm.

[0136] The thermally treated material is then mixed with untreated processed bauxite in a ratio of 60:40 (treated: untreated) to form a mixed treated material. This mixed material is combined with 3 wt.% of a starch-based binder solution or cementitious binder and fed into a pelletizer to form an aggregated product having a particle size range of 15-40 mm. Alternatively, a sintering step may be used in place of a binder to form the aggregate product.Example 3 - aggregate rock for pit backfill

[0137] Processed bauxite with an initial pH of 11.2 and an EC of 3.5 mS / cm in a 1 :5 suspension in water is subjected to a combined chemical and thermal treatment. The processed bauxite is neutralized using a 0.4M phosphoric acid solution in a batch treatment stirred pressure vessel for 45 minutes, and then thermally treated in a sintering furnace at 1000°C for 1 hour. Optionally, the processed bauxite is subject to solid / liquid separation to isolate treated material following treatment with phosphoric acid and before sintering.

[0138] After the combined treatments, the treated material has a pH of 8.8 and an EC of 1.8 mS / cm. The treated material is then mixed with 4 wt.% of a polyacrylamide binder solution and fed into a briquette former to form an aggregated product may having a particle size range of 30-45 cm. Alternatively, a sintering step may be used in place of a binder to form the aggregate product.

[0139] Example 4 - liming agent for use in agricultural applications

[0140] Processed bauxite with an initial pH of 10.3 and an EC of 2.9 mS / cm in a 1 :5 suspension in water is subjected to a sodicity reduction treatment followed by a mild thermal treatment. The processed bauxite is mixed with a solution containing 0.15M magnesium sulfate and 0.15M calcium chloride in a continuous stirred tank reactor for 2 hours. After washing and dewatering, the material is thermally treated in a calciner at 600°C for 45 minutes.

[0141] The treated material has a pH of 9.8, an EC of 2.2 mS / cm, and an ESP of 35%. This material is then mixed with 1.5 wt.% of a guar-based binder solution and fed into a granulator to form a product may have a particle size range of 1-15 mm.

Claims

Claims1 . A process of treating treated or untreated processed bauxite to form an aggregated product that can be returned to a natural environment, the process comprising:subjecting treated or untreated processed bauxite to chemical and / or thermal treatment to reduce pH and / or sodicity to form a treated material; andincreasing an aggregate size of the treated material to form the aggregated product.

2. A process of claim 1 , wherein chemical treatment includes neutralisation.

3. A process of claim 2, wherein the treated material has 5<pH<9, such as 5<pH<8.

4. A process of claim 2 or 3, wherein neutralisation includes contacting the treated or untreated processed bauxite with a neutralising agent that includes an inorganic acid including H2SO4, H3PO4, HNO3, HCI, an acid derived from contacting the treated or untreated processed bauxite with elemental sulphur, an organic acid including acetic, oxalic, citric, and / or lactic acid, and / or a species capable of reacting with the processed bauxite to reduce an alkalinity of the processed bauxite.

5. A process of claim 4, wherein a concentration of the acid ranges from about 0.1 M to 1.0M, including 0.2M to 0.5M.

6. A process of any one of claims 1 to 5, wherein chemical treatment includes contacting the treated or untreated processed bauxite with a treatment solution that contains divalent cations to reduce a sodicity of the treated or untreated processed bauxite by displacing sodium cations in the treated or untreated processed bauxite with the divalent cations in the treatment solution.

7. A process of claim 6, wherein the divalent cations include magnesium ions and calcium ions.

8. A process of claim 7, wherein the magnesium ions are derived from a magnesium sulphate.

9. A process of claim 7, wherein the calcium ions are derived from gypsum, calcium chloride and / or products formed from subjecting calcite or tri-calcium aluminate to acid.

10. A process of any one of claims 6 to 9, further comprising washing displaced sodium ions with a washing solution.

11. A process of any one of claims 1 to 10, wherein thermal treatment includes pyrometallurgy, vitrification, calcination or sintering to mineralise soda or make the soda less soluble in the treated material compared to the treated or untreated processed bauxite.

12. A process of any one of claims 1 to 11 , wherein the treated material formed by thermal treatment has a pH<11, EC<4mS / cm and exchangeable sodium percentage <70%, such as pH<10.5, EC<1 mS / cm and ESP~60%.

13. A process of any one of claims 1 to 12, further comprising mixing the treated or untreated processed bauxite with the treated material to form a mixed treated material.

14. A process of claim 13, wherein the mixed treated material is formed prior to increasing the aggregate size.

15. A process of claim 13 or 14, wherein the mixed treated material comprises from about 30wt.% to about 70wt.% untreated processed bauxite.

16. A process of any one of claims 1 to 15, wherein prior to chemical and / or thermal treatment the treated or untreated processed bauxite has pH<11 and EC<3mS / cm in a 1:5 suspension in water.

17. A process of any one of claims 1 to 16, further comprising drying the treated material to form a dried treated material prior to increasing the aggregate size.

18. A process of claim 17, wherein the dried treated material has a water content of <25wt.%.

19. A process of any one of claims 1 to 18, wherein increasing an aggregate size of the treated material includes mixing the treated material with a binder to bind treated material together.

20. A process of claim 19, wherein mixing the treated material with a binder includes adding water to the treated material to control a water content of the treated material.

21. A process of claim 19 or 20, wherein the binder includes a lignosulfonate species, starch,guar, an organic polymer and / or an organic species.

22. A process of any one of claims 19 to 21 , wherein the binder is added as a solution and / or a solid.

23. A process of any one of claims 19 to 22, wherein the binder is added up to 5wt.% of the treated material.

24. A process of any one of claims 1 to 23, further comprising drying the treated material after aggregation to form the aggregated product.

25. A process of any one of claims 1 to 24, wherein aggregating includes agglomeration, pelletising and / or briquetting.

26. A process of any one of claims 1 to 25, wherein the aggregated product has an aggregate size ranging from about 1 mm to about 50 cm, including from about 1 mm to about 50 mm.

27. A process of any one of claims 1 to 26, wherein the aggregated product is one of a liming agent, a water retention agent and / or nutrient retention agent, topsoil fill, and mining pit backfill.

28. An aggregated product that can be returned to a natural environment formed from the process of any one of claims 1 to 27.

29. An aggregated product that can be returned to a natural environment, the aggregated product comprising:aggregated processed bauxite having a pH<11, EC<10mS / cm, an exchangeable sodium percentage (ESP) <70%, and a particle size >1 mm.

30. An aggregated product of claim 29, wherein the aggregated processed bauxite has pH ranging from 5.0 to 7.5, EC <1mS / cm, and ESP<9.5.

31. An aggregated product of claim 30, having a size ranging from about 1 mm to about 10 mm.

32. An aggregated product of claim 30 or 31 , further comprising up to 5wt.% organic matter.

33. An aggregated product of claim 29, wherein the aggregated processed bauxite has pH ranging from 5.5 to 8.5, EC <1mS / cm, and ESP<9.5.

34. An aggregated product of claim 29, wherein the aggregated processed bauxite has pH ranging from 8.0 to 10.5, EC <10mS / cm, ESP<9.5 and a size ranging from about 1 mm to about 20 mm.

35. A method of treating an environment, comprising:applying the aggregated product of any one of claims 28 to 34 to a natural environment.

36. A treatment plant comprising:a treatment system configured to subject treated or untreated processed bauxite to chemical and / or thermal treatment to reduce pH and / or sodicity to form a treated material; andan aggregator system configured to increase an aggregate size of the treated material to form an aggregated product that can be returned to a natural environment.

37. A treatment plant of claim 36, wherein the aggregator system includes an agglomerator, pin pelletiser, briquette former or roll press.

38. A treatment plant of claim 37, wherein the agglomerator includes a disc or drum agglomerator.

39. A treatment plant of any one of claims 36 to 38, further comprising a binding agent mixer in fluid communication with the aggregator system and configured to form a solution that includes a binding agent that is used in the aggregator system to form the aggregated product.

40. A treatment plant of any one of claims 36 to 39, wherein the treatment system includes a neutralisation system configured to receive and neutralise treated or untreated processed bauxite by addition of a neutralising agent to form the treated material.

41. A treatment plant of any one of claims 36 to 40, wherein the treatment system includes a sodicity reduction system having a source of divalent cations, the sodicity reduction system configured to mix treated or untreated processed bauxite and the divalent cations to reduce a sodicity of the treated or untreated processed bauxite by displacing sodium cations in the treated or untreated processed bauxite with the divalent cations to form thetreated material and waste solution.

42. A treatment plant of claim 41 , wherein the sodicity reduction system includes a dewatering system configured to separate treated material from the waste solution, the dewatering system being positioned upstream of the aggregator and configured such that treated material separated by the dewatering system can be received by the aggregator.

43. A treatment plant of claim 42, further comprising a dryer positioned downstream of the dewatering system and upstream of the aggregator, the dryer configured to at least partially dry the treated material from the dewatering system prior to being received in the aggregator.

44. A treatment plant of any one of claims 41 to 43, further comprising a divalent cation mixer configured to receive and mix a source of divalent cations with a solution to form the solution of divalent cations.

45. A treatment plant of any one of claims 36 to 44, wherein the treatment system includes a pyrometallurgy reactor, calciner, vitrification reactor, or sintering reactor.

46. A treatment plant of any one of claims 36 to 45, further comprising a mixer configured to mix the treated material with untreated processed bauxite to form a mixed material, the mixer being positioned upstream of the aggregator such that the mixed material can be passed to the aggregator.

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