A method for separating and purifying desilication products from red mud

Abstract

The present application relates to a method for separating and purifying desilication products from red mud, drying the red mud, coarsely grinding it into powder, passing it through a 325 mesh vibrating screen, and performing multi-stage gravity separation on the undersize product until a gravity concentrate with a density less than 2.2 g / cm 3 is obtained, removing impurities from the obtained gravity concentrate with dilute alkali, and then performing solid-liquid separation, collecting the solid precipitate, and performing washing and drying treatment on the solid precipitate to obtain a desilication product purification product. The present application separates and purifies desilication products from red mud using a simple method without the need for high temperature and high pressure, etc., thereby maximizing the preservation of the original appearance and physicochemical properties of sodalite and calcium nepheline desilication products, which can be used as original samples for mineralogical analysis, elemental composition analysis, and microscopic morphology analysis of desilication products contained in red mud. The desilication products separated and purified by the present application have high purity, low investment and operating costs, and can be applied on a large scale in industry.

Description

Technical Field

[0001] This invention belongs to the technical field of harmless and resource-based application of red mud, specifically relating to a method for separating and purifying desilication products from red mud. Background Technology

[0002] Red mud is a solid or semi-solid, powdery waste discharged during alumina production. Due to its high salt and alkali content, strong corrosiveness, and certain radioactivity, red mud has low comprehensive utilization efficiency and is primarily stored by damming. The amount of red mud produced varies depending on the ore grade, production process, and technological level; for every 1 ton of alumina produced, 0.8 to 2.0 tons of red mud are discharged. The storage of red mud poses serious ecological risks to the surrounding groundwater, surface water, soil, and atmospheric environment; therefore, it is urgent to carry out harmless and resource-based treatment of red mud.

[0003] When producing alumina using the Bayer process, sintering process, or combined process, silica is easily supersaturated in sodium aluminate solution and precipitates as hydrated sodium aluminosilicate. This precipitate is called desilication products (DSPs). If DSPs precipitate during the dissolution process, they are stored in the discharged red mud, leading to the enrichment of Al2O3 and Na2O in the red mud. The formula for DSPs in red mud is [Na2O·Al2O3·(1.68-1.85)SiO2]·nNa2X·qH2O, and the main mineral phase is sodalite 2NaX·[Na6Al6Si6O] 24 ] and calcium nepheline 2CaCO3·[Na6Al6Si6O 24 If DSPs can be separated and purified from red mud, it will not only be beneficial for the qualitative and quantitative study of the mineral phases contained in red mud, but also for the dealkalization of red mud and the resource utilization of red mud.

[0004] Red mud has an extremely complex mineral composition, including boehmite, gibbsite, quartz, calcite, goethite, hematite, rutile, anatase, and DSPs, among others. When performing qualitative or quantitative X-ray diffraction analysis on the mineral phases of red mud, multiple overlapping peaks and the presence of several similar diffraction peaks make it difficult to analyze DSPs in red mud when multiple other minerals coexist. Therefore, it is necessary to first separate and purify DSPs from the complex composition to reduce the complexity of energy dispersive spectroscopy analysis.

[0005] Sodalite and nepheline, among other DSPs, are the main forms of solid alkaline minerals found in red mud and are the primary source of chemically bound alkalis, exhibiting extremely high acid neutralization capacity (ANC). Compared to free alkalis such as sodium hydroxide and sodium carbonate, which are readily soluble in the liquid phase, DSPs like sodalite and nepheline not only consume large amounts of acid or acidic gases during red mud dealkalization but also tend to remain incompletely in the red mud due to incomplete dissolution and transformation, ultimately affecting the efficiency of red mud dealkalization.

[0006] After separating and purifying DSPs such as sodalite and nepheline from red mud, they can be utilized as resources. DSPs are not only rich in Al2O3 and Na2O, which can be used as raw materials for recovering aluminum and sodium, but they can also be used to make products such as 4A zeolite, cryolite, and silica gel.

[0007] Currently, there is no efficient technology for extracting and purifying desilication products (DSPs) from red mud. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a relatively simple method for separating and purifying desilication products from red mud. This method does not require high temperature and high pressure, and preserves the original morphology and physicochemical properties of desilication products such as sodalite and nepheline to the greatest extent. The desilication products separated and purified by this invention have high purity, low investment and operating costs, and can be applied on a large scale industrial basis.

[0009] This invention is specifically achieved through the following technical solution: a method for separating and purifying desilication products from red mud according to this invention includes the following steps:

[0010] After drying, the red mud is coarsely ground into powder, then passed through a 325-mesh vibrating screen. The undersize product undergoes multi-stage gravity separation until a density of less than 2.2 g / cm³ is selected. 3 The gravity concentrate is subjected to dilute alkali to remove impurities, followed by solid-liquid separation. The solid precipitate is collected, washed, and dried to obtain the purified desilication product.

[0011] Furthermore, after passing through a 325-mesh vibrating screen, the particle size of the product on the screen is greater than 0.045 mm, mainly boehmite, gibbsite and quartz, while the particle size of the product under the screen is less than 0.045 mm, mainly desilication products (DSPs), calcite, goethite, hematite, rutile and anatase.

[0012] Furthermore, the main mineral components of the obtained gravity concentrate are desilication products (DSPs) and trace amounts of gibbsite, while the main mineral components of the gravity tailings are boehmite, hematite, goethite, rutile, anatase, quartz, and calcite.

[0013] Furthermore, the specific method for removing impurities from the obtained gravity concentrate using dilute alkali includes: soaking the gravity concentrate in a potassium hydroxide solution with a concentration of not less than 1.2 mol / L and shaking or stirring to remove impurities for 80–120 min, with a liquid-to-solid ratio of 9:1–11:1. During this removal process, trace amounts of gibbsite in the gravity concentrate dissolve in the dilute alkali solution. The gravity concentrate that has been removed is then subjected to solid-liquid separation, and the concentrate is washed and dried to finally obtain the purified desilication product (DSPs).

[0014] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, this invention achieves considerable technological advancement and practicality, and has broad application value, possessing at least the following advantages:

[0015] (1) This invention employs a simple method to separate and purify desilication products (DSPs) from red mud. The purified DSPs can be processed into products such as 4A zeolite, cryolite, and silica gel, and aluminum and alkali can also be recovered from them. The separation and purification process of this invention does not require high temperature and high pressure, thus preserving the original morphology and physicochemical properties of desilication products (DSPs) such as sodalite and nepheline to the greatest extent. These DSPs can be used as original samples for scientific research to perform mineralogical analysis, elemental composition analysis, and microscopic morphology analysis on the DSPs contained in red mud.

[0016] (2) The desiliconized products (DSPs) separated and purified by the method of the present invention have high purity, extremely low loss during the separation process, and do not use pressure or calcination, resulting in low investment and operating costs and enabling large-scale industrial application. Attached Figure Description

[0017] Figure 1 This is an SEM image of the purified DSPs product obtained in Example 1.

[0018] Figure 2 This is the EDS spectrum of the purified DSPs product obtained in Example 1. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, all conditions in the following examples were performed under standard conditions or conditions recommended by the manufacturer. Raw materials and reagents whose manufacturers are not specified are all commercially available products.

[0021] Example 1

[0022] Red mud was dried in an oven at 60℃ for 24 hours and then finely ground into a powder using a small ball mill. The content of particles smaller than 0.150mm in the powder was approximately 92% or more. The red mud powder was then passed through a 325-mesh vibrating screen. The undersize product was then passed through a primary spiral chute (5 turns, outer radius 150mm, inner radius 35mm, pitch 240mm, transverse inclination angle 9°, inlet flow rate 12.0L / min) to obtain primary gravity concentrate. The primary gravity concentrate was then passed through a secondary spiral chute (5 turns, outer radius 150mm, inner radius 35mm, pitch 240mm, transverse inclination angle 9°, inlet flow rate 5.0L / min) to obtain secondary gravity concentrate. The main mineral components of the secondary gravity concentrate were desilication products (DSPs) and trace amounts of gibbsite. 10g of secondary gravity concentrate was placed in 100mL of 1.2mol / L potassium hydroxide solution and stirred for 2h. During this impurity removal process, trace amounts of gibbsite in the secondary gravity concentrate dissolved in the dilute alkaline solution. The gravity concentrate that had been impurity removed was then subjected to solid-liquid separation. The impurity-removed concentrate was collected, washed with deionized water, and dried in an oven to obtain the purified DSPs product.

[0023] Figure 1 and Figure 2 The images show the SEM microstructure and EDS energy dispersive spectroscopy (EDS) spectra of the purified DSPs. Based on the mineral elemental composition and occurrence state, the purified products are mainly desilication products, nepheline and sodalite.

[0024] Example 2

[0025] Red mud was dried in an oven at 80℃ for 20 hours, and then finely ground into a powder using a small ball mill. The content of particles smaller than 0.150 mm in the powder was approximately 90% or more. The red mud powder was then passed through a 325-mesh vibrating screen. The undersize product was then passed through a primary spiral chute (5 turns, outer radius 150 mm, inner radius 35 mm, pitch 240 mm, transverse inclination angle 9°, inlet flow rate 12.0 L / min) to obtain primary gravity concentrate. The primary gravity concentrate was then passed through a secondary spiral chute (5 turns, outer radius 150 mm, inner radius 35 mm, pitch 240 mm, transverse inclination angle 9°, inlet flow rate 5.0 L / min) to obtain secondary gravity concentrate. The main mineral components of the secondary gravity concentrate were desilication products (DSPs) and trace amounts of gibbsite. 10g of secondary gravity concentrate was placed in 110mL of 1.5mol / L potassium hydroxide solution and stirred for 2h. During this impurity removal process, trace amounts of gibbsite in the secondary gravity concentrate dissolved in the dilute alkaline solution. The gravity concentrate that had been impurity removed was then subjected to solid-liquid separation. The impurity-removed concentrate was collected, washed with deionized water, and dried in an oven to obtain the purified DSPs product.

[0026] Example 3

[0027] Red mud was dried in an oven at 70℃ for 24 hours, and then finely ground into a powder using a small ball mill. The content of particles smaller than 0.150 mm in the powder was approximately 93% or more. The red mud powder was then passed through a 325-mesh vibrating screen. The undersize product was then passed through a primary spiral chute (5 turns, outer radius 150 mm, inner radius 35 mm, pitch 240 mm, transverse inclination angle 9°, inlet flow rate 12.0 L / min) to obtain primary gravity concentrate. The primary gravity concentrate was then passed through a secondary spiral chute (5 turns, outer radius 150 mm, inner radius 35 mm, pitch 240 mm, transverse inclination angle 9°, inlet flow rate 5.0 L / min) to obtain secondary gravity concentrate. The main mineral components of the secondary gravity concentrate were desilication products (DSPs) and trace amounts of gibbsite. 10g of secondary gravity concentrate was placed in a 90mL solution of 1.3mol / L potassium hydroxide and stirred for 2h. During this impurity removal process, trace amounts of gibbsite in the secondary gravity concentrate dissolved in the dilute alkaline solution. The gravity concentrate that had been impurity removed was then subjected to solid-liquid separation. The impurity-removed concentrate was collected, washed with deionized water, and dried in an oven to obtain the purified DSPs product.

[0028] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for the separation and purification of desilication product from red mud, characterised in that, The method comprises the following steps: After drying, the red mud is coarsely ground into powder, and then passed through a 325 mesh vibrating screen. The product on the screen has a particle size greater than 0.045 mm, and mainly comprises boehmite, gibbsite and quartz. The product under the screen has a particle size less than 0.045 mm, and mainly comprises desilication product, calcite, goethite, hematite, rutile and anatase. The product under the screen is subjected to multi-stage gravity separation until a gravity separation concentrate with a density less than 2.2 g / cm 3 is obtained. The main mineral components of the gravity separation concentrate are desilication product and trace gibbsite. The obtained gravity separation concentrate is subjected to dilute alkali impurity removal. The specific method of dilute alkali impurity removal comprises: soaking the gravity separation concentrate in a potassium hydroxide solution with a concentration not less than 1.2 mol / L for 80-120 min, and performing oscillation treatment or stirring treatment, with a liquid-solid ratio of 9:1-11:

1. Then, solid-liquid separation is performed, and the solid precipitate is collected. The solid precipitate is subjected to rinsing and drying treatment, and a desilication product purification product is obtained. The desilication product purification product mainly comprises kalsilite and sodalite.

2. The method of claim 1, wherein the desilication product is separated and purified from the red mud, characterized by, The undersize product is passed through a primary spiral chute and a secondary spiral chute for multi-stage gravity separation. The method comprises the following steps:

Images