Silicon-containing sodium aluminate solution desiliconizing agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of silicon adsorption, in particular to a silicon-containing sodium aluminate solution desiliconizing agent and a preparation method and application thereof. The invention relates to a preparation method of a desiliconizing agent for a silicon-containing sodium aluminate solution. The preparation method comprises the following steps: (1) carrying out crushing, acid pickling, washing and drying on a zeolite raw material to obtain pretreated zeolite; (2) dissolving polyethyleneimine in a solvent to prepare a polyethyleneimine solution; (3) adding the pretreated zeolite into a polyethyleneimine solution to obtain a mixed system; (4) adding a cross-linking agent into the mixed system, and stirring to obtain a reaction solution; and (5) carrying out solid-liquid separation on the reaction liquid, washing the obtained solid to be neutral, and drying to obtain the product. According to the invention, the selective adsorption capacity and deep desiliconization capacity of silicate are remarkably improved by utilizing the strong positive electricity and complexing capacity of PEI and combining the carrier characteristics of zeolite, and meanwhile, the PEI is firm in loading and good in stability in a strong alkaline environment. The efficient and environment-friendly desiliconizing agent provided by the invention effectively reduces the generation of solid wastes and reduces the production cost.

Description

Technical Field

[0001] This invention relates to the field of silicon adsorption technology, specifically to a sodium aluminosilicate solution desilication agent, its preparation method, and its application. Background Technology

[0002] my country's bauxite resources are mainly low- to medium-grade monohydrate gibbsite, therefore the Bayer process, characterized by high temperature and high alkali concentration, is primarily used domestically for alumina production. During the Bayer process, silicon-containing impurities in the bauxite dissolve and enter the solution as silicates or aluminosilicates. The active silicon (silicone ions) in the sodium aluminate solution reacts with aluminate ions to form silica slag with extremely low solubility (such as sodalite and hydrated sodium aluminosilicate). After multiple cycles, silicon impurities gradually accumulate in the sodium aluminate solution, leading to an increasingly high SiO2 concentration. These silicon-containing impurities not only cause losses of alumina and sodium oxide but also precipitate simultaneously with aluminum hydroxide during decomposition, affecting product quality and whiteness and limiting its application in the production of high-quality aluminum-based products. Controlling the SiO2 content in the sodium aluminate solution is crucial for producing high-quality alumina.

[0003] The existing methods for desilication of sodium aluminate solution in production processes include increasing temperature, extending time, reducing sodium aluminate solution concentration, or adding desilication agents. In current technologies, the main methods for desilication of sodium aluminate solution are: (1) adding lime for desilication, which is the most commonly used method, but it has problems such as large lime consumption, the generation of a large amount of difficult-to-handle desilication slag (calcium-silicon slag), the introduction of calcium ions which may affect subsequent processes, and limited desilication depth; (2) seeding desilication, which requires a long time, has low efficiency, and affects production capacity; (3) activated alumina adsorption method, which has limited adsorption capacity, low selectivity, and poor stability or regeneration performance in strongly alkaline sodium aluminate solution.

[0004] Patent CN 202124493 U discloses a purification system for the Bayer process of alumina production, which can reduce the concentration of impurity ions in the solution, but the process is relatively complex. Patent CN 112551564 A mixes vanadium hydrate ore with bauxite for Bayer process leaching, using the generated Mg(OH)2 colloid to adsorb organic matter and silicon and iron impurities, achieving solution purification; the resulting purified solution has a SiO2 concentration of approximately 0.7 g / L. Patent CN 104760978A proposes a deep purification process for high-concentration sodium aluminate solution. This process involves adding lime for desilication after oxidative removal of organic matter, resulting in a sodium aluminate solution with lower impurity content; however, the SiO2 concentration in the purified solution is still higher than 0.5 g / L.

[0005] Therefore, there is a need for a desilication agent that is simple to prepare, has excellent adsorption performance, and is stable. Summary of the Invention

[0006] The purpose of this application is to provide a sodium aluminosilicate solution desilication agent with a simple preparation process, strong modifier loading, excellent and stable adsorption performance, and its preparation method, and to apply the sodium aluminosilicate solution desilication agent to the deep desilication of sodium aluminate solution, so as to reduce desilication cost, reduce solid waste generation, improve desilication efficiency and alumina product quality.

[0007] To achieve the above objectives, this application provides the following technical solution: A method for preparing a sodium aluminosilicate solution-based desilication agent includes the following steps: (1) Zeolite pretreatment: Zeolite raw materials are crushed, acid washed, washed and dried to obtain pretreated zeolite; (2) Prepare a polyethyleneimine solution by dissolving polyethyleneimine in a solvent; (3) Impregnation modification: The pretreated zeolite is added to a polyethyleneimine solution and impregnated by stirring at 40-70°C to obtain a mixed system; (4) Crosslinking treatment: add a crosslinking agent to the mixture and stir at 30-60°C to obtain a reaction solution; (5) Post-processing: the reaction solution is subjected to solid-liquid separation, the obtained solid is washed with deionized water until neutral, and dried at 60-100°C to obtain the desiliconizing agent.

[0008] Preferably, in step (1), the zeolite raw material is clinoptilolite, mordenite, NaA zeolite, NaX zeolite, NaY zeolite or ZSM-5 zeolite.

[0009] More preferably, in step (1), the acid used for pickling is hydrochloric acid, nitric acid or sulfuric acid, and the concentration of the acid is 0.1 to 2 mol / L; the temperature of the drying treatment is 60 to 90°C, and the drying time is 1 to 4 hours; the particle size of the pretreated zeolite is 10 to 50 mesh.

[0010] Preferably, in step (2), the solvent is an alcohol-water mixture, and the volume ratio of alcohol to water is 1:1, and the mass percentage of polyethyleneimine in the polyethyleneimine solution is 5-20 wt%.

[0011] Preferably, in step (3), the solid-liquid mass-volume ratio of the pretreated zeolite to the polyethyleneimine solution is 1g:5-50mL.

[0012] Preferably, in step (4), the crosslinking agent is glutaraldehyde, and the molar ratio of the crosslinking agent to the amino group in polyethyleneimine is 0.1 to 1:1.

[0013] A sodium aluminosilicate solution desilication agent is prepared by the above-mentioned method for preparing sodium aluminosilicate solution desilication agent.

[0014] Application of a sodium aluminosilicate solution desilication agent, wherein the sodium aluminosilicate solution desilication agent is used for desilication of sodium aluminate solution.

[0015] The application of the above-mentioned sodium aluminosilicate solution desilication agent includes the following steps: S1. Add the desilication agent to the sodium aluminate solution at a dosage of 5-20 g / L; S2. Stir and mix at 40-60℃ for 1-3 hours to carry out adsorption and desilication; S3. After adsorption is complete, solid-liquid separation is performed to obtain a desilicationized sodium aluminate solution and a silicon-loaded desilication agent.

[0016] Beneficial effects: (1) Zeolite itself has certain adsorption and ion exchange capabilities and a stable structure, providing a good loading platform for PEI. Modified zeolite particles are easy to separate from the solution by conventional solid-liquid separation methods (such as filtration), and have good carrier advantages.

[0017] (2) Polyethyleneimine (PEI) is a water-soluble cationic polymer rich in amino groups (-NH2, -NH-), possessing strong complexing ability and high positive charge density. Loading it onto zeolites can significantly enhance the adsorption capacity of zeolites for silicate ions. On the one hand, the abundant amino groups inherent in PEI attract silicate ions (SiO3-). 2- HSiO3 - PEI possesses strong electrostatic attraction and coordination complexation properties, which can significantly improve the selective adsorption capacity and adsorption capacity of zeolite for silicon. This can reduce the silicon concentration in sodium aluminate solution to a much lower level (SiO2 concentration in the purified solution is 0.1–0.3 g / L SiO2), effectively inhibiting subsequent scaling on pipes and equipment. On the other hand, PEI's strong positive charge and complexing ability enable it to effectively adsorb silicon in large quantities of anions (such as Al(OH)4). - Even when coexisting, it can still preferentially adsorb silicate ions, reducing the co-adsorption loss of alumina, and exhibiting excellent selectivity.

[0018] (3) Through cross-linking treatment, PEI is firmly fixed on the zeolite carrier and is not easily dissolved or degraded in strongly alkaline, high-temperature, and high-ionic-strength sodium aluminate solution, which ensures the durability and reusability of adsorption performance and has good stability.

[0019] (4) The desiliconizing agent is regenerable and recyclable (it can be regenerated after elution with a 5% sulfuric acid solution), reducing operating costs. The process is relatively simple and easy to integrate into existing alumina production processes. The preparation method is simple and controllable. The preparation method of the desiliconizing agent has clear steps, mild conditions, and readily available raw materials, making it suitable for large-scale production. Compared with lime desiliconization, this invention significantly reduces or even avoids the generation of calcium silicate slag, lowers solid waste treatment costs and environmental pressure, and has the advantages of being green, environmentally friendly, and low-cost. Detailed Implementation

[0020] The present application will now be described in detail with reference to embodiments. The various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention should fall within the scope of protection of the embodiments of the present invention.

[0021] A method for preparing a sodium aluminosilicate solution-based desilication agent includes the following steps: (1) Zeolite pretreatment: The zeolite raw material is crushed, acid-washed, washed and dried to obtain pretreated zeolite; the zeolite raw material is clinoptilolite, mordenite, NaA zeolite, NaX zeolite, NaY zeolite or ZSM-5 zeolite; the acid used for acid washing is hydrochloric acid, nitric acid or sulfuric acid, and the concentration of acid is 0.1 to 2 mol / L; the drying temperature is 60 to 90℃, and the drying time is 1 to 4 h; the particle size of the pretreated zeolite is 10 to 50 mesh.

[0022] (2) Prepare a polyethyleneimine solution by dissolving polyethyleneimine in a solvent to prepare a polyethyleneimine solution; the solvent consists of alcohol and water in a volume ratio of 1:1, the alcohol being ethanol, isopropanol or n-butanol, and the mass percentage of polyethyleneimine in the polyethyleneimine solution is 5 to 20 wt%.

[0023] (3) Impregnation modification: The pretreated zeolite is added to the polyethyleneimine solution and impregnated by stirring at 40-70°C to obtain a mixed system; the solid-liquid mass-volume ratio of the pretreated zeolite to the polyethyleneimine solution is 1g: 5-50mL.

[0024] (4) Crosslinking treatment: add a crosslinking agent to the mixture and stir at 30-60°C to obtain a reaction solution; the crosslinking agent is glutaraldehyde and the molar ratio of the crosslinking agent to the amino group in polyethyleneimine is 0.1-1:1.

[0025] (5) Post-processing: the reaction solution is subjected to solid-liquid separation, the obtained solid is washed with deionized water until neutral, and dried at 60-100°C to obtain the desiliconizing agent.

[0026] An application of a sodium aluminosilicate solution desilication agent, which is used for desilication of sodium aluminate solution. The application of the sodium aluminosilicate solution desilication agent for desilication of sodium aluminate solution includes the following steps: S1. Add the desilication agent to the sodium aluminate solution at a dosage of 5-20 g / L; S2. Stir and mix at 40-60℃ for 1-3 hours to carry out adsorption and desilication; S3. After adsorption is complete, solid-liquid separation is performed to obtain a desilicationized sodium aluminate solution and a silicon-loaded desilication agent.

[0027] Example 1 A method for preparing a sodium aluminosilicate solution-based desilication agent includes the following steps: (1) 1L of clinoptilolite was crushed, washed with 1L of 5% hydrochloric acid for 1h, and drained to obtain pretreated zeolite with a particle size of 10-50 mesh. (2) Dissolve polyethyleneimine in ethanol and water in a volume ratio of 1:1 to prepare a polyethyleneimine solution with a mass percentage of 5%.

[0028] (3) Add the pretreated zeolite to a 5% polyethyleneimine solution and immerse the pretreated zeolite completely in the polyethyleneimine solution, and stir and soak at 40°C for 4 hours. (4) Add crosslinking agent glutaraldehyde, and the molar ratio of glutaraldehyde to amino group in polyethyleneimine is 0.1:1. Stir and react at 30°C for 2 hours, separate solid and liquid, and dry at 60°C for 10 hours to obtain desiliconizing agent.

[0029] The silicon content in sodium aluminate solution was determined according to GB / T 6610.4-2003. 6g of the desilication agent prepared in this example was added to 1L of sodium aluminate solution with a silicon content of 14.8g / L. The mixture was stirred at 60℃ for 2h for adsorption and desilication. After solid-liquid separation, the silicon content in the sodium aluminate solution was determined to be 0.3g / L, and the silicon precipitation rate was 97.8%.

[0030] Example 2 A method for preparing a sodium aluminosilicate solution-based desilication agent includes the following steps: Referring to Example 1, mordenite was crushed, acid-washed, washed, and dried to obtain pretreated zeolite. The pretreated zeolite was added to a 13% polyethyleneimine solution and stirred and impregnated at 60°C for 8 hours. Glutaraldehyde, a crosslinking agent, was added. The molar ratio of amino groups in the polyethyleneimine was 0.5:1. The mixture was stirred and reacted at 50°C for 3 hours. Solid-liquid separation was performed, and the mixture was dried at 80°C to obtain a desilication agent.

[0031] The silicon content in sodium aluminate solution was determined according to GB / T 6610.4-2003. 8g of the desilication agent prepared in this example was added to 1L of sodium aluminate solution with a silicon content of 17.3g / L. The mixture was stirred and mixed at 50℃ for 2h for adsorption and desilication. After solid-liquid separation, the silicon content in the sodium aluminate solution was determined to be 0.2g / L, and the silicon precipitation rate was 98.8%.

[0032] Example 3 A method for preparing a sodium aluminosilicate solution-based desilication agent includes the following steps: Referring to Example 1, NaA zeolite was crushed, acid-washed, washed, and dried to obtain pretreated zeolite. The pretreated zeolite was added to a 20% polyethyleneimine solution and stirred and impregnated at 70°C for 12 hours. Glutaraldehyde, a crosslinking agent, was added. The molar ratio of amino groups in polyethyleneimine was 1:1. The mixture was stirred and reacted at 60°C for 6 hours. Solid-liquid separation was performed, and the mixture was dried at 100°C to obtain a desilication agent.

[0033] The silicon content in sodium aluminate solution was determined according to GB / T 6610.4-2003. 5g of the desilication agent prepared in this example was added to 1L of sodium aluminate solution with a silicon content of 8.5g / L. The mixture was stirred and mixed at 40℃ for 3h for adsorption and desilication. After solid-liquid separation, the silicon content in the sodium aluminate solution was determined to be 0.1g / L, and the silicon precipitation rate was 98.8%.

[0034] Example 4 The desilicon agent adsorbed and desiliconized in 1L sodium aluminate solution in Example 3 was washed with 5% dilute sulfuric acid solution and dried at 100°C to obtain regenerated desilicon agent.

[0035] The silicon content in sodium aluminate solution was determined according to GB / T 6610.4-2003. 5g of regenerated desilication agent (washed and dried with dilute sulfuric acid as described in Example 5) was added to 1L of sodium aluminate solution with a silicon content of 10.5g / L. The solution was stirred and mixed at 40℃ for 3h for adsorption and desilication. After solid-liquid separation, the silicon content in the sodium aluminate solution was determined to be 0.15g / L, and the silicon precipitation rate was 98.5%.

[0036] In Examples 1-3 above, the desilication agent underwent adsorption desilication. After solid-liquid separation, the silicon content was measured to be 0.3 g / L, 0.2 g / L, and 0.1 g / L, respectively, with silicon precipitation rates of 97.8%, 98.8%, and 98.8%, respectively, which are lower than the SiO2 concentration in the purified solution in the prior art (higher than 0.5 g / L). This invention utilizes the strong positive charge and complexing ability of PEI, combined with the carrier characteristics of zeolite, to significantly improve the selective adsorption capacity and deep desilication ability for silicate ions. Furthermore, the PEI is firmly loaded and exhibits good stability in strongly alkaline environments. In addition, the desilication agent of this invention can be recycled after elution with a 5% sulfuric acid solution and drying. This invention effectively reduces solid waste generation, lowers production costs, and provides an efficient and environmentally friendly desilication agent for the alumina industry.

[0037] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0038] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a desilication agent containing sodium aluminosilicate solution, characterized in that, Includes the following steps: (1) Zeolite pretreatment: Zeolite raw materials are crushed, acid washed, washed and dried to obtain pretreated zeolite; (2) Prepare a polyethyleneimine solution by dissolving polyethyleneimine in a solvent; (3) Impregnation modification: The pretreated zeolite is added to a polyethyleneimine solution and impregnated by stirring at 40-70°C to obtain a mixed system; (4) Crosslinking treatment: add a crosslinking agent to the mixture and stir at 30-60°C to obtain a reaction solution; (5) Post-processing: the reaction solution is subjected to solid-liquid separation, the obtained solid is washed with deionized water until neutral, and dried at 60-100°C to obtain the desiliconizing agent.

2. The method for preparing the sodium aluminosilicate solution desilication agent according to claim 1, characterized in that, In step (1), the zeolite raw material is clinoptilolite, mordenite, NaA zeolite, NaX zeolite, NaY zeolite or ZSM-5 zeolite.

3. The method for preparing the sodium aluminosilicate solution desilication agent according to claim 2, characterized in that, In step (1), the acid used for pickling is hydrochloric acid, nitric acid or sulfuric acid, and the concentration of the acid is 0.1 to 2 mol / L; the temperature of the drying treatment is 60 to 90°C, and the drying time is 1 to 4 hours; the particle size of the pretreated zeolite is 10 to 50 mesh.

4. The method for preparing the sodium aluminosilicate solution desilication agent according to claim 1, characterized in that, In step (2), the solvent is an alcohol-water mixture, and the volume ratio of alcohol to water is 1:

1. The mass percentage of polyethyleneimine in the polyethyleneimine solution is 5 to 20 wt%.

5. The method for preparing the sodium aluminosilicate solution desilication agent according to claim 1, characterized in that, In step (3), the solid-liquid mass-volume ratio of the pretreated zeolite to the polyethyleneimine solution is 1g: 5-50mL.

6. The method for preparing the sodium aluminosilicate solution desilication agent according to claim 1, characterized in that, In step (4), the crosslinking agent is glutaraldehyde, and the molar ratio of the crosslinking agent to the amino group in polyethyleneimine is 0.1 to 1:

1.

7. A desilication agent containing sodium aluminosilicate solution, characterized in that, It is prepared by the method of any one of claims 1-6 for preparing sodium aluminosilicate solution desilication agent.

8. The application of the sodium aluminosilicate solution desilication agent as described in claim 7, characterized in that, The sodium aluminate solution desilication agent is used for desilication of sodium aluminate solution.

9. The application of the sodium aluminosilicate solution desilication agent according to claim 8, characterized in that, Includes the following steps: S1. Add the desilication agent to the sodium aluminate solution at a dosage of 5-20 g / L; S2. Stir and mix at 40-60℃ for 1-3 hours to carry out adsorption and desilication; S3. After adsorption is complete, solid-liquid separation is performed to obtain a desilicationized sodium aluminate solution and a silicon-loaded desilication agent.