Sewage treatment agent for thallium-containing heavy metal wastewater and preparation method of sewage treatment agent

Abstract

The invention discloses a sewage treatment agent for thallium-containing heavy metal wastewater and a preparation method thereof, and belongs to the technical field of environmental engineering, the sewage treatment agent has a large specific surface area and porosity, sufficient active sites and a molecular sieve effect, in a space structure, the sewage treatment agent is of a gradient porous structure, the inner layer is of a large-aperture structure, and the outer layer is of a large-aperture structure. The outer layer is of a small-aperture structure, the middle layer is a manganese dioxide site with an oxidation effect, through the gap between inner and outer pores, on one hand, the internal oxidation component manganese dioxide can be protected to play a role durably, interference of by-products on active sites is avoided, and on the other hand, the adsorption effect can be improved through the gradient porous structure characteristic; the removal effect on thallium is improved; the surfaces of the modified polystyrene microspheres contain sulfonic acid groups, and after the modified polystyrene microspheres and manganese ions are subjected to coordination interaction, the modified polystyrene microspheres can be combined with positively charged thallium ions through electrostatic attraction, so that adsorption and enrichment of the thallium ions are realized.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, specifically a wastewater treatment agent for thallium-containing heavy metal wastewater and its preparation method. Background Technology

[0002] Large amounts of thallium entering water bodies have caused serious environmental pollution. Furthermore, due to its neurotoxicity, thallium can enter the human body through drinking water and the food chain. During enzymatic reactions in the body, it can displace potassium and has a strong affinity for enzymes, causing toxic effects on the liver and kidneys, and in severe cases, can be fatal. Therefore, the harm thallium poses to the aquatic environment and humans has attracted widespread attention and high concern from environmental protection departments.

[0003] Currently, thallium-containing wastewater treatment technologies mainly include precipitation, adsorption, ion exchange, and solvent extraction. However, traditional adsorbents, such as clay minerals and natural metal oxides, suffer from poor selectivity, low adsorption capacity, and poor environmental friendliness, limiting their widespread application. Ion exchange requires specialized equipment and has poor material regeneration capabilities; solvent extraction consumes large amounts of organic reagents, wasting significant energy and causing secondary pollution, making industrial application difficult. Therefore, developing environmentally friendly and highly efficient purification and remediation materials is crucial. An ideal thallium adsorbent should possess characteristics such as stability, high efficiency, high selectivity, low cost, and reusability. In recent years, with the development of emerging technologies, the types of materials have rapidly increased, demonstrating significant advantages and potential in the field of environmental toxic element pollution control. New functional materials developed both domestically and internationally have achieved significant breakthroughs in adsorption performance and stability, showing promising application prospects.

[0004] Chinese Patent Publication No. CN112774621B discloses a hollow microsphere, its preparation method, and its application. Silica microspheres are synthesized using styrene emulsion as a template, and then iron is synthesized using the silica microspheres as a template. manganese oxide Silica microspheres are prepared by removing the silica to obtain hollow microspheres. The hollow microspheres obtained in this invention adsorb the highly toxic element thallium from wastewater. The thallium-adsorbed hollow microspheres naturally settle under the influence of a magnet, reducing the thallium content in the clarified supernatant to environmental protection standards. The thallium-adsorbed hollow microspheres can be recycled, avoiding the generation of hazardous waste and realizing the resource utilization of thallium. In this scheme, iron and manganese oxides are generated and precipitated on the hollow microspheres as reaction sites. However, the binding force between the iron and manganese oxides and the hollow microspheres is weak in this scheme, and they easily detach during wastewater treatment, leading to a decrease in treatment efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a wastewater treatment agent for thallium-containing wastewater and its preparation method. This agent has a large specific surface area and porosity, sufficient active sites, and exhibits a molecular sieve effect. In its spatial structure, the wastewater treatment agent has a gradient porous structure, with a large-pore inner layer, a small-pore outer layer, and a middle layer of manganese dioxide sites with oxidizing properties. The difference in pore size between the inner and outer layers protects the internal oxidizing component, manganese dioxide, from functioning continuously and prevents interference from byproducts on the active sites. Furthermore, the gradient porous structure increases adsorption and improves the removal of thallium.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater includes the following steps: Step 1: Modified polystyrene microspheres are prepared by sulfonating polystyrene microspheres with concentrated sulfuric acid.

[0007] Step 2: Using modified polystyrene microspheres as a carrier, and manganese sulfate, ammonium persulfate, and ammonium sulfate as raw materials, manganese dioxide is grown on the surface of the modified polystyrene microspheres to obtain manganese dioxide / polystyrene microspheres.

[0008] Step 3: Using hexadecyltrimethylammonium bromide as a pore-forming agent, a silica layer is coated onto manganese dioxide / polystyrene microspheres to obtain porous microspheres.

[0009] Step 4: Using porous microspheres as a carrier and tetradecyltrimethylammonium bromide as a pore-forming agent, a silica layer is coated again on the surface, and the polystyrene template is washed away to obtain gradient hollow microspheres.

[0010] Step 5: Calcium oxide precipitate is then deposited on the surface of the gradient hollow microspheres to obtain a wastewater treatment agent for thallium-containing heavy metal wastewater.

[0011] Furthermore, the specific preparation steps of the modified polystyrene microspheres are as follows: Polystyrene microspheres with a particle size of 25 nm and concentrated sulfuric acid solution with a mass fraction of 98% were added to a reaction vessel at a ratio of 3-4 g: 300-320 mL. The mixture was stirred for 12-14 h at 40-50 °C and 500-600 r / min. After filtration, the filter cake was washed with deionized water until the final washing liquid was centered. The mixture was then vacuum dried at 60-70 °C for 1-2 h to obtain modified polystyrene microspheres.

[0012] Furthermore, the specific preparation steps for manganese dioxide / polystyrene microspheres are as follows: Modified polystyrene microspheres and glycerol were added to a polytetrafluoroethylene reactor and stirred for 40-50 min at 40-50℃ and 400-500 r / min. Then, manganese sulfate, ammonium persulfate, ammonium sulfate, polyvinylpyrrolidone and deionized water were added, and the mixture was heated to 120-130℃ and stirred for 12-14 h. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The cake was then vacuum dried at 60-70℃ for 1-2 h to obtain manganese dioxide / polystyrene microspheres.

[0013] Furthermore, the ratio of modified polystyrene microspheres, glycerol, manganese sulfate, ammonium persulfate, ammonium sulfate, polyvinylpyrrolidone, and deionized water is 50-60g: 200-300mL: 1-2g: 2-4g: 2-3g: 0.05-0.07g: 40-50mL.

[0014] Furthermore, the specific preparation steps of porous microspheres are as follows: Manganese dioxide / polystyrene microspheres, ethanol, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 400-500 r / min for 20-30 min. Then, hexadecyltrimethylammonium bromide was added and stirring was continued for 30-40 min. Then, tetraethyl orthosilicate and ammonia were added and stirring was continued for 1-2 h. The mixture was filtered and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 h to obtain porous microspheres.

[0015] Furthermore, the ratio of manganese dioxide / polystyrene microspheres, ethanol, deionized water, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia is 40-50g: 400-500mL: 200-250mL: 0.8-1.0g: 40-50g: 10-15mL.

[0016] Furthermore, the specific preparation steps of the gradient hollow microspheres are as follows: Porous microspheres, ethanol, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 400-500 r / min for 20-30 min. Then tetradecyltrimethylammonium bromide was added, and stirring was continued for 30-40 min. Then tetraethyl orthosilicate and ammonia were added, and stirring was continued for 1-2 h. The mixture was filtered, and the filter cake was washed with N,N-dimethylformamide to remove the polystyrene template. Then it was washed 2-4 times with anhydrous ethanol and dried under vacuum at 60-70℃ for 1-2 h to obtain gradient hollow microspheres.

[0017] Furthermore, the ratio of porous microspheres, ethanol, deionized water, tetradecyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia is 32-35g: 400-500mL: 200-250mL: 0.8-1.0g: 40-50g: 10-15mL.

[0018] Furthermore, the specific preparation steps for the wastewater treatment agent used in thallium-containing heavy metal wastewater are as follows: Gradient hollow microspheres and a sodium bicarbonate solution with a mass fraction of 10-12% were added to a reaction vessel and vacuum impregnated for 2-3 hours at 20-25℃ and 500-600 r / min. Then, a calcium chloride solution with a mass fraction of 40-50% was added, and the reaction was continued for 1-2 hours. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The cake was then vacuum dried at 60-70℃ for 1-2 hours to obtain a wastewater treatment agent for thallium-containing wastewater.

[0019] Furthermore, the ratio of gradient hollow microspheres, sodium bicarbonate solution, and calcium chloride solution is 20-22g: 100-110mL: 40-50mL.

[0020] The beneficial effects of this invention are: 1. The wastewater treatment agent prepared by this invention for treating thallium-containing heavy metal wastewater has a large specific surface area and porosity, sufficient active sites, and a molecular sieve effect. In its spatial structure, the wastewater treatment agent has a gradient porous structure, with a large-pore structure in the inner layer, a small-pore structure in the outer layer, and manganese dioxide sites with oxidizing effect in the middle layer. Through the difference in pore size between the inner and outer layers, on the one hand, the internal oxidizing component manganese dioxide can be protected to maintain its function for a long time and avoid interference from by-products on the active sites. On the other hand, the gradient porous structure can increase the adsorption effect and improve the removal of thallium.

[0021] 2. The manganese dioxide / polystyrene microspheres prepared in this invention utilize the sulfonate groups present on the surface of the modified polystyrene microspheres, which coordinate with manganese ions, allowing manganese dioxide to grow uniformly on the surface of the modified polystyrene microspheres. This fixes the oxidation sites on the surface of the modified polystyrene microspheres, enabling the manganese dioxide to function for a long time. The loaded manganese dioxide has strong oxidizing and adsorption properties, and can specifically adsorb and convert thallium ions in wastewater. This invention obtains a gradient porous structure with small pore size on the outer layer and large pore size on the inner layer by coating the silica layer twice and using different pore-forming agents. The middle layer is the oxidation site layer. The difference in pore size between the inner and outer layers creates a molecular sieve effect, which can sieve thallium in thallium-containing wastewater, ensuring sufficient reduction and avoiding interference from impurities on the oxidation sites.

[0022] 3. The wastewater treatment agent for thallium-containing heavy metal wastewater of the present invention, through calcium carbonate loaded on the surface of gradient hollow microspheres, can form insoluble compounds with thallium ions to achieve chemical precipitation removal, and form a synergistic system of adsorption and precipitation with manganese dioxide; the modified polystyrene microspheres of the present invention contain sulfonic acid groups on their surface, which, after coordination interaction with manganese ions, are partially retained after the polystyrene template is removed, still carrying electronegativity, and can bind with positively charged thallium ions through electrostatic attraction, thereby achieving the adsorption and enrichment of thallium ions. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater, comprising the following steps: S1: Add 3g of polystyrene microspheres with a particle size of 25nm and 300mL of concentrated sulfuric acid solution with a mass fraction of 98% to a reaction vessel, stir for 12h at 40℃ and 500r / min, filter, wash the filter cake with deionized water until the final washing liquid is centered, and vacuum dry at 60℃ for 1h to obtain modified polystyrene microspheres.

[0025] S2: Add 50g of modified polystyrene microspheres and 200mL of glycerol to a polytetrafluoroethylene reactor and stir for 40min at 40℃ and 400r / min. Then add 1g of manganese sulfate, 2g of ammonium persulfate, 2g of ammonium sulfate, 0.05g of polyvinylpyrrolidone and 40mL of deionized water. Heat to 120℃ and continue stirring for 12h. Filter and wash the filter cake twice with deionized water and anhydrous ethanol, respectively. Dry under vacuum at 60℃ for 1h to obtain manganese dioxide / polystyrene microspheres.

[0026] S3: Add 40g of manganese dioxide / polystyrene microspheres, 400mL of ethanol and 200mL of deionized water to a reaction vessel, stir at 20℃ and 400r / min for 20min, then add 0.8g of hexadecyltrimethylammonium bromide, continue stirring for 30min, then add 40g of tetraethyl orthosilicate and 10mL of ammonia water, continue stirring for 1h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry it under vacuum at 60℃ for 1h to obtain porous microspheres.

[0027] S4: Add 32g of porous microspheres, 400mL of ethanol and 200mL of deionized water to a reaction vessel, stir at 20℃ and 400r / min for 20min, then add 0.8g of tetradecyltrimethylammonium bromide, continue stirring for 30min, then add 40g of tetraethyl orthosilicate and 10mL of ammonia water, continue stirring for 1h, filter, wash the filter cake with N,N-dimethylformamide to remove the polystyrene template, wash twice with anhydrous ethanol, and vacuum dry at 60℃ for 1h to obtain gradient hollow microspheres.

[0028] S5: Add 20g of gradient hollow microspheres and 100mL of 10% sodium bicarbonate solution to the reaction vessel, and vacuum impregnate for 2h at 20℃ and 500r / min. Then add 40mL of 40% calcium chloride solution and continue the reaction for 1h. Filter the mixture and wash the filter cake twice with deionized water and anhydrous ethanol, respectively. Dry the filter cake under vacuum at 60℃ for 1h to obtain a wastewater treatment agent for thallium-containing heavy metal wastewater.

[0029] Example 2: A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater, comprising the following steps: S1: Add 3.5g of polystyrene microspheres with a particle size of 25nm and 310mL of concentrated sulfuric acid solution with a mass fraction of 98% to a reaction vessel, stir for 13h at 45℃ and 550r / min, filter, wash the filter cake with deionized water until the final washing liquid is centered, and vacuum dry at 65℃ for 1.5h to obtain modified polystyrene microspheres.

[0030] S2: Add 55g of modified polystyrene microspheres and 250mL of glycerol to a polytetrafluoroethylene reactor and stir for 45min at 45℃ and 450r / min. Then add 1.5g of manganese sulfate, 3g of ammonium persulfate, 2.5g of ammonium sulfate, 0.06g of polyvinylpyrrolidone and 45mL of deionized water. Heat to 125℃ and continue stirring for 13h. Filter and wash the filter cake three times with deionized water and anhydrous ethanol respectively. Dry under vacuum at 65℃ for 1.5h to obtain manganese dioxide / polystyrene microspheres.

[0031] S3: Add 45g of manganese dioxide / polystyrene microspheres, 450mL of ethanol and 225mL of deionized water to a reaction vessel, stir at 22.5℃ and 450r / min for 25min, then add 0.9g of hexadecyltrimethylammonium bromide, continue stirring for 35min, then add 45g of tetraethyl orthosilicate and 12.5mL of ammonia water, continue stirring for 1.5h, filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 65℃ for 1.5h to obtain porous microspheres.

[0032] S4: Add 33.5g of porous microspheres, 450mL of ethanol and 225mL of deionized water to a reaction vessel, stir at 22.5℃ and 450r / min for 25min, then add 0.9g of tetradecyltrimethylammonium bromide, continue stirring for 35min, then add 45g of tetraethyl orthosilicate and 12.5mL of ammonia water, continue stirring for 1.5h, filter, wash the filter cake with N,N-dimethylformamide to remove the polystyrene template, then wash three times with anhydrous ethanol, and dry under vacuum at 65℃ for 1.5h to obtain gradient hollow microspheres.

[0033] S5: 21g of gradient hollow microspheres and 105mL of 11% sodium bicarbonate solution were added to the reaction vessel and impregnated under vacuum at 22.5℃ and 550r / min for 2.5h. Then, 45mL of 45% calcium chloride solution was added and the reaction was continued for 1.5h. The mixture was then filtered, and the filter cake was washed three times with deionized water and anhydrous ethanol, respectively. The mixture was then dried under vacuum at 65℃ for 1.5h to obtain a wastewater treatment agent for thallium-containing heavy metal wastewater.

[0034] Example 3: A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater, comprising the following steps: S1: Add 4g of polystyrene microspheres with a particle size of 25nm and 320mL of concentrated sulfuric acid solution with a mass fraction of 98% to a reaction vessel. Stir for 14h at 50℃ and 600r / min, filter, wash the filter cake with deionized water until the final washing liquid is centered, and vacuum dry at 70℃ for 2h to obtain modified polystyrene microspheres.

[0035] S2: Add 60g of modified polystyrene microspheres and 300mL of glycerol to a polytetrafluoroethylene reactor and stir for 50min at 50℃ and 500r / min. Then add 2g of manganese sulfate, 4g of ammonium persulfate, 3g of ammonium sulfate, 0.07g of polyvinylpyrrolidone and 50mL of deionized water. Heat to 130℃ and continue stirring for 14h. Filter and wash the filter cake four times with deionized water and anhydrous ethanol respectively. Dry under vacuum at 70℃ for 2h to obtain manganese dioxide / polystyrene microspheres.

[0036] S3: Add 50g of manganese dioxide / polystyrene microspheres, 500mL of ethanol and 250mL of deionized water to a reaction vessel, stir at 25℃ and 500r / min for 30min, then add 1.0g of hexadecyltrimethylammonium bromide, continue stirring for 40min, then add 50g of tetraethyl orthosilicate and 15mL of ammonia water, continue stirring for 2h, filter, wash the filter cake with deionized water and anhydrous ethanol 4 times respectively, and dry it under vacuum at 70℃ for 2h to obtain porous microspheres.

[0037] S4: Add 35g of porous microspheres, 500mL of ethanol and 250mL of deionized water to a reaction vessel, stir at 25℃ and 500r / min for 30min, then add 1.0g of tetradecyltrimethylammonium bromide, continue stirring for 40min, then add 50g of tetraethyl orthosilicate and 15mL of ammonia water, continue stirring for 2h, filter, wash the filter cake with N,N-dimethylformamide to remove the polystyrene template, then wash with anhydrous ethanol 4 times, and dry under vacuum at 70℃ for 2h to obtain gradient hollow microspheres.

[0038] S5: 22g of gradient hollow microspheres and 110mL of 12% sodium bicarbonate solution were added to the reaction vessel and vacuum impregnated for 3h at 25℃ and 600r / min. Then, 50mL of 50% calcium chloride solution was added and the reaction was continued for 2h. The mixture was filtered and the filter cake was washed 4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 70℃ for 2h to obtain a wastewater treatment agent for thallium-containing heavy metal wastewater.

[0039] Comparative Example 1: Based on Example 3, the modified polystyrene microspheres in step S2 were replaced with polystyrene microspheres.

[0040] Comparative Example 2: Based on Example 3, the gradient hollow microspheres in step S5 were replaced with porous microspheres prepared in step S3, and the porous microspheres were washed with N,N-dimethylformamide to remove the polystyrene template, resulting in hollow microspheres replacing the porous microspheres of the original scheme.

[0041] Comparative Example 3: Based on Example 3, the manganese dioxide / polystyrene microspheres in step S3 were replaced with a mixture of manganese dioxide and modified polystyrene microspheres.

[0042] The performance of the wastewater treatment agents prepared in Examples 1-3 and Comparative Examples 1-3 for treating thallium-containing heavy metal wastewater was tested, and the results are shown in Table 1. Take 100 mL of industrial wastewater from a non-ferrous metal smelter. The thallium content in this wastewater is 5.673 mg / L. Add 0.3 mL of 0.1 wt% polyaluminum ferric sulfate solution and stir for 5 min. Add calcium oxide to adjust the pH to 8.5. Add 1 g of wastewater treatment agent for thallium-containing heavy metal wastewater to carry out precipitation reaction and stir for 10 min. The wastewater treatment agent for thallium-containing heavy metal wastewater reacts with the thallium ions in the wastewater to carry out precipitation reaction, so that the thallium ions in the wastewater can be quickly converted into thallium complex precipitate. Finally, add 0.3 mL of 0.1 wt% polyacrylamide solution for flocculation treatment, stir for 5 min, let stand for 30 min, filter, and obtain filtrate and filter residue. After the filtrate meets the standards, it is discharged. The filter residue is returned to recover heavy metals, thus completing the treatment of thallium-containing wastewater.

[0043] Table 1

[0044] As can be seen from Table 1, the thallium removal rate of the wastewater treatment agents prepared in Examples 1-3 for thallium-containing heavy metal wastewater is significantly better than that of the comparative examples, indicating that the wastewater treatment agents prepared in this invention for thallium-containing heavy metal wastewater have a highly efficient removal effect on thallium.

[0045] In Comparative Example 1, the modified polystyrene microspheres in step S2 were replaced with polystyrene microspheres. The crucial role of the sulfonic acid groups was lost, leading to the failure of manganese dioxide loading. The unmodified polystyrene microspheres lacked sulfonic acid groups on their surface, preventing them from forming coordination interactions with manganese ions and forcing them to bind only through physical adsorption. This resulted in uneven dispersion and weak loading of manganese dioxide, with some manganese dioxide easily detaching. The number of oxidizing active sites was significantly reduced and their distribution became disordered. Both the stable oxidation sites provided by the sulfonic acid group-manganese ion coordination and the electrostatic adsorption and enrichment effect of the residual sulfonic acid groups were lost, leading to a decrease in thallium removal rate.

[0046] Comparative Example 2 replaced the gradient hollow microspheres in step S5 with the porous microspheres prepared in step S3, and removed the polystyrene template by washing with N,N-dimethylformamide to obtain hollow microspheres. Lacking the gradient hollow structure and calcium carbonate loading, it lost the synergistic thallium removal system and molecular sieve effect. The porous microspheres lacked gradient pore size design and could not form a gradient structure. Impurities could easily enter and interfere with the active sites of manganese dioxide.

[0047] In Comparative Example 3, the manganese dioxide / polystyrene microspheres in step S3 were replaced with a mixture of manganese dioxide and modified polystyrene microspheres. The manganese dioxide and modified polystyrene microspheres were not in-situ loaded and bound together, but were only physically mixed, which destroyed the stability and uniformity of the oxidation sites. Through coordination, manganese dioxide grew in situ on the surface of the microspheres to form a stable oxidation site layer. In the physical mixture, the manganese dioxide particles and microspheres were only bound together by van der Waals forces, resulting in poor dispersibility, easy agglomeration, and easy loss during subsequent washing and reaction processes.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater, characterized in that, Includes the following steps: Step 1: Modified polystyrene microspheres are prepared by sulfonating polystyrene microspheres with concentrated sulfuric acid; Step 2: Using modified polystyrene microspheres as a carrier, and manganese sulfate, ammonium persulfate, and ammonium sulfate as raw materials, manganese dioxide is grown on the surface of the modified polystyrene microspheres to obtain manganese dioxide / polystyrene microspheres; Step 3: Using hexadecyltrimethylammonium bromide as a pore-forming agent, a silica layer is coated onto manganese dioxide / polystyrene microspheres to obtain porous microspheres; Step 4: Using porous microspheres as a carrier and tetradecyltrimethylammonium bromide as a pore-forming agent, a silica layer is coated again on the surface, and the polystyrene template is washed away to obtain gradient hollow microspheres; Step 5: Calcium oxide precipitate is then deposited on the surface of the gradient hollow microspheres to obtain a wastewater treatment agent for thallium-containing heavy metal wastewater.

2. The method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 1, characterized in that, The specific preparation steps for the modified polystyrene microspheres are as follows: Polystyrene microspheres with a particle size of 25 nm and concentrated sulfuric acid solution with a mass fraction of 98% were added to a reaction vessel at a ratio of 3-4 g: 300-320 mL. The mixture was stirred for 12-14 h at 40-50 °C and 500-600 r / min. After filtration, the filter cake was washed with deionized water until the final washing liquid was centered. The mixture was then vacuum dried at 60-70 °C for 1-2 h to obtain modified polystyrene microspheres.

3. The method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 1, characterized in that, The specific preparation steps for the manganese dioxide / polystyrene microspheres are as follows: Modified polystyrene microspheres and glycerol were added to a polytetrafluoroethylene reactor and stirred for 40-50 min at 40-50℃ and 400-500 r / min. Then, manganese sulfate, ammonium persulfate, ammonium sulfate, polyvinylpyrrolidone and deionized water were added, and the mixture was heated to 120-130℃ and stirred for 12-14 h. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The cake was then vacuum dried at 60-70℃ for 1-2 h to obtain manganese dioxide / polystyrene microspheres.

4. The method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 3, characterized in that, The ratio of the modified polystyrene microspheres, glycerol, manganese sulfate, ammonium persulfate, ammonium sulfate, polyvinylpyrrolidone, and deionized water is 50-60g: 200-300mL: 1-2g: 2-4g: 2-3g: 0.05-0.07g: 40-50mL.

5. The method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 1, characterized in that, The specific preparation steps of the porous microspheres are as follows: Manganese dioxide / polystyrene microspheres, ethanol, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 400-500 r / min for 20-30 min. Then, hexadecyltrimethylammonium bromide was added and stirring was continued for 30-40 min. Then, tetraethyl orthosilicate and ammonia were added and stirring was continued for 1-2 h. The mixture was filtered and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-70℃ for 1-2 h to obtain porous microspheres.

6. A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 5, characterized in that, The ratio of manganese dioxide / polystyrene microspheres, ethanol, deionized water, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia is 40-50g: 400-500mL: 200-250mL: 0.8-1.0g: 40-50g: 10-15mL.

7. The method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 1, characterized in that, The specific preparation steps of the gradient hollow microspheres are as follows: Porous microspheres, ethanol, and deionized water were added to a reaction vessel and stirred at 20-25℃ and 400-500 r / min for 20-30 min. Then tetradecyltrimethylammonium bromide was added, and stirring was continued for 30-40 min. Then tetraethyl orthosilicate and ammonia were added, and stirring was continued for 1-2 h. The mixture was filtered, and the filter cake was washed with N,N-dimethylformamide to remove the polystyrene template. Then it was washed 2-4 times with anhydrous ethanol and dried under vacuum at 60-70℃ for 1-2 h to obtain gradient hollow microspheres.

8. A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 7, characterized in that, The ratio of the porous microspheres, ethanol, deionized water, tetradecyltrimethylammonium bromide, tetraethyl orthosilicate, and ammonia is 32-35g: 400-500mL: 200-250mL: 0.8-1.0g: 40-50g: 10-15mL.

9. A method for preparing a wastewater treatment agent for thallium-containing heavy metal wastewater according to claim 1, characterized in that, The specific preparation steps of the wastewater treatment agent for thallium-containing heavy metal wastewater are as follows: Gradient hollow microspheres and a sodium bicarbonate solution with a mass fraction of 10-12% were added to a reaction vessel and vacuum impregnated for 2-3 hours at 20-25℃ and 500-600 r / min. Then, a calcium chloride solution with a mass fraction of 40-50% was added and the reaction was continued for 1-2 hours. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The cake was then vacuum dried at 60-70℃ for 1-2 hours to obtain a wastewater treatment agent for thallium-containing heavy metal wastewater. The ratio of the gradient hollow microspheres, sodium bicarbonate solution, and calcium chloride solution is 20-22g: 100-110mL: 40-50mL.

10. A wastewater treatment agent for thallium-containing heavy metal wastewater, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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