Preparation method of industrial composite polyaluminum chloride water treatment agent

Abstract

The present application relates to water treatment agent preparation technical field, especially to a kind of industrial composite polyaluminum chloride water treatment agent preparation method, comprising the following steps: S1, under nitrogen protection, 2-amino-5-mercapto-1,3,4-thiadiazole and oxalyl chloride are reacted to obtain intermediate;S2, intermediate is dissolved in anhydrous DMF, under nitrogen atmosphere, fumarate is added under ice bath, and temperature is raised to 40-50 DEG C, and reaction is carried out for 12-24h, and modified fucoidan is obtained;S3, bentonite is loaded with polyaluminum chloride and dispersed in toluene, vinyl silane coupling agent and water are added, and modified polyaluminum chloride is obtained by reaction;S4, modified polyaluminum chloride is dispersed in DMF / water mixed solvent, modified fucoidan and benzophenone are added, and composite polyaluminum chloride water treatment agent is obtained by reaction.The composite polyaluminum chloride water treatment agent prepared by the present application significantly enhances the removal efficiency of heavy metal ions.

Description

Technical Field

[0001] This invention relates to the field of water treatment agent preparation technology, and in particular to a method for preparing an industrial composite polyaluminum chloride water treatment agent. Background Technology

[0002] Polyaluminum chloride (PAC), as a highly efficient inorganic flocculant, has been widely used in industrial wastewater treatment. It forms polynuclear hydroxyl complexes through the hydrolysis and polymerization of aluminum ions, exhibiting mechanisms such as charge neutralization, adsorption bridging, and sedimentation, effectively removing suspended solids, colloidal particles, and some organic pollutants from water. Compared to traditional flocculants such as aluminum sulfate and ferric chloride, PAC offers advantages such as rapid flocculation, a wide applicable pH range, low sludge production, and low residual aluminum ion concentration, making it widely used in water purification, industrial wastewater treatment, and sludge dewatering. However, with the increasingly complex composition of industrial wastewater, the treatment effect of PAC alone often fails to meet increasingly stringent discharge standards when treating wastewater containing heavy metal ions, recalcitrant organic matter, and special pollutants.

[0003] To improve the overall treatment performance of polyaluminum chloride (PAC), researchers have proposed several composite technical routes. For example, the existing technology CN202311218977.6 discloses a method for preparing PAC water purifier from aluminum sludge. This technology involves ball milling, washing, and acid hydrolysis of aluminum sludge to obtain an aluminum-containing solution, then adding calcium aluminate to adjust the aluminum content of the solution and aging it to prepare PAC. Cationic polyacrylamide and 2-ethylhexyl acrylate are then added to prepare a PAC flocculant. Simultaneously, modified carbon adsorbent material prepared from bamboo fiber loaded with magnesium aluminum hydrotalcite and catechol-modified cotton fiber oil adsorbent are used, ultimately resulting in a PAC water purifier with excellent adsorption, sedimentation, and temperature difference adaptability. Although this technology performs well in traditional flocculation treatment and oil removal, achieving effective reuse of aluminum resources, it still has significant technical limitations: First, this technology mainly relies on physical adsorption and traditional flocculation and sedimentation mechanisms, lacking specific chelation and selective binding capabilities for dissolved heavy metal ions, and cannot effectively treat Cu. 2+ Pb 2+ Cd 2+ Firstly, the modified carbon materials and oil adsorbents in this technology are mainly for oil pollutants and suspended particles. The treatment mechanism for heavy metal ions is singular and still relies on traditional physicochemical precipitation methods. The treatment effect and stability are insufficient, making it difficult to meet the increasingly stringent heavy metal emission standards. Summary of the Invention

[0004] In view of this, the present invention proposes a method for preparing an industrial composite polyaluminum chloride water treatment agent to solve the technical problem that existing polyaluminum chloride water treatment agents have limited effectiveness in treating complex industrial wastewater and are difficult to achieve stable and efficient synergistic treatment of heavy metal pollutants.

[0005] The technical solution of this invention is achieved as follows: This invention provides a method for preparing an industrial composite polyaluminum chloride water treatment agent, characterized in that the preparation method includes the following steps: S1. Under nitrogen protection, 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in anhydrous DMF, and oxalyl chloride was added under ice bath cooling. After the addition was complete, the reaction was continued at room temperature for 4-6 hours to obtain the intermediate.

[0006] S2. Dissolve the intermediate in anhydrous DMF, add triethylamine and fucoidan under a nitrogen atmosphere and ice bath, heat to 40-50℃, and react for 12-24 h to obtain modified fucoidan. S3. Bentonite-supported polyaluminum chloride is dispersed in toluene, vinyl silane coupling agent and water are added, and the reaction is carried out to obtain modified polyaluminum chloride; S4. Disperse the modified polyaluminum chloride in a DMF / water mixed solvent, add the modified fucoidan and benzophenone, and react under ultraviolet light at 50-60℃ for 6-8 hours to obtain the composite polyaluminum chloride water treatment agent.

[0007] Specifically, in step S1, an amide bond is formed by the reaction of amino groups with oxalyl chloride, while retaining the thiol group and the acyl chloride group at the other end. The intermediate prepared provides an active reaction site for the subsequent grafting reaction. In step S2, the abundant hydroxyl groups on the fucoidan molecular chain are used to carry out a heterogeneous grafting reaction with the acyl chloride group of the intermediate to achieve covalent grafting of the thiadiazole group onto the fucoidan backbone. Triethylamine acts as an acid-binding agent to maintain the stability of the reaction system. The modified fucoidan prepared has both the bioactivity of fucoidan and the chelating function of thiadiazole. In step S3, vinyl functional groups are introduced into the surface of bentonite-supported polyaluminum chloride through the hydrolysis and condensation reaction of the vinyl silane coupling agent. The coupling agent acts as a molecular bridge, which not only enhances the binding force between the carrier and the functional molecule, but also provides a reaction site for the subsequent photochemical reaction. In step S4, the thiol group on the modified fucoidan undergoes an addition reaction with the vinyl group on the surface of the modified polyaluminum chloride to achieve covalent bonding between the two phases.

[0008] Overall, in this invention, the introduction of a thiadiazole group serves two purposes: firstly, it acts as a rigid structure to promote the exposure of active groups on fucoidan; secondly, it acts as a strong chelating unit for Cu. 2+ Pb 2+ Cd 2+The polyaluminum chloride (PAC) exhibits excellent selective binding capacity for heavy metal ions. Fucoidan, as a bioactive carrier, complements the flocculation mechanism of PAC with its sulfate groups, achieving rapid flocculation while significantly enhancing the treatment capacity for heavy metal ions. Furthermore, the sulfate and hydroxyl groups abundant in fucoidan can form multiple chelate systems with thiadiazole groups, significantly improving the treatment efficiency for complex heavy metal pollutants. Bentonite-supported PAC plays a dual role: PAC provides highly efficient flocculation performance to treat various pollutants in industrial wastewater, including suspended solids, colloidal substances, organic pollutants, and some heavy metal ions; bentonite, as an inorganic carrier, enhances the mechanical strength and dispersion stability of the material. Through covalent bonding technology, organic functional molecules and the inorganic carrier form a stable three-dimensional network structure, effectively avoiding the loss and detachment of functional components in traditional physical mixing methods. The components achieve ordered arrangement and functional complementarity at the molecular level, maintaining the rapid flocculation characteristics of PAC while significantly enhancing the treatment capacity for heavy metal ions, providing technical support for the efficient purification of complex industrial wastewater.

[0009] Based on the above technical solutions, preferably, in step S1, the molar ratio of 2-amino-5-mercapto-1,3,4-thiadiazole and oxalyl chloride is 1:1.2-1.5.

[0010] Based on the above technical solution, preferably, in step S2, the mass ratio of fucoidan, intermediate and triethylamine is 100:30-50:5-15.

[0011] Based on the above technical solutions, preferably, in step S3, the preparation method of bentonite-supported polyaluminum chloride includes: Bentonite and sodium-modifying agent are added to water and mixed evenly to obtain a bentonite suspension; polyaluminum chloride is added to the bentonite suspension and reacted to obtain bentonite-supported polyaluminum chloride.

[0012] Specifically, sodium ions enter the interlayer structure of bentonite through cation exchange, transforming natural bentonite into sodium-based bentonite, significantly enhancing its interlayer swelling and dispersion stability. Then, through electrostatic attraction and ion exchange between polyaluminum chloride (PAC) and the negatively charged sites on the bentonite surface and interlayer, uniform dispersion and stable loading of PAC are achieved on the bentonite carrier. This loaded structure allows PAC to make more thorough contact with water, improving flocculation efficiency. Simultaneously, the adsorption properties of bentonite itself complement the flocculation effect of PAC, enhancing the comprehensive treatment effect on suspended solids, organic matter, and other pollutants.

[0013] Based on the above technical solutions, the preferred mass ratio of bentonite, sodium chelating agent and polyaluminum chloride is 100:2-5:30-60.

[0014] Based on the above technical solutions, preferably, the sodium-containing agent is sodium chloride or sodium carbonate.

[0015] Based on the above technical solutions, preferably, in step S3, the mass ratio of bentonite-supported polyaluminum chloride and vinyl silane coupling agent is 100:10-20.

[0016] Based on the above technical solutions, preferably, in step S3, the vinyl silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane.

[0017] Based on the above technical solutions, preferably, in step S4, the mass ratio of modified polyaluminum chloride, modified fucoidan, and benzophenone is 100:30-60:1-5.

[0018] This invention provides an industrial composite polyaluminum chloride water treatment agent, which is prepared by the preparation method described above.

[0019] The industrial composite polyaluminum chloride water treatment agent of the present invention has the following advantages over the prior art: This invention constructs a stable composite system of thiadiazole-fucose-bentonite-supported polyaluminum chloride, in which the nitrogen and sulfur heteroatoms of the thiadiazole group and the sulfate and hydroxyl groups of the fucoidan form a functionally complementary dual chelate system, significantly enhancing the resistance to Cu. 2+ Pb 2+ Cd 2+ The modified fucoidan enhances the binding capacity and selectivity of heavy metal ions. Simultaneously, the bioactivity of fucoidan complements the inorganic flocculation mechanism of polyaluminum chloride (PAC), maintaining the high flocculation efficiency of PAC for suspended solids and organic matter while significantly improving its selective treatment capacity for heavy metal ions. This achieves a synergistic effect of "rapid flocculation + precise chelation," providing a comprehensive and efficient treatment solution for complex industrial wastewater. Furthermore, by covalently binding the thiol groups on the modified fucoidan with the vinyl groups on the surface of bentonite-supported PAC, a strong binding force between the organic functional molecules and the inorganic carrier is ensured, effectively preventing the detachment and loss of functional components during use. Detailed Implementation

[0020] 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 a part of the embodiments of the present invention, and not all of the 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.

[0021] Example 1

[0022] This embodiment provides a method for preparing an industrial composite polyaluminum chloride water treatment agent, the preparation method including the following steps: (1) Under nitrogen protection, 133g of 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in 500ml of anhydrous DMF. 178g of oxalyl chloride was added in an ice bath (0-5℃). The addition time was controlled at 1.5h. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 5h. After the reaction was completed, the reaction solution was poured into ice water to precipitate the solid. The solid was filtered, washed with deionized water until neutral, and dried under vacuum to obtain the intermediate. (2) Dissolve 40g of the intermediate in 500ml of anhydrous DMF. Under a nitrogen atmosphere, add 10g of triethylamine and 100g of fucoidan in an ice bath (0-5℃). Heat to 45℃ and react for 18h. After the reaction is complete, slowly pour the reaction solution into ice water to precipitate the solid, which is then collected by filtration. Wash the solid with acetone and anhydrous ethanol in sequence, and then wash with deionized water until neutral. Dissolve the washed solid in deionized water and dialyze for 72h, changing the dialysate every 12h. Freeze-dry to obtain modified fucoidan. (3) Add 100g of bentonite and 3.5g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 45g of polyaluminum chloride in 200nl of deionized water to prepare a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 5h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (4) 100g of bentonite-supported polyaluminum chloride was dispersed in 400ml of toluene, 15g of vinyltrimethoxysilane and 8ml of water were added, and the mixture was refluxed at 85℃ for 7h. After the reaction was completed, the modified polyaluminum chloride was obtained by centrifugation, washing and drying. (5) Disperse 100g of modified polyaluminum chloride in 300ml of DMF / water mixed solvent (DMF to water volume ratio of 4:1), add 45g of modified fucoidan and 3g of benzophenone, and ultrasonically disperse evenly. Under nitrogen protection and ultraviolet light irradiation (365nm, light intensity of 20mW / cm²), the mixture is then subjected to further processing. 2 The reaction was carried out at 55℃ for 7 hours. After the reaction was completed, the product was separated by centrifugation, washed and dried to obtain the composite polyaluminum chloride water treatment agent.

[0023] Example 2

[0024] This embodiment provides a method for preparing an industrial composite polyaluminum chloride water treatment agent, the preparation method including the following steps: (1) Under nitrogen protection, 133g of 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in 500ml of anhydrous DMF. 152g of oxalyl chloride was added in an ice bath (0-5℃). The addition time was controlled at 1.5h. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 4h. After the reaction was completed, the reaction solution was poured into ice water to precipitate the solid. The solid was filtered, washed with deionized water until neutral, and dried under vacuum to obtain the intermediate. (2) Dissolve 30g of the intermediate in 500ml of anhydrous DMF. Under a nitrogen atmosphere, add 5g of triethylamine and 100g of fucoidan in an ice bath (0-5℃). Heat to 40℃ and react for 24h. After the reaction is complete, slowly pour the reaction solution into ice water to precipitate the solid, which is then collected by filtration. Wash the solid with acetone and anhydrous ethanol in sequence, and then wash with deionized water until neutral. Dissolve the washed solid in deionized water and dialyze for 72h, changing the dialysate every 12h. Freeze-dry to obtain modified fucoidan. (3) Add 100g of bentonite and 2g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 30g of polyaluminum chloride in 200nl of deionized water to make a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 4h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (4) 100g of bentonite-supported polyaluminum chloride was dispersed in 400ml of toluene, 10g of vinyltrimethoxysilane and 10ml of water were added, and the mixture was refluxed at 80℃ for 8h. After the reaction was completed, the modified polyaluminum chloride was obtained by centrifugation, washing and drying. (5) Disperse 100g of modified polyaluminum chloride in 300ml of DMF / water mixed solvent (DMF to water volume ratio of 4:1), add 30g of modified fucoidan and 1g of benzophenone, and ultrasonically disperse evenly. Under nitrogen protection and ultraviolet light irradiation (365nm, light intensity of 20mW / cm²), the mixture is then subjected to further processing. 2 The reaction was carried out at 50℃ for 8 hours. After the reaction was completed, the product was separated by centrifugation, washed and dried to obtain the composite polyaluminum chloride water treatment agent.

[0025] Example 3

[0026] This embodiment provides a method for preparing an industrial composite polyaluminum chloride water treatment agent, the preparation method including the following steps: (1) Under nitrogen protection, 133g of 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in 500ml of anhydrous DMF. 190g of oxaloyl chloride was added in an ice bath (0-5℃). The addition time was controlled at 1.5h. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 6h. After the reaction was completed, the reaction solution was poured into ice water to precipitate the solid. The solid was filtered, washed with deionized water until neutral, and dried under vacuum to obtain the intermediate. (2) Dissolve 50g of the intermediate in 500ml of anhydrous DMF. Under a nitrogen atmosphere, add 15g of triethylamine and 100g of fucoidan in an ice bath (0-5℃). Heat to 50℃ and react for 12h. After the reaction is complete, slowly pour the reaction solution into ice water to precipitate the solid, which is then collected by filtration. Wash the solid successively with acetone and anhydrous ethanol, and then with deionized water until neutral. Dissolve the washed solid in deionized water and dialyze for 72h, changing the dialysate every 12h. Freeze-dry to obtain modified fucoidan. (3) Add 100g of bentonite and 5g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 60g of polyaluminum chloride in 200nl of deionized water to make a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 6h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (4) 100g of bentonite-supported polyaluminum chloride was dispersed in 400ml of toluene, 20g of vinyltrimethoxysilane and 10ml of water were added, and the mixture was refluxed at 90℃ for 6h. After the reaction was completed, the modified polyaluminum chloride was obtained by centrifugation, washing and drying. (5) Disperse 100g of modified polyaluminum chloride in 300ml of DMF / water mixed solvent (DMF to water volume ratio of 4:1), add 60g of modified fucoidan and 5g of benzophenone, and ultrasonically disperse evenly. Under nitrogen protection and ultraviolet light irradiation (365nm, light intensity of 20mW / cm²), the mixture is then subjected to further processing. 2 The reaction was carried out at 60℃ for 6 hours. After the reaction was completed, the product was separated by centrifugation, washed and dried to obtain the composite polyaluminum chloride water treatment agent.

[0027] Comparative Example 1 This comparative example provides a method for preparing an industrial composite polyaluminum chloride water treatment agent, specifically including the following steps: (1) Add 100g of bentonite and 3.5g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 45g of polyaluminum chloride in 200nl of deionized water to make a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 5h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (2) 100g of bentonite-supported polyaluminum chloride, 45g of fucoidan, and 14.2g of 2-amino-5-mercapto-1,3,4-thiadiazole were sequentially added to a high-speed mixer and physically mixed at 1000 rpm for 7 hours at room temperature to obtain a physically blended water treatment agent. The mass of raw materials used was consistent with the theoretical feed amount of each component in Example 1.

[0028] Comparative Example 2 This comparative example provides a method for preparing an industrial composite polyaluminum chloride water treatment agent. The preparation method is the same as in Example 1, except that the fucoidan is not modified. The specific steps include: (1) Add 100g of bentonite and 3.5g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 45g of polyaluminum chloride in 200nl of deionized water to make a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 5h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (2) 100g of bentonite-supported polyaluminum chloride was dispersed in 400ml of toluene, 15g of vinyltrimethoxysilane and 8ml of water were added, and the mixture was refluxed at 85℃ for 7h. After the reaction was completed, the modified polyaluminum chloride was obtained by centrifugation, washing and drying. (3) Disperse 100g of modified polyaluminum chloride in 300ml of DMF / water mixed solvent (DMF to water volume ratio of 4:1), add 45g of fucoidan and 3g of benzophenone, and ultrasonically disperse evenly. Under nitrogen protection and ultraviolet light irradiation (365nm, light intensity of 20mW / cm²), the mixture is then subjected to further processing. 2 The reaction was carried out at 55℃ for 7 hours. After the reaction was completed, the product was separated by centrifugation, washed and dried to obtain the composite polyaluminum chloride water treatment agent.

[0029] Comparative Example 3 This comparative example provides a method for preparing an industrial composite polyaluminum chloride water treatment agent. The preparation method is the same as in Example 1, except that chitosan is replaced with fucoidan. The specific steps include: (1) Under nitrogen protection, 133g of 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in 500ml of anhydrous DMF. 178g of oxalyl chloride was added in an ice bath (0-5℃). The addition time was controlled at 1.5h. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 5h. After the reaction was completed, the reaction solution was poured into ice water to precipitate the solid. The solid was filtered, washed with deionized water until neutral, and dried under vacuum to obtain the intermediate. (2) Dissolve 40g of the intermediate in 500ml of anhydrous DMF. Under a nitrogen atmosphere, add 10g of triethylamine and 100g of fucoidan in an ice bath (0-5℃). Heat to 45℃ and react for 18h. After the reaction is complete, slowly pour the reaction solution into ice water to precipitate the solid, which is then collected by filtration. Wash the solid with acetone and anhydrous ethanol in sequence, and then wash with deionized water until neutral. Dissolve the washed solid in deionized water and dialyze for 72h, changing the dialysate every 12h. Freeze-dry to obtain modified fucoidan. (3) Add 100g of bentonite and 3.5g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 45g of polyaluminum chloride in 200nl of deionized water to prepare a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 5h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (4) 100g of bentonite-supported polyaluminum chloride was dispersed in 400ml of toluene, 15g of vinyltrimethoxysilane and 8ml of water were added, and the mixture was refluxed at 85℃ for 7h. After the reaction was completed, the modified polyaluminum chloride was obtained by centrifugation, washing and drying. (5) Disperse 100g of modified polyaluminum chloride in 300ml of DMF / water mixed solvent (DMF to water volume ratio of 4:1), add 45g of modified chitosan and 3g of benzophenone, and ultrasonically disperse evenly. Under nitrogen protection and ultraviolet light irradiation (365nm, light intensity of 20mW / cm²), the mixture is then subjected to further processing. 2 The reaction was carried out at 55℃ for 7 hours. After the reaction was completed, the product was separated by centrifugation, washed and dried to obtain the composite polyaluminum chloride water treatment agent.

[0030] Comparative Example 4 This comparative example provides a method for preparing an industrial composite polyaluminum chloride water treatment agent, specifically including the following steps: (1) Under nitrogen protection, 133g of 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in 500ml of anhydrous DMF. 178g of oxalyl chloride was added in an ice bath (0-5℃). The addition time was controlled at 1.5h. After the addition was completed, the temperature was raised to room temperature and the reaction continued for 5h. After the reaction was completed, the reaction solution was poured into ice water to precipitate the solid. The solid was filtered, washed with deionized water until neutral, and dried under vacuum to obtain the intermediate. (2) Dissolve 40g of the intermediate in 500ml of anhydrous DMF. Under a nitrogen atmosphere, add 10g of triethylamine and 100g of fucoidan in an ice bath (0-5℃). Heat to 45℃ and react for 18h. After the reaction is complete, slowly pour the reaction solution into ice water to precipitate the solid, which is then collected by filtration. Wash the solid with acetone and anhydrous ethanol in sequence, and then wash with deionized water until neutral. Dissolve the washed solid in deionized water and dialyze for 72h, changing the dialysate every 12h. Freeze-dry to obtain modified fucoidan. (3) Add 100g of bentonite and 3.5g of sodium chloride to 800ml of deionized water and stir at room temperature for 2h to disperse them fully, thus obtaining a bentonite suspension; dissolve 45g of polyaluminum chloride in 200nl of deionized water to prepare a solution, and then slowly add it to the bentonite suspension with stirring, and react at room temperature for 5h. After the reaction is completed, centrifuge, wash and dry to obtain bentonite-supported polyaluminum chloride; (4) Add 100g of bentonite-supported polyaluminum chloride and 45g of modified fucoidan to a high-speed mixer and physically mix at 1000rpm for 7h at room temperature to obtain a physically blended water treatment agent. The mass of modified fucoidan and bentonite-supported polyaluminum chloride used is consistent with the feed amount in Example 1.

[0031] Performance testing Performance tests were conducted on the examples and comparative examples. Industrial wastewater was used for treatment. The COD concentration in the wastewater was 280 mg / L, and the heavy metal pollutants included chromium, cadmium, copper, lead, and nickel. The chromium content was 25.4 mg / L, cadmium content was 72.8 mg / L, copper content was 112.8 mg / L, lead content was 32.5 mg / L, and nickel content was 12 mg / L. The amount of composite polyaluminum chloride water treatment agent added was 4% of the mass of industrial wastewater. The test indicators included the treatment efficiency of COD and heavy metal pollutants. The treatment efficiency = (pollutant content before treatment - pollutant content after treatment) / pollutant content before treatment × 100%. The test results are shown in Table 1.

[0032] Table 1 Performance Testing

[0033] As shown in Table 1, the composite polyaluminum chloride water treatment agent prepared by the technical solution of the present invention significantly improves the removal efficiency of COD and heavy metal pollutants. The removal efficiencies of Comparative Examples 1-4 are all low. The reasons for this are as follows: In Comparative Example 1, the preparation method used physical blending caused the polyaluminum chloride to prematurely encapsulate the fucoidan, resulting in the shielding of the active functional groups of the fucoidan and its inability to effectively adsorb, thus significantly reducing the treatment efficiency for COD and heavy metal ions; in Comparative Example 2, the fucoidan was unmodified, resulting in poor bonding stability with the carrier; simultaneously, its flexible polysaccharide segments are prone to folding and self-shielding, causing the active functional groups such as sulfate ester groups to be shielded and unable to be fully exposed to the water, thus reducing the effectiveness of the treatment of heavy metal ions, especially copper and cadmium. The treatment efficiency of the ions decreased significantly. In Comparative Example 3, chitosan was used to replace fucoidan. Although chitosan has active groups such as amino groups, it lacks sulfur-containing functional groups such as sulfate ester groups unique to fucoidan. Its chelation selectivity and binding strength for heavy metal ions are not as good as those of fucoidan, especially for heavy metal ions that require a soft coordination environment. In Comparative Example 4, the modified fucoidan and the carrier were only physically blended and lacked stable covalent bonds. During use, the functional components were easy to detach from the carrier surface, which reduced the stability and durability of the composite material and resulted in low treatment efficiency.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an industrial composite polyaluminum chloride water treatment agent, characterized in that: The preparation method includes the following steps: S1. Under nitrogen protection, 2-amino-5-mercapto-1,3,4-thiadiazole was dissolved in anhydrous DMF, and oxalyl chloride was added under ice bath cooling. After the addition was complete, the reaction was continued at room temperature for 4-6 hours to obtain the intermediate. S2. Dissolve the intermediate in anhydrous DMF, add triethylamine and fucoidan under a nitrogen atmosphere and ice bath, heat to 40-50℃, and react for 12-24 h to obtain modified fucoidan. S3. Bentonite-supported polyaluminum chloride is dispersed in toluene, and vinyl silane coupling agent and water are added to react and obtain modified polyaluminum chloride. S4. Disperse the modified polyaluminum chloride in a DMF / water mixed solvent, add the modified fucoidan and benzophenone, and react under ultraviolet light at 50-60℃ for 6-8 hours to obtain the composite polyaluminum chloride water treatment agent.

2. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 1, characterized in that: In step S1, the molar ratio of 2-amino-5-mercapto-1,3,4-thiadiazole to oxalyl chloride is 1:1.2-1.

5.

3. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 1, characterized in that: In step S2, the mass ratio of fucoidan, intermediate, and triethylamine is 100:30-50:5-15.

4. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 1, characterized in that: In step S3, the method for preparing bentonite-supported polyaluminum chloride includes: Bentonite and sodium-modifying agent are added to water and mixed evenly to obtain a bentonite suspension; polyaluminum chloride is added to the bentonite suspension and reacted to obtain bentonite-supported polyaluminum chloride.

5. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 4, characterized in that: The mass ratio of bentonite, sodium chelating agent and polyaluminum chloride is 100:2-5:30-60.

6. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 4, characterized in that: The sodium-containing agent is sodium chloride or sodium carbonate.

7. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 1, characterized in that: In step S3, the mass ratio of bentonite-supported polyaluminum chloride to vinylsilane coupling agent is 100:10-20.

8. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 1, characterized in that: In step S3, the vinyl silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane.

9. The method for preparing an industrial composite polyaluminum chloride water treatment agent as described in claim 1, characterized in that: In step S4, the mass ratio of modified polyaluminum chloride, modified fucoidan, and benzophenone is 100:30-60:1-5.

10. An industrial composite polyaluminum chloride water treatment agent, characterized in that: The composite polyaluminum chloride water treatment agent is prepared using the preparation method described in any one of claims 1-9.

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