A multifunctional water-purifying gel material and preparation method thereof

Abstract

The present invention belongs to the technical field of water purification materials, and specifically relates to a multifunctional water purification gel material and its preparation method. The material is composed of an outer film, a middle skeleton, and an inner carbon core; the outer film raw materials include sodium alginate, carboxymethyl starch, NaCl, and Tween-20; the middle skeleton raw materials include chitosan, modified sodium bentonite, and Fe-P nanopowder; and the inner carbon core raw materials include rice husk biochar, nano-CaCO3, FeCl3·6H2O, and FeSO4·7H2O. The present invention achieves efficient water purification through a three-layer synergistic structure. The outer Ca 2+ The cross-linked sodium alginate / carboxymethyl starch porous membrane intercepts particles and buffers metal ions; the middle layer integrates chitosan to chelate heavy metals, CTAB-bentonite to electrostatically adsorb anions, and Fe-P nanoparticles to precipitate phosphate / arsenate; the inner layer of biochar-Fe3O4 complex provides deep adsorption and catalytic oxidation functions.

Description

Technical Field

[0001] The present invention belongs to the technical field of water purification materials, and in particular relates to a multifunctional water purification gel material and a preparation method thereof. Background Art

[0002] At present, commonly used traditional sewage treatment technologies, such as activated sludge, biochemical oxidation, and chemical precipitation, have achieved certain results in removing most conventional pollutants, but their efficiency in treating difficult-to-degrade pollutants and high-concentration heavy metal ions is still limited. In addition, traditional methods often have high energy consumption and expensive operating costs, and are prone to produce large amounts of sludge or residual monomers during the treatment process, posing a risk of secondary pollution. Faced with the increasingly severe dual challenges of water shortage and water pollution, there is an urgent need for a new type of water purification material that is efficient, low-consumption, easy to operate, and environmentally friendly. Hydrogels are hailed as an ideal water purification material platform due to their three-dimensional porous network structure and excellent biomimetic properties. In early studies, although single-component hydrogels based on sodium alginate (SA) or polyvinyl alcohol (PVA) have certain adsorption capabilities, their mechanical strength is insufficient and the adsorption capacity is limited. Under dynamic water flow conditions, pure SA hydrogels are prone to structural rupture, and traditional physically cross-linked gels have a low maximum adsorption capacity for heavy metal ions, making it difficult to meet the requirements of high-concentration wastewater treatment. At the same time, these materials lack specific recognition of pollutants, resulting in treatment efficiency being greatly affected by water composition and environmental conditions (such as pH value and ionic strength). Even some chemical cross-linkers may have residual toxicity during the synthesis process, thereby bringing new environmental risks. Therefore, based on the above problems, it is extremely necessary to develop a multifunctional clean hydrogel material with both high mechanical strength and long-term stability. Summary of the Invention

[0003] In view of the defects of the prior art, the object of the present invention is to provide a multifunctional hydrogel material and a preparation method thereof.

[0004] The technical effect of the present invention is achieved through the following technical scheme: a multifunctional hydrogel material, which consists of an outer film, a middle skeleton and an inner carbon core; the raw materials of the outer film include, by weight, 8 to 10 parts of sodium alginate, 6 to 8 parts of carboxymethyl starch, 0.4 to 0.6 parts of NaCl and 0.03 to 0.05 parts of Tween-20; the raw materials of the middle skeleton include, by weight, 10 to 15 parts of chitosan, 10 to 15 parts of modified sodium bentonite, and 1 to 1.5 parts of Fe-P nanopowder; the raw materials of the inner carbon core include, by weight, 38 to 45 parts of rice husk biochar, 10 to 12 parts of nano-CaCO3, 2 to 3 parts of FeCl3·6H2O and 1 to 2 parts of FeSO4·7H2O.

[0005] Preferably, the specific preparation steps of the Fe-P nanopowder are as follows:

[0006] S1: Dissolve FeCl3·6H2O in deionized water and stir to dissolve evenly to obtain 0.1M Fe 3+ Solution: Dissolve KH2PO4 in deionized water and stir to dissolve evenly to obtain 0.1M PO4 3- solution;

[0007] S2: Add 0.1M Fe 3+ The solution was heated to 70°C and stirred at 500 rpm, and then the 0.1 M PO4 solution from step S1 was slowly added dropwise at a rate of 1 mL / min. 3- The solution was added dropwise and the pH was adjusted to 6.5-7 using 1M NaOH solution. After the addition was completed, the mixture was stirred at 70°C and 500 rpm for 2-3 hours.

[0008] S3: After the aging treatment in step S2 is completed, the mixture is centrifuged at 8000 rpm for 10-15 minutes, the precipitate is collected, washed five times with deionized water, dried under vacuum at 60°C for 12-16 hours, and crushed and sieved through a 200-mesh sieve to obtain Fe-P nanopowder;

[0009] Preferably, in step S2, the Fe 3+ Solution and PO4 3- The volume ratio of the solution is 1:1;

[0010] Preferably, the specific preparation steps of the modified sodium bentonite are as follows:

[0011] S101: sodium bentonite is added to deionized water, stirred and dispersed uniformly at 60° C., and a 1M HCl solution is added dropwise to adjust the pH to 4.5-5.5 to obtain a sodium bentonite dispersion; hexadecyltrimethylammonium bromide is added to deionized water, stirred and dissolved uniformly at 50-60° C. to obtain a CTAB solution;

[0012] S102: slowly adding the CTAB solution dropwise to the sodium bentonite dispersion, stirring at 500 rpm at 60° C. for 2-4 hours, and after the reaction is completed, adding 1 M NaOH solution dropwise to adjust the pH to 7, centrifuging, filtering, washing with deionized water, drying at 80° C. for 12-16 hours, and sieving through a 200-mesh sieve to obtain modified sodium bentonite;

[0013] Preferably, in step S101, the ratio of the amount of the sodium bentonite to the amount of deionized water is 1-1.2 g:10 mL; the ratio of the amount of the hexadecyltrimethylammonium bromide to the amount of deionized water is 1.4-1.5 g:50 mL;

[0014] Preferably, in step S102, the volume ratio of the CTAB solution to the sodium bentonite dispersion is 1.5:1;

[0015] Preferably, another aspect of the present invention is to provide a method for preparing a multifunctional clean hydrogel material, comprising the following preparation steps:

[0016] S201: Add rice husk biochar to 5 parts by weight of deionized water, stir and disperse evenly, then add nano-CaCO3, ultrasonically disperse evenly, vacuum impregnate, add 0.05M FeCl3·6H2O solution and 0.025M FeSO4·7H2O solution, defoam with nitrogen, maintain nitrogen atmosphere at 60°C and stir for 20-30 minutes, then add 2M NaOH solution dropwise to adjust the pH to 9.5-10, continue aging at 60°C for 30-50 minutes, centrifuge, remove the supernatant, wash with deionized water until neutral, calcined at 150-250°C in nitrogen atmosphere for 1-2 hours, screened through a 20-mesh sieve, and dried with hot air at 40°C for 2 hours to obtain an inner carbon core;

[0017] S202: dissolving chitosan in a 1 wt % glacial acetic acid solution to obtain a 3 wt % chitosan solution; adding modified sodium bentonite to deionized water and uniformly dispersing the mixture through ultrasonic treatment to obtain a 3 wt % modified bentonite dispersion; ultrasonically dispersing Fe-P nanopowder into the chitosan solution, and then combining the Fe-P nanopowder with the modified bentonite dispersion and stirring at 1000 rpm for 10 to 20 minutes to obtain an emulsion slurry;

[0018] S203: Add the inner carbon core of step S201 to a magnetic stirring container, add the emulsion slurry of step S202 dropwise, stir at 300-500 rpm for 10-15 minutes, and let it stand for 20-30 minutes; spray 1M NaOH solution at a ratio of 1-3 mL / g, let it stand for 10-20 minutes to solidify, and wash with deionized water until neutral to obtain coated beads;

[0019] S204: Sodium alginate and carboxymethyl starch are added to deionized water, and Tween-20 is added, stirred at 600 rpm for 30 to 60 minutes, and vacuum degassed for 10 minutes to obtain a 2.5 wt% composite solution. The coated beads of step S203 are immersed in the composite solution for 10 seconds, rotated at 300 rpm to degas for 20 seconds, sprayed with 1M CaCl2 solution at 1.5 mL / g, and allowed to stand for curing for 15 to 30 minutes. Then, 10 wt% NaCl solution is added for salting out and pore formation, and the beads are immersed in 0.05M CaCl2 solution for 1 to 3 minutes. The beads are washed with deionized water and dried with hot air at 40°C for 1 to 2 hours to obtain a clean hydrogel material.

[0020] Preferably, in step S201, the specific parameters of the vacuum impregnation are: vacuuming to 5-20 kPa and maintaining for 30-60 minutes before returning to normal pressure;

[0021] Preferably, in step S204, the specific parameters of the salting-out pore-inducing process are: treatment at 40° C. for 15 to 25 minutes, treatment at 50° C. for 30 to 50 minutes, and vacuum dehydration treatment at 60° C. for 20 to 30 minutes.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention utilizes sodium alginate / carboxymethyl starch film to pass through Ca 2+ Cross-linking and NaCl pore formation form a porous shell with stable thickness and pore size distribution in the order of several microns, through which water can freely pass, while larger suspended particles and bacteria are trapped on the membrane surface or pore mouths; at the same time, the carboxylic acid groups evenly distributed on the film reversibly coordinate with the metal ions entering the water, so that the metal ions are buffered to a lower concentration before flowing into the interior, thereby reducing the instantaneous load of the inner layer adsorption sites; the film as a whole is negatively charged, and this surface charge can inhibit the deposition of natural organic matter and prolong the time the material maintains flux and integrity under conditions of continuous water inflow for up to twenty days. When water enters the middle layer skeleton, the chitosan molecules are deprotonated after alkali solidification, and the free amino groups are reactive to Pb 2+ 、Cd 2+The CTAB-bentonite interwoven with chitosan provides a dual adsorption mechanism. On the one hand, the quaternary ammonium cations of CTAB impart a persistent positive charge to the bentonite sheets, enabling electrostatic adsorption of anionic dyes, phosphates, and various antibiotics. On the other hand, the intercalated hexadecyl chains increase the hydrophobic interlayer area, exhibiting a microphase extraction-like enrichment effect for hydrophobic organic pollutants. Furthermore, the Fe-P nanoparticles are uniformly embedded within the same framework network. Their surface hydroxyl groups can coordinate and precipitate with phosphate or arsenate, and are stably anchored within the framework, making them less susceptible to water removal during long-term operation. Due to the inherent positive electric field of the CTAB-bentonite, the negatively charged phosphates are first adsorbed at the periphery and then further bound to the Fe-P surface for precipitation. Within the same space, chitosan amino-metal coordination sites also exist. Once captured by chitosan, heavy metal ions form insoluble complexes with the phosphates to be precipitated at the Fe-P interface, reducing competition between the two pollutants and exhibiting synergistic adsorption behavior. Upon entering the innermost layer, the hierarchical pores of rice husk biochar and the graphite-sheet layers provide π-π and hydrophobic interaction sites, further enriching persistent organic matter. When CaCO3 particles encounter acidic wastewater or high concentrations of metal ions, they gradually dissolve, releasing carbonate ions and forming low-solubility carbonates with the metals. This process not only neutralizes the acid impact that may be caused by industrial wastewater but also precipitates some metal ions on the pore walls. Furthermore, Fe3O4 nanocrystals, obtained by FeCl3 / FeSO4 coprecipitation, are dispersed within the biochar pores, enabling solid-liquid separation within tens of seconds using a conventional permanent magnet. Fe3O4 also exhibits Fenton-like catalytic activity, generating hydroxyl radicals in the presence of trace amounts of hydrogen peroxide or dissolved oxygen, which in situ oxidatively decompose dye molecules already enriched in the biochar. The carbonate ions released by CaCO3 buffer maintain a near-neutral environment, preventing the Fenton reaction from causing a sharp drop in pH and damaging the outer layer structure.

[0024] In summary, the outer layer intercepts large particles and some metals, the middle layer uses the synergistic effect of positively charged CTAB sheets, amino chelation and Fe-P precipitation to efficiently capture anions and metal ions, and the inner layer uses a biochar-Fe3O4 combination to complete deep adsorption and catalytic oxidation. Each functional component used in the present invention is connected to the adjacent materials through electrostatic forces, hydrogen bonds or coordination bonds, rather than simple physical mixing, which significantly avoids the loss of active particles during operation; in the 20-day continuous water inflow simulation, the pollutant removal rate always remains at a high level, ensuring that the particle structure is not significantly damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 1 is a graph showing the calcium ion sustained release test results of the clean hydrogel materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 and 4;

[0027] Figure 2 The PO4 of the purified hydrogel materials prepared in Examples 1 to 3 and Comparative Examples 1 and 4 of the present invention after calcium ion sustained release test 3- Adsorption test result diagram;

[0028] Figure 3 1 is a graph showing the acid buffer test results of the clean hydrogel materials prepared in Example 1 and Comparative Examples 1 to 4 of the present invention;

[0029] Figure 4 1 is a graph showing the Pb2+ adsorption test results of the clean hydrogel materials prepared in Example 1 and Comparative Examples 1 to 4 of the present invention;

[0030] Figure 5 The CrO4 of the clean hydrogel material prepared in Example 1 and Comparative Examples 1 to 4 of the present invention 2- Adsorption test result diagram;

[0031] Figure 6 This is a SEM scanning electron microscope image of the clean hydrogel material prepared in Example 1 of the present invention after being subjected to a calcium ion sustained release test. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. It should be noted that unless otherwise specified, the raw materials involved in the present invention were purchased through conventional commercial channels.

[0033] Example 1: A multifunctional hydrogel material, which consists of an outer film, a middle skeleton and an inner carbon core; the raw materials of the outer film include, by weight: 9 parts of sodium alginate, 7 parts of carboxymethyl starch, 0.5 parts of NaCl and 0.04 parts of Tween-20; the raw materials of the middle skeleton include, by weight: 12 parts of chitosan, 12 parts of modified sodium bentonite, and 1.2 parts of Fe-P nanopowder; the raw materials of the inner carbon core include, by weight: 42 parts of rice husk biochar, 11 parts of nano-CaCO3, 2.5 parts of FeCl3·6H2O and 1.5 parts of FeSO4·7H2O.

[0034] 1. The specific preparation steps of Fe-P nanopowder are as follows:

[0035] S1: Dissolve 0.01 mol FeCl3·6H2O in 100 mL deionized water and stir to dissolve evenly to obtain 0.1 M Fe 3+ Solution: Dissolve 0.01 mol KH2PO4 in 100 mL deionized water and stir to dissolve evenly to obtain 0.1 M PO4 3- solution;

[0036] S2: Add 100 mL of 0.1 M Fe 3+ The solution was heated to 70°C and stirred at 500 rpm, and then 100 mL of 0.1 M PO4 from step S1 was slowly added dropwise at a rate of 1 mL / min. 3- The solution was added dropwise and the pH was adjusted to 6.5 using 1 M NaOH solution. After the addition was completed, the mixture was stirred at 70 ° C and 500 rpm for 2.5 h.

[0037] S3: After the aging treatment in step S2, the mixture was centrifuged at 8000 rpm for 12 min, the precipitate was collected, washed five times with deionized water, dried under vacuum at 60°C for 15 h, and crushed and sieved through a 200-mesh sieve to obtain Fe-P nanopowder;

[0038] 2. The specific preparation steps of modified sodium bentonite are as follows:

[0039] S101: 10 g of sodium bentonite was added to 100 mL of deionized water, stirred and dispersed at 60° C., and a 1 M HCl solution was added dropwise to adjust the pH to 5 to obtain a sodium bentonite dispersion. 4.2 g of hexadecyltrimethylammonium bromide was added to 150 mL of deionized water, stirred and dissolved at 55° C. to obtain a CTAB solution.

[0040] S102: 150 mL of CTAB solution was slowly added dropwise to 100 mL of sodium bentonite dispersion, and the mixture was stirred at 500 rpm at 60° C. for 3 h. After the reaction was completed, 1 M NaOH solution was added dropwise to adjust the pH to 7. The mixture was centrifuged, filtered, washed with deionized water, dried at 80° C. for 15 h, and sieved through a 200-mesh sieve to obtain modified sodium bentonite.

[0041] 3. The preparation steps of the multifunctional hydrogel material are as follows:

[0042] S201: Add rice husk biochar to 5 parts by weight of deionized water, stir and disperse evenly, then add nano-CaCO3, ultrasonically disperse evenly, evacuate to 10 kPa and maintain for 50 minutes, then return to normal pressure, add 0.05M FeCl3·6H2O solution and 0.025M FeSO4·7H2O solution, defoam with nitrogen, maintain nitrogen atmosphere at 60°C and stir for 25 minutes, then add 2M NaOH solution dropwise to adjust the pH to 9.5, continue aging at 60°C for 40 minutes, centrifuge, remove the supernatant, wash with deionized water until neutral, calcined at 200°C in nitrogen atmosphere for 1.5 hours, screened through a 20-mesh sieve, and dried with hot air at 40°C for 2 hours to obtain an inner carbon core;

[0043] S202: dissolving chitosan in a 1 wt % glacial acetic acid solution to obtain a 3 wt % chitosan solution; adding modified sodium bentonite to deionized water and uniformly dispersing the mixture through ultrasonic treatment to obtain a 3 wt % modified bentonite dispersion; ultrasonically dispersing Fe-P nanopowder into the chitosan solution, and then combining the Fe-P nanopowder with the modified bentonite dispersion and stirring at 1000 rpm for 15 minutes to obtain an emulsion slurry;

[0044] S203: The inner carbon core of step S201 was added to a magnetic stirring container, and the emulsion slurry of step S202 was added dropwise. After stirring at 500 rpm for 12 minutes, the mixture was allowed to stand for 25 minutes. 1M NaOH solution was sprayed at a ratio of 1.5 mL / g, and the mixture was allowed to stand for 15 minutes to solidify. The mixture was then washed with deionized water until neutral to obtain coated beads.

[0045] S204: Sodium alginate and carboxymethyl starch were added to deionized water, and Tween-20 was added, stirred at 600 rpm for 50 min, and vacuum degassed for 10 min to obtain a 2.5 wt% composite solution. The coated beads of step S203 were immersed in the composite solution for 10 s, rotated at 300 rpm for 20 s, sprayed with 1 M CaCl2 solution at 1.5 mL / g, and allowed to stand for solidification for 25 min. Then, 10 wt% NaCl solution was added for salting out and pore formation. The solution was treated at 40°C for 20 min, 50°C for 40 min, and vacuum dehydrated at 60°C for 25 min. The solution was soaked in 0.05 M CaCl2 solution for 2 min, washed with deionized water, and dried with hot air at 40°C for 1.5 h to obtain a clean hydrogel material.

[0046] Example 2: A multifunctional clean hydrogel material, which consists of an outer film, a middle skeleton and an inner carbon core; the raw materials of the outer film include, by weight: 8 parts of sodium alginate, 6 parts of carboxymethyl starch, 0.4 parts of NaCl and 0.03 parts of Tween-20; the raw materials of the middle skeleton include, by weight: 10 parts of chitosan, 10 parts of modified sodium bentonite, and 1 part of Fe-P nanopowder; the raw materials of the inner carbon core include, by weight: 38 parts of rice husk biochar, 10 parts of nano-CaCO3, 2 parts of FeCl3·6H2O and 1 part of FeSO4·7H2O.

[0047] 1. The specific preparation steps of Fe-P nanopowder are as follows:

[0048] S1: Dissolve 0.01 mol FeCl3·6H2O in 100 mL deionized water and stir to dissolve evenly to obtain 0.1 M Fe 3+ Solution: Dissolve 0.01 mol KH2PO4 in 100 mL deionized water and stir to dissolve evenly to obtain 0.1 M PO4 3- solution;

[0049] S2: Add 100 mL of 0.1 M Fe 3+ The solution was heated to 70°C and stirred at 500 rpm, and then 100 mL of 0.1 M PO4 from step S1 was slowly added dropwise at a rate of 1 mL / min. 3- The solution was added dropwise and the pH was adjusted to 7 using 1 M NaOH solution. After the addition was completed, the mixture was stirred at 70 ° C and 500 rpm for 2 h.

[0050] S3: After the aging treatment in step S2, the mixture was centrifuged at 8000 rpm for 10 min, the precipitate was collected, washed five times with deionized water, dried under vacuum at 60°C for 12 h, and crushed and sieved through a 200-mesh sieve to obtain Fe-P nanopowder;

[0051] 2. The specific preparation steps of modified sodium bentonite are as follows:

[0052] S101: 11 g of sodium bentonite was added to 100 mL of deionized water, stirred and dispersed at 60° C., and a 1 M HCl solution was added dropwise to adjust the pH to 5.5 to obtain a sodium bentonite dispersion. 4.3 g of hexadecyltrimethylammonium bromide was added to 150 mL of deionized water, stirred and dissolved at 50° C. to obtain a CTAB solution.

[0053] S102: 150 mL of CTAB solution was slowly added dropwise to 100 mL of sodium bentonite dispersion, and the mixture was stirred at 500 rpm at 60° C. for 2 h. After the reaction was completed, 1 M NaOH solution was added dropwise to adjust the pH to 7. The mixture was centrifuged, filtered, washed with deionized water, dried at 80° C. for 12 h, and sieved through a 200-mesh sieve to obtain modified sodium bentonite.

[0054] 3. The preparation steps of the multifunctional hydrogel material are as follows:

[0055] S201: Add rice husk biochar to 5 parts by weight of deionized water, stir and disperse evenly, then add nano-CaCO3, ultrasonically disperse evenly, evacuate to 20 kPa and maintain for 60 minutes, then return to normal pressure, add 0.05M FeCl3·6H2O solution and 0.025M FeSO4·7H2O solution, defoam with nitrogen, maintain nitrogen atmosphere at 60°C and stir for 20 minutes, then add 2M NaOH solution dropwise to adjust the pH to 9.8, continue aging at 60°C for 30 minutes, centrifuge, remove the supernatant, wash with deionized water until neutral, calcined at 150°C in nitrogen atmosphere for 2 hours, screened through a 20-mesh sieve, and dried with hot air at 40°C for 2 hours to obtain an inner carbon core;

[0056] S202: dissolving chitosan in a 1 wt % glacial acetic acid solution to obtain a 3 wt % chitosan solution; adding modified sodium bentonite to deionized water and uniformly dispersing the mixture through ultrasonic treatment to obtain a 3 wt % modified bentonite dispersion; ultrasonically dispersing Fe-P nanopowder into the chitosan solution, and then combining the Fe-P nanopowder with the modified bentonite dispersion and stirring at 1000 rpm for 10 minutes to obtain an emulsion slurry;

[0057] S203: The inner carbon core of step S201 was added to a magnetic stirring container, and the emulsion slurry of step S202 was added dropwise. After stirring at 300 rpm for 15 minutes, the mixture was allowed to stand for 20 minutes. 1M NaOH solution was sprayed at a ratio of 1 mL / g, and the mixture was allowed to stand for 10 minutes to solidify. The mixture was then washed with deionized water until neutral to obtain coated beads.

[0058] S204: Sodium alginate and carboxymethyl starch were added to deionized water, and Tween-20 was added, stirred at 600 rpm for 30 minutes, and vacuum degassed for 10 minutes to obtain a 2.5 wt% composite solution. The coated beads of step S203 were immersed in the composite solution for 10 seconds, rotated at 300 rpm for 20 seconds, sprayed with 1M CaCl2 solution at 1.5 mL / g, and allowed to stand for solidification for 15 minutes. Then, 10 wt% NaCl solution was added for salting out and pore formation. The solution was treated at 40°C for 15 minutes, 50°C for 30 minutes, and vacuum dehydrated at 60°C for 20 minutes. The solution was soaked in 0.05 MCaCl2 solution for 1 minute, washed with deionized water, and dried with hot air at 40°C for 1 hour to obtain a clean hydrogel material.

[0059] Example 3: A multifunctional hydrogel material, which consists of an outer film, a middle skeleton and an inner carbon core; the raw materials of the outer film include, by weight: 10 parts of sodium alginate, 8 parts of carboxymethyl starch, 0.6 parts of NaCl and 0.05 parts of Tween-20; the raw materials of the middle skeleton include, by weight: 15 parts of chitosan, 15 parts of modified sodium bentonite, and 1.5 parts of Fe-P nanopowder; the raw materials of the inner carbon core include, by weight: 45 parts of rice husk biochar, 12 parts of nano-CaCO3, 3 parts of FeCl3·6H2O and 2 parts of FeSO4·7H2O.

[0060] 1. The specific preparation steps of Fe-P nanopowder are as follows:

[0061] S1: Dissolve 0.01 mol FeCl3·6H2O in 100 mL deionized water and stir to dissolve evenly to obtain 0.1 M Fe 3+ Solution: Dissolve 0.01 mol KH2PO4 in 100 mL deionized water and stir to dissolve evenly to obtain 0.1 M PO4 3- solution;

[0062] S2: Add 100 mL of 0.1 M Fe 3+ The solution was heated to 70°C and stirred at 500 rpm, and then 100 mL of 0.1 M PO4 from step S1 was slowly added dropwise at a rate of 1 mL / min. 3- The solution was added dropwise and the pH was adjusted to 6.8 using 1 M NaOH solution. After the addition was completed, the mixture was stirred at 70 ° C and 500 rpm for 3 h.

[0063] S3: After the aging treatment in step S2, the mixture was centrifuged at 8000 rpm for 15 min, the precipitate was collected, washed five times with deionized water, dried under vacuum at 60°C for 16 h, and crushed and sieved through a 200-mesh sieve to obtain Fe-P nanopowder;

[0064] 2. The specific preparation steps of modified sodium bentonite are as follows:

[0065] S101: 12 g of sodium bentonite was added to 100 mL of deionized water, stirred and dispersed at 60° C., and a 1 M HCl solution was added dropwise to adjust the pH to 4.5 to obtain a sodium bentonite dispersion. 4.5 g of hexadecyltrimethylammonium bromide was added to 150 mL of deionized water, stirred and dissolved at 60° C. to obtain a CTAB solution.

[0066] S102: 100 mL of CTAB solution was slowly added dropwise to 150 mL of sodium bentonite dispersion, and the mixture was stirred at 500 rpm at 60° C. for 4 h. After the reaction was completed, 1 M NaOH solution was added dropwise to adjust the pH to 7. The mixture was centrifuged, filtered, washed with deionized water, dried at 80° C. for 16 h, and sieved through a 200-mesh sieve to obtain modified sodium bentonite.

[0067] 3. The preparation steps of the multifunctional hydrogel material are as follows:

[0068] S201: Add rice husk biochar to 5 parts by weight of deionized water, stir and disperse evenly, then add nano-CaCO3, ultrasonically disperse evenly, evacuate to 5kPa and maintain for 30 minutes, then return to normal pressure, add 0.05M FeCl3·6H2O solution and 0.025M FeSO4·7H2O solution, defoam with nitrogen, maintain nitrogen atmosphere at 60℃ and stir for 30 minutes, then add 2M NaOH solution dropwise to adjust the pH to 10, continue aging at 60℃ for 50 minutes, centrifuge, remove the supernatant, wash with deionized water until neutral, calcined at 250℃ in nitrogen atmosphere for 1 hour, screened through a 20-mesh sieve, and dried with hot air at 40℃ for 2 hours to obtain an inner carbon core;

[0069] S202: dissolving chitosan in a 1 wt % glacial acetic acid solution to obtain a 3 wt % chitosan solution; adding modified sodium bentonite to deionized water and uniformly dispersing the mixture through ultrasonic treatment to obtain a 3 wt % modified bentonite dispersion; ultrasonically dispersing Fe-P nanopowder into the chitosan solution, and then combining the Fe-P nanopowder with the modified bentonite dispersion and stirring at 1000 rpm for 20 minutes to obtain an emulsion slurry;

[0070] S203: The inner carbon core of step S201 was added to a magnetic stirring container, and the emulsion slurry of step S202 was added dropwise. After stirring at 450 rpm for 10 minutes, the mixture was allowed to stand for 30 minutes. 1M NaOH solution was sprayed at a ratio of 3 mL / g, and the mixture was allowed to stand for 20 minutes to solidify. The mixture was then washed with deionized water until neutral to obtain coated beads.

[0071] S204: Sodium alginate and carboxymethyl starch were added to deionized water, and Tween-20 was added, stirred at 600 rpm for 60 min, and vacuum degassed for 10 min to obtain a 2.5 wt% composite solution. The coated beads of step S203 were immersed in the composite solution for 10 s, rotated at 300 rpm for 20 s, sprayed with 1 M CaCl2 solution at 1.5 mL / g, and allowed to stand for solidification for 30 min. Then, 10 wt% NaCl solution was added for salting out and pore formation. The beads were treated at 40°C for 25 min, 50°C for 50 min, and vacuum dehydrated at 60°C for 30 min. The beads were soaked in 0.05 M CaCl2 solution for 3 min, washed with deionized water, and dried with hot air at 40°C for 2 h to obtain a clean hydrogel material.

[0072] Comparative Example 1: The operating process parameters of Comparative Example 1 are basically the same as those of Example 1. The main difference is that the salting-out pore-forming process of step S204 is cancelled in Comparative Example 1, and conventional cross-linking is used, that is, step S204: sodium alginate and carboxymethyl starch are added to deionized water, and Tween-20 is added, stirred at 600 rpm for 50 minutes, and vacuum degassed for 10 minutes to obtain a 2.5 wt% composite solution, the coated beads of step S203 are immersed in the composite solution for 10 seconds, rotated at 300 rpm for 20 seconds, sprayed with 1MCaCl2 at 1.5 mL / g, allowed to stand and solidify for 25 minutes, washed with deionized water, and dried with hot air at 40°C for 1.5 hours to obtain a multifunctional clean hydrogel material.

[0073] Comparative Example 2: The operating process parameters of Comparative Example 2 are basically the same as those of Example 1, the main difference being that sodium bentonite is used in place of modified sodium bentonite in Comparative Example 2.

[0074] Comparative Example 3: The operating process parameters of Comparative Example 3 are basically the same as those of Example 1. The main difference is that in Comparative Example 3, the addition of Fe-P nanopowder is eliminated and replaced with FeCl3 solution with the same iron content.

[0075] Comparative Example 4: The operating process parameters of Comparative Example 4 are basically the same as those of Example 1. The main difference is that in Comparative Example 4, vacuum impregnation is eliminated, that is, rice husk biochar, nano-CaCO3 and nano-Fe3O4 are directly mixed, and the subsequent calcination step process is completely consistent.

[0076] Performance testing:

[0077] Calcium ion release test: 0.5 g of the clean hydrogel material prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was placed in 100 mL of reaction solution (2 mM CaCl2 + 1 mM MgSO4 + 5 mg / L humic acid + 0.1 M NaCl, pH 7.5). HEPES buffer was used as the control group. After addition, the entire system should be in a slow flow state (0.6 m / s) to simulate a slight disturbance in a river or circulating water body. This time was defined as 0 h, and at 0.5 h, 2 h, 6 h, 24 h, 72 h and 168 h after addition, 5 mL of supernatant was taken (an equal volume and equal composition of fresh buffer was immediately added after each sampling), and the calcium ion concentration was accurately quantified by AAS, and the cumulative release amount was calculated = the calcium ion concentration measured by AAS at time t × the total volume of the medium / the initial mass of the dry gel. All examples and comparative examples were tested in parallel using 3 independent batches of samples, and the average value of each data point was taken. The results are shown in Figure 2. Figure 1 As shown; the material after calcium release was taken out and transferred to 500mL containing 10mg / L PO4 3-The residual phosphorus concentration was measured after shaking at 25°C for 24 hours. All examples and comparative examples were tested in parallel using three independent batches of samples, and the average value of each data point was taken. The results are shown in Figure 2. Figure 2 shown.

[0078] Depend on Figure 1 The results show that the calcium ions of the hydrogel materials prepared in Examples 1 to 3 of the present invention can be continuously released, and long-term effective use can be achieved; from the results of Comparative Example 1, it can be seen that after the salting out is eliminated, the outer membrane has a high density and a small pore size, and Na + Difficult to quickly enter the middle layer to replace Ca 2+ The release rate of CaCO3 decreased significantly in the first 24 hours, and then entered the stage of CaCO3 diffusion-dissolution control. However, the release rate increased significantly after 24 hours, and the overall release showed obvious uneven release. This may be due to the uneven dissolution of the dense structure under the action of humic acid, resulting in the expansion of the pores. From the results of comparative example 2, it can be seen that CaCO3 2+ The exudation rate is slightly slower than that of the embodiment, which may be due to the lack of positively charged CTAB sheets, which makes it easier for humic acid to adhere to the pore wall, resulting in a lower release rate. 2+ The rapid seepage rate may be due to the mild acidification caused by the hydrolysis of FeCl3, which promotes the dissolution of CaCO3 to a certain extent, thus leading to the 2+ The seepage speed is accelerated; from the results of comparative example 4, it can be seen that without vacuum impregnation, CaCO3 is mostly accumulated on the surface of the carbon core or the large pores, with the largest direct contact area with the fluid. 2+ The instantaneous concentration is significant; however, the subsequent release gradually slows down and decreases, which may be due to the gradual passivation of the exposed CaCO3 within 72 hours. Figure 2 The results show that after 7 days of scouring test, the hydrogel material prepared by the present invention still has hydroxyl exchange sites for Fe-P and Fe3O4, and cooperates with CTAB-bentonite to form a long-term positive charge, which can effectively adsorb residual PO4 3- , forming an extremely low detection value; from the results of Comparative Example 1, it can be seen that due to the outer membrane blockage, Fe / sheet is more difficult to quickly contact the solution, PO4 3- The residual amount is large; from the results of Comparative Example 2, it can be seen that the absence of CTAB-bentonite leads to a significant reduction in effective strong adsorption points. Although Fe-P and chitosan are still there, they are not very effective for PO4 3- The collaborative precipitation needs to be captured to a certain concentration before it is triggered. After the pre-enrichment effect of CTAB is weakened, the entire precipitation-fixation link starts slowly and has low efficiency, resulting in PO4 3- The residual amount is slightly increased; from the results of Comparative Example 3, it can be seen that after replacing Fe-P with FeCl3, Fe 3+ Under neutral / slightly alkaline conditions, Fe(OH)3 is mostly suspended, and FePO4 precipitation is rarely generated, which loses the ability to PO4 3-The chemical precipitation lock function causes PO4 3- The residual amount is significantly increased; the results of Comparative Example 4 show that the exposed CaCO3 passivation, the positive sheet layer has been partially covered by humic acid in the 168h running water, PO4 3- The residual volume is significantly increased.

[0079] Acid buffer test: 1 g of the clean hydrogel materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was placed in 500 mL of 0.1 M H2SO4 solution, the pH change was recorded, and the buffer capacity (mmol H) was calculated. + / g) = (H + initial concentration - H after test) + Concentration) × solution volume / sample mass, record weight loss (%) after 2 hours = (weight before test - weight after test) / weight before test × 100%, all examples and comparative examples are tested in parallel using 3 batches of independent samples, and the average value of each data point is taken. The results are shown in Figure 2. Figure 3 shown.

[0080] Depend on Figure 3 The results show that the hydrogel materials prepared in Examples 1 to 3 of the present invention have good instantaneous resistance and buffering properties to strong acid, and will not be easily broken through by strong acid, resulting in performance failure; from the results of Comparative Example 1, it can be seen that the dense membrane of Comparative Example 1 has poor buffering performance, and the weight change in 2h is large, which may be due to local corrosion forming pinholes, and the acid removes part of the chitosan skeleton edge and calcium carbonate along the pores; from the results of Comparative Example 2, after CTAB falls off, the bentonite layers are no longer stretched, and the hydrophobic chains and quaternary ammonium positively charged system The system is absent, the layers are closer together, and are more easily blocked by humic acid, resulting in a lower pH change, a slight increase in buffering capacity, and a slight increase in weight loss; from the results of Comparative Example 3, it can be seen that FeCl3 will immediately hydrolyze and dissolve under strong acid, which is equivalent to additional acid corrosion of the skeleton, the buffering capacity will decrease slightly, and the weight loss will increase significantly. From the results of Comparative Example 4, it can be seen that there is a lack of vacuum impregnation, and CaCO3 is mostly exposed in the carbon core. Although it shows excellent instantaneous buffering performance, the weight loss is significant, the subsequent endurance performance is almost zero, and the sustained release effect cannot be achieved.

[0081] Purified water adsorption test: prepare 20mg / L of Pb 2+ and CrO4 2- The solution was then added with 1 g of the clean hydrogel material prepared in Examples 1 to 3 and Comparative Examples 1 to 4 into 1 L of the above four heavy metal ion solutions, and treated in a constant temperature water bath at 25°C. 1 mL of samples were taken at 0.5 h, 1 h, 3 h, 6 h, 12 h and 24 h (the same volume of solution was added), the residual concentration was determined, and the adsorption rate (%) was calculated as (initial concentration - concentration at the test time point) / initial concentration × 100%. All examples and comparative examples were tested in parallel using 3 independent batches of samples, and the average value of each data point was taken. The results are shown in the figure. Figure 4 and Figure 5 shown.

[0082] Depend on Figure 4 and Figure 5 The results show that the hydrogel materials prepared in Examples 1 to 3 of the present invention have excellent heavy metal adsorption performance; the results of Comparative Example 1 show that there is no salting out and pores, acid / Na + Enter slowly, Ca 2+ The replacement and CaCO3 dissolution are both delayed, the adsorption is poor in the early stage, and the adsorption is significantly improved in the later stage; from the results of comparative example 2, it can be seen that the bentonite layer without modification no longer has a permanent positive charge, loses its strong adsorption of anions, and the pore wall is more easily recharged. The lack of hydrophobic chains makes the pore wall hydrophilic, and foreign anions are more likely to reversely occupy the site, CrO4 2- The adsorption decreased significantly; from the results of Comparative Example 3, it can be seen that there is no iron-phosphorus-metal co-precipitation site, Pb 2+ Need to rely on chitosan-NH2 and CaCO3 to treat separately, Pb 2+ The adsorption effect is reduced, and the use of FeCl3 with its own H + , the skeleton is locally acidified, the charge of CTAB sheet decreases, CrO4 2- The adsorption decreased significantly; from the results of Comparative Example 4, it can be seen that most of the CaCO3 is exposed to the outside, and it reacts violently with the acid in the early stage, and the reduction of Cr(VI) by the Fe3O4 catalyst is limited, and the overall adsorption effect is significantly reduced.

[0083] Spectrum test: Scanning electron microscopy was used to scan the purified hydrogel material sample of Example 1 after the calcium ion release test to obtain a SEM scanning electron microscopy image. The results are as follows: Figure 6 shown.

[0084] Depend on Figure 6 The results show that thin flakes of 5 to 10 µm square with hexagonal or polygonal edges can be clearly seen in the figure, which is consistent with the typical morphology of bentonite flakes spread flat on the pore wall after drying; the picture shows that after 168 hours of water shearing, the outer membrane is peeled off, but the middle chitosan-bentonite-Fe-P skeleton remains intact, and the honeycomb / through pores remain connected; in addition, a thin coating that is brighter and denser than the main body can be seen at the edges of the flakes and at the intersection of fibers. This may be a manifestation of a slight thickening of the skeleton pore wall due to long-term immersion and electrolyte environment. The overall connectivity of the clean hydrogel material still has good performance.

[0085] In summary, the water-purifying gel materials prepared in Examples 1 to 3 have excellent sustained-release properties and long-lasting water purification effects. They can quickly adsorb heavy metal ions in the early stage to achieve water purification effects, and can stably release calcium ions in the middle and late stages to achieve phosphorus fixation and removal. At the same time, the water-purifying gel materials prepared in Examples 1 to 3 have excellent acid resistance, which can ensure stability for use in extreme environments. However, in-depth comparative analysis reveals that Example 1 performs better in key performance indicators and is the best choice for comprehensive performance: in the calcium ion release test, the CaCO3 content of Example 1 is at the optimal sustained-release level, which can ensure the rapid release of sufficient Ca in the initial stage. 2+ , raising the system pH to a range that is favorable for metal coordination (such as forming PbCO3 / Pb3(CO3)2(OH)2) and phosphorus precipitation (such as forming Ca5(PO4)3OH or CaHPO4), while avoiding the depletion of the alkaline source in a short period of time; although the total amount of calcium ion release in Example 3 is slightly higher than that in Example 1 (this may be related to its slightly higher CaCO3 feed amount), its phosphorus fixation effect after 168h sustained release test is significantly weaker than that in Example 1, because the rapid release of Ca 2+ The release may cause Example 3 to form a dense calcium phosphate crust on the outer membrane surface faster than Example 1, blocking the pores and hindering the subsequent diffusion and precipitation of phosphorus, thereby increasing the amount of dissolved phosphorus residue. Therefore, Example 1 has more advantages in the sustained release effect and the final phosphorus fixation efficiency. In terms of buffering capacity (β value), Example 3 is slightly higher than Example 1, which may be related to its higher CaCO3 content. However, under the same 2h acid shock conditions, the weight loss of Example 3 (7.6%) is significantly higher than that of Example 1 (6.4%), which indicates that more CaCO3 on the surface of Example 3 is consumed in a one-time violent reaction. Although it provides an instantaneous high buffering capacity, this may be at the expense of the material structure and subsequent long-term buffering capacity. When the acid shock weakens or needs to cope with subsequent shocks, the effectiveness of its deep alkalinity source will be less than that of Example 1. Compared with the buffering capacity index, the excessive weight loss of Example 3 will cause the overall long-term performance of the material to be significantly weaker than that of Example 1. Example 2 has a higher weight loss than Example 1 and a slightly decreased buffering capacity due to the low CaCO3 and Fe-P feed rates, indicating that its outer membrane is more severely corroded and the effective alkalinity source reserve is insufficient. Its acid shock resistance is significantly weaker than that of Examples 1 and 3. Taking into account the β value and weight loss (especially the weight loss index), Example 1 exhibits better acid buffering stability and long-term effectiveness. Example 1 is significantly better than Example 2 and Example 3 in terms of adsorption start-up speed and final removal efficiency. 2+ The adsorption of CrO4 in Example 1 can reach an adsorption rate of about 80% within 0.5 hours, and a high removal rate of 99% in 24 hours; while in Examples 2 and 3, 2-4% still remain after 24 hours. 2-: Example 1 reaches the 70% removal rate line faster and reaches an adsorption rate of more than 95% in 24 hours; the final adsorption rates of Example 2 and Example 3 are only between 94 and 95%; Example 1 shows a more stable adsorption rate throughout the adsorption process. Specifically, although Example 3 may perform slightly better in a single indicator (such as the total amount of calcium ion release and instantaneous buffering capacity), it has other more obvious disadvantages (such as reduced phosphorus fixation efficiency, increased structural weight loss, and impaired long-term effectiveness), while Example 2 performs insufficiently in multiple indicators. In contrast, Example 1 shows excellent and balanced performance in all key properties, including the long-term effectiveness of sustained calcium ion release (effectively supporting phosphorus fixation), structural stability (low weight loss) and sustainable buffering capacity under acid shock, and rapid and efficient adsorption of multiple pollutants. Therefore, based on the above analysis, the raw material ratio and process parameters of Example 1 can be used to obtain a clean hydrogel material with the best comprehensive performance.

[0086] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A multifunctional water-purifying gel material, characterized in that: The invention comprises an outer film, a middle skeleton and an inner carbon core; the outer film raw materials include, by weight, 8 to 10 parts of sodium alginate, 6 to 8 parts of carboxymethyl starch, 0.4 to 0.6 parts of NaCl and 0.03 to 0.05 parts of Tween-20; the middle skeleton raw materials include, by weight, 10 to 15 parts of chitosan, 10 to 15 parts of modified sodium bentonite and 1 to 1.5 parts of Fe-P nanopowder; the inner carbon core raw materials include, by weight, 38 to 45 parts of rice husk biochar, 10 to 12 parts of nano-CaCO3, 2 to 3 parts of FeCl3·6H2O and 1 to 2 parts of FeSO4·7H2O; The modified sodium bentonite is prepared by the following steps: S101: adding sodium bentonite to deionized water, stirring and dispersing the mixture under heating, and adding HCl solution dropwise to adjust the pH to obtain a sodium bentonite dispersion; adding hexadecyltrimethylammonium bromide to the deionized water, stirring and dissolving the mixture to obtain a CTAB solution; S102: slowly adding the CTAB solution dropwise to the sodium bentonite dispersion, heating and stirring, and after the reaction is completed, adding NaOH solution dropwise to adjust the pH, centrifuging, filtering, washing with deionized water, drying, and screening to obtain modified sodium bentonite; The preparation steps of the multifunctional clean hydrogel material are as follows: S201: adding rice husk biochar to deionized water, stirring and dispersing it evenly, then adding nano-CaCO3, ultrasonically dispersing it evenly, vacuum impregnating it, adding FeCl3·6H2O solution and FeSO4·7H2O solution, degassing it with nitrogen, heating and stirring it under a nitrogen atmosphere, adding NaOH solution dropwise to adjust the pH, continuing aging treatment, centrifuging, removing the supernatant, washing it with deionized water until it is neutral, calcining it under a nitrogen atmosphere, screening it, and drying it with hot air to obtain an inner carbon core; S202: dissolving chitosan in glacial acetic acid solution to obtain a chitosan solution; adding modified sodium bentonite to deionized water and dispersing it uniformly by ultrasonic treatment to obtain a modified bentonite dispersion; ultrasonically dispersing Fe-P nanopowder into the chitosan solution, and then combining it with the modified bentonite dispersion and stirring to obtain an emulsion slurry; S203: adding the inner carbon core of step S201 into a magnetic stirring container, adding the emulsion slurry of step S202 dropwise, stirring, and standing; spraying NaOH solution by atomization, standing and solidifying, and washing with deionized water until neutral, to obtain coated beads; S204: Sodium alginate and carboxymethyl starch are added to deionized water, and Tween-20 is added, stirred, and vacuum degassed to obtain a composite solution. The coated beads of step S203 are immersed in the composite solution, rotated to remove the liquid, sprayed with CaCl2 solution, and allowed to stand for solidification. Then, NaCl solution is added for salting out and pore formation, and the beads are immersed in CaCl2 solution. The beads are washed with deionized water and dried with hot air to obtain a clean hydrogel material.

2. The multifunctional water-purifying gel material according to claim 1, characterized in that: The specific preparation steps of the Fe-P nanopowder are as follows: S1: Dissolve FeCl3·6H2O in deionized water and stir to dissolve evenly to obtain Fe 3+ Solution: Dissolve KH2PO4 in deionized water, stir and dissolve evenly to obtain PO4 3- solution; S2: Fe in step S1 3+ Heat the solution, continue stirring, and then slowly add PO4 from step S1 3- The solution was added dropwise and the pH was adjusted using NaOH solution. After the addition was completed, the mixture was stirred and aged. S3: After completing the aging treatment in step S2, centrifuge the solution, take the precipitate, repeatedly wash it with deionized water, vacuum dry it, crush it, and screen it to obtain Fe-P nanopowder.

3. The multifunctional water-purifying gel material according to claim 2, characterized in that: In step S2, the Fe 3+ Solution and PO4 3- The volume ratio of the solution is 1:

1.

4. The multifunctional water-purifying gel material according to claim 3, characterized in that: In step S101, the ratio of the amount of the sodium bentonite to the amount of deionized water is 1-1.2 g:10 mL; the ratio of the amount of the hexadecyltrimethylammonium bromide to the amount of deionized water is 1.4-1.5 g:50 mL.

5. The multifunctional water-purifying gel material according to claim 4, characterized in that: In step S102, the volume ratio of the CTAB solution to the sodium bentonite dispersion is 1.5:

1.

6. The multifunctional water-purifying gel material according to claim 5, characterized in that: In step S201, the specific parameters of the vacuum impregnation are: vacuuming to 5-20 kPa and maintaining it for 30-60 minutes before returning to normal pressure.

7. The multifunctional water-purifying gel material according to claim 6, characterized in that: In step S204, the specific parameters of the salting-out pore-inducing process are: treatment at 40°C for 15 to 25 minutes, treatment at 50°C for 30 to 50 minutes, and vacuum dehydration treatment at 60°C for 20 to 30 minutes.

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