Composite water purifying agent and preparation method thereof

Abstract

The invention relates to the field of water treatment, in particular to a composite water body purifying agent and a preparation method thereof.The composite water body purifying agent is prepared from, by mass, 65-75 parts of modified biochar, 4-6 parts of tetrasulfonic iron phthalocyanine, 10-15 parts of modified graphene, 4-6 parts of sodium alginate and 2-6 parts of chitosan. Compared with the prior art, the adsorption-catalysis-slow release integrated functional system has the advantages that the synergistic interaction of targeted removal of pollutants and selective release of medicaments is realized, the decomposition efficiency of refractory organic matters is greatly improved, and meanwhile, the adsorption-catalysis-slow release integrated functional system is prepared by virtue of the characteristics of magnetic recovery and natural degradable materials. The secondary pollution risk and the operation cost are remarkably reduced, and the method has a wide application prospect in the fields of industrial wastewater treatment, black and odorous river restoration and other environmental treatment fields.

Description

Technical Field

[0001] This invention relates to the field of water treatment, and in particular to a composite water purification agent and its preparation method. Background Technology

[0002] Composite water purifiers are complex systems that achieve efficient adsorption, catalytic degradation, and controlled release of pollutants in water through the synergistic effect of multiple functional materials. In recent years, such purifiers have received much attention in the field of water treatment, especially for scenarios involving recalcitrant organic pollution such as industrial wastewater and black and odorous water bodies.

[0003] In existing technologies, activated carbon-supported metal catalysts, which are widely used in traditional purifiers, suffer from high raw material costs and are prone to detachment of catalytic components due to physical friction or chemical erosion. This directly leads to a rapid decline in catalytic efficiency with repeated use. Furthermore, traditional synthetic polymer coating materials are difficult to release in response to environmental conditions. In acidic industrial wastewater, excessively dense coatings hinder the contact between the catalyst and pollutants, resulting in wasted catalytic activity. In neutral water bodies, ineffective release exacerbates the risk of secondary pollution. While magnetic materials are easy to recycle, their synthesis relies on highly toxic reducing agents such as hydrazine hydrate. Residual toxic components seep into water bodies as the materials degrade, creating new ecological safety hazards.

[0004] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a composite water purification agent and its preparation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a composite water purifier and its preparation method to solve the problems of easy separation of carrier and catalytic components, lack of environmental responsiveness of coating materials, and efficiency decay caused by the residue of highly toxic reducing agents in the prior art.

[0006] To achieve the above objectives, the present invention provides a composite water purification agent and its preparation method.

[0007] A composite water purification agent is composed of the following components in parts by weight: 65-75 parts modified biochar, 4-6 parts tetrasulfonated iron phthalocyanine, 10-15 parts modified graphene, 4-6 parts sodium alginate, and 2-6 parts chitosan. The modified biochar is biochar modified with iron oxide nanoparticles. The modified graphene is hydrazine hydrate modified graphene.

[0008] Preferably, the modified biochar preparation steps are as follows: Step A1: Under a nitrogen atmosphere, add rice husks into a tube furnace, heat to 550-650℃, pyrolyze for 1.5-2.5 hours. After pyrolysis is complete, cool and grind through a 200-mesh sieve to obtain biochar. Step A2: Add biochar to 3 mol / L potassium hydroxide solution, heat to 70-90℃, stir and activate for 3-5 hours. After activation is complete, wash until neutral, dry, and obtain activated biochar. Step A3: Under a nitrogen atmosphere, add activated biochar to deionized water, add iron oxide nanoparticles, ultrasonically disperse for 20-40 min, heat to 50-70℃, add ammonia water, adjust pH to 10.5-10.7, stir for 5-7 h, the reaction is complete, place next to a 0.5T magnet and let stand for 3-7 min, pour off the supernatant, wash with anhydrous ethanol, vacuum dry, grind and sieve to obtain modified biochar; By replacing activated carbon with rice husk biochar, agricultural waste can be recycled. Chitosan and sodium alginate, both of which are natural biodegradable polymers, are then used for coating, and the decomposition products are non-toxic and harmless. At the same time, ammonia catalysis reduces the use of hydrazine hydrate and lowers its toxicity.

[0009] Preferably, the mass ratio of biochar to potassium hydroxide solution in step A2 is 1:10-12; The mass ratio of activated biochar to iron oxide nanoparticles in step A3 is 1:0.16-0.18.

[0010] Preferably, the modified graphene is prepared using the following steps: Add graphene oxide to deionized water, sonicate for 50-70 minutes at 400-600W, add 25%wt ammonia, stir until homogeneous, add hydrazine hydrate, heat to 70-90℃, stir and react for 22-26 hours. After the reaction is complete, cool to 20-30℃, filter, wash, vacuum dry, and grind to obtain modified graphene.

[0011] Preferably, the mass ratio of graphene oxide, deionized water, ammonia water and hydrazine hydrate is 1:950-1050:0.008-0.012:1-1.1.

[0012] A method for preparing a composite water purification agent, comprising the following steps: Step S1: Add the modified graphene to N,N-dimethylformamide solvent, sonicate for 50-70 min, add tetrasulfonic acid iron phthalocyanine, heat to 60-80℃, stir for 10-14 h, the reaction is complete, centrifuge and wash, vacuum dry to obtain the composite. Modified biochar provides a high specific surface area, thereby adsorbing and enriching pollutants. Then, the interaction between tetrasulfonic acid-based iron phthalocyanine and modified graphene forms a biomimetic catalytic interface, efficiently activating hydrogen peroxide to generate hydroxyl radicals. This imparts magnetic properties to the iron oxide nanoparticles, enabling rapid separation and recovery. Step S2: Add the complex to an ethanol solution, stir to disperse, add modified biochar, heat to 20-30℃, sonicate for 1-3 hours, the reaction is complete, distill under reduced pressure to obtain biochar microspheres; Step S3: Add chitosan to a 1% acetic acid solution, heat to 30-50℃, stir for 1-3 hours to obtain a chitosan solution; Step S4: Add sodium alginate to deionized water, heat to 50-70℃, stir for 50-70 min, add chitosan solution, stir for 4-6 min at 7000-9000 rpm, add 0.1 mol / L sodium hydroxide solution, adjust pH to 4.9-5.1, and obtain a mixed solution; Sodium alginate contains anionic polysaccharides and cationic polysaccharides of chitosan. Under acidic conditions, the electrostatic interaction between the two is weakened, resulting in a relaxed network structure and promoting the release of internal catalytic components. Under neutral or alkaline conditions, its structure is dense, inhibiting ineffective release.

[0013] Step S5: Add biochar microspheres to the mixed solution, cool to 0-5℃, place in a high-speed homogenizer, process for 10-20 min at a speed of 4000-6000 rpm, add 2% calcium chloride solution, let stand and solidify for 20-40 min, after solidification is complete, wash, freeze dry to obtain composite water purification agent; Modified graphene fixes the phthalocyanine molecules of tetrasulfonic acid iron phthalocyanine through π-π bonds, thereby achieving a pre-composite effect between the two. Then, hydrogen bonds are formed between the hydroxyl and carboxyl groups on the surface of modified biochar and the modified graphene to increase their interfacial bonding force. Finally, sodium alginate and chitosan form a shell to prevent the loss of nanocatalysts and achieve the stability of active sites.

[0014] Preferably, the mass ratio of the modified graphene to tetrasulfonate iron phthalocyanine in step S1 is 1:0.32-0.34.

[0015] Preferably, the mass ratio of the composite to the modified biochar in step S2 is 1:3.4-3.6.

[0016] Preferably, the mass ratio of chitosan to acetic acid solution in step S3 is 1:48-50; The mass ratio of sodium alginate, deionized water and chitosan solution in step S4 is 1:48-50:24-26.

[0017] Preferably, the mass ratio of the biocarbon microspheres, the mixed solution, and the calcium chloride solution in step S5 is 1:3-5:19-21.

[0018] The beneficial effects of this invention are: This invention provides a composite water purifier and its preparation method. The invention constructs an integrated functional system of adsorption-catalysis-slow release by loading a biomimetic catalytic complex onto a modified biochar carrier and encapsulating it with a pH-controlled release natural polymer. Compared with existing technologies, this invention achieves synergistic effects of targeted removal of pollutants and selective release of agents, significantly improving the decomposition efficiency of recalcitrant organic matter. At the same time, relying on magnetic recovery and the characteristics of natural biodegradable materials, it significantly reduces the risk of secondary pollution and operating costs, and has broad application prospects in environmental governance fields such as industrial wastewater treatment and black and odorous river restoration. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0020] Example 1: The steps for preparing modified biochar are as follows: S1: Under a nitrogen atmosphere, 1000g of rice husks were added to a tube furnace, heated to 550℃, and pyrolyzed for 2.5h. After pyrolysis was completed, the husks were cooled, ground, and passed through a 200-mesh sieve to obtain biochar. S2: Add 100g of biochar to 1000g of 3mol / L potassium hydroxide solution, heat to 70℃, stir and activate for 5h. After activation is complete, wash until neutral, dry, and obtain activated biochar. S3: Under a nitrogen atmosphere, 100g of activated biochar was added to 200mL of deionized water, along with 16g of iron oxide nanoparticles. The mixture was ultrasonically dispersed for 20min, heated to 70℃, and ammonia was added to adjust the pH to 10.5-10.7. The mixture was stirred for 5h until the reaction was complete. The mixture was then placed next to a 0.5T magnet and allowed to stand for 3min. The supernatant was discarded, and the mixture was washed with anhydrous ethanol, vacuum dried, ground, and sieved to obtain modified biochar.

[0021] Example 2: The preparation steps of modified biochar are as follows: S1: Under a nitrogen atmosphere, 1000g of rice husks were added to a tube furnace, heated to 600℃, and pyrolyzed for 2 hours. After pyrolysis was completed, the husks were cooled, ground, and passed through a 200-mesh sieve to obtain biochar. S2: Add 100g of biochar to 1100g of 3mol / L potassium hydroxide solution, heat to 80℃, stir and activate for 4h. After activation is complete, wash until neutral, dry, and obtain activated biochar. S3: Under a nitrogen atmosphere, 100g of activated biochar was added to 200mL of deionized water, along with 17g of iron oxide nanoparticles. The mixture was ultrasonically dispersed for 30min, heated to 60℃, and ammonia was added to adjust the pH to 10.5-10.7. The mixture was stirred for 6h until the reaction was complete. The mixture was then placed next to a 0.5T magnet and allowed to stand for 5min. The supernatant was discarded, and the mixture was washed with anhydrous ethanol, vacuum dried, ground, and sieved to obtain modified biochar.

[0022] Example 3: The preparation steps of modified biochar are as follows: S1: Under a nitrogen atmosphere, 1000g of rice husks were added to a tube furnace, heated to 650℃, and pyrolyzed for 1.5h. After pyrolysis was completed, the husks were cooled, ground, and passed through a 200-mesh sieve to obtain biochar. S2: Add 100g of biochar to 1200g of 3mol / L potassium hydroxide solution, heat to 90℃, stir and activate for 3h. After activation is complete, wash until neutral, dry, and obtain activated biochar. S3: Under a nitrogen atmosphere, 100g of activated biochar was added to 200mL of deionized water, along with 18g of iron oxide nanoparticles. The mixture was ultrasonically dispersed for 20min, heated to 70℃, and ammonia was added to adjust the pH to 10.5-10.7. The mixture was stirred for 5h until the reaction was complete. The mixture was then placed next to a 0.5T magnet and allowed to stand for 7min. The supernatant was discarded, and the mixture was washed with anhydrous ethanol, vacuum dried, ground, and sieved to obtain modified biochar.

[0023] Example 4: The preparation steps of the modified graphene are as follows: 1g of graphene oxide was added to 950g of deionized water and sonicated for 50min at 600W. 8mg of 25%wt ammonia was added and stirred until homogeneous. 1g of hydrazine hydrate was added, and the temperature was raised to 70℃. The mixture was stirred and reacted for 26h until the reaction was complete. The mixture was then cooled to 20℃, filtered, washed, vacuum dried, and ground to obtain modified graphene.

[0024] Example 5: The preparation steps of the modified graphene are as follows: Add 1g of graphene oxide to 1000mL of deionized water, sonicate for 60min at 500W, add 10mg of 25%wt ammonia, stir until homogeneous, add 1.05g of hydrazine hydrate, heat to 80℃, stir and react for 24h until the reaction is complete, cool to 25℃, filter, wash, vacuum dry, and grind to obtain modified graphene.

[0025] Example 6: The preparation steps of the modified graphene are as follows: 1g of graphene oxide was added to 1050g of deionized water and sonicated for 70min at 400W. 12mg of 25%wt ammonia was added and stirred until homogeneous. 1.1g of hydrazine hydrate was added, and the temperature was raised to 90℃. The mixture was stirred and reacted for 22h until the reaction was complete. The mixture was then cooled to 30℃, filtered, washed, vacuum dried, and ground to obtain modified graphene.

[0026] Example 7: A method for preparing a composite water purification agent S1: Add 100g of modified graphene to 200mL of N,N-dimethylformamide solvent, sonicate for 50min, add 32g of tetrasulfonic acid iron phthalocyanine, heat to 60℃, stir for 14h, the reaction is complete, centrifuge and wash, vacuum dry to obtain the composite. S2: Add 100g of the complex to 500mL of ethanol solution, stir and disperse, add 340g of modified biochar, heat to 20℃, sonicate for 3h, the reaction is completed, distill under reduced pressure to obtain biochar microspheres. S3: Add 10g of chitosan to 480g of 1% acetic acid solution, heat to 30℃, stir for 3h to obtain chitosan solution; S4: Add 10g of sodium alginate to 480g of deionized water, heat to 50℃, stir for 70min, add 240g of chitosan solution, stir for 4min at 9000rpm, add 0.1mol / L sodium hydroxide solution, adjust pH to 4.9-5.1, and obtain a mixed solution. S5: Add 10g of biochar microspheres to 30g of mixed solution, cool to 0℃, place in a high-speed homogenizer, process for 20min at 4000rpm, add 190g of 2% calcium chloride solution, let stand and solidify for 40min, after solidification is complete, wash, freeze dry to obtain composite water purification agent.

[0027] Example 8: A method for preparing a composite water purification agent S1: Add 100g of modified graphene to 200mL of N,N-dimethylformamide solvent, sonicate for 60min, add 33g of tetrasulfonic acid iron phthalocyanine, heat to 70℃, stir for 12h, the reaction is complete, centrifuge and wash, vacuum dry to obtain the composite. S2: Add 100g of the complex to 500mL of ethanol solution, stir and disperse, add 340g of modified biochar, heat to 25℃, sonicate for 2h, the reaction is completed, distill under reduced pressure to obtain biochar microspheres. S3: Add 10g of chitosan to 490g of 1% acetic acid solution, heat to 40℃, stir for 2h to obtain chitosan solution; S4: Add 10g of sodium alginate to 490g of deionized water, heat to 60℃, stir for 60min, add 250g of chitosan solution, stir for 5min at 8000rpm, add 0.1mol / L sodium hydroxide solution, adjust pH to 4.9-5.1, and obtain a mixed solution. S5: Add 10g of biochar microspheres to 40g of mixed solution, cool to 3℃, place in a high-speed homogenizer, process for 15min at 5000rpm, add 200g of 2% calcium chloride solution, let stand and solidify for 30min, after solidification is complete, wash, freeze dry to obtain composite water purification agent.

[0028] Example 9: A method for preparing a composite water purification agent S1: Add 100g of modified graphene to 200mL of N,N-dimethylformamide solvent, sonicate for 70min, add 34g of tetrasulfonic acid iron phthalocyanine, heat to 60℃, stir for 14h, the reaction is complete, centrifuge and wash, vacuum dry to obtain the composite. S2: Add 100g of the complex to 500mL of ethanol solution, stir and disperse, add 360g of modified biochar, heat to 30℃, sonicate for 1h, the reaction is completed, distill under reduced pressure to obtain biochar microspheres. S3: Add 10g of chitosan to 500g of 1% acetic acid solution, heat to 50℃, stir for 1h to obtain chitosan solution; S4: Add 10g of sodium alginate to 500g of deionized water, heat to 70℃, stir for 50min, add 260g of chitosan solution, stir for 6min at 7000rpm, add 0.1mol / L sodium hydroxide solution, adjust pH to 4.9-5.1, and obtain a mixed solution. S5: Add 10g of biochar microspheres to 50g of mixed solution, cool to 5℃, place in a high-speed homogenizer, process for 10min at 6000rpm, add 210g of 2% calcium chloride solution, let stand for 20min to solidify, after solidification, wash, freeze dry to obtain composite water purification agent.

[0029] Comparative Example 1: Compared with Example 7, this comparative example did not add iron oxide nanoparticles during the preparation of modified biochar. All other steps and parameters were the same, and will not be repeated here. The final product was a composite water purifier.

[0030] Comparative Example 2: This comparative example differs from Example 7 only in that "modified biochar" is replaced with "activated carbon". All other steps and parameters are the same, and will not be repeated here. The final result is a composite water purifier.

[0031] Comparative Example 3: Compared with Example 7, this comparative example only replaces "sodium alginate and chitosan" with an equal mass of "polyacrylamide". All other steps and parameters are the same, and will not be repeated here. The final result is a composite water purifier.

[0032] Comparative Example 4: Compared with Example 7, this comparative example did not add ammonia during the preparation of modified graphene. All other steps and parameters were the same, and will not be repeated here. The final product was a composite water purifier.

[0033] Comparative Example 5: Compared with Example 7, this comparative example did not add tetrasulfonic acid iron phthalocyanine during the preparation of the composite water purifier. All other steps and parameters were the same, and will not be repeated here. The final composite water purifier was obtained.

[0034] Performance testing: Simulated dyeing and printing wastewater: containing 100 mg / L Acid Red 14 dye, 50 mg / L phenol, and 30 mg / L sodium dodecyl sulfate. =500±10 mg / L, pH adjusted to 3.0±0.1 and 7.0±0.1 respectively.

[0035] Catalytic efficiency test Referring to the testing standard GB / T 11914-89 Determination of Chemical Oxygen Demand in Water - Dichromate Method, a rapid COD analyzer and a TOC analyzer were used. 1. Take 0.1g of each of the composite water purification agents from Examples 7-9 and Comparative Examples 1-5, and add them to 500mL of simulated wastewater with pH=3.0 and 500mL of simulated wastewater with pH=7.0 respectively, and add 5mL of 30% H2O. 2, Heat to 25°C, stir for 60 minutes at 800 rpm; 2. Take 10 mL of the supernatant after the reaction, add it to a HACH COD pre-prepared tube, and measure it with a COD rapid analyzer at a temperature of 150℃ for 120 min. Read the value after cooling. 3. Filter the supernatant through a 0.45μm filter membrane and determine the TOC using a TOC analyzer; 4. Removal rate: C0: Initial COD or TOC value; C t COD or TOC values ​​after the reaction Table 1. Catalytic efficiency test results of the examples and comparative examples Structural stability test The test was conducted using an ICP-OES inductively coupled plasma optical emission spectrometer, in accordance with the testing standard GB / T 32465-2015 General Rules for Stability Evaluation of Functional Materials. 1. Take 0.1g of each of the composite water purification agents of Examples 7-9 and Comparative Examples 1-5, add them to 100mL of simulated wastewater with pH=7.0, stir for 60min at 600rpm; 2. Place the reaction solution in a 0.5T magnetic field for 3 minutes to separate, recover the solid purifying agent, wash with deionized water 3 times, and repeat steps 1-2 a total of 5 times; 3. After the fifth cycle, add the purifying agent to 100 mL of deionized water, place it on a constant temperature shaker, heat it to 25°C, shake it at 180 rpm for 24 h, take the leachate, centrifuge it at 8000 rpm for 10 min, filter it through a 0.22 μm filter membrane, and detect the Fe leakage by ICP-OES.

[0036] Magnetic recovery rate test 0.5T NdFeB permanent magnets are used; 1. Take 0.1g of each of the composite water purification agents of Examples 7-9 and Comparative Examples 1-5, add them to 100mL of simulated wastewater with pH=7.0, and ultrasonically disperse for 30s at 200W. 2. Place the beaker in the center of a 0.5T magnetic field, let it stand for 180±1s, pour off the supernatant, collect the magnetic material, and vacuum dry it at 60℃ until constant weight. 3. Recovery rate calculation: W0: Initial dosage mass; W1: Mass after recovery and drying Table 2 Test Results of Examples and Comparative Examples Ecotoxicity testing According to ISO 11348-3:2007 "Determination of the effect of water quality on the inhibition of luminescence of Vibrio filamentosa – Part 3: Lyophilized bacterial method", a luminescent spectrophotometer was used to test the lyophilized Vibrio fischeri (NRRL B-11177) bacterial powder. 1. Take 0.1g of each of the composite water purification agents of Examples 7-9 and Comparative Examples 1-5, add 100mL of sterile deionized water, heat to 25℃, rotate at 120rpm, extract for 24h, filter, and obtain the extract. 2. Add the freeze-dried bacterial powder to a 2% NaCl solution, heat to 4℃, activate for 15 min, and detect the baseline luminescence value using a luminometer; 3. Add 100 μL of extract and 100 μL of bacterial solution to a 96-well black plate, heat to 15℃, react for 15 min, and measure the luminescence intensity (RLU). The blank control group is 2% NaCl solution. 4. Calculate the inhibition rate: .

[0037] Sustained-release performance test A PinAAcle 900T atomic absorption spectrometer was used. The buffer solutions were 0.1 mol / L HCl-KCl buffer solution with pH=3.0 and 0.1 mol / L PBS phosphate buffer solution with pH=7.0. 1. Take 1.0 g of each of the composite water purification agents from Examples 7-9 and Comparative Examples 1-5, and add 40 mL of 0.1 mol / L HCl-KCl buffer (pH=3.0) and 40 mL of 0.1 mol / L PBS phosphate buffer (pH=7.0), respectively. Heat to 25°C and rotate at 120 rpm for 240 min. Take 2 mL of the supernatant, filter it through a 0.22 μm filter membrane, and determine the Fe concentration in the filtrate using atomic absorption spectrometry. 2. Cumulative release rate: , Ct: Fe concentration at time t (mg / L); Vt: Sampling volume (L); M0: Total Fe mass of the purifying agent (mg).

[0038] Table 3. Test results of the examples and comparative examples Data Analysis: As can be seen from Tables 1-3, the composite water purifier prepared by the invention has higher catalytic efficiency, excellent structural stability, significantly reduced ecotoxicity, and intelligent slow-release characteristics. In contrast, Comparative Example 1, due to the absence of iron oxide nanoparticles in the preparation of modified biochar, experienced a sharp drop in catalytic efficiency and a magnetic recovery rate of only 45.0%. This is because iron oxide nanoparticles are the only component that imparts magnetism to the material, and their absence prevents the purifier from being captured by the 0.5T magnetic field. Furthermore, iron oxide nanoparticles can catalyze the production of ·OH from H2O2, and their complete absence leads to the failure of the synergistic effect between them and iron phthalocyanine, resulting in reduced ·OH production and incomplete decomposition of recalcitrant organic matter. In addition, the absence of iron oxide nanoparticles causes the iron phthalocyanine-graphene composite to rely solely on hydrogen bonds for bonding, which reduces its mechanical stability. During stirring, the catalytic components fall off, further reducing the catalytic efficiency. Comparative Example 2, due to the replacement of modified biochar with activated carbon, resulted in a high Fe leakage rate of 8.75 mg / L and a sharp drop in catalytic efficiency. This is because after the pyrolysis of rice husks forms a porous carbon framework, it is activated by KOH to generate abundant oxygen-containing functional groups (-COOH, -OH). Under alkaline conditions, these groups can undergo a chemical co-precipitation reaction with iron(III) oxide nanoparticles, thereby forming Fe-OC covalent bonds with their surface -OH groups. In contrast, activated carbon has a low surface functional group density and mainly relies on physical adsorption to load Fe3O4. Under acidic conditions, H+... +Erosion occurs because Fe3O4 cannot adhere to activated carbon solely through van der Waals forces, leading to its detachment. Simultaneously, activated carbon cannot provide sufficient carboxyl and hydroxyl groups, making it difficult to form a hydrogen bond network with modified graphene. During high-speed stirring, Fe3O4 on the activated carbon surface, lacking chemical bonds for fixation, continues to dissolve under shear force, resulting in decreased stability. Furthermore, the leaked Fe3O4 particles cannot participate in constructing the biomimetic catalytic interface, leading to reduced H2O2 activation efficiency. Additionally, the detached particles clog the pores of activated carbon, hindering the diffusion of pollutants to residual catalytic sites, thus reducing catalytic efficiency. Comparative Example 3, by replacing sodium alginate and chitosan with polyacrylamide, resulted in low catalytic efficiency, loss of selective release function, and a significant increase in ecotoxicity. This is because polyacrylamide, as a synthetic polymer, contains only electrically neutral amide groups in its molecular chain and lacks ionizable groups. In contrast, in this invention, the carboxyl groups of sodium alginate and the amino groups of chitosan undergo a protonation reaction in an acidic environment, leading to a weakening of electrostatic interaction and a loosening of the network structure. Simultaneously, the amide groups of polyacrylamide remain electrically neutral at pH 3.0, preventing protonation and maintaining a dense coating structure that hinders catalyst contact with pollutants. Furthermore, polyacrylamide forms a rigid network through hydrogen bonding, and its swelling behavior is regulated by the ionic strength of the solution, independent of pH. In acidic wastewater, the polyacrylamide coating layer exhibits a slow swelling rate, failing to meet the time-sensitive requirements for pollutant degradation. Additionally, polyacrylamide often retains acrylamide monomers, which dissolve during extraction, further contributing to environmental toxicity. Comparative Example 4 showed a surge in ecotoxicity and a decrease in catalytic efficiency due to the absence of ammonia in the preparation of modified graphene. This was because hydrazine did not decompose completely in the absence of alkalinity, and residual hydrazine was embedded in the interlayer of graphene. The residual hydrazine was oxidized to azidoic acid in water. At the same time, the insufficient reduction of graphene weakened the π-π stacking force between the phthalocyanine ring of tetrasulfonic acid iron phthalocyanine and graphene, and the reduced electron transfer efficiency led to a decrease in the rate of H2O2 activation to generate ·OH. Comparative Example 5, due to the absence of tetrasulfonic acid-based iron phthalocyanine in the preparation of the composite water purification agent, suffered from catalytic activity failure, disruption of interfacial synergistic effects, and aggravation of side reaction pathways. This is because the core function of iron phthalocyanine lies in its Fe-N4 planar macrocyclic structure, which can mimic the active center of natural peroxidases, forming a high-speed electron transfer channel. Its absence causes the •OH generated on the Fe3O4 surface to be encapsulated by the carbon layer, hindering diffusion and preventing the complete mineralization of recalcitrant organic matter. Simultaneously, iron phthalocyanine is fixed to the graphene surface through π-π stacking, forming atomically dispersed active sites. Its absence leads to the easy aggregation of Fe3O4 nanoparticles, reducing the effective specific surface area and consequently decreasing the activation amount of H2O2 per unit catalyst. Furthermore, the sulfonic acid groups of iron phthalocyanine maintain the pH stability of the active center microenvironment; their absence further hinders the activation of H2O2. + Erosion of the Fe3O4 lattice leads to Fe 2+Increased dissolution, soluble Fe 2+ It triggers a homogeneous Fenton reaction, which briefly improves efficiency before being completely deactivated due to the deposition of iron mud.

[0039] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0040] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A composite water purification agent, characterized in that, It is composed of the following components in parts by weight: 65-75 parts modified biochar, 4-6 parts tetrasulfonated iron phthalocyanine, 10-15 parts modified graphene, 4-6 parts sodium alginate, and 2-6 parts chitosan. The modified biochar is biochar modified with iron oxide nanoparticles. The modified graphene is hydrazine hydrate modified graphene.

2. The composite water purifier according to claim 1, characterized in that, The modified biochar preparation steps are as follows: Step A1: Under a nitrogen atmosphere, add rice husks into a tube furnace, heat to 550-650℃, pyrolyze for 1.5-2.5 hours. After pyrolysis is complete, cool and grind through a 200-mesh sieve to obtain biochar. Step A2: Add biochar to 3 mol / L potassium hydroxide solution, heat to 70-90℃, stir and activate for 3-5 hours. After activation is complete, wash until neutral, dry, and obtain activated biochar. Step A3: Under a nitrogen atmosphere, add activated biochar to deionized water, add iron oxide nanoparticles, ultrasonically disperse for 20-40 min, heat to 50-70℃, add ammonia water, adjust pH to 10.5-10.7, stir for 5-7 h, the reaction is complete, place next to a 0.5T magnet and let stand for 3-7 min, pour off the supernatant, wash with anhydrous ethanol, vacuum dry, grind and sieve to obtain modified biochar.

3. The composite water purifier according to claim 2, characterized in that, The mass ratio of biochar to potassium hydroxide solution in step A2 is 1:10-12; The mass ratio of activated biochar to iron oxide nanoparticles in step A3 is 1:0.16-0.

18.

4. The composite water purifier according to claim 1, characterized in that, The modified graphene is prepared in the following steps: Add graphene oxide to deionized water, sonicate for 50-70 minutes at 400-600W, add 25%wt ammonia, stir until homogeneous, add hydrazine hydrate, heat to 70-90℃, stir and react for 22-26 hours. After the reaction is complete, cool to 20-30℃, filter, wash, vacuum dry, and grind to obtain modified graphene.

5. The composite water purification agent according to claim 4, characterized in that, The mass ratio of graphene oxide, deionized water, ammonia water and hydrazine hydrate is 1:950-1050:0.008-0.012:1-1.

1.

6. A method for preparing a composite water purification agent according to any one of claims 1-5, characterized in that, The preparation steps are as follows: Step S1: Add the modified graphene to N,N-dimethylformamide solvent, sonicate for 50-70 min, add tetrasulfonic acid iron phthalocyanine, heat to 60-80℃, stir for 10-14 h, the reaction is complete, centrifuge and wash, vacuum dry to obtain the composite. Step S2: Add the complex to an ethanol solution, stir to disperse, add modified biochar, heat to 20-30℃, sonicate for 1-3 hours, the reaction is complete, distill under reduced pressure to obtain biochar microspheres; Step S3: Add chitosan to a 1% acetic acid solution, heat to 30-50℃, stir for 1-3 hours to obtain a chitosan solution; Step S4: Add sodium alginate to deionized water, heat to 50-70℃, stir for 50-70 min, add chitosan solution, stir for 4-6 min at 7000-9000 rpm, add 0.1 mol / L sodium hydroxide solution, adjust pH to 4.9-5.1, and obtain a mixed solution; Step S5: Add biochar microspheres to the mixed solution, cool to 0-5℃, place in a high-speed homogenizer, process for 10-20 min at a speed of 4000-6000 rpm, add 2% calcium chloride solution, let stand and solidify for 20-40 min, after solidification is complete, wash, freeze dry to obtain composite water purification agent.

7. The method for preparing a composite water purification agent according to claim 6, characterized in that, The mass ratio of the modified graphene to tetrasulfonic acid iron phthalocyanine in step S1 is 1:0.32-0.

34.

8. The method for preparing a composite water purification agent according to claim 6, characterized in that, The mass ratio of the composite to the modified biochar in step S2 is 1:3.4-3.

6.

9. The method for preparing a composite water purification agent according to claim 6, characterized in that, The mass ratio of chitosan to acetic acid solution in step S3 is 1:48-50; The mass ratio of sodium alginate, deionized water and chitosan solution in step S4 is 1:48-50:24-26.

10. The method for preparing a composite water purification agent according to claim 6, characterized in that, In step S5, the mass ratio of the bio-carbon microspheres, the mixed solution, and the calcium chloride solution is 1:3-5:19-21.

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