A deep treatment method based on heavy metal wastewater

Abstract

The present application relates to heavy metal wastewater treatment technical field, specifically disclose a kind of based on heavy metal wastewater's advanced treatment method, prepare a kind of load multilayer adsorbent-biochar-polyurethane sponge and a sulfonated polyether ether ketone chlorine-resistant exchange membrane, after loading multilayer adsorbent-biochar-polyurethane sponge is added to heavy metal wastewater, stationary settlement several hours, at this time, heavy metal in wastewater is adsorbed and settled to wastewater bottom, again, supernatant is siphoned into the membrane stack consisting of sulfonated polyether ether ketone chlorine-resistant exchange membrane, under the action of electrodialysis, chlorine in wastewater moves to the same side through exchange membrane, thereby reducing chlorine content in wastewater, so that wastewater meets the demand of discharge.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heavy metal wastewater treatment, in particular to a deep treatment method based on heavy metal wastewater. BACKGROUND

[0002] Heavy metal wastewater is a kind of environmental pollutant with wide sources and far-reaching harm. Mining wastewater, metallurgical wastewater, electroplating wastewater and chemical wastewater are all main sources thereof. Because heavy metals cannot be naturally decomposed, they are deposited in water and can be enriched through the food chain, i.e. the amplification effect, even if we do not come into contact with heavy metal wastewater, through our diet, heavy metals can also affect us. In water, heavy metals can inhibit the activity of microorganisms, in soil, they can cause soil fertility to decline, and after entering the human body, they can damage our organ function and even cause cancer. Therefore, treating heavy metal wastewater and reducing the content of heavy metal ions and soluble chlorine in wastewater are inevitable problems in the process of industrial green development and sustainable development. SUMMARY

[0003] The purpose of the present application is to provide a deep treatment method based on heavy metal wastewater, which deeply removes heavy metal ions and soluble chlorine in wastewater, and solves the problem of high content of heavy metal ions and soluble chlorine in wastewater, which does not meet the discharge requirements.

[0004] In order to solve the above technical problems, the present application provides the following technical solutions:

[0005] A deep treatment method based on heavy metal wastewater, specifically comprising:

[0006] First, adjust the pH of the heavy metal wastewater, then add the loaded multilayer adsorbent-biochar-polyurethane sponge, stir uniformly, and then stand for 4-8h, after the sedimentation is completed, the lower sludge is washed with nitric acid, and the loaded multilayer adsorbent-biochar-polyurethane sponge is screened out, the supernatant is siphoned into an electrodialysis membrane stack containing a chlororesistant exchange membrane of sulfonated polyether ether ketone, and then electrodialysis is carried out to obtain deep treatment heavy metal wastewater.

[0007] As a limitation of the present application, the pH of the heavy metal wastewater is adjusted to 4.0-5.0, and the solid-liquid ratio of the loaded multilayer adsorbent-biochar-polyurethane sponge to the heavy metal wastewater is 1.0g / L-1.5g / L; during electrodialysis, the voltage is set to 1.0V-1.4V, and the water flow rate is 20-30mL / min.

[0008] As a limitation of the present application, the preparation method of the loaded multilayer adsorbent-biochar-polyurethane sponge is as follows:

[0009] The straw is washed, crushed and dried, pyrolysis is carried out under nitrogen protection at 500-600 DEG C for 1.5-2h, after pyrolysis is completed, it is sealed and cooled to room temperature, and then ground to 80-120 meshes, and then immersed in hydrochloric acid for 20-24h to obtain biochar;

[0010] Polyvinyl alcohol is added to deionized water, heated to 80-90 DEG C and stirred for 1-1.5h, cooled to room temperature, and then divided into two parts, one part is mixed with biochar, ultrasonic dispersion is carried out for 20-30min to obtain biochar slurry, and the other part is mixed with multilayer adsorbent particles, ultrasonic dispersion is carried out for 20-30min to obtain adsorbent dispersion liquid;

[0011] The polyurethane sponge is cut into small pieces, immersed in sodium hydroxide solution for 1-2h to remove impurities, washed with deionized water, dried, and then added to the biochar slurry, then vacuum treatment is carried out, taken out after being immersed at (-0.08) MPa to (-0.04) MPa for 15-25min, dried at 60-70 DEG C for 1-1.5h, and then added to the adsorbent dispersion liquid and slowly stirred, and the sponge is taken out after 5-15min, and then placed in a sealed container with glutaraldehyde solution, and reacted at 60-70 DEG C for 3-4h, taken out after the reaction is completed, washed with deionized water, and dried at 40-50 DEG C for 3-5h to obtain the multilayer adsorbent-biochar-polyurethane sponge.

[0012] The polyurethane sponge is used as the matrix of the adsorbent material, providing a three-dimensional porous structure skeleton for the biochar and the adsorbent, the biochar adsorbs heavy metal pollutants through the pore structure and the surface active functional groups, and the adsorbent promotes the breakage of the heavy metal complex and the adsorption of the heavy metal, the reaction of glutaraldehyde and the hydroxyl group of polyvinyl alcohol is bonded, and the biochar and the multilayer adsorbent are fixed on the polyurethane sponge at the same time, so that the mechanical and chemical stability of the material is improved, and the adsorbent and the biochar are prevented from being carried away by the water flow.

[0013] As the limitation of the application, the concentration of biochar in the biochar slurry is 0.8-1.2g / mL, the concentration of multilayer adsorbent particles in the adsorbent dispersion liquid is 0.4-0.6g / mL, the mass ratio of polyurethane sponge to biochar is (5-7):(2.8-3.2), and the mass ratio of polyurethane sponge to multilayer adsorbent particles is (5-7):(0.8-1.2).

[0014] As the limitation of the application, the preparation method of the multilayer adsorbent particles is as follows:

[0015] Mix tartaric acid and ferrous sulfate uniformly, after co-milling with potassium persulfate for 20-30 min, granulation is carried out, 1.5-2mm adsorbent core granules are obtained, aluminum sulfate is mixed with glycerol, stirring is uniformly carried out, aluminum paste is formed, the adsorbent core granules are added into the aluminum paste, after stirring uniformly, filtration is carried out, solidification is carried out at 60-70 DEG C for 1.5-2h, aluminum salt granules are obtained, wherein the thickness of the aluminum layer is 30-50um, sodium alginate and chitosan are added into 1% acetic acid solution, after stirring for 1-2h when the temperature is raised to 60-70 DEG C, the temperature is cooled to room temperature, the aluminum salt granules are added, after slow stirring for 10-15min, filtration is carried out, the granules are transferred into 1% calcium chloride solution for crosslinking for 5-10min, after 5-10min, filtration is carried out, washing is carried out with deionized water, drying is carried out at 40-50 DEG C for 4-5h, 3-5mm multilayer adsorbent granules are obtained.

[0016] With persulfate, tartaric acid and ferrous sulfate as the active center of the adsorbent, after the release of ferrous ions, the persulfate is activated to initiate free radical reaction, the decomposition of heavy metal complex is promoted, tartaric acid complexes ferrous ions, prevents ferrous ions from releasing in advance to activate persulfate, the outer layer of aluminum sulfate protects ferrous ions, at the same time, aluminum sulfate is dissociated into colloids in water, forms a flocculation system with the outer layer of chitosan, promotes the flocculation and sedimentation of adsorption sponges and heavy metals, is beneficial to the separation of heavy metals and wastewater, after crosslinking, sodium alginate and chitosan as the outermost layer of the adsorbent, the release rate of the substances in the adsorbent is effectively controlled, the medicament cost is saved, at the same time, secondary pollution caused by excessive addition of medicament is avoided.

[0017] As the limitation of the application, the mass ratio of tartaric acid, ferrous sulfate and potassium persulfate is (1-3):(1.8-2.2):(4-6); the mass ratio of aluminum sulfate and glycerol is (18-22):(1-3); the mass ratio of sodium alginate and chitosan is (2-4):(2-3).

[0018] As the limitation of the application, the preparation method of the sulfonated polyether ether ketone chlorine exchange resistant membrane is as follows:

[0019] Polyether ether ketone is added into concentrated sulfuric acid, sulfonation is carried out at 50-60 DEG C for 4-6h, after sulfonation is completed, 0 DEG C deionized water is added, a precipitate is precipitated, filtration is carried out, washing is carried out with deionized water until neutral, vacuum drying is carried out at 60-70 DEG C for 5-6h, 70%-80% sulfonated polyether ether ketone is obtained, in the same way, polyether ether ketone is sulfonated for 3-4h and 1.5-2.5h respectively, 60%-70% sulfonated polyether ether ketone and 45%-55% sulfonated polyether ether ketone are obtained;

[0020] The 70%-80% sulfonated polyether ether ketone and diaminodiphenyl disulfide are added into dimethyl sulfoxide, the dispersion is poured into a mold after ultrasonic dispersion for 20-30 min, a direct current voltage of 1.4-1.5 V is output by a platinum electrode with a spacing of 4-6 cm, and the outer layer of the film is obtained after curing at 60-70 DEG C for 3-4 h, the 60%-70% sulfonated polyether ether ketone and sulfonated cerium dioxide nanoparticles are added into dimethyl sulfoxide, the transition layer of the film is formed on the outer layer of the film after pouring and curing at 60-70 DEG C for 1.5-2.5 h after ultrasonic dispersion for 20 min, the thickness of the transition layer of the film is 70-90 mu m, the 45%-55% sulfonated polyether ether ketone and diethylenetriamine pentaacetic acid are added into dimethyl sulfoxide, the inner layer of the film is formed on the transition layer of the film after pouring and curing at 60-70 DEG C for 1-1.5 h after ultrasonic dispersion for 20-30 min, the thickness of the inner layer of the film is 60-80 mu m, and the sulfonated polyether ether ketone chlorine exchange-resistant membrane is obtained.

[0021] The polyether ether ketone with different sulfonation degrees is poured into an ion exchange membrane, under the action of an applied voltage, the concentration of sulfonic acid groups in the membrane is distributed in a gradient along the thickness direction, the sulfonation degree of the outer layer of the film is higher, the density of sulfonic acid groups is large, the migration efficiency of chlorine ions is improved, the adsorption of chlorine in waste water is promoted, the density of sulfonic acid groups in the inner layer of the film is gradually reduced, the migration of chlorine ions in the membrane along the gradient density is promoted, the sulfonic acid groups in the inner layer are less, the adsorption capacity of chlorine ions is weak, which is beneficial to reduce the residence of migrated chlorine ions on the surface of the membrane and avoid concentration polarization; on this basis, the dynamic disulfide bond is introduced into the outer layer to repair the surface of the membrane, reduce the damage of chlorine to the surface of the membrane, enhance the service life and dechlorination effect of the membrane, and the sulfonated cerium dioxide nanoparticles are introduced into the inner layer, the valence state of cerium ions is recycled, active chlorine is consumed to protect the substrate, and membrane poisoning is avoided.

[0022] As the limitation of the application, the solid-liquid ratio of the polyether ether ketone and concentrated sulfuric acid is (10-15) g / (150-200) mL; the concentration of sulfonated polyether ether ketone in the three dispersions for pouring the sulfonated polyether ether ketone chlorine exchange-resistant membrane is 0.13-0.17 g / mL; the mass ratio of diaminodiphenyl disulfide to 70%-80% sulfonated polyether ether ketone is (0.5-1.0):(13-17); the mass ratio of sulfonated cerium dioxide nanoparticles to 60%-70% sulfonated polyether ether ketone is (0.5-1.0):(22-26); and the mass ratio of diethylenetriamine pentaacetic acid to 45%-55% sulfonated polyether ether ketone is (0.01-0.03):(19-23).

[0023] As the limitation of the application, the preparation method of the sulfonated cerium dioxide nanoparticles is as follows:

[0024] The cerium nitrate hexahydrate is added into a mixed solution of ethanol and deionized water, after being stirred uniformly, the sodium citrate is added, and stirred at 70-80 DEG C for 2-3h, after the stirring is completed, the pH is adjusted to 9-10, to form a cerium dioxide sol, the sulfur propyl trimethoxysilane is added, and after being reacted at 60-70 DEG C for 3-4h, the hydrogen peroxide is added, and the reaction is continued for 1-2h, after the reaction is completed, centrifugal separation is carried out, and the cerium dioxide nanoparticles are obtained by washing with ethanol and drying.

[0025] As the limitation of the application, the mass ratio of the cerium nitrate hexahydrate, the sodium citrate, the sulfur propyl trimethoxysilane and the hydrogen peroxide is (4-5):(5.6-6.0):(0.4-0.6):(1-1.5).

[0026] The cerium ion is combined with hydroxyl ions to form cerium hydroxide under alkaline conditions, and then dehydrated to form cerium dioxide under heating conditions, in the process, the sodium citrate is added to complex the cerium ion, delay the rate of generating cerium hydroxide, so as to control the particle size of the generated cerium dioxide, and then the hydroxyl ions on the surface of the cerium dioxide nanoparticles further condense with the sulfur propyl trimethoxysilane, and then oxidized by the hydrogen peroxide, to graft the sulfonic acid groups on the surface of the cerium dioxide nanoparticles, which not only can avoid the agglomeration of the nanoparticles in the group, but also can form a continuous proton transfer path with the sulfonic acid groups in the matrix.

[0027] Compared with the prior art, the application has the beneficial effects that:

[0028] The polyurethane sponge is used as the matrix of the adsorbent, and the biochar and the multilayer adsorbent particles are loaded on the polyurethane sponge, so that the heavy metals in the wastewater are removed from the complex state under the action of the adsorbent, and flocculated and settled to the bottom of the water on the polyurethane sponge, so that the heavy metals in the wastewater are efficiently removed in one step, and at the same time, a sulfonated polyether ether ketone gradient exchange membrane with good chlorine resistance is designed, so as to promote the migration of chlorine in the electrodialysis process, and after the heavy metals are removed and the chlorine is removed, the wastewater meets the discharge requirements. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be clearly and completely described below, obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0030] The heavy metal wastewater (zinc: 460mg / L, chromium: 180mg / L, copper: 280mg / L, lead: 140mg / L, chlorine: 6.2*10 4 mg / L), polyurethane sponge (density: 0.015g / cm 3), polyether ether ketone (PEEK 450G, MFI: 16 g / 10 min).

[0031] Example 1: A deep treatment method based on heavy metal wastewater, specifically:

[0032] Step 1: Wash and crush the straw, then dry it. Under nitrogen protection, heat it to 500°C and pyrolyze for 2 hours. After pyrolysis, cool it to room temperature, grind it to 100 mesh, and then immerse it in 1 mol / L hydrochloric acid for 24 hours to obtain biochar;

[0033] Step 2: Mix 20g of tartaric acid and 20g of ferrous sulfate uniformly, and co-mill with 50g of potassium persulfate for 20 minutes to obtain adsorbent core particles with a particle size of 2mm. Mix 20g of aluminum sulfate and 2g of glycerol uniformly to form an aluminum slurry. Add the adsorbent core particles to the aluminum slurry, stir uniformly, and then filter. Solidify at 60°C for 2 hours to obtain aluminum salt particles, wherein the thickness of the aluminum layer is 50μm. Add 3g of sodium alginate and 2g of chitosan to 100mL of 1% acetic acid solution, heat to 60°C, stir for 2 hours, and then cool to room temperature. Add 80g of aluminum salt particles, slowly stir for 10 minutes, and then filter. Transfer the particles to a 1% calcium chloride solution and crosslink for 5 minutes. After 5 minutes, filter and wash with deionized water. Dry at 40°C for 5 hours to obtain multi-layer adsorbent particles with a particle size of 5mm;

[0034] Step 3: Add 2.5g of polyvinyl alcohol to 50mL of deionized water, heat to 90°C and stir for 1 hour. After cooling to room temperature, take 30mL and mix with 30g of biochar, ultrasonic dispersion for 20 minutes to obtain biochar slurry. The remaining 20mL is mixed with 10g of multi-layer adsorbent particles, ultrasonic dispersion for 20 minutes to obtain adsorbent dispersion liquid;

[0035] Step 4: Cut the recovered polyurethane sponge into small pieces, immerse it in a 5% sodium hydroxide solution for 1 hour to remove impurities, wash with deionized water, dry, and then weigh 60g and add to the biochar slurry. Then vacuum treatment, immerse for 20 minutes at -0.08MPa, take out, dry at 60°C for 1.5 hours, and then add to the adsorbent dispersion liquid and slowly stir. After 10 minutes, take out the sponge and place it in a sealed container with 5mL of 25% glutaraldehyde solution at 60°C for 4 hours. After the reaction is complete, take it out, wash it with deionized water, and dry it at 40°C for 5 hours to obtain multi-layer adsorbent-biochar-polyurethane sponge;

[0036] Step 5: 43.4g cerium nitrate hexahydrate was added into a mixed solution of 400mL ethanol and 400mL deionized water, after stirring evenly, 58.8g sodium citrate was added, stirring at 70-80℃ for 2-3h, after stirring was completed, the pH was adjusted to 9-10, forming ceria sol, 5g sulfopropyl trimethoxysilane was added, after reaction at 60-70℃ for 3-4h, 10g hydrogen peroxide was added, continuing to react for 1-2h, after the reaction was completed, centrifugation, washing with ethanol, drying, obtaining sulfonated ceria nanoparticles;

[0037] Step 6: 10g polyether ether ketone was added into 150mL concentrated sulfuric acid, sulfonated at 50℃ for 5h, after sulfonation was completed, 500mL 0℃ deionized water was added, precipitate was separated out, filtration, washing with deionized water until neutral, drying at 60℃ under vacuum for 6h, obtaining 75%sulfonated polyether ether ketone, in the same way, 10g polyether ether ketone was sulfonated for 3.5h and 2h respectively, obtaining 65%sulfonated polyether ether ketone and 50%sulfonated polyether ether ketone;

[0038] Step 7: 15g 75%sulfonated polyether ether ketone and 0.75g diamino diphenyl disulfide were added into 100mL dimethyl sulfoxide, after ultrasonic dispersion for 20min, the dispersion was poured into a mold, under the action of 1.5V direct current voltage output by platinum electrode with a spacing of 5cm, curing at 60℃ for 4h, obtaining membrane outer layer, thickness was 50μm, 24g 65%sulfonated polyether ether ketone and 0.72g sulfonated ceria nanoparticles were added into 160mL dimethyl sulfoxide, after ultrasonic dispersion for 20min, casting on the membrane outer layer, curing at 60℃ for 2h, forming membrane transition layer with a thickness of 80μm on the membrane outer layer, 21g 50%sulfonated polyether ether ketone and 0.02g diethylenetriamine pentaacetic acid were added into 140mL dimethyl sulfoxide, after ultrasonic dispersion for 20min, casting on the membrane transition layer, under the action of 0.5V direct current voltage output by platinum electrode with a spacing of 5cm, curing at 60℃ for 1h, forming membrane inner layer with a thickness of 70μm on the membrane transition layer, obtaining sulfonated polyether ether ketone chlorine-resistant exchange membrane;

[0039] Step 8: The pH of heavy metal wastewater was adjusted to 4.0-5.0, according to the dosage of 1.0g / L, the loaded multilayer adsorbent-biochar-polyurethane sponge was added into the heavy metal wastewater, after stirring evenly, standing and settling for 4h, the settled sludge was cleaned with 5% nitric acid, then the loaded multilayer adsorbent-biochar-polyurethane sponge was screened out, the adsorbent dispersion was immersed again for regeneration, the supernatant was siphoned into the electrodialysis membrane stack containing sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis, the electrodialysis voltage was set to 1.2V, the water inlet flow was 20mL / min, after electrodialysis, the deep treated heavy metal wastewater was obtained.

[0040] Example 2: A deep treatment method based on heavy metal wastewater, specifically:

[0041] Step 1: The straw was washed, crushed and dried. Under nitrogen protection, it was pyrolyzed at 500℃ for 2h. After pyrolysis, it was cooled to room temperature, ground to 100 mesh, immersed in 1 mol / L hydrochloric acid for 24h to obtain biochar;

[0042] Step 2: 20g of tartaric acid and 20g of ferrous sulfate were mixed uniformly, and 50g of potassium persulfate was ball-milled for 20min to form adsorbent core particles with a particle size of 2mm. 20g of aluminum sulfate and 2g of glycerol were mixed and stirred uniformly to form an aluminum slurry. The adsorbent core particles were added to the aluminum slurry, stirred uniformly, filtered, and solidified at 60℃ for 2h to obtain aluminum salt particles, wherein the thickness of the aluminum layer was 50μm. 3g of sodium alginate and 2g of chitosan were added to 100mL of 1% acetic acid solution, heated to 60℃ and stirred for 2h, then cooled to room temperature. 80g of aluminum salt particles were added, slowly stirred for 10min, then filtered. The particles were transferred to a 1% calcium chloride solution and crosslinked for 5min. After 5min, it was filtered, washed with deionized water, and dried at 40℃ for 5h to obtain multilayer adsorbent particles with a particle size of 5mm;

[0043] Step 3: 2.5g of polyvinyl alcohol was added to 50mL of deionized water, heated to 90℃ and stirred for 1h. After cooling to room temperature, 30mL of the mixture was taken and mixed with 30g of biochar, ultrasonically dispersed for 20min to obtain a biochar slurry. The remaining 20mL was mixed with 12g of multilayer adsorbent particles, ultrasonically dispersed for 20min to obtain an adsorbent dispersion liquid;

[0044] Step 4: The recovered polyurethane sponge was cut into small pieces, immersed in a 5% sodium hydroxide solution for 1h to remove impurities, washed with deionized water, dried, and weighed 55g. It was added to the biochar slurry, then vacuum treated, immersed for 20min at-0.08MPa, taken out, dried at 60℃ for 1.5h, then added to the adsorbent dispersion liquid and slowly stirred. After 10min, the sponge was taken out, placed in a sealed container with 5mL of 25% glutaraldehyde solution, and reacted at 60℃ for 4h. After the reaction was completed, it was taken out, washed with deionized water, and dried at 40℃ for 5h to obtain a multilayer adsorbent-biochar-polyurethane sponge;

[0045] Step 5: 43.4g of cerium nitrate hexahydrate was added to a mixture of 400mL of ethanol and 400mL of deionized water, stirred uniformly, then 58.8g of sodium citrate was added, stirred at 70-80℃ for 2-3h, the pH was adjusted to 9-10 to form a cerium dioxide sol, 5g of sulfopropyltrimethoxysilane was added, reacted at 60-70℃ for 3-4h, then 10g of hydrogen peroxide was added and continued to react for 1-2h. After the reaction was completed, it was centrifuged, washed with ethanol, and dried to obtain sulfonated cerium dioxide nanoparticles.

[0046] Step 6: 10 g of polyether ether ketone was added to 150 mL of concentrated sulfuric acid and sulfonated at 50℃ for 5 h. After sulfonation was completed, 500 mL of 0℃ deionized water was added, and a precipitate was separated out. The precipitate was filtered, washed with deionized water until neutral, and dried at 60℃ under vacuum for 6 h to obtain 75% sulfonated polyether ether ketone. In the same way, 10 g of polyether ether ketone was sulfonated for 3.5 h and 2 h to obtain 65% sulfonated polyether ether ketone and 50% sulfonated polyether ether ketone, respectively;

[0047] Step 7: 15 g of 75% sulfonated polyether ether ketone and 0.9 g of diamino diphenyl disulfide were added to 100 mL of dimethyl sulfoxide, and the dispersion was ultrasonically dispersed for 20 min. The dispersion was then poured into a mold, and a membrane outer layer with a thickness of 50 μm was obtained by solidifying at 60℃ for 4 h under the action of a direct current voltage of 1.5 V output by platinum electrodes with a spacing of 5 cm. 24 g of 65% sulfonated polyether ether ketone and 0.85 g of sulfonated cerium dioxide nanoparticles were added to 160 mL of dimethyl sulfoxide, and the dispersion was ultrasonically dispersed for 20 min. The dispersion was then cast on the membrane outer layer, and a membrane transition layer with a thickness of 80 μm was formed on the membrane outer layer by solidifying at 60℃ for 2 h. 21 g of 50% sulfonated polyether ether ketone and 0.025 g of diethylenetriamine pentaacetic acid were added to 140 mL of dimethyl sulfoxide, and the dispersion was ultrasonically dispersed for 20 min. The dispersion was then cast on the membrane transition layer, and a membrane inner layer with a thickness of 70 μm was formed on the membrane transition layer by solidifying at 60℃ for 1 h under the action of a direct current voltage of 0.5 V output by platinum electrodes with a spacing of 5 cm. A sulfonated polyether ether ketone chlorine-resistant exchange membrane was obtained.

[0048] Step 8: The pH of the heavy metal wastewater was adjusted to 4.0-5.0, and the loaded multilayer adsorbent-biochar-polyurethane sponge was added to the heavy metal wastewater at a dosage of 1.2 g / L. After stirring and uniform mixing, the mixture was allowed to stand and settle for 4 h. The settled sludge was washed with 5% nitric acid, and the loaded multilayer adsorbent-biochar-polyurethane sponge was sieved out. The adsorbent dispersion was re-immersed and regenerated, and the supernatant was siphoned into an electrodialysis membrane stack containing a sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis. The electrodialysis voltage was set to 1.2 V, and the water inflow rate was 20 mL / min. After electrodialysis, the heavy metal wastewater was obtained.

[0049] Example 3: A method for deep treatment of heavy metal wastewater, specifically comprising:

[0050] Step 1: The straw was washed, crushed, and dried. Under nitrogen protection, the temperature was raised to 500℃ for pyrolysis for 2 h. After pyrolysis was completed, the mixture was cooled to room temperature in a sealed container. The mixture was ground to 100 mesh and immersed in 1 mol / L hydrochloric acid for activation for 24 h to obtain biochar.

[0051] Step 2: 20 g of tartaric acid and 20 g of ferrous sulfate were mixed uniformly, and after being ball-milled with 50 g of potassium persulfate for 20 min, granulation was performed to obtain adsorbent core particles with a particle size of 2 mm. 20 g of aluminum sulfate and 2 g of glycerol were mixed and stirred uniformly to form an aluminum slurry. The adsorbent core particles were added to the aluminum slurry, which was stirred uniformly and then filtered. The particles were solidified at 60°C for 2 h to obtain aluminum salt particles, wherein the thickness of the aluminum layer was 50 μm. 3 g of sodium alginate and 2 g of chitosan were added to 100 mL of an acetic acid solution with a mass fraction of 1%. After being stirred at 60°C for 2 h and then cooled to room temperature, 80 g of the aluminum salt particles were added. After being slowly stirred for 10 min, the particles were filtered and transferred to a calcium chloride solution with a mass fraction of 1% for crosslinking for 5 min. After 5 min, the particles were filtered, washed with deionized water, and dried at 40°C for 5 h to obtain multilayer adsorbent particles with a particle size of 5 mm;

[0052] Step 3: 2.5 g of polyvinyl alcohol was added to 50 mL of deionized water, which was heated to 90°C and stirred for 1 h. After being cooled to room temperature, 30 mL of the solution was mixed with 30 g of biochar to obtain a biochar slurry by ultrasonic dispersion for 20 min. The remaining 20 mL was mixed with 14 g of multilayer adsorbent particles to obtain an adsorbent dispersion liquid by ultrasonic dispersion for 20 min.

[0053] Step 4: The recovered polyurethane sponge was cut into small pieces, immersed in a sodium hydroxide solution with a mass fraction of 5% for 1 h to remove impurities, washed with deionized water, dried, and then weighed 50 g and added to the biochar slurry. Subsequently, vacuum treatment was performed, and the sponge was taken out after being immersed at -0.08 MPa for 20 min. After being dried at 60°C for 1.5 h, the sponge was added to the adsorbent dispersion liquid and slowly stirred. After 10 min, the sponge was taken out and placed in a sealed container together with 5 mL of glutaraldehyde solution with a mass fraction of 25%. The reaction was performed at 60°C for 4 h. After the reaction was completed, the sponge was taken out, washed with deionized water, and dried at 40°C for 5 h to obtain a multilayer adsorbent-biochar-polyurethane sponge.

[0054] Step 5: 43.4 g of cerium nitrate hexahydrate was added to a mixed solution of 400 mL of ethanol and 400 mL of deionized water, which was stirred uniformly. Then, 58.8 g of sodium citrate was added, and the mixture was stirred at 70-80°C for 2-3 h. After the stirring was completed, the pH was adjusted to 9-10 to form a ceria sol. 5 g of sulfopropyltrimethoxysilane was added, and the reaction was performed at 60-70°C for 3-4 h. Then, 10 g of hydrogen peroxide was added, and the reaction was continued for 1-2 h. After the reaction was completed, the mixture was centrifuged, washed with ethanol, and dried to obtain sulfonated ceria nanoparticles.

[0055] Step 6: 10 g of polyether ether ketone was added to 150 mL of concentrated sulfuric acid and sulfonated at 50°C for 5 h. After sulfonation was completed, 500 mL of 0°C deionized water was added, and a precipitate was separated out. The precipitate was filtered, washed with deionized water until neutral, and dried at 60°C under vacuum for 6 h to obtain 75% sulfonated polyether ether ketone. In the same way, 10 g of polyether ether ketone was sulfonated for 3.5 h and 2 h, respectively, to obtain 65% sulfonated polyether ether ketone and 50% sulfonated polyether ether ketone;

[0056] Step 7: 15 g of 75% sulfonated polyether ether ketone and 1.0 g of diamino diphenyl disulfide were added to 100 mL of dimethyl sulfoxide, and the dispersion was ultrasonically dispersed for 20 min. The dispersion was then poured into a mold, and a 1.5 V direct current voltage was applied to platinum electrodes with a 5 cm spacing to solidify the dispersion at 60°C for 4 h to obtain a film outer layer with a thickness of 50 μm. 24 g of 65% sulfonated polyether ether ketone and 1.0 g of sulfated cerium dioxide nanoparticles were added to 160 mL of dimethyl sulfoxide, and the dispersion was ultrasonically dispersed for 20 min. The dispersion was then cast on the film outer layer and solidified at 60°C for 2 h to form a film transition layer with a thickness of 80 μm on the film outer layer. 21 g of 50% sulfonated polyether ether ketone and 0.03 g of diethylenetriamine pentaacetic acid were added to 140 mL of dimethyl sulfoxide, and the dispersion was ultrasonically dispersed for 20 min. The dispersion was then cast on the film transition layer and solidified at 60°C for 1 h under the action of a 0.5 V direct current voltage applied to platinum electrodes with a 5 cm spacing to form a film inner layer with a thickness of 70 μm on the film transition layer. A sulfonated polyether ether ketone chlorine-resistant exchange membrane was thus obtained.

[0057] Step 8: The pH of the heavy metal wastewater was adjusted to 4.0-5.0, and the loaded multilayer adsorbent-biochar-polyurethane sponge was added to the heavy metal wastewater at a dosage of 1.4 g / L. After stirring and uniform mixing, the mixture was allowed to stand and settle for 4 h. The settled sludge was washed with 5% nitric acid, and the loaded multilayer adsorbent-biochar-polyurethane sponge was sieved out. The adsorbent dispersion was re-immersed and regenerated, and the supernatant was siphoned into an electrodialysis membrane stack containing a sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis. The electrodialysis voltage was set to 1.2 V, and the water inflow rate was 20 mL / min. After electrodialysis, the heavy metal wastewater was obtained.

[0058] Based on Example 1, the following comparative experiments were performed, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below.

[0059] Comparative Example 1: This comparative example relates to a method for deep treatment of heavy metal wastewater. The difference between this comparative example and Example 1 is that no sulfated cerium dioxide nanoparticles were added to the electrodialysis membrane.

[0060] Step 1: The straw was washed, crushed, and dried. Under nitrogen protection, the straw was pyrolyzed at 500°C for 2 h. After pyrolysis was completed, the mixture was cooled to room temperature in a sealed container. The mixture was ground to 100 mesh and immersed in 1 mol / L hydrochloric acid for 24 h to obtain biochar.

[0061] Step 2: 20 g of tartaric acid and 20 g of ferrous sulfate were mixed uniformly, and after being co-milled with 50 g of potassium persulfate for 20 min, granulation was performed to obtain adsorbent core particles with a particle size of 2 mm. 20 g of aluminum sulfate and 2 g of glycerol were mixed and stirred uniformly to form an aluminum slurry. The adsorbent core particles were added to the aluminum slurry, which was stirred uniformly and then filtered. The particles were solidified at 60°C for 2 h to obtain aluminum salt particles, wherein the thickness of the aluminum layer was 50 μm. 3 g of sodium alginate and 2 g of chitosan were added to 100 mL of an acetic acid solution with a mass fraction of 1%. After being heated to 60°C and stirred for 2 h, the solution was cooled to room temperature. 80 g of aluminum salt particles were added, and after being slowly stirred for 10 min, the particles were filtered and transferred to a calcium chloride solution with a mass fraction of 1% for crosslinking for 5 min. After 5 min, the particles were filtered, washed with deionized water, and dried at 40°C for 5 h to obtain multi-layer adsorbent particles with a particle size of 5 mm;

[0062] Step 3: 2.5 g of polyvinyl alcohol was added to 50 mL of deionized water, heated to 90°C, and stirred for 1 h. After being cooled to room temperature, 30 mL of the solution was mixed with 30 g of biochar to obtain a biochar slurry after ultrasonic dispersion for 20 min. The remaining 20 mL was mixed with 10 g of multi-layer adsorbent particles to obtain an adsorbent dispersion liquid after ultrasonic dispersion for 20 min;

[0063] Step 4: The recovered polyurethane sponge was cut into small pieces, immersed in a 5% sodium hydroxide solution for 1 h to remove impurities, washed with deionized water, dried, and then weighed 60 g and added to the biochar slurry. Subsequently, vacuum treatment was performed, and the sponge was removed after being immersed at -0.08 MPa for 20 min. After being dried at 60°C for 1.5 h, the sponge was added to the adsorbent dispersion liquid and slowly stirred. After 10 min, the sponge was removed and placed in a sealed container together with 5 mL of a 25% glutaraldehyde solution. The reaction was performed at 60°C for 4 h. After the reaction was completed, the sponge was removed, washed with deionized water, and dried at 40°C for 5 h to obtain a multi-layer adsorbent-biochar-polyurethane sponge;

[0064] Step 5: 10 g of polyether ether ketone was added to 150 mL of concentrated sulfuric acid and sulfonated at 50°C for 5 h. After the sulfonation was completed, 500 mL of deionized water at 0°C was added, and a precipitate was obtained. The precipitate was filtered, washed with deionized water until neutral, and dried at 60°C under vacuum for 6 h to obtain 75% sulfonated polyether ether ketone. In the same way, 10 g of polyether ether ketone was sulfonated for 3.5 h and 2 h to obtain 65% sulfonated polyether ether ketone and 50% sulfonated polyether ether ketone, respectively;

[0065] Step 6: 15 g of 75% sulfonated polyether ether ketone and 0.75 g of diaminodiphenyl disulfide were added to 100 mL of dimethyl sulfoxide, and the dispersion was poured into a mold after ultrasonic dispersion for 20 min. Under the action of a direct current voltage of 1.5 V output by platinum electrodes with a spacing of 5 cm, the film outer layer was cured at 60℃ for 4 h. 24 g of 65% sulfonated polyether ether ketone was added to 160 mL of dimethyl sulfoxide, and the film transition layer with a thickness of 80 μm was formed on the film outer layer after ultrasonic dispersion for 20 min and casting. 21 g of 50% sulfonated polyether ether ketone and 0.02 g of diethylenetriamine pentaacetic acid were added to 140 mL of dimethyl sulfoxide, and the film inner layer with a thickness of 70 μm was formed on the film transition layer after ultrasonic dispersion for 20 min and casting under the action of a direct current voltage of 0.5 V output by platinum electrodes with a spacing of 5 cm at 60℃ for 1 h. A sulfonated polyether ether ketone chlorine-resistant exchange membrane was obtained.

[0066] Step 7: The pH of the heavy metal wastewater was adjusted to 4.0-5.0, and the loaded multi-layer adsorbent-biochar-polyurethane sponge was added to the heavy metal wastewater at a dosage of 1.0 g / L. After stirring uniformly, the sludge was settled for 4 h, and the loaded multi-layer adsorbent-biochar-polyurethane sponge was screened out after cleaning with 5% nitric acid. The adsorbent dispersion was regenerated by re-immersion, and the supernatant was siphoned into an electrodialysis membrane stack containing a sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis. The electrodialysis voltage was set to 1.2 V, and the water flow rate was 20 mL / min. After electrodialysis, the heavy metal wastewater was obtained.

[0067] Comparative Example 2: This comparative example relates to a method for deep treatment of heavy metal wastewater, which is different from Example 1 in that the multi-layer adsorbent particles are not coated with sodium alginate-chitosan as the outer shell of the adsorbent. Specifically:

[0068] Step 1: The straw was washed, crushed, and dried. Under nitrogen protection, the temperature was raised to 500℃ for pyrolysis for 2 h. After pyrolysis, the system was cooled to room temperature, ground to 100 mesh, and immersed in 1 mol / L hydrochloric acid for 24 h to obtain biochar.

[0069] Step 2: 20 g of tartaric acid and 20 g of ferrous sulfate were mixed uniformly, and 50 g of potassium persulfate was ball-milled together for 20 min to obtain adsorbent core particles with a particle size of 2 mm. 20 g of aluminum sulfate and 2 g of glycerol were mixed and stirred uniformly to form an aluminum slurry. The adsorbent core particles were added to the aluminum slurry, stirred uniformly, and then filtered. The multi-layer adsorbent particles were obtained after curing at 60℃ for 2 h, with an aluminum layer thickness of 50 μm.

[0070] Step 3: 2.5 g of polyvinyl alcohol was added to 50 mL of deionized water, heated to 90°C and stirred for 1 h, after cooling to room temperature, 30 mL of which was mixed with 30 g of biochar, ultrasonic dispersion for 20 min, to obtain a biochar slurry, and the remaining 20 mL was mixed with 10 g of multi-layer adsorbent particles, ultrasonic dispersion for 20 min, to obtain an adsorbent dispersion liquid;

[0071] Step 4: The recovered polyurethane sponge was cut into small pieces, immersed in a 5% sodium hydroxide solution for 1 h to remove impurities, washed with deionized water, dried, and then 60 g was added to the biochar slurry, followed by vacuum treatment, immersed for 20 min at -0.08 MPa, and then removed, dried at 60°C for 1.5 h, and then added to the adsorbent dispersion liquid and slowly stirred, and after 10 min the sponge was removed and placed in a sealed container with 5 mL of a 25% glutaraldehyde solution, and reacted at 60°C for 4 h, after the reaction was completed, it was removed and washed with deionized water, and dried at 40°C for 5 h to obtain a multi-layer adsorbent-biochar-polyurethane sponge loaded with biochar;

[0072] Step 5: 43.4 g of cerium nitrate hexahydrate was added to a mixture of 400 mL of ethanol and 400 mL of deionized water, stirred until uniform, then 58.8 g of sodium citrate was added, stirred at 70-80°C for 2-3 h, and then the pH was adjusted to 9-10 to form a ceria sol, 5 g of sulfopropyltrimethoxysilane was added, and reacted at 60-70°C for 3-4 h, then 10 g of hydrogen peroxide was added and the reaction was continued for 1-2 h, after the reaction was completed, it was centrifuged, washed with ethanol, and dried to obtain sulfonated ceria nanoparticles;

[0073] Step 6: 10 g of polyether ether ketone was added to 150 mL of concentrated sulfuric acid and sulfonated at 50°C for 5 h, after sulfonation was complete, 500 mL of 0°C deionized water was added, and a precipitate was separated, filtered, washed with deionized water until neutral, and dried at 60°C under vacuum for 6 h to obtain 75% sulfonated polyether ether ketone, in the same way, 10 g of polyether ether ketone was sulfonated for 3.5 h and 2 h to obtain 65% sulfonated polyether ether ketone and 50% sulfonated polyether ether ketone, respectively;

[0074] Step 7: 15 g of 75% sulfonated polyether ether ketone and 0.75 g of diaminodiphenyl disulfide were added to 100 mL of dimethyl sulfoxide, and the dispersion was poured into a mold after ultrasonic dispersion for 20 min. A film outer layer with a thickness of 50 μm was obtained by solidifying at 60°C for 4 h under the action of a direct current voltage of 1.5 V output by platinum electrodes with a spacing of 5 cm. 24 g of 65% sulfonated polyether ether ketone and 0.72 g of sulfonated cerium dioxide nanoparticles were added to 160 mL of dimethyl sulfoxide, and the dispersion was poured onto the film outer layer after ultrasonic dispersion for 20 min. A film transition layer with a thickness of 80 μm was formed on the film outer layer by solidifying at 60°C for 2 h. 21 g of 50% sulfonated polyether ether ketone and 0.02 g of diethylenetriamine pentaacetic acid were added to 140 mL of dimethyl sulfoxide, and the dispersion was poured onto the film transition layer after ultrasonic dispersion for 20 min. A film inner layer with a thickness of 70 μm was formed on the film transition layer by solidifying at 60°C for 1 h under the action of a direct current voltage of 0.5 V output by platinum electrodes with a spacing of 5 cm. A sulfonated polyether ether ketone chlorine-resistant exchange membrane was obtained.

[0075] Step 8: The pH of the heavy metal wastewater was adjusted to 4.0-5.0, and the loaded multi-layer adsorbent-biochar-polyurethane sponge was added to the heavy metal wastewater at a dosage of 1.0 g / L. After stirring uniformly, the mixture was allowed to stand and settle for 4 h. The settled sludge was washed with 5% nitric acid, and the loaded multi-layer adsorbent-biochar-polyurethane sponge was sieved out. The adsorbent dispersion was re-immersed and regenerated, and the supernatant was siphoned into an electrodialysis membrane stack containing a sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis. The electrodialysis voltage was set to 1.2 V, and the water flow rate was 20 mL / min. After electrodialysis, the heavy metal wastewater was obtained.

[0076] Comparative Example 3: This comparative example relates to a method for resource utilization of waste incineration fly ash, which differs from Example 1 in that no multi-layer adsorbent particles are added. Specifically:

[0077] Step 1: The straw was washed, crushed, and dried. Under nitrogen protection, the temperature was raised to 500°C for pyrolysis for 2 h. After pyrolysis, the system was cooled to room temperature, ground to 100 mesh, and immersed in 1 mol / L hydrochloric acid for activation for 24 h to obtain biochar.

[0078] Step 2: 2.5 g of polyvinyl alcohol was added to 50 mL of deionized water, heated to 90°C and stirred for 1 h. After cooling to room temperature, 30 mL of the mixture was mixed with 30 g of biochar, and ultrasonic dispersion was performed for 20 min to obtain a biochar slurry. The remaining 20 mL was mixed with 10 g of multi-layer adsorbent particles, and ultrasonic dispersion was performed for 20 min to obtain an adsorbent dispersion.

[0079] Step 3: The recovered polyurethane sponge was cut into small pieces, immersed in a 5% sodium hydroxide solution for 1 h to remove impurities, washed with deionized water, dried, and then weighed 60 g and added to the biochar slurry. Then vacuum treatment was performed, and after 20 min of immersion at-0.08 MPa, it was removed and placed in a sealed container with 5 mL of 25% glutaraldehyde solution. The reaction was carried out at 60°C for 4 h. After the reaction was completed, it was removed, washed with deionized water, and dried at 40°C for 5 h to obtain the multi-layer adsorbent-biochar-polyurethane sponge loaded;

[0080] Step 4: 43.4 g of cerium nitrate hexahydrate was added to a mixture of 400 mL of ethanol and 400 mL of deionized water. After stirring evenly, 58.8 g of sodium citrate was added. Stirring was carried out at 70-80°C for 2-3 h. After stirring was completed, the pH was adjusted to 9-10 to form a ceria sol. 5 g of sulfopropyltrimethoxysilane was added. After reacting at 60-70°C for 3-4 h, 10 g of hydrogen peroxide was added and the reaction was continued for 1-2 h. After the reaction was completed, it was centrifuged, washed with ethanol, and dried to obtain sulfonated ceria nanoparticles;

[0081] Step 5: 10 g of polyether ether ketone was added to 150 mL of concentrated sulfuric acid and sulfonated at 50°C for 5 h. After sulfonation was completed, 500 mL of 0°C deionized water was added and a precipitate was separated. After filtration, it was washed with deionized water until neutral. After vacuum drying at 60°C for 6 h, 75% sulfonated polyether ether ketone was obtained. In the same way, 10 g of polyether ether ketone was sulfonated for 3.5 h and 2 h to obtain 65% sulfonated polyether ether ketone and 50% sulfonated polyether ether ketone, respectively;

[0082] Step 6: 15 g of 75% sulfonated polyether ether ketone and 0.75 g of diamino diphenyl disulfide were added to 100 mL of dimethyl sulfoxide. After ultrasonic dispersion for 20 min, the dispersion was poured into a mold. Under the action of a 1.5 V direct current voltage output by platinum electrodes with a spacing of 5 cm, it was cured at 60°C for 4 h to obtain a membrane outer layer with a thickness of 50 μm. 24 g of 65% sulfonated polyether ether ketone and 0.72 g of sulfonated ceria nanoparticles were added to 160 mL of dimethyl sulfoxide and ultrasonically dispersed for 20 min. After casting on the membrane outer layer, it was cured at 60°C for 2 h to form a membrane transition layer with a thickness of 80 μm on the membrane outer layer. 21 g of 50% sulfonated polyether ether ketone and 0.02 g of diethylenetriamine pentaacetic acid were added to 140 mL of dimethyl sulfoxide and ultrasonically dispersed for 20 min. After casting on the membrane transition layer, it was cured at 60°C for 1 h under the action of a 0.5 V direct current voltage output by platinum electrodes with a spacing of 5 cm to form a membrane inner layer with a thickness of 70 μm on the membrane transition layer. A sulfonated polyether ether ketone chlorine-resistant exchange membrane was obtained;

[0083] Step 7: The pH of the heavy metal wastewater is adjusted to 4.0-5.0, and the loaded multi-layer adsorbent-biochar-polyurethane sponge is added to the heavy metal wastewater at a dosage of 1.0 g / L. After stirring uniformly, the heavy metal wastewater is allowed to stand and settle for 4 h. The settled sludge is washed with 5% nitric acid, and the loaded multi-layer adsorbent-biochar-polyurethane sponge is screened out. The adsorbent dispersion liquid is re-immersed and regenerated, and the supernatant is siphoned into an electrodialysis membrane stack containing a sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis. The electrodialysis voltage is set to 1.2 V, and the water inlet flow rate is 20 mL / min. After electrodialysis, the deep-treated heavy metal wastewater is obtained.

[0084] Detection experiment:

[0085] The same batch of heavy metal wastewater is treated according to the treatment methods of each embodiment and the comparative example, respectively, and the deep-treated heavy metal wastewater obtained is subjected to water heavy metal content testing and chlorine content testing.

[0086] Chlorine content testing: The total residual chlorine online analyzer (CL17sc, HACH) is used to test the chlorine content in the deep-treated heavy metal wastewater. First, zero-point calibration is performed, then range calibration is performed using a 1.0 mg / L chlorine standard solution, and finally, the instrument inlet pipe is inserted into the deep-treated heavy metal wastewater, and the measurement is started to obtain the chlorine content result.

[0087] Heavy metal content testing: The water quality heavy metal detector (XFGJS-12PSD) is used to test the content of heavy metals in the deep-treated wastewater. First, the instrument is started, then deionized water and heavy metal ion standard solution are added to generate a calibration curve, then 10 mL of deep-treated heavy metal wastewater is taken, filtered, and inserted into the working electrode, and the measurement mode is started to obtain the heavy metal content result.

[0088] Chlorine-resistant performance testing: The sulfonated polyether ether ketone chlorine-resistant exchange membrane is prepared according to the preparation method provided by each embodiment and the comparative example of the present application. Compared with the ordinary 75% sulfonated polyether ether ketone cast exchange membrane, the initial mechanical strength of the membrane is tested using a mechanical testing machine, and then the sample is immersed in a sodium hypochlorite aqueous solution with a chlorine content of 500 ppm, and is heated in a water bath at 80°C with synchronous oscillation. After 500 h, it is taken out, washed with deionized water to remove the residual solution on the surface of the membrane, and then dried. The mechanical strength of the membrane is measured again, and the mechanical strength retention rate is calculated.

[0089]

[0090] Conclusion: From the test data, it can be seen that, compared with Example 1, the processing technology provided by Comparative Example 1 is to load diatomic adsorbents on the electrodialysis membrane, and the chlorine content in the treated wastewater is obviously higher than that of Example 1. In Comparative Examples 2 and 3, one is not coated with sodium alginate-chitosan outside the heavy metal adsorbent, and one is not added with heavy metal adsorbent. The heavy metal content in the treated wastewater is obviously higher than that of Example 1. The deep treatment method for heavy metal wastewater provided by the application can effectively treat the heavy metals and chlorine in the wastewater, so as to meet the needs of wastewater discharge. In addition, compared with the ordinary 75% sulfonated polyether ether ketone cast exchange membrane, the mechanical strength retention rate of the sulfonated polyether ether ketone chlorine-resistant exchange membrane provided by the example is greater than 80% after being soaked in 500h 80℃ sodium hypochlorite solution, while the mechanical strength retention rate of the ordinary 75% sulfonated polyether ether ketone cast exchange membrane is only 41%, which shows that the sulfonated polyether ether ketone chlorine-resistant exchange membrane provided by the application indeed has good chlorine resistance.

[0091] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered as exemplary and non-limiting, and the scope of the application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application.

Claims

1. A method for advanced treatment of heavy metal wastewater, characterized in that: Specifically: First, adjust the pH of the heavy metal wastewater, then add the loaded multilayer adsorbent-biochar-polyurethane sponge, stir evenly and let it stand for 4-8 hours to settle. After settling, the lower layer sludge is washed with nitric acid and the loaded multilayer adsorbent-biochar-polyurethane sponge is screened out. The supernatant is siphoned into an electrodialysis membrane stack containing a sulfonated polyether ether ketone chlorine-resistant exchange membrane for electrodialysis to obtain deeply treated heavy metal wastewater. The preparation method of the multilayer adsorbent-biochar-polyurethane sponge is as follows: After washing, crushing and drying the straw, heat it to 500-600℃ for 1.5-2 hours under nitrogen protection. After pyrolysis, cool it to room temperature in a sealed container, grind it to 80-120 mesh, and then activate it in hydrochloric acid for 20-24 hours to obtain biochar. Polyvinyl alcohol is added to deionized water, heated to 80-90℃ and stirred for 1-1.5h. After cooling to room temperature, it is divided into two parts. One part is mixed with biochar and ultrasonically dispersed for 20-30min to obtain biochar slurry. The other part is mixed with multilayer adsorbent particles and ultrasonically dispersed for 20-30min to obtain adsorbent dispersion. Polyurethane sponge was cut into small pieces, immersed in sodium hydroxide solution for 1-2 hours to remove impurities, washed with deionized water, dried, and added to biochar slurry. Then, it was vacuum treated and immersed at (-0.08) MPa-(-0.04) MPa for 15-25 minutes. After that, it was taken out and dried at 60-70℃ for 1-1.5 hours. Then, it was added to the adsorbent dispersion and stirred slowly. After 5-15 minutes, the sponge was taken out and placed together with glutaraldehyde solution in a sealed container. It was reacted at 60-70℃ for 3-4 hours. After the reaction was completed, it was taken out, washed with deionized water, and dried at 40-50℃ for 3-5 hours to obtain a multilayered adsorbent-biochar-polyurethane sponge. The preparation method of sulfonated polyether ether ketone chloride-resistant exchange membrane is as follows: Polyether ether ketone (PEE ketone) is added to concentrated sulfuric acid and sulfonated at 50-60℃ for 4-6 hours. After sulfonation, deionized water at 0℃ is added to precipitate the precipitate. The precipitate is filtered, washed with deionized water until neutral, and then vacuum dried at 60-70℃ for 5-6 hours to obtain 70%-80% sulfonated PEEK. Using the same method, PEEK is sulfonated for 3-4 hours and 1.5-2.5 hours respectively to obtain 60%-70% and 45%-55% sulfonated PEEK. Cerium nitrate hexahydrate was added to a mixed solution of ethanol and deionized water and stirred until homogeneous. Sodium citrate was then added and stirred at 70-80℃ for 2-3 hours. After stirring, the pH was adjusted to 9-10 to form a cerium dioxide sol. Thiopropyltrimethoxysilane was then added and reacted at 60-70℃ for 3-4 hours. Hydrogen peroxide was then added and the reaction was continued for 1-2 hours. After the reaction was completed, the mixture was centrifuged, washed with ethanol, and dried to obtain sulfonated cerium dioxide nanoparticles. 70%-80% of sulfonated polyether ether ketone and diaminodiphenyl disulfide were added to dimethyl sulfoxide and ultrasonically dispersed for 20-30 minutes. The dispersion was then poured into a mold and cured at 60-70°C for 3-4 hours under a DC voltage of 1.4-1.5V output from platinum electrodes spaced 4-6 cm apart. This yielded an outer membrane layer with a thickness of 40-60 μm. Then, 60%-70% of sulfonated polyether ether ketone and sulfonated cerium dioxide nanoparticles were added to dimethyl sulfoxide and ultrasonically dispersed for 20 minutes. This mixture was then cast onto the outer membrane layer and cured at 60-70°C. Curing at 0℃ for 1.5-2.5h forms a membrane transition layer with a thickness of 70-90μm on the outer layer. 45%-55% sulfonated polyether ether ketone and diethylenetriaminepentaacetic acid are added to dimethyl sulfoxide and ultrasonically dispersed for 20-30min before being cast onto the membrane transition layer. Under the action of a DC voltage of 0.5-0.6V output by platinum electrodes with a spacing of 4-6cm, curing at 60-70℃ for 1-1.5h forms an inner layer with a thickness of 60-80μm on the membrane transition layer, thus obtaining a sulfonated polyether ether ketone chloride-resistant exchange membrane.

2. The method for advanced treatment of heavy metal wastewater according to claim 1, characterized in that: The pH of the heavy metal wastewater was adjusted to 4.0-5.0, and the solid-liquid ratio of the added loaded multilayer adsorbent-biochar-polyurethane sponge to the heavy metal wastewater was 1.0g / L-1.5g / L. During electrodialysis, the voltage was set to 1.0V-1.4V, and the influent flow rate was 20-30mL / min.

3. The method for advanced treatment of heavy metal wastewater according to claim 1, characterized in that: The concentration of biochar in the biochar slurry is 0.8-1.2 g / mL, and the concentration of multilayer adsorbent particles in the adsorbent dispersion is 0.4-0.6 g / mL; the mass ratio of polyurethane sponge to biochar is (5-7):(2.8-3.2), and the mass ratio of polyurethane sponge to multilayer adsorbent particles is (5-7):(0.8-1.2).

4. The method for advanced treatment of heavy metal wastewater according to claim 1, characterized in that: The preparation method of multilayer adsorbent particles is as follows: Tartaric acid and ferrous sulfate are mixed evenly and ball-milled with potassium persulfate for 20-30 minutes to obtain adsorbent core particles with a particle size of 1.5-2 mm. Aluminum sulfate and glycerol are mixed and stirred evenly to form an aluminum slurry. The adsorbent core particles are added to the aluminum slurry, stirred evenly, filtered, and cured at 60-70℃ for 1.5-2 hours to obtain aluminum salt particles with an aluminum layer thickness of 30-50 μm. Sodium alginate and chitosan are added to a 1% acetic acid solution, heated to 60-70℃ and stirred for 1-2 hours, then cooled to room temperature. Aluminum salt particles are added, stirred slowly for 10-15 minutes, filtered, and the particles are transferred to a 1% calcium chloride solution for crosslinking for 5-10 minutes. After 5-10 minutes, the particles are filtered, washed with deionized water, and dried at 40-50℃ for 4-5 hours to obtain multilayer adsorbent particles with a particle size of 3-5 mm.

5. The method for advanced treatment of heavy metal wastewater according to claim 4, characterized in that: The mass ratio of tartaric acid, ferrous sulfate and potassium persulfate is (1-3):(1.8-2.2):(4-6); the mass ratio of aluminum sulfate and glycerol is (18-22):(1-3); and the mass ratio of sodium alginate and chitosan is (2-4):(2-3).

6. The method for advanced treatment of heavy metal wastewater according to claim 1, characterized in that: The solid-liquid ratio of polyetheretherketone (PEEK) to concentrated sulfuric acid is (10-15) g / (150-200) mL; in the three dispersions used for casting sulfonated PEEK chloride exchange membranes, the concentration of sulfonated PEEK is 0.13-0.17 g / mL; the mass ratio of diaminodiphenyl disulfide to 70%-80% sulfonated PEEK is (0.5-1.0):(13-17); the mass ratio of sulfonated cerium dioxide nanoparticles to 60%-70% sulfonated PEEK is (0.5-1.0):(22-26); and the mass ratio of diethylenetriaminepentaacetic acid to 45%-55% sulfonated PEEK is (0.01-0.03):(19-23).

7. The method for advanced treatment of heavy metal wastewater according to claim 1, characterized in that: The mass ratio of cerium nitrate hexahydrate, sodium citrate, thiopropyltrimethoxysilane and hydrogen peroxide is (4-5):(5.6-6.0):(0.4-0.6):(1-1.5).

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