Zinc smelting wastewater treatment method

Abstract

The invention discloses a zinc smelting wastewater treatment method, which belongs to the technical field of wastewater treatment, and comprises the steps of zinc recovery, vulcanization treatment, precipitation treatment, flocculation, electrodialysis membrane treatment, evaporative crystallization and post-treatment. The precipitation treatment comprises the following steps: adding a metal ion remover into the sulfurized wastewater, stirring at normal temperature, standing, and carrying out solid-liquid separation to obtain wastewater subjected to precipitation treatment; the flocculation comprises the following steps: adding a composite flocculant into the wastewater subjected to precipitation treatment, stirring at normal temperature, standing, and carrying out solid-liquid separation to obtain flocculated wastewater; the method provided by the invention can realize resource utilization of zinc ions, zinc oxide, potassium ions and sodium ions in the wastewater, ensures that wastewater discharge reaches the standard, also can reduce the problem of blockage of an electrodialyzer in treatment, realizes treatment of heavy metal ions, improves the flocculation effect and flocculation speed during flocculation, and reduces the treatment cost. And the zinc smelting wastewater does not need to be repeatedly subjected to alkali addition, material washing and filter pressing, and a large amount of alkali does not need to be consumed.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for treating zinc smelting wastewater. Background Art

[0002] Of the capacity and output of zinc smelting in my country, about 80% comes from the hydrometallurgical process, about 15% comes from the ISP zinc smelting process, and the rest comes from the backward vertical tank zinc smelting process. In the hydrometallurgical process, there is a large amount of wastewater. In addition to a large amount of zinc ions, zinc oxide, potassium ions, and sodium ions, the wastewater also contains heavy metal ions, organic matter, suspended matter, etc. If the wastewater is discharged directly, it will pollute the environment. At the same time, it is also a waste for the zinc ions, zinc oxide, potassium ions, and sodium ions in the wastewater.

[0003] In order to realize the resource utilization of zinc ions, zinc oxide, potassium ions and sodium ions and ensure that the wastewater discharge meets the standards for zinc smelting wastewater from the hydrometallurgical process, the applicant adopted a method combining zinc recovery, sulfidation treatment, flocculation, electrodialysis membrane treatment, evaporation crystallization and post-treatment when designing the wastewater treatment plan. Zinc recovery includes alkali addition, material washing, filter pressing, leaching, ion exchange and electrolysis. The purpose of adding alkali in zinc recovery is to convert zinc ions in zinc smelting wastewater into zinc hydroxide, the purpose of material washing and filter pressing is to separate zinc hydroxide and zinc oxide in the wastewater, and obtain a mixture of zinc hydroxide and zinc oxide and wastewater after zinc separation, the purpose of leaching is to convert zinc hydroxide and zinc oxide into zinc sulfate aqueous solution, and sulfate anion exchange resin columns are used in ion exchange to remove anionic impurities other than sulfate ions in zinc sulfate aqueous solution, and the purpose of electrolysis is to electrolyze zinc ions in zinc sulfate aqueous solution into zinc element. The purpose of sulfidation treatment is to precipitate heavy metal ions in the wastewater after zinc separation. The purpose of flocculation is to precipitate suspended matter in the wastewater after zinc separation. The purpose of electrodialysis membrane treatment is to separate salt and concentrate. Evaporation and crystallization can concentrate the concentrated water produced in electrodialysis to obtain a mixed salt of sodium chloride and potassium chloride. The purpose of post-treatment is to pass the fresh water produced in electrodialysis membrane treatment into the ozone catalytic oxidation system and the gas stripping deammonification system to reduce the COD and ammonia nitrogen in the wastewater, and then discharge it after meeting the discharge standards.

[0004] However, when treating zinc smelting wastewater according to the above method, the following problems exist: first, in zinc recovery, the zinc hydroxide obtained after adding alkali has a hydrolysis problem in water, resulting in the presence of some zinc ions in the wastewater after zinc separation, and the zinc ions are hydrolyzed in electrodialysis. The hydrolyzed zinc hydroxide is easy to block the electrodialyzer used in the electrodialysis, affecting the efficiency of the electrodialyzer, and further affecting the water output efficiency of the electrodialyzer; second, the amount of sulfide used in the sulfidation treatment is difficult to control. If the amount of sulfide is too large, it will also form a water-soluble complex with heavy metal ions, resulting in a high heavy metal content in the treated wastewater; third, polyaluminum chloride or polyacrylamide is generally used in flocculation, but both have the problems of poor flocculation effect and slow flocculation speed, resulting in a high content of soluble macromolecules and suspended matter in the wastewater entering the electrodialysis membrane treatment, and the suspended matter is easy to block the membrane pores of the electrodialysis membrane, resulting in the blockage of the electrodialyzer, and the soluble macromolecules are adsorbed in the membrane pores of the electrodialysis membrane, which will also cause the electrodialyzer to be blocked during long-term operation.

[0005] In view of the above problems, after searching, the commonly used solutions are: first, repeatedly adding alkali, washing and filtering the zinc smelting wastewater, but this method will complicate the treatment method; second, during the addition of alkali, the pH is controlled to about 8.5, and after the zinc ions are precipitated, alkali is continued to be added to the wastewater after zinc separation to further increase the pH and precipitate all heavy metal ions, but this method will consume a lot of alkali; third, during flocculation, polyaluminum chloride and polyacrylamide are used in combination, polyaluminum chloride can play an adsorption role, and polyacrylamide can play a bridging role, thereby promoting flocculation, but in When polyaluminium chloride and polyacrylamide are used in combination, if the two are added together, there will be mutual influence. Therefore, polyaluminium chloride is generally added first, and polyaluminium chloride neutralizes the negatively charged particles in the zinc smelting wastewater, reducing the repulsion between the negatively charged particles and forming stable small flocs. Then polyacrylamide is added, and the small flocs are combined into large flocs by utilizing the adsorption and bridging effect of polyacrylamide. Therefore, after polyaluminium chloride and polyacrylamide are used in combination, although the flocculation effect can be improved, polyaluminium chloride and polyacrylamide need to be added in batches, and there is still the problem of slow flocculation speed. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for treating zinc smelting wastewater. Through the method of combining zinc recovery, sulfidation treatment, flocculation, electrodialysis membrane treatment and evaporation crystallization, the zinc ions, zinc oxide, potassium ions and sodium ions in the wastewater can be utilized as resources to ensure that the wastewater discharge meets the standards. The clogging problem of the electrodialyzer during the treatment can be reduced, the heavy metal ions can be treated, and the flocculation effect and flocculation speed during flocculation can be improved. There is no need to repeatedly add alkali, wash the material and filter the zinc smelting wastewater, and there is no need to consume a large amount of alkali.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for treating zinc smelting wastewater, comprising: zinc recovery, sulfidation treatment, precipitation treatment, flocculation, electrodialysis membrane treatment, evaporation crystallization, and post-treatment; The zinc recovery includes: adding alkali, washing, leaching, ion exchange, and electrolysis; The alkali is added, sodium hydroxide is added to the zinc smelting wastewater while stirring to adjust the pH to 8.4-8.6, filtering, taking the filter residue as a mixture of zinc hydroxide and zinc oxide, and taking the filtrate as wastewater after zinc separation; The washing material is washing the mixture of zinc hydroxide and zinc oxide with water to obtain the washed mixture of zinc hydroxide and zinc oxide; The leaching comprises leaching a mixture of zinc chloride and zinc oxide using an aqueous sulfuric acid solution to obtain an aqueous zinc sulfate solution; In the leaching, the concentration of the aqueous sulfuric acid solution is 7-9wt%; The ion exchange comprises using a sulfate anion exchange resin column to perform ion exchange on the zinc sulfate aqueous solution to obtain an ion-exchanged zinc sulfate aqueous solution; The electrolysis is to electrolyze the ion-exchanged zinc sulfate aqueous solution to obtain elemental zinc; The sulfidation treatment comprises adding sodium sulfide to the wastewater after zinc separation, stirring at room temperature for 5-15 minutes, standing for 1.5-2 hours, and performing solid-liquid separation to obtain wastewater after sulfidation treatment; In the sulfidation treatment, the molar ratio of heavy metals to sodium sulfide in the wastewater after zinc separation is 10:14-15; The precipitation treatment comprises adding a metal ion remover to the wastewater after sulfidation treatment, stirring at room temperature for 20-30 minutes, standing for 1-1.5 hours, and performing solid-liquid separation to obtain wastewater after precipitation treatment; In the precipitation treatment, the amount of metal ion remover added is 75-80 g / ton of wastewater after sulfidation treatment; The preparation method of the metal ion remover comprises the following steps: mixing citric acid and the first portion of water, stirring at room temperature for 10-30 minutes, adding activated carbon, stirring for 2-3 hours, adding aluminum chloride, stirring for 40-60 minutes, adding sodium hydroxide aqueous solution to adjust the pH to 7, filtering, taking the filter residue and washing it with water, mixing it with the second portion of water, stirring at room temperature for 10-30 minutes, heating it to 60-65° C., adding a hydrolyzed polyacrylamide aqueous solution, continuing to stir for 20-25 hours, filtering, taking the filter residue and washing it with water, and drying it to obtain the metal ion remover; In the preparation of the metal ion remover, the dosage ratio of citric acid, the first portion of water, activated carbon, aluminum chloride, the second portion of water, and the hydrolyzed polyacrylamide aqueous solution is 60-65 g: 1000-1200 mL: 140-150 g: 8-9 g: 1000-1200 mL: 1500-1600 mL; The particle size of the activated carbon is 2 mm; The concentration of the sodium hydroxide aqueous solution is 10wt%; The concentration of the hydrolyzed polyacrylamide aqueous solution is 5 g / L; The molecular weight of the hydrolyzed polyacrylamide in the hydrolyzed polyacrylamide aqueous solution is 12 million, and the degree of hydrolysis is 25%; The flocculation comprises adding a composite flocculant to the wastewater after the sedimentation treatment, stirring at room temperature for 15-20 minutes, standing for 20-30 minutes, and separating the solid and the liquid to obtain the flocculated wastewater; In the flocculation, the amount of the composite flocculant added is 180-200 g / ton of wastewater after precipitation treatment; The preparation method of the composite flocculant comprises: preparing cross-linked sodium lignin sulfonate, molecular assembly, and mixing; The preparation of cross-linked sodium lignin sulfonate comprises mixing sodium lignin sulfonate, sodium hydroxide aqueous solution and acetone, stirring at 35-40° C. for 20-30 minutes, adding epichlorohydrin, heating to 55-65° C. after the addition is completed, stirring for 5-6 hours, cooling to room temperature, filtering, taking the filter residue, washing it with water, and drying it to obtain a metal ion remover; In the preparation of cross-linked sodium lignin sulfonate, the dosage ratio of sodium lignin sulfonate, sodium hydroxide aqueous solution, acetone, and epichlorohydrin is 120-130 g: 250-280 mL: 500-600 mL: 120-140 mL; The concentration of the sodium hydroxide aqueous solution is 10wt%; The addition rate of epichlorohydrin is 5-6 mL / min; The molecular assembly comprises mixing cross-linked sodium lignin sulfonate and water, stirring at room temperature for 10-30 minutes, adding a cationic polyacrylamide aqueous solution, and stirring at room temperature for 2.5-3 hours after the addition is completed to obtain a molecular assembly solution; The amount ratio of the sodium lignin sulfonate in the preparation of the cross-linked sodium lignin sulfonate to the water and cationic polyacrylamide aqueous solution in the molecular assembly is 120-130 g: 400-450 mL: 3700-4000 mL; In the molecular assembly, the concentration of the cationic polyacrylamide aqueous solution is 3 g / L; The cationic polyacrylamide in the cationic polyacrylamide aqueous solution has a weight average molecular weight of 12 million and an ionicity of 20%; The cationic polyacrylamide aqueous solution is added at a rate of 400-600 mL / min; The mixing comprises mixing the molecular assembly liquid and polyaluminium chloride, and stirring at room temperature for 1-1.5 hours to obtain a composite flocculant; The amount ratio of the cationic polyacrylamide aqueous solution in the molecular assembly to the polyaluminium chloride in the mixture is 3700-4000mL:270-300g; The electrodialysis membrane treatment separates salt and concentrates the flocculated wastewater to obtain electrodialysis concentrated water and electrodialysis fresh water; In the electrodialysis membrane treatment, the electrodialysis membrane used is composed of a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a cation exchange membrane with a sulfonic acid group, which can selectively pass monovalent cations and block divalent cations; the anion exchange membrane is an anion exchange membrane with a quaternary ammonium group, which can selectively pass monovalent anions and block divalent anions. The evaporation crystallization is to evaporate and crystallize the electrodialysis concentrated water to obtain a mixed salt of sodium chloride and potassium chloride; The post-treatment is to pass the electrodialysis fresh water into an ozone catalytic oxidation system and a gas stripping deammonification system to reduce COD and ammonia nitrogen, and then discharge it after reaching the emission standard.

[0008] Compared with the prior art, the present invention has the following beneficial effects: (1) The zinc smelting wastewater treatment method of the present invention uses a metal ion remover and a composite flocculant. The preparation method of the metal ion remover is as follows: after citric acid and activated carbon are mixed, the citric acid is adsorbed on the surface of the activated carbon, and then aluminum chloride is added and the pH is adjusted to convert the citric acid on the surface of the activated carbon into aluminum citrate, and then hydrolyzed polyacrylamide is added to cross-link the hydrolyzed polyacrylamide with the aluminum citrate. The metal ion remover finally obtained is an activated carbon with a cross-linked product of hydrolyzed polyacrylamide and aluminum citrate coated on the surface. The cross-linked product of hydrolyzed polyacrylamide and aluminum citrate can adsorb heavy metals and complexes formed by heavy metals. In addition, the cross-linked product of hydrolyzed polyacrylamide and aluminum citrate also contains citric acid radicals that are not combined with aluminum ions and can combine with zinc ions, thereby removing zinc ions from the wastewater. The preparation method of the composite flocculant includes preparing cross-linked sodium lignin sulfonate, molecular assembly, mixing, and preparing cross-linked sodium lignin sulfonate. In order to cross-link sodium lignin sulfonate with epichlorohydrin to obtain cross-linked sodium lignin sulfonate, the molecular assembly is to utilize the electrostatic adsorption effect between the negatively charged sulfonic acid group in the cross-linked sodium lignin sulfonate and the positively charged cationic polyacrylamide, and the cationic polyacrylamide is coated on the surface of the cross-linked sodium lignin sulfonate to improve the dispersibility of the cross-linked sodium lignin sulfonate in water, and then mixed with polyaluminum chloride, the polyaluminum chloride is positively charged, and the cationic polyacrylamide coated on the surface of the cross-linked sodium lignin sulfonate repel each other, further improving the stabilizer of the composite flocculant, and then when treating wastewater, the polyaluminum chloride quickly adsorbs the negatively charged particles in the wastewater, and the two are neutralized to obtain neutralized particles, and then under stirring, the cationic polyacrylamide plays a bridging role, adsorbs the neutralized particles on the surface of the cross-linked sodium lignin sulfonate to form large flocs, and then quickly settles, thereby improving the flocculation effect and flocculation speed; (2) The zinc smelting wastewater treatment method of the present invention can realize resource utilization of zinc ions, zinc oxide, potassium ions and sodium ions in the wastewater, ensuring that the wastewater discharge meets the standards; (3) The zinc smelting wastewater treatment method of the present invention can reduce the clogging problem of the electrodialyzer during treatment. No clogging problem occurs after continuous operation of the method of the present invention for 15 days; (4) The zinc smelting wastewater treatment method of the present invention can achieve the treatment of heavy metal ions and improve the flocculation effect and flocculation speed during flocculation. For wastewater with an ammonia nitrogen content of 417.13 mg / L, a COD value of 160.14 mg / L, a zinc content of 5.94 mg / L, a thallium content of 52.29 mg / L, a manganese content of 2.31 mg / L, a cadmium content of 21.93 mg / L, a lead content of 1.88 mg / L, a cobalt content of 1.34 mg / L, and a chromium content of 1.36 mg / L, the flocculation speed is 100%; After chemical treatment, precipitation treatment and flocculation, the ammonia nitrogen content is 2.7-3.1 mg / L, the COD value is 26.2-28.5 mg / L, the zinc content is 0.20-0.21 mg / L, the thallium content is 0.002-0.004 mg / L, the manganese content is 0.003-0.004 mg / L, the cadmium content is 0.006-0.007 mg / L, the lead content is 0.029-0.031 mg / L, the cobalt content is 0.003 mg / L, and the chromium content is 0.018-0.019 mg / L; (5) The zinc smelting wastewater treatment method of the present invention does not require repeated addition of alkali, washing, and filter pressing of the zinc smelting wastewater, nor does it require consumption of a large amount of alkali. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The present invention is a flow chart of the treatment of zinc smelting wastewater; DETAILED DESCRIPTION

[0010] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0011] Preparation Example 1 Preparation of metal ion remover Mix 60g of citric acid and 1000mL of water, stir at room temperature for 10min, add 140g of activated carbon, stir for 2h, add 8g of aluminum chloride, stir for 40min, add sodium hydroxide aqueous solution to adjust the pH to 7, filter, take the filter residue and wash with water, mix with 1000mL of water, stir at room temperature for 10min, heat to 60°C, add 1500mL of hydrolyzed polyacrylamide aqueous solution, continue stirring for 20h, filter, take the filter residue and wash with water, and dry to obtain a metal ion remover; The particle size of the activated carbon is 2 mm; The concentration of the sodium hydroxide aqueous solution is 10wt%; The concentration of the hydrolyzed polyacrylamide aqueous solution is 5 g / L; The molecular weight of the hydrolyzed polyacrylamide in the hydrolyzed polyacrylamide aqueous solution is 12 million, and the degree of hydrolysis is 25%.

[0012] Preparation Example 2 Preparation of Metal Ion Remover Mix 65g of citric acid and 1200mL of water, stir at room temperature for 30min, add 150g of activated carbon, stir for 3h, add 9g of aluminum chloride, stir for 60min, add sodium hydroxide aqueous solution to adjust the pH to 7, filter, take the filter residue and wash with water, mix with 1200mL of water, stir at room temperature for 30min, heat to 65°C, add 1600mL of hydrolyzed polyacrylamide aqueous solution, continue stirring for 25h, filter, take the filter residue and wash with water, and dry to obtain a metal ion remover; The particle size of the activated carbon is 2 mm; The concentration of the sodium hydroxide aqueous solution is 10wt%; The concentration of the hydrolyzed polyacrylamide aqueous solution is 5 g / L; The weight average molecular weight of the hydrolyzed polyacrylamide in the hydrolyzed polyacrylamide aqueous solution is 12 million, and the degree of hydrolysis is 25%.

[0013] Preparation Example 3 Preparation of composite flocculant 1. Preparation of cross-linked sodium lignin sulfonate: 120 g of sodium lignin sulfonate, 250 mL of sodium hydroxide aqueous solution, and 500 mL of acetone were mixed, stirred at 35 ° C for 20 min, 120 mL of epichlorohydrin was added at a rate of 5 mL / min, and the temperature was raised to 55 ° C after the addition was completed, stirred for 5 h, cooled to room temperature, filtered, and the filter residue was washed with water and dried to obtain a metal ion remover; The concentration of the sodium hydroxide aqueous solution is 10wt%; 2. Molecular assembly: Mix all the cross-linked sodium lignin sulfonate obtained in step 1 with 400 mL of water, stir at room temperature for 10 min, add 3700 mL of cationic polyacrylamide aqueous solution at a rate of 400 mL / min, and stir at room temperature for 2.5 h after the addition is completed to obtain a molecular assembly solution; The concentration of the cationic polyacrylamide aqueous solution is 3g / L; The cationic polyacrylamide in the cationic polyacrylamide aqueous solution has a weight average molecular weight of 12 million and an ionicity of 20%.

[0014] 3. Mixing: Mix all the molecular assembly liquid obtained in step 2 and 270 g of polyaluminium chloride, and stir at room temperature for 1 hour to obtain a composite flocculant.

[0015] Preparation Example 4 Preparation of composite flocculant 1. Preparation of cross-linked sodium lignin sulfonate: 130 g of sodium lignin sulfonate, 280 mL of sodium hydroxide aqueous solution, and 600 mL of acetone were mixed, stirred at 40 ° C for 30 min, 140 mL of epichlorohydrin was added at a rate of 6 mL / min, and the temperature was raised to 65 ° C after the addition was completed, stirred for 6 h, cooled to room temperature, filtered, and the filter residue was washed with water and dried to obtain a metal ion remover; The concentration of the sodium hydroxide aqueous solution is 10wt%; 2. Molecular assembly: Mix all the cross-linked sodium lignin sulfonate obtained in step 1 with 450 mL of water, stir at room temperature for 30 min, add 4000 mL of cationic polyacrylamide aqueous solution at a rate of 600 mL / min, and stir at room temperature for 3 h after the addition is completed to obtain a molecular assembly solution; The concentration of the cationic polyacrylamide aqueous solution is 3g / L; The cationic polyacrylamide in the cationic polyacrylamide aqueous solution has a weight average molecular weight of 12 million and an ionicity of 20%.

[0016] 3. Mixing: Mix all the molecular assembly liquid obtained in step 2 and 300 g of polyaluminium chloride, and stir at room temperature for 1.5 h to obtain a composite flocculant.

[0017] Example 1 like Figure 1 As shown, a method for treating zinc smelting wastewater is specifically: 1. Zinc recovery: (1) Adding alkali: adding sodium hydroxide to the zinc smelting wastewater while stirring to adjust the pH to 8.55, filtering, taking the filter residue as a mixture of zinc hydroxide and zinc oxide, and taking the filtrate as the wastewater after zinc separation; The ammonia nitrogen content in the wastewater after zinc separation is 417.13 mg / L, the COD value is 160.14 mg / L, the sodium content is 16538.51 mg / L, the potassium content is 12603.12 mg / L, the zinc content is 5.94 mg / L, the thallium content is 52.29 mg / L, the manganese content is 2.31 mg / L, the cadmium content is 21.93 mg / L, the lead content is 1.88 mg / L, the cobalt content is 1.34 mg / L, and the chromium content is 1.36 mg / L; (2) Washing: washing the mixture of zinc hydroxide and zinc oxide with water to obtain a washed mixture of zinc hydroxide and zinc oxide; (3) Leaching: using a sulfuric acid aqueous solution to leach the mixture of zinc chloride and zinc oxide to obtain a zinc sulfate aqueous solution; The concentration of the aqueous sulfuric acid solution is 8wt%; (4) Ion exchange: using a sulfate anion exchange resin column to perform ion exchange on the zinc sulfate aqueous solution to obtain an ion-exchanged zinc sulfate aqueous solution; (5) Electrolysis: electrolyzing the aqueous zinc sulfate solution after ion exchange to obtain elemental zinc; 2. Sulfidation treatment: Add sodium sulfide to the wastewater after zinc separation, stir for 5 minutes at room temperature, let stand for 1.5 hours, separate the solid and liquid, and obtain the wastewater after sulfidation treatment; The molar ratio of heavy metals to sodium sulfide in the wastewater after zinc separation is 10:14; 3. Precipitation treatment: Add the metal ion remover prepared in Preparation Example 1 to the wastewater after sulfidation treatment, stir for 20 minutes at room temperature, let stand for 1 hour, separate the solid and liquid, and obtain wastewater after precipitation treatment; The amount of metal ion remover added is 75g / ton of wastewater after sulfidation treatment; 4. Flocculation: Add the composite flocculant prepared in Preparation Example 3 to the wastewater after the sedimentation treatment, stir for 15 minutes at room temperature, let stand for 20 minutes, separate the solid and liquid, and obtain the flocculated wastewater; The addition amount of composite flocculant is 180g / ton of wastewater after sedimentation treatment; The ammonia nitrogen content in the wastewater after flocculation is 3.1 mg / L, the COD value is 28.5 mg / L, the sodium content is 16508.2 mg / L, the potassium content is 12674.6 mg / L, the zinc content is 0.21 mg / L, the thallium content is 0.002 mg / L, the manganese content is 0.004 mg / L, the cadmium content is 0.007 mg / L, the lead content is 0.031 mg / L, the cobalt content is 0.003 mg / L, and the chromium content is 0.018 mg / L; 5. Electrodialysis: Separate and concentrate the wastewater after flocculation to obtain electrodialysis concentrated water and electrodialysis fresh water; In the electrodialysis membrane treatment, the electrodialysis membrane used is composed of a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a cation exchange membrane with a sulfonic acid group, which can selectively pass monovalent cations and block divalent cations; the anion exchange membrane is an anion exchange membrane with a quaternary ammonium group, which can selectively pass monovalent anions and block divalent anions. 6. Evaporation and crystallization: Evaporate and crystallize the concentrated water from electrodialysis to obtain a mixed salt of sodium chloride and potassium chloride; 7. Post-treatment: The electrodialysis fresh water is passed through the ozone catalytic oxidation system and the gas stripping deammonification system to reduce COD and ammonia nitrogen. After meeting the emission standards, it is discharged.

[0018] Example 2 like Figure 1 As shown, a method for treating zinc smelting wastewater is specifically: 1. Zinc recovery: (1) Adding alkali: adding sodium hydroxide to the zinc smelting wastewater while stirring to adjust the pH to 8.55, filtering, taking the filter residue as a mixture of zinc hydroxide and zinc oxide, and taking the filtrate as the wastewater after zinc separation; The ammonia nitrogen content in the wastewater after zinc separation is 417.13 mg / L, the COD value is 160.14 mg / L, the sodium content is 16538.51 mg / L, the potassium content is 12603.12 mg / L, the zinc content is 5.94 mg / L, the thallium content is 52.29 mg / L, the manganese content is 2.31 mg / L, the cadmium content is 21.93 mg / L, the lead content is 1.88 mg / L, the cobalt content is 1.34 mg / L, and the chromium content is 1.36 mg / L; (2) Washing: washing the mixture of zinc hydroxide and zinc oxide with water to obtain a washed mixture of zinc hydroxide and zinc oxide; (3) Leaching: using a sulfuric acid aqueous solution to leach the mixture of zinc chloride and zinc oxide to obtain a zinc sulfate aqueous solution; The concentration of the aqueous sulfuric acid solution is 8wt%; (4) Ion exchange: using a sulfate anion exchange resin column to perform ion exchange on the zinc sulfate aqueous solution to obtain an ion-exchanged zinc sulfate aqueous solution; (5) Electrolysis: electrolyzing the aqueous zinc sulfate solution after ion exchange to obtain elemental zinc; 2. Sulfidation treatment: Add sodium sulfide to the wastewater after zinc separation, stir for 15 minutes at room temperature, let stand for 2 hours, separate the solid and liquid, and obtain the wastewater after sulfidation treatment; The molar ratio of heavy metals to sodium sulfide in the wastewater after zinc separation is 10:15; 3. Precipitation treatment: Add the metal ion remover prepared in Preparation Example 2 to the wastewater after sulfidation treatment, stir for 30 minutes at room temperature, let stand for 1.5 hours, separate the solid and liquid, and obtain wastewater after precipitation treatment; The amount of metal ion remover added is 80g / ton of wastewater after sulfidation treatment; 4. Flocculation: Add the composite flocculant prepared in Preparation Example 4 to the wastewater after sedimentation treatment, stir for 20 minutes at room temperature, let stand for 30 minutes, separate the solid and liquid, and obtain flocculated wastewater; The addition amount of composite flocculant is 200g / ton of wastewater after sedimentation treatment; The ammonia nitrogen content in the wastewater after flocculation is 2.7 mg / L, the COD value is 26.2 mg / L, the sodium content is 16572.1 mg / L, the potassium content is 12662.5 mg / L, the zinc content is 0.20 mg / L, the thallium content is 0.004 mg / L, the manganese content is 0.003 mg / L, the cadmium content is 0.006 mg / L, the lead content is 0.029 mg / L, the cobalt content is 0.003 mg / L, and the chromium content is 0.019 mg / L; 5. Electrodialysis membrane treatment: The wastewater after flocculation is separated and concentrated to obtain electrodialysis concentrated water and electrodialysis fresh water; In the electrodialysis membrane treatment, the electrodialysis membrane used is composed of a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a cation exchange membrane with a sulfonic acid group, which can selectively pass monovalent cations and block divalent cations; the anion exchange membrane is an anion exchange membrane with a quaternary ammonium group, which can selectively pass monovalent anions and block divalent anions. 6. Evaporation and crystallization: Evaporate and crystallize the concentrated water from electrodialysis to obtain a mixed salt of sodium chloride and potassium chloride; 7. Post-treatment: The electrodialysis fresh water is passed through the ozone catalytic oxidation system and the gas stripping deammonification system to reduce COD and ammonia nitrogen. After meeting the emission standards, it is discharged.

[0019] Example 3 A method for treating zinc smelting wastewater, specifically comprising: 1. Zinc recovery: (1) Adding alkali: adding sodium hydroxide to the zinc smelting wastewater while stirring to adjust the pH to 8.55, filtering, taking the filter residue as a mixture of zinc hydroxide and zinc oxide, and taking the filtrate as the wastewater after zinc separation; The ammonia nitrogen content in the wastewater after zinc separation is 417.13 mg / L, the COD value is 160.14 mg / L, the sodium content is 16538.51 mg / L, the potassium content is 12603.12 mg / L, the zinc content is 5.94 mg / L, the thallium content is 52.29 mg / L, the manganese content is 2.31 mg / L, the cadmium content is 21.93 mg / L, the lead content is 1.88 mg / L, the cobalt content is 1.34 mg / L, and the chromium content is 1.36 mg / L; (2) Washing: washing the mixture of zinc hydroxide and zinc oxide with water to obtain a washed mixture of zinc hydroxide and zinc oxide; (3) Leaching: using a sulfuric acid aqueous solution to leach the mixture of zinc chloride and zinc oxide to obtain a zinc sulfate aqueous solution; The concentration of the aqueous sulfuric acid solution is 8wt%; (4) Ion exchange: using a sulfate anion exchange resin column to perform ion exchange on the zinc sulfate aqueous solution to obtain an ion-exchanged zinc sulfate aqueous solution; (5) Electrolysis: electrolyzing the aqueous zinc sulfate solution after ion exchange to obtain elemental zinc; 2. Sulfidation treatment: Add sodium sulfide to the wastewater after zinc separation, stir for 5 minutes at room temperature, let stand for 1.5 hours, separate the solid and liquid, and obtain the wastewater after sulfidation treatment; The molar ratio of heavy metals to sodium sulfide in the wastewater after zinc separation is 10:14; 3. Flocculation: Add composite flocculant to the wastewater after sulfidation treatment, stir for 15 minutes at room temperature, let stand for 20 minutes, separate the solid and liquid, and obtain flocculated wastewater; The preparation method of the composite flocculant is as follows: 400 mL of water, 3700 mL of cationic polyacrylamide aqueous solution, and 270 g of polyaluminium chloride are mixed, and stirred at room temperature for 1 hour to obtain the composite flocculant; The concentration of the cationic polyacrylamide aqueous solution is 3g / L; The cationic polyacrylamide in the cationic polyacrylamide aqueous solution has a weight average molecular weight of 12 million and an ionicity of 20%; The addition amount of composite flocculant is 180g / ton of wastewater after sulfidation treatment; The ammonia nitrogen content in the wastewater after flocculation is 31.4 mg / L, the COD value is 77.1 mg / L, the sodium content is 16547.2 mg / L, the potassium content is 12648.3 mg / L, the zinc content is 3.61 mg / L, the thallium content is 0.053 mg / L, the manganese content is 0.025 mg / L, the cadmium content is 0.034 mg / L, the lead content is 0.167 mg / L, the cobalt content is 0.117 mg / L, and the chromium content is 0.128 mg / L; 4. Electrodialysis membrane treatment: The wastewater after flocculation is separated and concentrated to obtain electrodialysis concentrated water and electrodialysis fresh water; In the electrodialysis membrane treatment, the electrodialysis membrane used is composed of a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a cation exchange membrane with a sulfonic acid group, which can selectively pass monovalent cations and block divalent cations; the anion exchange membrane is an anion exchange membrane with a quaternary ammonium group, which can selectively pass monovalent anions and block divalent anions. 5. Evaporation and crystallization: Evaporate and crystallize the concentrated water from electrodialysis to obtain a mixed salt of sodium chloride and potassium chloride; 6. Post-treatment: The electrodialysis fresh water is passed through the ozone catalytic oxidation system and the gas stripping deammonification system to reduce COD and ammonia nitrogen. After meeting the emission standards, it is discharged.

[0020] Example 4 A method for treating zinc smelting wastewater, specifically comprising: 1. Zinc recovery: (1) Adding alkali: adding sodium hydroxide to the zinc smelting wastewater while stirring to adjust the pH to 8.55, filtering, taking the filter residue as a mixture of zinc hydroxide and zinc oxide, and taking the filtrate as the wastewater after zinc separation; The ammonia nitrogen content in the wastewater after zinc separation is 417.13 mg / L, the COD value is 160.14 mg / L, the sodium content is 16538.51 mg / L, the potassium content is 12603.12 mg / L, the zinc content is 5.94 mg / L, the thallium content is 52.29 mg / L, the manganese content is 2.31 mg / L, the cadmium content is 21.93 mg / L, the lead content is 1.88 mg / L, the cobalt content is 1.34 mg / L, and the chromium content is 1.36 mg / L; (2) Washing: washing the mixture of zinc hydroxide and zinc oxide with water to obtain a washed mixture of zinc hydroxide and zinc oxide; (3) Leaching: using a sulfuric acid aqueous solution to leach the mixture of zinc chloride and zinc oxide to obtain a zinc sulfate aqueous solution; The concentration of the aqueous sulfuric acid solution is 8wt%; (4) Ion exchange: using a sulfate anion exchange resin column to perform ion exchange on the zinc sulfate aqueous solution to obtain an ion-exchanged zinc sulfate aqueous solution; (5) Electrolysis: electrolyzing the aqueous zinc sulfate solution after ion exchange to obtain elemental zinc; 2. Sulfidation treatment: Add sodium sulfide to the wastewater after zinc separation, stir for 5 minutes at room temperature, let stand for 1.5 hours, separate the solid and liquid, and obtain the wastewater after sulfidation treatment; The molar ratio of heavy metals to sodium sulfide in the wastewater after zinc separation is 10:14; 3. Flocculation: Add composite flocculant to the wastewater after sulfidation treatment, stir for 45 minutes at room temperature, let stand for 60 minutes, separate the solid and liquid, and obtain flocculated wastewater; The preparation method of the composite flocculant is as follows: 3700 mL of cationic polyacrylamide aqueous solution and 270 g of polyaluminium chloride are mixed, and stirred at room temperature for 1 hour to obtain the composite flocculant; The concentration of the cationic polyacrylamide aqueous solution is 3g / L; The cationic polyacrylamide in the cationic polyacrylamide aqueous solution has a weight average molecular weight of 12 million and an ionicity of 20%; The addition amount of composite flocculant is 180g / ton of wastewater after sulfidation treatment; The ammonia nitrogen content in the wastewater after flocculation is 15.8 mg / L, the COD value is 53.7 mg / L, the sodium content is 16420.1 mg / L, the potassium content is 12593.6 mg / L, the zinc content is 3.73 mg / L, the thallium content is 0.051 mg / L, the manganese content is 0.025 mg / L, the cadmium content is 0.031 mg / L, the lead content is 0.142 mg / L, the cobalt content is 0.110 mg / L, and the chromium content is 0.104 mg / L; 4. Electrodialysis membrane treatment: The wastewater after flocculation is separated and concentrated to obtain electrodialysis concentrated water and electrodialysis fresh water; In the electrodialysis membrane treatment, the electrodialysis membrane used is composed of a cation exchange membrane and an anion exchange membrane. The cation exchange membrane is a cation exchange membrane with a sulfonic acid group, which can selectively pass monovalent cations and block divalent cations; the anion exchange membrane is an anion exchange membrane with a quaternary ammonium group, which can selectively pass monovalent anions and block divalent anions. 5. Evaporation and crystallization: Evaporate and crystallize the concentrated water from electrodialysis to obtain a mixed salt of sodium chloride and potassium chloride; 6. Post-treatment: The electrodialysis fresh water is passed through the ozone catalytic oxidation system and the gas stripping deammonification system to reduce COD and ammonia nitrogen. After meeting the emission standards, it is discharged.

[0021] It can be seen from the indicators of the wastewater after flocculation in Examples 1-4 that Example 3 does not use a metal ion remover, and the composite flocculant used is composed only of a cationic polyacrylamide aqueous solution and polyaluminum chloride. The ammonia nitrogen content, COD value, zinc content, thallium content, manganese content, lead content, cobalt content, and chromium content in the wastewater after flocculation are all higher than those in Example 1. Example 4 extends the stirring time and standing time in flocculation on the basis of Example 3. The zinc content, thallium content, manganese content, lead content, cobalt content, and chromium content in the wastewater after flocculation do not change much compared with those in Example 3. The ammonia nitrogen content and COD value in the wastewater after flocculation are lower than those in Example 3, but are still higher than those in Example 1, indicating that the metal ion remover can reduce the zinc content, thallium content, manganese content, lead content, cobalt content, and chromium content in the wastewater; the composite flocculant can reduce the ammonia nitrogen content and COD value in the wastewater.

[0022] Test Case The purpose of this test example is to further verify the effect of high zinc ion content on electrodialysis. The specific test method is to treat the same batch of zinc smelting wastewater according to the method of Examples 1-4, and run it continuously for 15 days. The treatment volume is controlled at 8m 3 / h, observe whether the electrodialyzer is blocked during operation. The criterion for blockage is that the water output of the electrodialyzer decreases by more than 10%. The observation results are as follows:

[0023] It can be seen from the results of the test example that when zinc smelting wastewater is treated according to the methods of Example 3 and Example 4, the problem of electrodialyzer clogging is more likely to occur, indicating that wastewater with high zinc ion concentration, ammonia nitrogen content and COD value is prone to cause electrodialyzer clogging.

[0024] Unless otherwise specified, all percentages used in the present invention are by mass.

[0025] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating zinc smelting wastewater, characterized in that: include: Zinc recovery, sulfidation treatment, precipitation treatment, flocculation, electrodialysis membrane treatment, evaporation crystallization, post-treatment; The precipitation treatment comprises adding a metal ion remover to the wastewater after sulfidation treatment, stirring at room temperature for 20-30 minutes, standing for 1-1.5 hours, and performing solid-liquid separation to obtain wastewater after precipitation treatment; The preparation method of the metal ion remover comprises adding activated carbon to a citric acid aqueous solution, stirring, adding aluminum chloride, stirring, adjusting the pH to 7, filtering, washing, mixing with water, stirring at room temperature, heating to 60-65° C., adding a hydrolyzed polyacrylamide aqueous solution, stirring, filtering, washing, and drying to obtain the metal ion remover; The flocculation comprises adding a composite flocculant to the wastewater after the sedimentation treatment, stirring at room temperature for 15-20 minutes, standing for 20-30 minutes, and separating the solid and the liquid to obtain the flocculated wastewater; The preparation method of the composite flocculant comprises: preparing cross-linked sodium lignin sulfonate, molecular assembly, and mixing; The molecular assembly comprises mixing cross-linked sodium lignin sulfonate and water, stirring at room temperature, adding a cationic polyacrylamide aqueous solution, and stirring to obtain a molecular assembly liquid; In the mixing, the molecular assembly liquid and polyaluminium chloride are mixed and stirred at room temperature to obtain a composite flocculant.

2. The method for treating zinc smelting wastewater according to claim 1, characterized in that: The zinc recovery comprises: adding alkali, washing, leaching, ion exchange and electrolysis.

3. The method for treating zinc smelting wastewater according to claim 2, characterized in that: The alkali is added, sodium hydroxide is added to the zinc smelting wastewater while stirring to adjust the pH to 8.4-8.6, filtering, taking the filter residue as a mixture of zinc hydroxide and zinc oxide, and taking the filtrate as wastewater after zinc separation; The washing material is washing the mixture of zinc hydroxide and zinc oxide with water to obtain the washed mixture of zinc hydroxide and zinc oxide; The leaching comprises leaching a mixture of zinc chloride and zinc oxide using an aqueous sulfuric acid solution to obtain an aqueous zinc sulfate solution; In the leaching, the concentration of the aqueous sulfuric acid solution is 7-9wt%; The ion exchange comprises using a sulfate anion exchange resin column to perform ion exchange on the zinc sulfate aqueous solution to obtain an ion-exchanged zinc sulfate aqueous solution; The electrolysis electrolyzes the ion-exchanged zinc sulfate aqueous solution to obtain elemental zinc.

4. The method for treating zinc smelting wastewater according to claim 1, characterized in that: The sulfidation treatment comprises adding sodium sulfide to the wastewater after zinc separation, stirring at room temperature for 5-15 minutes, standing for 1.5-2 hours, and performing solid-liquid separation to obtain wastewater after sulfidation treatment; In the sulfidation treatment, the molar ratio of heavy metals to sodium sulfide in the wastewater after zinc separation is 10:14-15.

5. The method for treating zinc smelting wastewater according to claim 1, characterized in that: In the precipitation treatment, the amount of metal ion remover added is 75-80 g / ton of wastewater after sulfidation treatment.

6. The method for treating zinc smelting wastewater according to claim 1, characterized in that: In the preparation of the metal ion remover, the ratio of citric acid to water in the citric acid aqueous solution is 60-65 g: 1000-1200 mL; The dosage ratio of citric acid, activated carbon, aluminum chloride, water, and hydrolyzed polyacrylamide aqueous solution in the citric acid aqueous solution is 60-65 g: 140-150 g: 8-9 g: 1000-1200 mL: 1500-1600 mL; The particle size of the activated carbon is 2 mm; The concentration of the hydrolyzed polyacrylamide aqueous solution is 5 g / L; The molecular weight of the hydrolyzed polyacrylamide in the hydrolyzed polyacrylamide aqueous solution is 12 million, and the degree of hydrolysis is 25%.

7. The method for treating zinc smelting wastewater according to claim 1, characterized in that: In the flocculation, the addition amount of the composite flocculant is 180-200 g / ton of wastewater after precipitation treatment.

8. The method for treating zinc smelting wastewater according to claim 1, characterized in that: The preparation of cross-linked sodium lignin sulfonate comprises mixing sodium lignin sulfonate, sodium hydroxide aqueous solution and acetone, stirring at 35-40° C., adding epichlorohydrin, heating to 55-65° C. after the addition is completed, stirring, cooling to room temperature, filtering, washing and drying to obtain a metal ion remover; In the preparation of cross-linked sodium lignin sulfonate, the dosage ratio of sodium lignin sulfonate, sodium hydroxide aqueous solution, acetone, and epichlorohydrin is 120-130 g: 250-280 mL: 500-600 mL: 120-140 mL; The concentration of the sodium hydroxide aqueous solution is 10wt%; The addition rate of the epichlorohydrin is 5-6 mL / min.

9. The method for treating zinc smelting wastewater according to claim 8, characterized in that: The amount ratio of the sodium lignin sulfonate in the preparation of the cross-linked sodium lignin sulfonate to the water and cationic polyacrylamide aqueous solution in the molecular assembly is 120-130 g: 400-450 mL: 3700-4000 mL; In the molecular assembly, the concentration of the cationic polyacrylamide aqueous solution is 3 g / L; The cationic polyacrylamide in the cationic polyacrylamide aqueous solution has a weight average molecular weight of 12 million and an ionicity of 20%; The cationic polyacrylamide aqueous solution is added at a rate of 400-600 mL / min; The usage ratio of the cationic polyacrylamide aqueous solution in the molecular assembly to the polyaluminium chloride in the mixture is 3700-4000mL:270-300g.

10. The method for treating zinc smelting wastewater according to claim 1, characterized in that: The electrodialysis membrane treatment separates salt and concentrates the flocculated wastewater to obtain electrodialysis concentrated water and electrodialysis fresh water; In the electrodialysis membrane treatment, the electrodialysis membrane used is composed of a cation exchange membrane and an anion exchange membrane, wherein the cation exchange membrane is a cation exchange membrane with a sulfonic acid group, which can selectively pass monovalent cations and block divalent cations; The anion exchange membrane is an anion exchange membrane with quaternary ammonium groups, which can selectively pass monovalent anions and block divalent anions; The evaporation crystallization is to evaporate and crystallize the electrodialysis concentrated water to obtain a mixed salt of sodium chloride and potassium chloride; The post-treatment is to pass the electrodialysis fresh water into an ozone catalytic oxidation system and a gas stripping deammoniation system for treatment before discharging it.

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