Environment-friendly treatment process for waste liquid containing nickel and zinc

Abstract

The invention discloses a nickel-zinc-containing waste liquid environment-friendly treatment process, which belongs to the technical field of electroplating waste liquid treatment, and comprises the following steps: collecting electroplating nickel-zinc-containing waste liquid, and adjusting the pH value to 6-9 to obtain pretreated nickel-zinc-containing waste liquid; adding modified charcoal and a hydrogen peroxide solution into the pretreated nickel-zinc-containing waste liquid, and stirring to react for 1-2 hours under the irradiation of an ultraviolet lamp, so as to obtain an oxidized nickel-zinc-containing waste liquid after the reaction is finished; the oxidized waste liquid containing nickel and zinc is introduced into a reduction pool, an unreacted hydrogen peroxide solution is reduced, a precipitator is added, stirring is conducted for 10-20 min, then a flocculant is added, stirring is conducted for 30-60 min, standing is conducted for 2 h, solid-liquid separation is conducted, solid sludge and filtrate are obtained, and the filtrate is to-be-discharged water; according to the invention, the modified biochar realizes synergistic interaction through an activation-complex breaking-capture mechanism; the multi-stage collaborative strategy effectively solves the problem of poor treatment effect of the nickel-zinc-containing waste liquid in the traditional Fenton process, and an innovative solution is provided for treatment of the nickel-zinc-containing waste liquid.

Description

Technical Field

[0001] The invention belongs to the technical field of electroplating waste liquid treatment, and particularly relates to an environmentally friendly treatment process for nickel-zinc-containing waste liquid. Background Art

[0002] Alloy electroplating, a surface treatment technology that has rapidly developed in recent years, involves coatings of two or more metals. Compared to single-metal coatings, these coatings offer advantages such as increased hardness, high density, wear resistance, corrosion resistance, high temperature resistance, ease of welding, and aesthetics. Zn-Ni alloys have been widely used in the past decade. Their corrosion resistance is 7-10 times greater than that of zinc coatings, their appearance can remain unchanged for 10 years, and their sensitivity to hydrogen embrittlement is minimal, exhibiting exceptional corrosion resistance in harsh atmospheric and marine environments. Due to the significant differences in the properties of zinc and nickel, their precipitation potentials differ significantly. To ensure the stability and co-deposition of zinc and nickel in the coating, complexing and liganding agents are typically added to adjust the precipitation potentials of the two metal ions. This shifts the equilibrium potential of the more positive metal negatively, thereby aligning the equilibrium potentials of the two metals with significantly different potentials, allowing for better co-deposition.

[0003] Zinc-nickel alloy electroplating wastewater usually comes from the rinsing process of plated parts and residual tank liquid. According to testing, alkaline zinc-nickel alloy plating solution mainly contains zinc ions, nickel ions, sodium hydroxide, triethanolamine, ligands, etc. The ligands are mainly aliphatic polyamine ligands. Due to the addition of ligands, the metal ions exist in the form of complexes with high stability. Conventional alkali precipitation method is used to treat the wastewater, which is generally difficult to meet the requirements of treatment standards. The treatment effect of hydrogen peroxide oxidation method at room temperature is also poor, facing the problem of high nickel-zinc ion and COD residual content. Therefore, improving an efficient and environmentally friendly treatment process for nickel-zinc wastewater is a technical problem that needs to be solved at present. Summary of the Invention

[0004] The invention provides an environmentally friendly treatment process for nickel-zinc-containing waste liquid, which can solve the problem of poor treatment effect in the prior art of nickel-zinc-containing waste liquid treatment.

[0005] The purpose of the present invention can be achieved through the following technical solutions: An environmentally friendly treatment process for nickel-zinc-containing waste liquid comprises the following steps: S1, collecting nickel-zinc electroplating wastewater, adding acid to adjust the pH value to 6-9, and obtaining pretreated nickel-zinc waste liquid; S2, introducing the pretreated nickel-zinc-containing waste liquid into an oxidation tank, adding modified biochar and hydrogen peroxide solution to the oxidation tank, stirring and reacting under ultraviolet light for 1-2 hours, and obtaining oxidized nickel-zinc-containing waste liquid after the reaction is completed; S3, introducing the oxidized nickel-zinc-containing waste liquid into a reduction tank, adding acid to adjust the pH value to 5, adding sodium metabisulfite solution and stirring to react for 10-30 minutes, reducing the unreacted hydrogen peroxide solution to obtain reduced nickel-zinc-containing waste liquid; S4. Introduce the reduced nickel-zinc waste liquid into the sedimentation tank, add a precipitant into the sedimentation tank, stir for 10-20 minutes, then add a flocculant, stir for 30-60 minutes, let it stand for 2 hours, separate the solid and liquid, and obtain solid sludge and filtrate. The filtrate is the water to be discharged.

[0006] Furthermore, the acid used to adjust the pH in S1 and S3 is at least one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, preferably sulfuric acid.

[0007] Furthermore, 5-10 kg of hydrogen peroxide solution is added to each ton of pretreated nickel-zinc-containing waste liquid in S2, the mass fraction of the hydrogen peroxide solution is 30%, and 0.1-1 kg of modified biochar is added to each ton of pretreated nickel-zinc-containing waste liquid.

[0008] Furthermore, the modified biochar is biochar loaded with tetracarboxyphenylporphyrin iron and 2-mercaptobenzothiazole.

[0009] Furthermore, the method for preparing the modified biochar comprises the following steps: Tetracarboxylphenylporphyrin iron and 2-mercaptobenzothiazole are added to dichloromethane, stirred evenly, and then biochar is added. The mixture is stirred at room temperature for 12-24 hours, filtered, and the filter cake is dried to obtain modified biochar.

[0010] Furthermore, the mass ratio of tetracarboxyphenylporphyrin iron, 2-mercaptobenzothiazole and biochar is 1:1:4-8.

[0011] Furthermore, the English name of the tetracarboxyphenylporphyrin iron is CPP-Fe(2+), cas: 60146-43-2.

[0012] Furthermore, the amount of dichloromethane used is 8-20 times the mass of the biochar.

[0013] Furthermore, the biochar is one or more of wood charcoal, rice husk charcoal, and straw charcoal.

[0014] Furthermore, the stirring speed in S2 is 60-300 r / min.

[0015] Furthermore, the UV lamp in S2 is located 5-10 cm above the surface of the nickel-zinc oxidized waste liquid, the wavelength of the UV lamp is 365 nm, and the light intensity is 1×10 -2 W / cm 2 .

[0016] Furthermore, during the addition of the sodium metabisulfite solution in S3, a potentiometer is used to control the ORP value of the solution in the reduction tank to be -300 to -200 mV, and the mass fraction of the sodium metabisulfite solution is 10%.

[0017] Furthermore, the volume ratio of the reduced nickel-zinc waste liquid and the precipitant in S4 is 100:2-4, the precipitant is a sodium dimethyldithiocarbamate aqueous solution, and the mass fraction of the sodium dimethyldithiocarbamate aqueous solution is 10%. Furthermore, the volume ratio of the reduced nickel-zinc waste liquid and the flocculant in S4 is 100:1-2, the flocculant is a polyacrylamide aqueous solution, and the mass fraction of the polyacrylamide aqueous solution is 0.5-1%. Furthermore, the pH value of the nickel-zinc electroplating wastewater in S1 is 10-12, the COD content is 400-800 mg / L, the nickel ion content is 15-20 m / L, and the zinc ion content is 30-60 mg / L.

[0018] Beneficial effects of the present invention: 1. To address the problem of difficult treatment of complexed nickel and zinc in nickel-zinc wastewater, the present invention first breaks the complexes through ultraviolet light irradiation + hydrogen peroxide oxidation and degrades the organic pollution in the wastewater. Then, the metal ions and organic pollutants are further removed through precipitation and flocculation, so that the discharged water meets the requirements of GB21900-2008 "Electroplating Pollutant Emission Standard".

[0019] 2. This invention uses modified biochar as a core activation aid, co-loading tetracarboxyphenylporphyrin iron and 2-mercaptobenzothiazole on the biochar surface to construct a composite catalytic system with a three-dimensional synergistic effect. This system achieves efficient treatment of nickel-zinc-containing wastewater through a multi-level mechanism of action. Its technical advantages are reflected in the following aspects: Fe chelated in tetracarboxyphenylporphyrin iron molecule 2+ As a Fenton-like reaction active center, it activates hydrogen peroxide to produce hydroxyl radicals (·OH) through electron transfer, which can effectively break the coordination bonds of nickel-zinc complexes; its planar macrocyclic structure confers a triple strengthening effect: ① It forms a stable anchor with oxygen-containing functional groups (carboxyl and hydroxyl) on the surface of biochar through a hydrogen bond network, significantly improving the Fe 2+ ② The stability of the catalyst enables it to efficiently exert its activation effect; ② The aromatic complexing agent molecules are adsorbed by π-π conjugation to achieve in-situ enrichment of pollutants on the catalyst surface, shortening the free radical attack path; ③ The carboxylate radical of tetracarboxyphenylporphyrin iron forms a stable chelate with heavy metal ions, enhancing the removal effect of metal ions in wastewater; Mercaptobenzothiazole has a good complexing effect on nickel and zinc ions, and can also enhance the removal of metal ions in wastewater. In addition, the metal complex formed by 2-mercaptobenzothiazole is adsorbed on the surface of biochar, forming large particle flocs, which significantly improves sedimentation performance. The surface of biochar is rich in oxygen-containing functional groups, such as carboxyl, hydroxyl and carbonyl, which can also activate hydrogen peroxide to produce strong oxidizing free radicals, thereby improving the oxidation effect; In summary, the modified biochar of the present invention achieves synergistic efficiency through the "activation-decomposition-capture" mechanism; this multi-stage synergistic strategy effectively solves the problem of poor treatment effect of nickel-zinc waste liquid in the traditional Fenton process, and provides an innovative solution for the treatment of nickel-zinc waste liquid. DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0021] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0022] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0024] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0025] Preparation Example 1 The preparation steps of modified biochar are as follows: 1 g of tetracarboxyphenylporphyrin iron and 1 g of 2-mercaptobenzothiazole were added to 32 g of dichloromethane and stirred evenly. Then, 4 g of rice husk char was added and stirred at room temperature for 12 h. The mixture was filtered and the filter cake was dried to obtain modified biochar. The preparation of rice husk charcoal was the same as that in Preparation Example 1.

[0026] Preparation Example 2 The preparation steps of modified biochar are as follows: 1 g of tetracarboxyphenylporphyrin iron and 1 g of 2-mercaptobenzothiazole were added to 60 g of dichloromethane and stirred evenly. Then, 6 g of rice husk char was added and stirred at room temperature for 18 h. The mixture was filtered and the filter cake was dried to obtain modified biochar. The preparation of rice husk charcoal was the same as that in Preparation Example 1.

[0027] Preparation Example 3 The preparation steps of modified biochar are as follows: 1 g of tetracarboxyphenylporphyrin iron and 1 g of 2-mercaptobenzothiazole were added to 160 g of dichloromethane and stirred evenly. Then, 8 g of rice husk char was added and stirred at room temperature for 24 h. The mixture was filtered and the filter cake was dried to obtain modified biochar. The preparation of rice husk charcoal was the same as that in Preparation Example 1.

[0028] Comparative Example 1 The preparation of the modified biochar is different from that of Preparation Example 2, in that the 2-mercaptobenzothiazole in Preparation Example 2 is replaced by an equal mass of tetracarboxyphenylporphyrin iron.

[0029] Comparative Example 2 The preparation of the modified biochar is different from that of Preparation Example 2, in that the tetracarboxyphenylporphyrin iron in Preparation Example 2 is replaced by an equal mass of 2-mercaptobenzothiazole.

[0030] Comparative Example 3 The preparation steps of modified biochar are as follows: 2 g of ferrous sulfate heptahydrate was added to 60 g of deionized water, stirred evenly, and then 6 g of rice husk charcoal was added. The mixture was stirred at room temperature for 18 h, filtered, and the filter cake was dried to obtain modified biochar. The preparation of rice husk charcoal was the same as that in Preparation Example 1.

[0031] Example 1 An environmentally friendly treatment process for nickel-zinc-containing waste liquid comprises the following steps: S1, collecting nickel-zinc electroplating wastewater, adding 40wt% dilute sulfuric acid to adjust the pH value to 9, to obtain pretreated nickel-zinc waste liquid; S2, the pretreated nickel-zinc-containing waste liquid is introduced into the oxidation pond, and the modified biochar prepared in Preparation Example 1 and 30 wt% hydrogen peroxide solution are added to the oxidation pond, 5 kg of 30 wt% hydrogen peroxide solution is added to each ton of the pretreated nickel-zinc-containing waste liquid, and 0.1 kg of modified biochar is added to each ton of the pretreated nickel-zinc-containing waste liquid. Under ultraviolet light irradiation, the ultraviolet light is located 5 cm above the liquid surface of the oxidized nickel-zinc-containing waste liquid, the wavelength of the ultraviolet light is 365 nm, and the light intensity is 1×10 -2 W / cm 2 , stirring at a speed of 60-300 r / min for 1 hour, and after the reaction is completed, an oxidized nickel-zinc-containing waste liquid is obtained; S3, introducing the oxidized nickel-zinc waste liquid into a reduction tank, adding 40wt% dilute sulfuric acid to adjust the pH value to 5, adding 10wt% sodium metabisulfite solution, controlling the ORP value of the solution in the reduction tank to -300mV with a potentiometer, stirring and reacting for 10min, and reducing the unreacted hydrogen peroxide solution to obtain reduced nickel-zinc waste liquid; S4. Introduce the reduced nickel-zinc waste liquid into the sedimentation tank, add 10wt% sodium dimethyldithiocarbamate aqueous solution into the sedimentation tank, and the volume ratio of the reduced nickel-zinc waste liquid and the 10wt% sodium dimethyldithiocarbamate aqueous solution is 100:2. After stirring for 10 minutes, add 0.5wt% polyacrylamide aqueous solution, and the volume ratio of the reduced nickel-zinc waste liquid and the polyacrylamide aqueous solution is 100:1. Stir for 30 minutes, let it stand for 2 hours, separate the solid and liquid, and obtain solid sludge and filtrate. The filtrate is the water to be discharged.

[0032] Example 2 An environmentally friendly treatment process for nickel-zinc-containing waste liquid comprises the following steps: S1, collecting nickel-zinc electroplating wastewater, adding 40wt% dilute sulfuric acid to adjust the pH value to 8, to obtain pretreated nickel-zinc waste liquid; S2, the pretreated nickel-zinc-containing waste liquid is introduced into the oxidation pond, and the modified biochar prepared in Preparation Example 1 and 30 wt% hydrogen peroxide solution are added to the oxidation pond, 8 kg of 30 wt% hydrogen peroxide solution is added to each ton of the pretreated nickel-zinc-containing waste liquid, and 0.5 kg of modified biochar is added to each ton of the pretreated nickel-zinc-containing waste liquid. The ultraviolet lamp is irradiated at 8 cm above the liquid surface of the oxidized nickel-zinc-containing waste liquid, the wavelength of the ultraviolet lamp is 365 nm, and the light intensity is 1×10 -2 W / cm 2 , stirring at a speed of 100 r / min for 1.5 h, and after the reaction is completed, an oxidized nickel-zinc-containing waste liquid is obtained; S3, introducing the oxidized nickel-zinc waste liquid into a reduction tank, adding 40wt% dilute sulfuric acid to adjust the pH value to 5, adding 10wt% sodium metabisulfite solution, controlling the ORP value of the solution in the reduction tank to -200mV with a potentiometer, stirring and reacting for 20min, and reducing the unreacted hydrogen peroxide solution to obtain reduced nickel-zinc waste liquid; S4. Introduce the reduced nickel-zinc waste liquid into the sedimentation tank, add 10wt% sodium dimethyldithiocarbamate aqueous solution into the sedimentation tank, and the volume ratio of the reduced nickel-zinc waste liquid and the 10wt% sodium dimethyldithiocarbamate aqueous solution is 100:3. After stirring for 15 minutes, add 0.8wt% polyacrylamide aqueous solution, and the volume ratio of the reduced nickel-zinc waste liquid and the polyacrylamide aqueous solution is 100:1.5. Stir for 40 minutes, let it stand for 2 hours, separate the solid and liquid, and obtain solid sludge and filtrate. The filtrate is the water to be discharged.

[0033] Example 3 An environmentally friendly treatment process for nickel-zinc-containing waste liquid comprises the following steps: S1, collecting nickel-zinc electroplating wastewater, adding 40wt% dilute sulfuric acid to adjust the pH value to 9, to obtain pretreated nickel-zinc waste liquid; S2, the pretreated nickel-zinc-containing waste liquid is introduced into the oxidation pond, and the modified biochar prepared in Preparation Example 1 and 30 wt% hydrogen peroxide solution are added to the oxidation pond, 10 kg of 30 wt% hydrogen peroxide solution is added to each ton of the pretreated nickel-zinc-containing waste liquid, and 1 kg of modified biochar is added to each ton of the pretreated nickel-zinc-containing waste liquid. Under ultraviolet light irradiation, the ultraviolet light is located 10 cm above the surface of the oxidized nickel-zinc-containing waste liquid, the wavelength of the ultraviolet light is 365 nm, and the light intensity is 1×10 -2 W / cm 2 , stirring at a speed of 300 r / min for 2 h, and after the reaction is completed, an oxidized nickel-zinc-containing waste liquid is obtained; S3, introducing the oxidized nickel-zinc waste liquid into a reduction tank, adding 40wt% dilute sulfuric acid to adjust the pH value to 5, adding 10wt% sodium metabisulfite solution, controlling the ORP value of the solution in the reduction tank to -300 to -200mV using a potentiometer, stirring and reacting for 30min, and reducing the unreacted hydrogen peroxide solution to obtain reduced nickel-zinc waste liquid; S4. Introduce the reduced nickel-zinc waste liquid into a sedimentation tank, add 10wt% sodium dimethyldithiocarbamate aqueous solution into the sedimentation tank, and the volume ratio of the reduced nickel-zinc waste liquid and the 10wt% sodium dimethyldithiocarbamate aqueous solution is 100:4. After stirring for 20 minutes, add 1wt% polyacrylamide aqueous solution, and the volume ratio of the reduced nickel-zinc waste liquid and the polyacrylamide aqueous solution is 100:2. Stir for 60 minutes, let it stand for 2 hours, separate the solid and liquid, and obtain solid sludge and filtrate. The filtrate is the water to be discharged.

[0034] Example 4 An environmentally friendly treatment process for nickel-zinc-containing waste liquid, compared with Example 2, the only difference is that the modified biochar in Example 2 is replaced by the product obtained in Preparation Example 2 of equal mass.

[0035] Example 5 An environmentally friendly treatment process for nickel-zinc-containing waste liquid, compared with Example 2, the only difference is that the modified biochar in Example 2 is replaced by the product obtained in Preparation Example 3 of equal mass.

[0036] Comparative Example 1 An environmentally friendly treatment process for nickel-zinc-containing waste liquid, compared with Example 2, the only difference is that the modified biochar in Example 2 is replaced by the product obtained in Control Example 1 of equal quality.

[0037] Comparative Example 2 An environmentally friendly treatment process for nickel-zinc-containing waste liquid, compared with Example 2, the only difference is that the modified biochar in Example 2 is replaced by the product obtained in Control Example 2 of equal quality.

[0038] Comparative Example 3 An environmentally friendly treatment process for nickel-zinc-containing waste liquid, compared with Example 2, the only difference is that the modified biochar in Example 2 is replaced by the product obtained in Control Example 3 of equal quality.

[0039] Comparative Example 4 An environmentally friendly treatment process for nickel-zinc-containing waste liquid, compared with Example 2, the only difference is that the modified biochar in Example 2 is replaced by ferrous sulfate of equal mass.

[0040] The treatment process described in Examples 1 to 6 and Comparative Examples 1 to 4 was used to treat a zinc-nickel alloy electroplating wastewater in Guangdong. The pH value of the zinc-nickel alloy electroplating wastewater was 11, the COD content was 582 mg / L, the nickel ion content was 18.2 m / L, and the zinc ion content was 56.7 mg / L. After the treatment, the discharged water was tested to detect the contents of COD, nickel ions, and zinc ions. The results are shown in Table 1: Table 1 project COD (mg / L) Nickel ion (mg / L) Zinc ion (mg / L) Example 1 28 0.09 0.98 Example 2 21 0.06 0.68 Example 3 13 0.05 0.37 Example 4 24 0.07 0.71 Example 5 26 0.08 0.83 Comparative Example 1 20 0.21 1.34 Comparative Example 2 45 0.45 2.56 Comparative Example 3 67 0.74 2.78 Comparative Example 4 82 0.96 3.27 As shown in Table 1, the COD content in the treated water from Examples 1 to 5 was ≤28 mg / L, the nickel ion content was ≤0.1 mg / L, and the zinc ion content was less than 1.0 mg / L. These results are significantly superior to those from Comparative Examples 1 to 4. This demonstrates that the present invention utilizes modified biochar as the core activation agent, co-loading tetracarboxyphenylporphyrin iron and 2-mercaptobenzothiazole on the biochar surface to construct a composite catalytic system with a three-dimensional synergistic effect. This system achieves efficient treatment of nickel-zinc-containing wastewater through a multi-level mechanism.

[0041] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0042] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly treatment process for nickel-zinc-containing waste liquid, characterized in that: The following steps are involved: S1, collecting nickel-zinc electroplating wastewater, adding acid to adjust the pH value to 6-9, and obtaining pretreated nickel-zinc waste liquid; S2, introducing the pretreated nickel-zinc-containing waste liquid into an oxidation tank, adding modified biochar and hydrogen peroxide solution to the oxidation tank, stirring and reacting under ultraviolet light for 1-2 hours, and obtaining oxidized nickel-zinc-containing waste liquid after the reaction is completed; S3, introducing the oxidized nickel-zinc waste liquid into the reduction tank, adding acid to adjust the pH value to 5, adding sodium metabisulfite solution and stirring the reaction for 10-30 minutes to obtain the reduced nickel-zinc waste liquid; S4, introducing the reduced nickel-zinc waste liquid into a sedimentation tank, adding a precipitant to the sedimentation tank, stirring for 10-20 minutes, then adding a flocculant, stirring for 30-60 minutes, standing for 2 hours, and separating the solid and liquid to obtain solid sludge and filtrate, the filtrate being the water to be discharged; The modified biochar is biochar loaded with tetracarboxylphenylporphyrin iron and 2-mercaptobenzothiazole.

2. The environmentally friendly treatment process for nickel-zinc waste liquid according to claim 1, characterized in that: In S2, 5-10 kg of hydrogen peroxide solution is added to each ton of pretreated nickel-zinc-containing waste liquid, the mass fraction of the hydrogen peroxide solution is 30%, and 0.1-1 kg of modified biochar is added to each ton of pretreated nickel-zinc-containing waste liquid.

3. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 1, characterized in that: The method for preparing the modified biochar comprises the following steps: Tetracarboxylphenylporphyrin iron and 2-mercaptobenzothiazole are added to dichloromethane, stirred evenly, and then biochar is added. The mixture is stirred at room temperature for 12-24 hours, filtered, and the filter cake is dried to obtain modified biochar.

4. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 3, characterized in that: The mass ratio of tetracarboxyphenylporphyrin iron, 2-mercaptobenzothiazole and biochar is 1:1:4-8.

5. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 3, characterized in that: The biochar is one or more of wood charcoal, rice husk charcoal and straw charcoal.

6. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 1, characterized in that: The UV lamp in S2 is located 5-10 cm above the surface of the nickel-zinc oxidized waste liquid. The wavelength of the UV lamp is 365 nm and the light intensity is 1×10 -2 W / cm 2 .

7. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 1, characterized in that: During the addition of the sodium metabisulfite solution in S3, a potentiometer is used to control the ORP value of the solution in the reduction tank to -300 to -200 mV. The mass fraction of the sodium metabisulfite solution is 10%.

8. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 1, characterized in that: The volume ratio of the reduced nickel-zinc-containing waste liquid and the precipitant in S4 is 100:2-4, and the precipitant is a sodium dimethyldithiocarbamate aqueous solution, and the mass fraction of the sodium dimethyldithiocarbamate aqueous solution is 10%.

9. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 1, characterized in that: The volume ratio of the reduced nickel-zinc-containing waste liquid and the flocculant in S4 is 100:1-2, the flocculant is a polyacrylamide aqueous solution, and the mass fraction of the polyacrylamide aqueous solution is 0.5-1%.

10. The environmentally friendly treatment process for nickel-zinc-containing waste liquid according to claim 1, characterized in that: The pH value of nickel-zinc electroplating wastewater in S1 is 10-12, the COD content is 400-800 mg / L, the nickel ion content is 15-20 m / L, and the zinc ion content is 30-60 mg / L.