Electrolysis-oxidation synergic treatment method and device for electroless plating wastewater

Abstract

The application belongs to the technical field of electroplating wastewater treatment, and particularly relates to a method and device for treating electroplating wastewater by electrolysis-oxidation coordination. The electroplating wastewater is adjusted and matched to obtain pretreated wastewater, and the electroplating wastewater contains heavy metal elements; the pretreated wastewater is separated by a charged nanofiltration membrane to obtain complex heavy metal wastewater and ionic heavy metal wastewater; the complex heavy metal wastewater is treated by ozone oxidation to obtain oxidized wastewater, and the oxidized wastewater is treated by first diaphragm electrolysis to recover heavy metals; and the ionic heavy metal wastewater is treated by second diaphragm electrolysis to recover heavy metals. The application realizes efficient separation and resource recovery of copper and nickel in the electroplating wastewater, and combines electroplating wastewater treatment and resource recovery, thus having a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electroplating wastewater treatment, and particularly relates to a method and device for treating chemical plating wastewater by electrolysis and oxidation. BACKGROUND

[0002] The chemical copper / nickel plating process is widely used in the fields of printed circuit board and surface treatment of electronic components, and a large amount of wastewater containing heavy metals such as copper and nickel is generated every year. Compared with traditional electroplating wastewater, this kind of wastewater has the following significant characteristics:

[0003] (1) A large amount of complexing agents (such as EDTA, citrate, tartrate, etc.) are contained, forming stable metal complexes, and the traditional chemical precipitation method has poor treatment effect;

[0004] (2) There are both complexed and ionic forms of heavy metals, which have large differences in properties and are difficult to treat uniformly;

[0005] (3) Reducing agents (such as hypophosphite, borohydride, etc.) are left over, which interfere with subsequent treatment;

[0006] (4) The pH value fluctuates greatly, and various additives are often contained, increasing the difficulty of treatment.

[0007] At present, the treatment of chemical plating wastewater mainly adopts technologies such as chemical precipitation, ion exchange and membrane separation, but there are disadvantages such as low treatment efficiency, high cost and difficulty in metal recovery. SUMMARY

[0008] The purpose of the present application is to provide a method and device for treating chemical plating wastewater by electrolysis and oxidation, which realizes efficient separation and resource recovery of heavy metals (copper / nickel) in chemical plating wastewater, and realizes wastewater discharge in line with standards, has high treatment efficiency and low cost, and has a wide application prospect.

[0009] In order to achieve the above purpose, the present application provides the following technical scheme:

[0010] The present application provides a method for treating chemical plating wastewater by electrolysis and oxidation, comprising the following steps:

[0011] The chemical plating wastewater is adjusted and matched to obtain pretreated wastewater, the chemical plating wastewater contains heavy metal elements, the adjustment and matching includes pH adjustment and addition of oxidizing agent, and the pH value of the pretreated wastewater is less than 6.5;

[0012] The pretreated wastewater is separated by charged nanofiltration membrane to obtain complexed heavy metal wastewater and ionic heavy metal wastewater;

[0013] The complex heavy metal wastewater is subjected to ozone oxidation treatment to obtain oxidized wastewater, and the oxidized wastewater is subjected to first diaphragm electrolysis treatment to recover heavy metals;

[0014] The ionic heavy metal wastewater is subjected to second diaphragm electrolysis treatment to recover heavy metals.

[0015] Preferably, the electroless plating wastewater includes electroless nickel plating wastewater or electroless copper plating wastewater; and the pretreatment wastewater includes pretreatment copper wastewater or pretreatment nickel wastewater.

[0016] Preferably, the oxidant is hydrogen peroxide, the concentration of H2O2 in the hydrogen peroxide is 50-75 mg / L, and the hydraulic retention time of the adjustment and matching is 30-40 min.

[0017] Preferably, the pH value of the pretreatment copper wastewater is 5.8-6.2, and the pH value of the pretreatment nickel wastewater is 5.3-5.7.

[0018] Preferably, the conditions of the electrically charged nanofiltration membrane separation include that the surface of the membrane material is negatively charged, the molecular weight cut-off value is 300-500 Da, the membrane module is a roll-type nanofiltration membrane element or a flat-plate type nanofiltration membrane element, the effective membrane area is 15-20 m 2 , the operating pressure is 0.6-0.9 MPa, the temperature is 20-30 DEG C, and the cross-flow speed is 0.3-0.5 m / s.

[0019] Preferably, the ozone oxidation treatment uses ozone and the electroless plating wastewater in a ratio of 50-100 mg / L, and a metal oxide catalyst is further used in the ozone oxidation treatment.

[0020] Preferably, the metal oxide catalyst includes MnO2 / TiO2 composite catalyst and / or CeO2 / Al2O3 composite catalyst, and the metal oxide catalyst and the electroless plating wastewater are used in a ratio of 0.4-0.8 g / L.

[0021] Preferably, the first diaphragm electrolysis treatment and the second diaphragm electrolysis treatment use a cation exchange membrane as a diaphragm and use a copper plate or a stainless steel plate as a cathode.

[0022] Preferably, the conditions of the first diaphragm electrolysis treatment and the second diaphragm electrolysis treatment include that the current density is 1.5-3.5 A / dm 2 , and the electrolysis temperature is 30-40 DEG C.

[0023] The application provides a device used in the method for treating electroless plating wastewater by using the method for treating electroless plating wastewater by separating and electrolyzing the wastewater in different qualities and oxidizing the wastewater.

[0024] The application provides a method for treating electroless plating wastewater by electrolysis-oxidation synergy, comprising the following steps: adjusting and compounding electroless plating wastewater to obtain pretreated wastewater, wherein the electroless plating wastewater contains heavy metal elements, the adjusting and compounding comprises pH adjustment and adding oxidizing agent, and the pH value of the pretreated wastewater is less than 6.5; separating the pretreated wastewater by charged nanofiltration membrane to obtain complex heavy metal wastewater and ionic heavy metal wastewater; treating the complex heavy metal wastewater by ozone oxidation to obtain post-oxidation wastewater, and treating the post-oxidation wastewater by first diaphragm electrolysis to recover heavy metals; and treating the ionic heavy metal wastewater by second diaphragm electrolysis to recover heavy metals. The application adjusts the pH value of the electroless plating wastewater by adjusting and compounding, and adjusts the oxidation-reduction potential of the electroless plating wastewater by oxidizing reducing agents in the electroless plating wastewater with oxidizing agents, so as to create suitable conditions for subsequent separation. After adjusting and compounding, the application separates the obtained pretreated wastewater by charged nanofiltration membrane: the nanofiltration membrane blocks macromolecules and the electrostatic effect of the surface charge layer of the nanofiltration membrane makes ionic heavy metals (for example, Cu 2+ or Ni 2+ ) pass through the nanofiltration membrane, and organic matters (EDTA-Cu, nickel citrate, etc.) are retained in the wastewater, so as to divide the wastewater into two parts: complex heavy metal wastewater and ionic heavy metal wastewater. The application treats the complex heavy metal wastewater by ozone oxidation first, releases heavy metal ions by destroying the structure of metal complexes with ozone, and then recovers heavy metals by first diaphragm electrolysis. The application directly recovers heavy metals by second diaphragm electrolysis for the ionic heavy metal wastewater. Compared with the prior art, the application has the following beneficial effects:

[0025] The application realizes effective separation and treatment of complex heavy metals and ionic heavy metals by reasonable process setting, has high metal purity: the recovery purity of copper and nickel can reach more than 98%, and the metals can be directly used in electroplating process; has high metal recovery rate: the copper recovery rate is more than 96%, and the nickel recovery rate is more than 95%; saves reagent cost: compared with the traditional precipitation method, the reagent dosage is reduced by 70-80%; has low operation cost: the energy consumption is about 60% of that of the conventional treatment process; has good wastewater treatment effect: the indexes of the effluent meet the discharge standard of the electroplating industry. In summary, the application realizes efficient separation and resource recovery of copper and nickel in electroless plating wastewater, organically combines electroless plating wastewater treatment and resource recovery, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The application provides a flow chart of the method for treating electroless plating wastewater by electrolysis-oxidation synergy. DETAILED DESCRIPTION

[0027] The application provides a method for treating electroless plating wastewater by electrolysis-oxidation cooperation, comprising the following steps:

[0028] The electroless plating wastewater is adjusted and matched to obtain pretreated wastewater, wherein the electroless plating wastewater contains heavy metal elements, the adjustment and matching comprises pH adjustment and addition of oxidizing agent, and the pH value of the pretreated wastewater is less than 6.5.

[0029] The pretreated wastewater is separated by charged nanofiltration membrane to obtain complex heavy metal wastewater and ionic heavy metal wastewater.

[0030] The complex heavy metal wastewater is treated by ozone oxidation to obtain post-oxidation wastewater, and the post-oxidation wastewater is treated by first diaphragm electrolysis to recover heavy metals.

[0031] The ionic heavy metal wastewater is treated by second diaphragm electrolysis to recover heavy metals.

[0032] In the application, all the preparation raw materials / components are commercially available products known to those skilled in the art, unless otherwise specified.

[0033] In the application, the electroless plating wastewater contains heavy metal elements. The heavy metal elements preferably include copper elements or nickel elements. The electroless plating wastewater preferably includes electroless nickel plating wastewater or electroless copper plating wastewater. The electroless plating wastewater preferably includes ionic heavy metals, complex heavy metals and reducing agents, wherein the complex heavy metals preferably include one or more of EDTA salt, citrate salt, lactate salt and tartrate salt. The reducing agents preferably include hypophosphite and / or borohydride. In the application, the concentration of Cu 2+ in the electroless copper plating wastewater is preferably 400-600 mg / L, which can be 500 mg / L in the examples, the concentration of EDTA copper salt is preferably 1000-1500 mg / L, which can be 1200 mg / L in the examples, and the pH value of the electroless copper plating wastewater is preferably 4-5, which is 4.5 in the examples. In the application, the concentration of Ni 2+ in the electroless nickel plating wastewater is preferably 400-500 mg / L, which can be 450 mg / L in the examples. The pH value of the electroless nickel plating wastewater is preferably 5.5±0.2.

[0034] In the present application, the conditioning preferably comprises pH adjustment and addition of oxidizing agent. The conditioning preferably comprises: first adjusting the pH of the electroless plating wastewater, and then adding oxidizing agent to perform oxidation reaction, to obtain the pretreated wastewater. The oxidizing agent is preferably hydrogen peroxide, and the concentration of H2O2 in the hydrogen peroxide is preferably 50-75 mg / L. The amount of the oxidizing agent is determined according to the complete oxidation of the reducing agent in the electroless plating wastewater. The hydraulic retention time of the conditioning is preferably 30-40 min. The pH of the pretreated wastewater is < 6.5. In the present application, the pretreated wastewater comprises pretreated copper wastewater or pretreated nickel wastewater. The pH of the pretreated copper wastewater is preferably 5.8-6.2. The pH of the pretreated nickel wastewater is preferably 5.3-5.7.

[0035] After obtaining the pretreated wastewater, the pretreated wastewater is subjected to charged nanofiltration membrane separation in the present application, to obtain complex heavy metal wastewater and ionic heavy metal wastewater. In the present application, the conditions of the charged nanofiltration membrane separation preferably comprise: the membrane material surface is preferably negatively charged. The molecular weight cut-off value is preferably 300-500 Da. The membrane module is preferably a roll-type nanofiltration membrane element or a flat-plate type nanofiltration membrane element. The effective membrane area is preferably 15-20 m 2 . The operating pressure is preferably 0.6-0.9 MPa; the temperature is preferably 20-30℃; the recovery rate is preferably 65-75%; and the cross-flow velocity is preferably 0.3-0.5 m / s.

[0036] In the present application, when the pretreated wastewater is preferably pretreated copper wastewater, the membrane material is preferably a poly-piperazine composite nanofiltration membrane, the surface is negatively charged, the molecular weight cut-off value is preferably 300-400 Da; the membrane module is preferably a roll-type nanofiltration membrane element, and the effective membrane area is preferably 20 m 2 . The operating parameters preferably comprise: the operating pressure is preferably 0.6-0.8 MPa; the temperature is preferably 25±2℃; the recovery rate is preferably controlled at 70-75%; and the cross-flow velocity is preferably 0.3-0.4 m / s. The separation principle of the present application is that the negative charge on the surface of the nanofiltration membrane has almost no blocking effect on Cu 2+ metal cations, but has a high interception effect on the macromolecular EDTA-Cu complex; the separation effect is that 80% of ionic copper passes through the membrane into the permeate, and more than 90% of the EDTA-Cu complex is intercepted in the concentrate; the concentrate containing complex copper and the permeate enriched in ionic copper are collected respectively.

[0037] In the present application, when the pretreated wastewater is preferably pretreated nickel wastewater, the membrane material is preferably a sulfonated polyether sulfone modified nanofiltration membrane, the surface is negatively charged, and the molecular weight cut-off value is preferably 400-500 Da; the membrane module is preferably a flat-plate type nanofiltration membrane element, and the effective membrane area is preferably 15 m 2; the operating parameters preferably include: the operating pressure is preferably 0.7-0.9 MPa; the temperature is preferably 28±2℃; the recovery rate is preferably controlled at 65-70%, and the cross-flow velocity is preferably 0.4-0.5 m / s. Before the pretreated nickel wastewater is subjected to the charged nanofiltration membrane separation, the pretreated nickel wastewater is preferably pretreated, and the pretreatment preferably includes: mixing the pretreated nickel wastewater with an antifouling agent, and the antifouling agent is preferably used to improve the separation effect of the pretreated nickel wastewater. The antifouling agent is preferably polyacrylamide. The mass-to-volume ratio of the antifouling agent to the electroless plating wastewater is preferably 0.3-0.8 mg / L, and in the examples, it can be 0.5 mg / L. The effect of the charged nanofiltration membrane separation on the pretreated nickel wastewater is that 75% of the ionic nickel passes through the membrane into the permeate, and more than 85% of the complexed nickel is retained in the concentrate.

[0038] In the present application, during the charged nanofiltration membrane separation process, the membrane is preferably cleaned with a solution of citric acid and EDTA after being operated for 48 hours. The pH value of the solution of citric acid and EDTA is preferably 3.0, and the content of EDTA is preferably 0.5 wt%.

[0039] After obtaining the complexed heavy metal wastewater, the complexed heavy metal wastewater is subjected to ozone oxidation treatment to obtain oxidized wastewater. In the present application, the dosage ratio of ozone to the electroless plating wastewater used in the ozone oxidation treatment is preferably 50-100 mg / L, and in the examples, it can be 60 mg / L or 80 mg / L. The control accuracy of ozone is preferably ±5 mg / L. The ozone oxidation treatment preferably also uses a metal oxide catalyst. The metal oxide catalyst preferably includes a MnO2 / TiO2 composite catalyst and / or a CeO2 / Al2O3 composite catalyst. The dosage ratio of the metal oxide catalyst to the electroless plating wastewater is preferably 0.4-0.8 g / L, and in the examples, it can be 0.5 g / L or 0.6 g / L. The time of the ozone oxidation treatment is preferably 30-60 min, and in the examples, it can be 30 min or 40 min. The pH value of the ozone oxidation treatment is preferably 6-7, and in the examples, it can be 6.5-7 or 6-6.5. The present application preferably destroys the complex structure of the complexed heavy metal by the ozone oxidation treatment to release free heavy metal ions.

[0040] After obtaining the oxidized wastewater, the oxidized wastewater is subjected to first diaphragm electrolysis treatment to recover heavy metals. After obtaining the ionic heavy metal wastewater, the ionic heavy metal wastewater is subjected to second diaphragm electrolysis treatment to recover heavy metals.

[0041] In the present application, the first and second diaphragm electrolysis processes use cation exchange membrane as diaphragm and copper plate or stainless steel plate as cathode. When the oxidized wastewater and ion state heavy metal wastewater contain copper ions, the cathode is copper plate. When the oxidized wastewater and ion state heavy metal wastewater contain nickel ions, the cathode is stainless steel plate.

[0042] In the present application, when the oxidized wastewater and ion state heavy metal wastewater contain copper ions, the anode material of the first and second diaphragm electrolysis processes is preferably coated titanium electrode (DSA). When the oxidized wastewater and ion state heavy metal wastewater contain nickel ions, the anode material of the first and second diaphragm electrolysis processes is preferably coated titanium electrode.

[0043] In the present application, the conditions of the first and second diaphragm electrolysis processes preferably include: current density is preferably 1.5-3.5 A / dm 2 , in the examples can be 2.5 A / dm 2 or 2.8 A / dm 2 . Electrolysis temperature is 30-40℃. Electrolysis time is preferably 50-80 min, in the examples can be 60 min or 70 min.

[0044] The present application provides a device for the above-mentioned chemical plating wastewater quality electrolysis-oxidation synergistic treatment method, which comprises sequentially connected adjusting and compounding unit, charged nanofiltration membrane separation unit, ozone oxidation unit and diaphragm electrolysis unit.

[0045] In the present application, the charged nanofiltration membrane separation unit separates to obtain complex state heavy metal wastewater and ion state heavy metal wastewater.

[0046] In the present application, the ozone oxidation unit preferably comprises ozone generator, gas-liquid mixer, catalytic oxidation reactor and tail gas treatment device.

[0047] In the present application, the diaphragm electrolysis unit preferably comprises cathode chamber, anode chamber, cation exchange membrane, direct current power supply and electrolyte circulation system.

[0048] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application. The following examples are carried out according to the flow block diagram shown in Figure 1 to carry out the quality electrolysis-oxidation synergistic treatment of chemical plating wastewater.

[0049] Example 1: Chemical copper plating wastewater treatment

[0050] Taking the treatment of chemical copper plating wastewater of an electronic factory as an example (Cu 2+The concentration of EDTA is 1200 mg / L, and the pH value is 4.5. The specific steps are as follows:

[0051] Adjustment: The electroless copper plating wastewater is introduced into the adjustment tank, and the pH value is adjusted to 6.0±0.2; hydrogen peroxide (H2O2 concentration 50 mg / L) is added to oxidize the residual reducing agent in the electroless copper plating wastewater, and the amount of hydrogen peroxide is sufficient to remove the reducing agent; the hydraulic retention time is 30 min, and the pretreated wastewater is obtained.

[0052] Charged nanofiltration membrane separation: the pretreated wastewater is pumped into the nanofiltration membrane separation system; membrane material: poly-piperazine composite nanofiltration membrane with negative charge on the surface, molecular weight cutoff value 300-400 Da; membrane module: roll-type nanofiltration membrane element, effective membrane area 20 m 2 ; operating parameters: operating pressure: 0.6-0.8 MPa; temperature: 25±2℃; recovery rate: controlled at 70-75%; cross-flow velocity: 0.3-0.4 m / s. Separation principle: the negative charge on the surface of the nanofiltration membrane has almost no blocking effect on Cu 2+ and other metal cations, but has a high interception effect on the macromolecular EDTA-Cu complex; separation effect: 80% of the ionic copper passes through the membrane into the permeate, and more than 90% of the EDTA-Cu complex is intercepted in the concentrate; the concentrate containing complex copper and the permeate enriched with ionic copper are collected respectively, and the complex copper wastewater and the ionic copper wastewater are obtained.

[0053] Complex copper wastewater treatment: the complex copper wastewater enters the ozone oxidation unit; ozone dosage: 60 mg / L; catalyst: MnO2 / TiO2 composite catalyst, dosage 0.5 g / L; reaction time: 30 min; reaction pH: 6.5-7.0; ozone destroys the EDTA complex structure and releases Cu 2+ ions, and the oxidized copper ion wastewater is obtained.

[0054] Ionic copper wastewater recovery: the ionic copper wastewater separated by the charged nanofiltration membrane directly enters the diaphragm electrolysis unit; cathode material: high-purity copper plate; anode material: coated titanium electrode (DSA); diaphragm: cation exchange membrane; current density: 2.5 A / dm 2 ; electrolysis time: 60 min; Cu 2+ is deposited on the cathode to form metallic copper.

[0055] Oxidized copper ion wastewater recovery: the ozone-oxidized copper ion wastewater enters the diaphragm electrolysis unit; the same electrolysis parameters as the ionic copper wastewater recovery are used; the copper ions released by ozone oxidation are recovered.

[0056] The experimental results of the embodiment are as follows: the copper recovery rate reaches 97.5%; the purity of the recovered copper reaches 99.2%; the copper content in the effluent after treatment is less than 0.5 mg / L, meeting the discharge standard; and the energy consumption is 3.2 kWh / kg-Cu.

[0057] Example 2: Treatment of electroless nickel plating wastewater

[0058] The electroless nickel plating wastewater from an electronic factory was taken as an example (Ni 2+ The concentration of the wastewater was 450 mg / L, and the wastewater contained complexing agents such as citrate and lactate. The specific steps were as follows:

[0059] Adjustment: The electroless nickel plating wastewater was introduced into an adjustment tank, and the pH value was adjusted to 5.5±0.2. Hydrogen peroxide (H2O2 concentration: 75 mg / L) was added to oxidize the residual hypophosphite in the electroless nickel plating wastewater. The amount of hydrogen peroxide was sufficient to remove the hypophosphite. The residence time was 40 min, and pretreated wastewater was obtained.

[0060] Charged nanofiltration membrane separation: The pretreated wastewater was pumped into a nanofiltration membrane separation system. The membrane material was a sulfonated polyether sulfone modified nanofiltration membrane with a negative charge on the surface and a molecular weight cutoff of 400-500 Da. The membrane module was a flat-plate nanofiltration membrane element with an effective membrane area of 15 m 2 ; The operating parameters were as follows: operating pressure: 0.7-0.9 MPa; temperature: 28±2℃; recovery rate: controlled at 65-70%; cross-flow velocity: 0.4-0.5 m / s. The electroless nickel plating wastewater needed to be pretreated: 0.5 mg / L of polyacrylamide was added to the pretreated wastewater as a fouling inhibitor. The separation effect was as follows: about 75% of the ionic nickel passed through the membrane into the permeate, and more than 85% of the complexed nickel was retained in the concentrate. Membrane cleaning: after 48 hours of operation, a combination of citric acid (pH=3.0) and EDTA (0.5%) solution was used for cleaning, and complexed nickel wastewater and ionic nickel wastewater were obtained.

[0061] Treatment of complexed nickel wastewater: The complexed nickel wastewater entered an ozone oxidation unit. The ozone dosage was 80 mg / L. The catalyst was a CeO2 / Al2O3 composite catalyst, and the dosage was 0.6 g / L. The reaction time was 40 min, and the reaction pH was 6.0-6.5. The ozone destroyed the structure of the complexed nickel, released Ni 2+ ions, and obtained oxidized nickel ion wastewater.

[0062] Recovery of ionic nickel wastewater: The ionic nickel copper wastewater separated by the charged nanofiltration membrane directly entered a diaphragm electrolysis unit. The cathode material was a stainless steel plate, the anode material was a coated titanium electrode, the current density was 2.8 A / dm 2 , and the electrolysis time was 70 min. The recovered nickel could be obtained by stripping or dissolution and electroplating.

[0063] Nickel ion wastewater recovery after oxidation: the nickel ion wastewater after ozone oxidation enters the diaphragm electrolysis unit; the same electrolysis parameters as the ion nickel wastewater recovery are adopted; the diaphragm is a cation exchange membrane.

[0064] The experimental results of the embodiment: the nickel recovery rate reaches 95.8%; the purity of the recovered nickel reaches 98.5%; the nickel content of the effluent after treatment is 0.5 mg / L; and the energy consumption is 4.1 kWh / kg-Ni.

[0065] Comparative Example 1: omitting the hydrogen peroxide oxidation step in pretreatment

[0066] The same wastewater (Ni 2+ concentration 450 mg / L) as in Example 2 is used, but the hydrogen peroxide oxidation step in pretreatment is omitted, and the charged nanofiltration membrane is directly used for separation. The treatment conditions are: only the pH is adjusted to 5.5±0.2, without adding hydrogen peroxide, and directly entering the nanofiltration membrane separation system. The experimental results are: the nickel recovery rate is 76.3% (decreased by 19.5% compared with Example 2). The purity of the recovered nickel is 88.2% (decreased by 10.3% compared with Example 2). The nickel content of the effluent is 1.8 mg / L (increased by 1.3 mg / L compared with Example 2). The energy consumption is 5.2 kWh / kg-Ni (increased by 26.8% compared with Example 2). The membrane is seriously polluted, needs to be cleaned frequently, and the operation cycle is shortened to 24 hours.

[0067] Comparative Example 2: omitting the ozone oxidation step

[0068] The same pretreatment and nanofiltration membrane separation as in Example 2 are used, but the ozone oxidation treatment of the complex nickel wastewater is omitted, and direct electrolysis recovery is performed. The treatment conditions are: the concentrated solution of the complex nickel wastewater does not undergo ozone oxidation treatment, and directly enters the diaphragm electrolysis unit. The experimental results are: the nickel recovery rate is 58.7% (decreased by 37.1% compared with Example 2). The purity of the recovered nickel is 82.4% (decreased by 16.1% compared with Example 2). The nickel content of the effluent is 3.2 mg / L (increased by 2.7 mg / L compared with Example 2). The energy consumption is 6.8 kWh / kg-Ni (increased by 65.9% compared with Example 2). The complex nickel is difficult to be electrolytically separated, and a large amount of nickel ions remain in the wastewater.

[0069] Comparative Example 3: changing key operation parameters

[0070] (1) reducing the ozone dosage

[0071] The ozone dosage was reduced from 80 mg / L to 40 mg / L, and other conditions were the same as in Example 2. Experimental results: nickel recovery rate: 81.2% (14.6% lower than Example 2). Purity of recovered nickel: 91.3% (7.2% lower than Example 2). Nickel content in effluent: 1.1 mg / L (0.6 mg / L higher than Example 2). Energy consumption: 4.8 kWh / kg-Ni (17.1% higher than Example 2).

[0072] (2) Reducing current density

[0073] The current density was reduced from 2.8 A / dm 2 to 1.5 A / dm 2 , and other conditions were the same as in Example 2.

[0074] Experimental results: nickel recovery rate: 72.4% (23.4% lower than Example 2). Purity of recovered nickel: 94.1% (4.4% lower than Example 2). Nickel content in effluent: 1.6 mg / L (1.1 mg / L higher than Example 2). Energy consumption: 3.2 kWh / kg-Ni (although the unit energy consumption decreased, the overall economic benefit decreased significantly due to the significant decrease in recovery rate).

[0075] (3) Not using catalyst

[0076] CeO2 / Al2O3 composite catalyst was not added during ozone oxidation, and other conditions were the same as in Example 2. Experimental results: nickel recovery rate: 68.9% (26.9% lower than Example 2). Purity of recovered nickel: 89.7% (8.8% lower than Example 2). Nickel content in effluent: 2.3 mg / L (1.8 mg / L higher than Example 2). Energy consumption: 5.7 kWh / kg-Ni (39.0% higher than Example 2).

[0077] Comparative Example 4: Changing nanofiltration membrane operating pressure

[0078] The nanofiltration membrane operating pressure was adjusted from 0.7 to 0.9 MPa to 0.4 to 0.5 MPa, and other conditions were the same as in Example 2. Experimental results: nickel recovery rate: 84.3% (11.5% lower than Example 2). Purity of recovered nickel: 96.8% (1.7% lower than Example 2). Nickel content in effluent: 0.8 mg / L (0.3 mg / L higher than Example 2). Energy consumption: 4.6 kWh / kg-Ni (12.2% higher than Example 2). Membrane flux decreased significantly, and treatment efficiency decreased.

[0079] It can be concluded from the above comparative examples that omitting the pretreatment oxidation step will cause the membrane pollution to be intensified and the recovery efficiency to be significantly reduced; omitting the ozone oxidation step will make the complex state nickel unable to be effectively separated, and seriously affect the overall recovery effect; reducing the key operation parameters (such as ozone dosage, current density, operating pressure) will cause the nickel recovery rate and purity to be reduced; and not using the catalyst will significantly affect the oxidation and decomposition effect of the complex.

[0080] It can be known from the above examples that the method provided by the present application realizes the efficient separation and resource recovery of copper and nickel in wastewater through the treatment process of the synergistic effect of the charged nanofiltration membrane separation, ozone oxidation and diaphragm electrolysis, and solves the treatment problem caused by the coexistence of complex state and ionic state heavy metals in the electroless copper / nickel wastewater. The method provided by the present application realizes the organic combination of electroless plating wastewater treatment and resource recovery, conforms to the concept of circular economy, and has a broad industrialization prospect.

[0081] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained under the premise of no creativity according to the present embodiments, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for the synergistic treatment of electroless plating wastewater by quality-based electrolysis-oxidation, characterized in that, Includes the following steps: Chemical plating wastewater is adjusted and formulated to obtain pretreated wastewater containing heavy metal elements. The adjustment and formulation includes pH adjustment and addition of oxidant. The pH value of the pretreated wastewater is <6.

5. The pretreated wastewater is separated by charged nanofiltration membrane to obtain complexed heavy metal wastewater and ionic heavy metal wastewater. The complexed heavy metal wastewater is treated with ozone oxidation to obtain oxidized wastewater, which is then fed into a membrane electrolysis unit for first membrane electrolysis treatment to recover heavy metals. The ionic heavy metal wastewater is fed into a membrane electrolysis unit for second membrane electrolysis treatment to recover the heavy metals.

2. The method for the graded electrolysis-oxidation synergistic treatment of chemical plating wastewater according to claim 1, characterized in that, The chemical plating wastewater includes chemical nickel plating wastewater or chemical copper plating wastewater; the pretreated wastewater includes pretreated copper wastewater or pretreated nickel wastewater.

3. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 1 or 2, characterized in that, The oxidant is hydrogen peroxide, and the concentration of H2O2 in the hydrogen peroxide is 50~75 mg / L; the hydraulic residence time for adjusting the compatibility is 30~40 min.

4. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 2, characterized in that, The pH value of the pretreated copper wastewater is 5.8~6.2; the pH value of the pretreated nickel wastewater is 5.3~5.

7.

5. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 1, characterized in that, The conditions of the charged nanofiltration membrane separation include that the surface of the membrane material is negatively charged, the molecular weight cut-off value is 300-500 Da, the membrane module is a roll type nanofiltration membrane element or a flat plate type nanofiltration membrane element, the effective membrane area is 15-20 m 2 ; the operating pressure is 0.6-0.9 MPa; the temperature is 20-30 DEG C; and the cross flow speed is 0.3-0.5 m / s.

6. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 1, characterized in that, The ratio of ozone used in the ozone oxidation treatment to the chemical plating wastewater is 50~100 mg / L; the ozone oxidation treatment also uses a metal oxide catalyst.

7. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 6, characterized in that, The metal oxide catalyst includes a MnO2 / TiO2 composite catalyst and / or a CeO2 / Al2O3 composite catalyst; the ratio of the metal oxide catalyst to the chemical plating wastewater is 0.4~0.8 g / L.

8. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 1, characterized in that, The first and second membrane electrolysis processes use cation exchange membranes as diaphragms and copper or stainless steel plates as cathodes.

9. The method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater according to claim 1 or 8, characterized in that, The conditions of the first diaphragm electrolysis treatment and the second diaphragm electrolysis treatment include an electric current density of 1.5 to 3.5 A / dm 2 and an electrolysis temperature of 30 to 40°C.

10. The apparatus used in the fractional electrolysis-oxidation co-treatment method for chemical plating wastewater according to any one of claims 1 to 9, characterized in that, It includes a regulation and compatibility unit, a charged nanofiltration membrane separation unit, an ozone oxidation unit, and a diaphragm electrolysis unit connected in sequence.

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