Quality-divided electrolysis-oxidation cooperative treatment method and device for chemical plating wastewater

Abstract

The invention belongs to the technical field of electroplating wastewater treatment, and particularly relates to a quality-divided electrolysis-oxidation cooperative treatment method and device for chemical plating wastewater. The chemical plating wastewater is subjected to adjustment and compatibility to obtain pretreated wastewater, and the chemical plating wastewater contains heavy metal elements; carrying out charged nanofiltration membrane separation on the pretreated wastewater to obtain complex-state heavy metal wastewater and ionic-state heavy metal wastewater; carrying out ozone oxidation treatment on the complex-state heavy metal wastewater to obtain oxidized wastewater, carrying out first diaphragm electrolysis treatment on the oxidized wastewater, and recovering heavy metals; and carrying out second diaphragm electrolysis treatment on the ion-state heavy metal wastewater, and recovering heavy metals. According to the method, efficient separation and resource recycling of copper and nickel in the chemical plating wastewater are achieved, chemical plating wastewater treatment and resource recycling are organically combined, and the method has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of electroplating wastewater treatment technology, specifically relating to a method and apparatus for the synergistic treatment of chemical plating wastewater by electrolysis and oxidation. Background Technology

[0002] Chemical copper / nickel plating is widely used in printed circuit boards and surface treatment of electronic components, generating a large amount of wastewater containing heavy metals such as copper and nickel annually. This type of wastewater has the following significant characteristics compared to traditional electroplating wastewater: (1) It contains a large amount of complexing agents (such as EDTA, citrate, tartrate, etc.), forming stable metal complexes, which are poorly treated by traditional chemical precipitation methods; (2) Heavy metals exist in both complexed and ionic forms, with significant differences in properties, making them difficult to treat uniformly; (3) Residual reducing agents (such as hypophosphite, borohydride, etc.) can interfere with subsequent treatments; (4) The pH value fluctuates greatly and often contains a variety of additives, which increases the difficulty of processing.

[0003] Currently, chemical plating wastewater treatment mainly employs technologies such as reagent precipitation, ion exchange, and membrane separation, but these methods suffer from drawbacks such as low treatment efficiency, high cost, and difficulty in metal recovery. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for the synergistic treatment of electrolytic oxidation of chemical plating wastewater. The method provided by this invention achieves efficient separation and resource recovery of heavy metals (copper / nickel) in chemical plating wastewater, while ensuring that the wastewater meets discharge standards. It has high treatment efficiency and low cost, and has broad application prospects.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater, comprising 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 subjected to ozone oxidation treatment to obtain oxidized wastewater, and the oxidized wastewater is subjected to first membrane electrolysis treatment to recover heavy metals. The ionic heavy metal wastewater is treated by second membrane electrolysis to recover the heavy metals.

[0006] Preferably, 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.

[0007] Preferably, 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.

[0008] Preferably, the pH value of the pretreated copper wastewater is 5.8 to 6.2; and the pH value of the pretreated nickel wastewater is 5.3 to 5.7.

[0009] Preferably, the conditions for separation by the charged nanofiltration membrane include: the membrane material surface carries a negative charge, and the molecular weight cutoff is 300~500 Da; the membrane module is a spiral wound nanofiltration membrane element or a flat sheet nanofiltration membrane element, and the effective membrane area is 15~20 m². 2 Operating pressure: 0.6~0.9MPa; temperature: 20~30℃; cross-flow velocity: 0.3~0.5m / s.

[0010] Preferably, 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.

[0011] Preferably, 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.

[0012] Preferably, the first and second membrane electrolysis processes use cation exchange membranes as diaphragms and copper or stainless steel plates as cathodes.

[0013] Preferably, the conditions for the first and second membrane electrolysis treatments include a current density of 1.5~3.5 A / dm³. 2 The electrolysis temperature is 30~40℃.

[0014] The present invention provides an apparatus for the electrolytic-oxidation co-treatment method for chemical plating wastewater as described in the above technical solution, comprising a regulating and compatibility unit, a charged nanofiltration membrane separation unit, an ozone oxidation unit, and a diaphragm electrolysis unit connected in sequence.

[0015] This invention provides a method for the synergistic treatment of electroless plating wastewater by electrolysis and oxidation, comprising the following steps: adjusting and compatibility of the electroless plating wastewater to obtain pretreated wastewater containing heavy metal elements; the adjustment and compatibility includes pH adjustment and addition of an oxidant; the pH value of the pretreated wastewater is <6.5; separating the pretreated wastewater using a charged nanofiltration membrane to obtain complexed heavy metal wastewater and ionic heavy metal wastewater; subjecting the complexed heavy metal wastewater to ozone oxidation to obtain oxidized wastewater; subjecting the oxidized wastewater to a first membrane electrolysis treatment to recover heavy metals; and subjecting the ionic heavy metal wastewater to a second membrane electrolysis treatment to recover heavy metals. This invention adjusts the pH value of the electroless plating wastewater by adjusting the compatibility, and simultaneously uses an oxidant to oxidize the reducing agent in the wastewater, thereby adjusting the redox potential of the wastewater and creating suitable conditions for subsequent separation. After adjusting the formulation, the present invention performs charged nanofiltration membrane separation on the obtained pretreated wastewater: utilizing the blocking effect of the nanofiltration membrane on macromolecules and the electrostatic effect of the charge layer on the surface of the nanofiltration membrane, ionic heavy metals (such as Cu) are separated. 2+ or Ni 2+ This invention uses nanofiltration membranes, while organic matter (EDTA-Cu, nickel citrate, etc.) remains in the wastewater, thus dividing the wastewater into two parts: complexed heavy metal wastewater and ionic heavy metal wastewater. For the complexed heavy metal wastewater, ozone oxidation is first used to destroy the metal complex structure, releasing heavy metal ions, followed by electrolytic treatment through a first membrane to recover the heavy metals. For the ionic heavy metal wastewater, heavy metals are directly recovered through electrolytic treatment through a second membrane. Compared with existing technologies, this invention has the following advantages: This invention addresses the technical challenge of heavy metal recovery from electroless plating wastewater due to the simultaneous presence of complexed and ionic heavy metals. Through a rationally designed treatment process, it achieves effective separation and treatment of complexed and ionic heavy metals. The recovered metals exhibit high purity: copper and nickel recovery purity can reach over 98%, allowing for direct use in electroplating processes. Metal recovery rates are high: copper recovery rate >96%, nickel recovery rate >95%. It also saves on reagent costs: compared to traditional precipitation methods, reagent usage is reduced by 70-80%. Operating costs are low: energy consumption is approximately 60% of conventional treatment processes. Furthermore, the wastewater treatment effect is excellent: all effluent indicators consistently meet the discharge standards of the electroplating industry. In summary, this invention achieves efficient separation and resource recovery of copper and nickel from electroless plating wastewater, organically combining electroless plating wastewater treatment with resource recovery, and has broad application prospects. Attached Figure Description

[0016] Figure 1 This is a flowchart of the electrolytic oxidation co-treatment method for chemical plating wastewater provided by the present invention. Detailed Implementation

[0017] This invention provides a method for the graded electrolytic-oxidation synergistic treatment of chemical plating wastewater, comprising 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 subjected to ozone oxidation treatment to obtain oxidized wastewater, and the oxidized wastewater is subjected to first membrane electrolysis treatment to recover heavy metals. The ionic heavy metal wastewater is treated by second membrane electrolysis to recover the heavy metals.

[0018] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0019] This invention adjusts and mixes chemical plating wastewater to obtain pretreated wastewater. In this invention, the chemical plating wastewater contains heavy metal elements. The heavy metal elements preferably include copper or nickel. The chemical plating wastewater preferably includes chemical nickel plating wastewater or chemical copper plating wastewater. The chemical plating wastewater preferably includes ionic heavy metals, complexed heavy metals, and a reducing agent. The complexed heavy metals preferably include one or more of EDTA salts, citrates, lactates, and tartrates. The reducing agent preferably includes hypophosphite and / or borohydrides. In this invention, the Cu in the chemical copper plating wastewater... 2+ The preferred concentration of the active ingredient is 400-600 mg / L, and in the example, it can be 500 mg / L. The preferred concentration of EDTA copper salt is 1000-1500 mg / L, and in the example, it can be 1200 mg / L. The preferred pH value of the electroless copper plating wastewater is 4-5, and in the example, it is 4.5. In this invention, the Ni in the electroless nickel plating wastewater... 2+ The concentration is preferably 400~500 mg / L, and in the example it can be 450 mg / L. The pH value of the chemical nickel plating wastewater is preferably 5.5±0.2.

[0020] In this invention, the conditioning and compatibility preferably includes pH adjustment and the addition of an oxidant. The conditioning and compatibility preferably includes: first adjusting the pH of the chemical plating wastewater, then adding an oxidant to carry out an oxidation reaction, to obtain the pretreated wastewater. The oxidant is preferably hydrogen peroxide, and the concentration of H2O2 in the hydrogen peroxide is preferably 50-75 mg / L. The amount of oxidant used is based on the complete oxidation of the reducing agent in the chemical plating wastewater. The hydraulic retention time of the conditioning and compatibility is preferably 30-40 min. The pH value of the pretreated wastewater is <6.5. In this invention, the pretreated wastewater includes pretreated copper wastewater or pretreated nickel wastewater. The pH value of the pretreated copper wastewater is preferably 5.8-6.2. The pH value of the pretreated nickel wastewater is preferably 5.3-5.7.

[0021] After obtaining the pretreated wastewater, the present invention performs charged nanofiltration membrane separation on the pretreated wastewater to obtain complexed heavy metal wastewater and ionic heavy metal wastewater. In the present invention, the preferred conditions for charged nanofiltration membrane separation include: the membrane material surface preferably carries a negative charge; the molecular weight cutoff value is preferably 300~500 Da; the membrane module is preferably a spiral wound nanofiltration membrane element or a flat sheet nanofiltration membrane element; and the effective membrane area is preferably 15~20 m². 2 The preferred operating pressure is 0.6~0.9MPa; the preferred temperature is 20~30℃; the preferred recovery rate is 65~75%; and the preferred cross-flow velocity is 0.3~0.5m / s.

[0022] In this invention, when the pretreated wastewater is preferably copper wastewater, the membrane material is preferably a polypiperazine composite nanofiltration membrane with a negatively charged surface and a molecular weight cutoff of 300-400 Da; the membrane module is preferably a spiral wound nanofiltration membrane element with an effective membrane area of ​​20 m². 2 The preferred operating parameters include: operating pressure of 0.6~0.8 MPa; temperature of 25±2℃; recovery rate of 70~75%; and cross-flow velocity of 0.3~0.4 m / s. The separation principle of this invention is: the negative charge on the nanofiltration membrane surface affects Cu... 2+ Metal cations have almost no blocking effect, but have a high interception effect on large EDTA-Cu complexes; separation effect: 80% of ionic copper passes through the membrane into the permeate, while more than 90% of EDTA-Cu complexes are retained in the concentrate; the concentrate containing complexed copper and the permeate enriched with ionic copper are collected separately.

[0023] In this invention, when the pretreated wastewater is preferably pretreated nickel wastewater, the membrane material is preferably a sulfonated polyethersulfone modified nanofiltration membrane with a negatively charged surface and a molecular weight cutoff of 400-500 Da; the membrane module is preferably a flat-plate nanofiltration membrane element with an effective membrane area of ​​15 m². 2The preferred operating parameters include: operating pressure of 0.7~0.9 MPa; temperature of 28±2℃; recovery rate of 65~70%; and cross-flow velocity of 0.4~0.5 m / s. Before the pretreated nickel wastewater undergoes separation via the charged nanofiltration membrane, the present invention preferably pretreats the pretreated nickel wastewater. The pretreatment preferably includes mixing the pretreated nickel wastewater with an antifouling agent. The present invention preferably uses the antifouling agent to improve the separation effect of the pretreated nickel wastewater. The antifouling agent is preferably polyacrylamide. The mass ratio of the antifouling agent to the volume of the chemical plating wastewater is preferably 0.3~0.8 mg / L, and in the embodiment, it can be 0.5 mg / L. The effect of the charged nanofiltration membrane in separating the pretreated nickel wastewater is that 75% of the ionic nickel passes through the membrane into the permeate, while more than 85% of the complexed nickel is retained in the concentrate.

[0024] In this invention, during the charged nanofiltration membrane separation process, it is preferable to perform membrane cleaning with a solution of citric acid and EDTA after 48 hours of operation. The pH value of the citric acid and EDTA solution is preferably 3.0, and the EDTA content is preferably 0.5 wt%.

[0025] After obtaining the complexed heavy metal wastewater, the present invention subjectes the complexed heavy metal wastewater to ozone oxidation treatment to obtain oxidized wastewater. In the present invention, the preferred ratio of ozone to the chemical plating wastewater used in the ozone oxidation treatment is 50-100 mg / L, and in the embodiments it can be 60 mg / L or 80 mg / L. The ozone control precision 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 preferred ratio of the metal oxide catalyst to the chemical plating wastewater is 0.4-0.8 g / L, and in the embodiments it can be 0.5 g / L or 0.6 g / L. The preferred ozone oxidation treatment time is 30-60 min, and in the embodiments it can be 30 min or 40 min. The preferred pH value of the ozone oxidation treatment is 6-7, and in the embodiments it can be 6.5-7 or 6-6.5. The present invention preferably uses ozone oxidation treatment to destroy the complex structure of complexed heavy metals and release free heavy metal ions.

[0026] After obtaining the oxidized wastewater, the present invention performs a first membrane electrolysis treatment on the oxidized wastewater to recover heavy metals. After obtaining the ionic heavy metal wastewater, the present invention performs a second membrane electrolysis treatment on the ionic heavy metal wastewater to recover heavy metals.

[0027] In this invention, the first and second membrane electrolysis treatments use cation exchange membranes as diaphragms and copper or stainless steel plates as cathodes. When the oxidized wastewater and ionic heavy metal wastewater contain copper ions, the cathode is a copper plate. When the oxidized wastewater and ionic heavy metal wastewater contain nickel ions, the cathode is a stainless steel plate.

[0028] In this invention, when the oxidized wastewater and ionic heavy metal wastewater contain copper ions, the anode materials for the first and second diaphragm electrolysis treatments are preferably coated titanium electrodes (DSA). When the oxidized wastewater and ionic heavy metal wastewater contain nickel ions, the anode materials for the first and second diaphragm electrolysis treatments are preferably coated titanium electrodes.

[0029] In this invention, the conditions for the first and second membrane electrolysis treatments preferably include: a current density preferably of 1.5~3.5 A / dm³. 2 In the embodiment, it can be 2.5A / dm 2 Or 2.8A / dm 2 The electrolysis temperature is 30~40℃. The preferred electrolysis time is 50~80min, but in the examples it can be 60min or 70min.

[0030] The present invention provides an apparatus for the electrolytic-oxidation co-treatment method for chemical plating wastewater as described in the above technical solution, comprising a regulating and compatibility unit, a charged nanofiltration membrane separation unit, an ozone oxidation unit, and a diaphragm electrolysis unit connected in sequence.

[0031] In this invention, the charged nanofiltration membrane separation unit separates complexed heavy metal wastewater and ionic heavy metal wastewater.

[0032] In this invention, the ozone oxidation unit preferably includes an ozone generator, a gas-liquid mixer, a catalytic oxidation reactor, and a tail gas treatment device.

[0033] In this invention, the diaphragm electrolysis unit preferably includes a cathode chamber, an anode chamber, a cation exchange membrane, a DC power supply, and an electrolyte circulation system.

[0034] To further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention. The following embodiments are based on... Figure 1 The flowchart shown illustrates the synergistic treatment of chemical plating wastewater through electrolysis and oxidation.

[0035] Example 1: Treatment of wastewater from chemical copper plating Taking the treatment of chemical copper plating wastewater from an electronics factory as an example (Cu) 2+The concentration is 500 mg / L, the EDTA concentration is 1200 mg / L, and the pH value is 4.5. The specific steps are as follows: Adjustment and compatibility: Introduce the chemical copper plating wastewater into the equalization tank and adjust the pH value to 6.0±0.2; add hydrogen peroxide (H2O2 concentration 50mg / L) to oxidize the reducing agent in the residual chemical copper plating wastewater. The amount of hydrogen peroxide should be sufficient to remove the reducing agent; the hydraulic retention time is 30min to obtain pretreated wastewater.

[0036] Charged nanofiltration membrane separation: Pretreated wastewater is pumped into the nanofiltration membrane separation system; Membrane material: Polypiperazine composite nanofiltration membrane, with a negatively charged surface and a molecular weight cutoff of 300~400 Da; Membrane module: Spiral wound nanofiltration membrane element, with an effective membrane area of ​​20 m². 2 Operating parameters: Operating pressure: 0.6~0.8MPa; Temperature: 25±2℃; Recovery rate: controlled at 70~75%; Crossflow velocity: 0.3~0.4m / s. Separation principle: The negative charge on the nanofiltration membrane surface affects Cu... 2+ Metal cations have almost no blocking effect, but have a high interception effect on large molecular EDTA-Cu complexes; separation effect: 80% of ionic copper passes through the membrane into the permeate, while more than 90% of EDTA-Cu complexes are retained in the concentrate; the concentrate containing complexed copper and the permeate enriched with ionic copper are collected separately to obtain complexed copper wastewater and ionic copper wastewater.

[0037] Treatment of complexed copper wastewater: Complexed 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, releasing Cu. 2+ The ions were oxidized to produce copper ion wastewater.

[0038] Ionic copper wastewater recovery: Ionic copper wastewater separated by charged nanofiltration membranes 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 / dm³ 2 Electrolysis time: 60 min; Cu 2+ Metallic copper is deposited at the cathode.

[0039] Copper ion wastewater recovery after oxidation: Copper ion wastewater after ozone oxidation enters the membrane electrolysis unit; the same electrolysis parameters as those for ionized copper wastewater recovery are used; copper ions released by ozone oxidation are recovered.

[0040] The experimental results of this embodiment are as follows: copper recovery rate reached 97.5%; recovered copper purity reached 99.2%; copper content in the treated effluent was <0.5mg / L, meeting the discharge standards; energy consumption was 3.2kWh / kg-Cu.

[0041] Example 2: Treatment of wastewater from electroless nickel plating Taking the treatment of chemical nickel plating wastewater from an electronics factory as an example (Ni 2+ The concentration is 450 mg / L, containing the complexing agents citrate and lactate. The specific steps are as follows: Adjustment and compatibility: Introduce the electroless nickel plating wastewater into the equalization tank and adjust the pH value to 5.5±0.2; add hydrogen peroxide (H2O2 concentration 75mg / L) to oxidize the residual hypophosphite in the electroless nickel plating wastewater; the amount of hydrogen peroxide used should be sufficient to remove hypophosphite, and the retention time is 40min to obtain pretreated wastewater.

[0042] Charged nanofiltration membrane separation: Pretreated wastewater is pumped into the nanofiltration membrane separation system; Membrane material: Sulfonated polyethersulfone modified nanofiltration membrane, with a negatively charged surface and a molecular weight cutoff of 400~500 Da; Membrane module: Flat-sheet nanofiltration membrane element, with an effective membrane area of ​​15 m². 2 Operating parameters: Operating pressure: 0.7~0.9MPa; Temperature: 28±2℃; Recovery rate: controlled at 65~70%; Cross-flow velocity: 0.4~0.5m / s. Pretreatment of electroless nickel plating wastewater is required: 0.5mg / L of polyacrylamide is added to the pretreated wastewater as an antifouling agent. Separation effect: Approximately 75% of ionic nickel passes through the membrane into the permeate, while over 85% of complexed nickel is retained in the concentrate. Membrane cleaning: After 48 hours of operation, a combination of citric acid (pH=3.0) and EDTA (0.5%) solution is used for cleaning to obtain complexed nickel wastewater and ionic nickel wastewater.

[0043] Treatment of complexed nickel wastewater: Complexed nickel wastewater enters the ozone oxidation unit; ozone dosage: 80 mg / L; catalyst: CeO2 / Al2O3 composite catalyst, dosage 0.6 g / L; reaction time: 40 min; reaction pH: 6.0~6.5. Ozone destroys the complexed nickel structure, releasing Ni. 2+ The ions were used to obtain nickel ion wastewater after oxidation.

[0044] Ionic nickel wastewater recovery: Ionic nickel-copper wastewater separated by charged nanofiltration membranes directly enters the membrane electrolysis unit; Cathode material: stainless steel plate; Anode material: coated titanium electrode; Current density: 2.8 A / dm³ 2 Electrolysis time: 70 min; The recovered nickel can be obtained by stripping or dissolving and then electroplating.

[0045] Nickel ion wastewater recovery after oxidation: The nickel ion wastewater after ozone oxidation enters the membrane electrolysis unit; the same electrolysis parameters as those for ionic nickel wastewater recovery are used; the membrane is a cation exchange membrane.

[0046] The experimental results of this embodiment are as follows: nickel recovery rate reached 95.8%; recovered nickel purity reached 98.5%; nickel content in the treated effluent was 0.5 mg / L; energy consumption was 4.1 kWh / kg-Ni.

[0047] Comparative Example 1: The hydrogen peroxide oxidation step in the pretreatment was omitted. The same wastewater (Ni) as in Example 2 was used. 2+ The concentration was 450 mg / L, but the hydrogen peroxide oxidation step in the pretreatment was omitted, and separation was directly performed using a charged nanofiltration membrane. Treatment conditions: The pH was adjusted to 5.5 ± 0.2 only; no hydrogen peroxide was added, and the solution was directly fed into the nanofiltration membrane separation system. Experimental results: Nickel recovery rate: 76.3% (19.5% lower than Example 2). Recovered nickel purity: 88.2% (10.3% lower than Example 2). Effluent nickel content: 1.8 mg / L (1.3 mg / L higher than Example 2). Energy consumption: 5.2 kWh / kg-Ni (26.8% higher than Example 2). Severe membrane fouling required frequent cleaning, shortening the operating cycle to 24 hours.

[0048] Comparative Example 2: Ozone oxidation step omitted The same pretreatment and nanofiltration membrane separation as in Example 2 were used, but ozone oxidation treatment of the complexed nickel wastewater was omitted, and it was directly recovered by electrolysis. Treatment conditions: The concentrated complexed nickel wastewater was directly fed into the membrane electrolysis unit without ozone oxidation treatment. Experimental results: Nickel recovery rate: 58.7% (37.1% lower than Example 2). Recovered nickel purity: 82.4% (16.1% lower than Example 2). Effluent nickel content: 3.2 mg / L (2.7 mg / L higher than Example 2). Energy consumption: 6.8 kWh / kg-Ni (65.9% higher than Example 2). Complexed nickel is difficult to separate by electrolysis, and a large amount of nickel ions remain in the wastewater.

[0049] Comparative Example 3: Changing Key Operating Parameters (1) Reduce ozone dosage The ozone dosage was reduced from 80 mg / L to 40 mg / L, while other conditions remained the same as in Example 2. Experimental results: Nickel recovery rate: 81.2% (14.6% lower than Example 2). Recovered nickel purity: 91.3% (7.2% lower than Example 2). Effluent nickel content: 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).

[0050] (2) Reduce current density The current density was reduced from 2.8 A / dm 2 Reduced to 1.5A / dm 2 Other conditions are the same as in Example 2.

[0051] Experimental results: Nickel recovery rate: 72.4% (23.4% lower than Example 2). Recovered nickel purity: 94.1% (4.4% lower than Example 2). Effluent nickel content: 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 benefits were significantly reduced due to the substantial decrease in recovery rate).

[0052] (3) No catalyst used No CeO2 / Al2O3 composite catalyst was 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). Recovered nickel purity: 89.7% (8.8% lower than Example 2). Effluent nickel content: 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).

[0053] Comparative Example 4: Changing the operating pressure of the nanofiltration membrane The nanofiltration membrane operating pressure was adjusted from 0.7-0.9 MPa to 0.4-0.5 MPa, while other conditions remained the same as in Example 2. Experimental results: Nickel recovery rate: 84.3% (11.5% lower than Example 2). Recovered nickel purity: 96.8% (1.7% lower than Example 2). Effluent nickel content: 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, resulting in reduced treatment efficiency.

[0054] The above comparative examples show that: omitting the pretreatment oxidation step will lead to increased membrane fouling and a significant decrease in recovery efficiency; omitting the ozone oxidation step will prevent the effective separation of complexed nickel, seriously affecting the overall recovery effect; reducing key operating parameters (such as ozone dosage, current density, and operating pressure) will lead to a decrease in nickel recovery rate and purity; and not using a catalyst will significantly affect the oxidative decomposition effect of the complex.

[0055] As demonstrated by the above embodiments, the method provided by this invention achieves efficient separation and resource recovery of copper and nickel in wastewater through a synergistic treatment process of charged nanofiltration membrane separation, ozone oxidation, and membrane electrolysis. This solves the treatment problem caused by the simultaneous presence of complexed and ionic heavy metals in chemical copper / nickel plating wastewater. The method provided by this invention organically combines chemical plating wastewater treatment with resource recovery, aligning with the concept of a circular economy and possessing broad industrialization prospects.

[0056] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for the graded electrolysis-oxidation synergistic treatment of chemical plating wastewater, 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 subjected to ozone oxidation treatment to obtain oxidized wastewater, and the oxidized wastewater is subjected to first membrane electrolysis treatment to recover heavy metals. The ionic heavy metal wastewater is treated by second membrane electrolysis 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 for separation by the charged nanofiltration membrane include: the membrane material surface carries a negative charge, and the molecular weight cutoff is 300~500 Da; the membrane module is a spiral wound nanofiltration membrane element or a flat sheet nanofiltration membrane element, and the effective membrane area is 15~20 m². 2 Operating pressure: 0.6~0.9MPa; temperature: 20~30℃; cross-flow velocity: 0.3~0.5m / 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 for the first and second membrane electrolysis treatments include: a current density of 1.5~3.5 A / dm³. 2 The electrolysis temperature is 30~40℃.

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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