A membrane coupling-based complexed copper wastewater treatment system and method

Abstract

This invention discloses a membrane coupling-based system and method for treating copper complex wastewater. The method includes: S1 pre-oxidation and complex-breaking treatment; S2 adding a heavy collector to the wastewater and performing cross-flow filtration using a membrane separation device equipped with an electrochemically activated membrane module to obtain a concentrated solution of the heavy collector-copper complex; S3 adjusting the pH of the concentrated solution and performing secondary filtration using the same membrane separation device, retaining the heavy collector for reuse, with the permeate being an acidic solution containing free copper ions; S4 chemically depositing and separating the acidic copper-containing solution to recover copper. In the S2 enrichment stage, a reducing electric field is applied using the membrane as the cathode, and in the backwashing stage, an oxidizing electric field is applied as the anode. The heavy collector is a graft copolymer or terpolymer of polyacrylic acid and β-cyclodextrin, which forms a loose, porous gel layer on the membrane surface during enrichment and naturally peels off. This invention achieves efficient complex breaking of copper complexes, high-purity recovery of copper resources, recycling of the heavy collector, and effective control of membrane fouling.

Description

Technical Field

[0001] This invention relates to the field of copper-containing wastewater treatment, and specifically to a complex copper wastewater treatment system and method based on membrane coupling. Background Technology

[0002] Copper complexation wastewater is widely generated in industries such as electroplating, electronics, and printed circuit boards. In this type of wastewater, copper ions form stable complexes with complexing agents such as ethylenediaminetetraacetic acid (EDTA), citric acid, ammonia, and tartaric acid, making it difficult to remove copper effectively using conventional methods. With increasingly stringent environmental protection requirements, how to efficiently treat copper complexation wastewater and achieve copper resource recovery has become an important issue in the field of industrial wastewater treatment.

[0003] Treatment technologies for copper complex wastewater mainly include chemical precipitation, Fenton oxidation, electrochemical methods, and membrane separation. Chemical precipitation involves adding an alkaline agent to form copper hydroxide precipitate; however, due to the high stability of the complex, copper ions are difficult to completely release, limiting the treatment effect and often resulting in effluent copper concentrations failing to meet standards. Fenton oxidation utilizes hydroxyl radicals to break down the complex structure, followed by neutralization and precipitation to remove copper ions. While effective, it suffers from high reagent consumption, high iron sludge production, and high treatment costs. Electrochemical methods achieve complex breaking and copper recovery through electrocatalytic oxidation or galvanic cell reactions, eliminating the need for reagents; however, electrode costs are high, and treatment efficiency is easily affected by water quality fluctuations. Membrane separation uses nanofiltration or reverse osmosis membranes to directly retain the copper complex, achieving copper concentration. However, membrane fouling is a significant problem, and since the complex remains intact, the concentrate still requires further treatment.

[0004] Overall, existing technologies for treating copper complex wastewater generally suffer from problems such as incomplete complex disruption, high reagent consumption, severe membrane fouling, and low resource recovery rates. A single treatment process cannot balance treatment efficiency and operating costs, and it remains significantly inadequate, particularly in the removal of highly stable copper complexes and the high-value recovery of copper resources. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel treatment system and method for complexed copper, which can achieve the treatment of complexed copper wastewater in a more green and environmentally friendly way.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows.

[0007] This invention provides a method for treating complexed copper wastewater based on membrane coupling, comprising the following steps: S1. Pump the complexed copper wastewater into the pre-oxidation and complex-breaking reactor, adjust the pH to 3.0-5.0, add Fenton reagent or Fenton-like catalyst, and control the redox potential between 200mV and 400mV. S2. Add a heavy collector to the wastewater treated by S1, the dosage of which is 1.5 to 3.0 times the molar amount of copper, adjust the pH to 5.0 to 6.5, and perform cross-flow filtration using a membrane separation device to obtain a concentrated solution of heavy collector-copper complex; the membrane separation device is equipped with an electrochemically activated membrane module, which uses a conductive membrane as the cathode or anode, and applies an electric field to the membrane surface to generate free radicals in situ on the membrane surface; S3. Adjust the pH of the concentrated solution obtained in S2 to 1.5-2.5, and perform secondary filtration using the same membrane separation device to retain the heavy collector. The permeate is an acidic solution containing free copper ions. S4. The acidic copper-containing solution obtained in S3 is subjected to chemical deposition separation to recover copper; S5. The heavy collector retained in S3 is adjusted to pH 5.0-6.5 and then refluxed back to S2.

[0008] In S2, the redox environment on the membrane surface is differentially controlled by adjusting the electrode polarity, current density and application time of the electrochemically activated membrane module: in the enrichment stage, the membrane is used as the cathode and a reducing electric field is applied; in the backwashing or fouling control stage, the membrane is switched to the anode and an oxidizing electric field is applied.

[0009] As a preferred technical solution, in the enrichment stage, the electrochemically activated membrane module described in S2 uses the membrane as the cathode, and the current density of the reducing electric field is controlled at 0.5A / m² to 5A / m²; in the backwashing or fouling control stage, the membrane is switched to the anode, and the current density of the oxidizing electric field is controlled at 2A / m² to 15A / m².

[0010] As a preferred technical solution, the conductive film in S2 is a conductive ceramic film. The conductive ceramic film uses titanium oxide or tin oxide as a substrate, and is coated with an antimony-doped tin dioxide or fluorine-doped tin dioxide conductive layer. The film pore size is 50nm to 100nm, and the film surface resistance is not greater than 100Ω / sq.

[0011] As a preferred technical solution, the heavy collector in S2 is polyacrylic acid, carboxymethyl chitosan, or a mixture of polyacrylic acid and carboxymethyl chitosan, wherein the mass ratio of polyacrylic acid to carboxymethyl chitosan in the mixture is 1:0.2 to 1:1; after adding the heavy collector, it is mixed using an online dynamic mixer for a mixing time of 30s to 120s, so that the heavy collector and copper ions are fully complexed before entering the membrane separation device.

[0012] As a preferred technical solution, the cross-flow filtration linear velocity of the membrane separation device in S2 and S3 is 2m / s to 5m / s, and the operating temperature is controlled between 15℃ and 35℃; in the enrichment stage of S2, the concentration factor is 5 to 10 times; in the secondary filtration stage of S3, the concentration factor is 2 to 4 times.

[0013] As a preferred technical solution, the heavy collector in S2 is a graft copolymer of polyacrylic acid and β-cyclodextrin, with a grafting rate of 5% to 15%; the cavity structure of the β-cyclodextrin encapsulates and complexes the aromatic complexing agents in the copper wastewater.

[0014] As a preferred technical solution, the heavy collector in S2 is a terpolymer of polyacrylic acid, β-cyclodextrin and polyethyleneimine, wherein the mass percentage of polyethyleneimine is 10% to 20%; the primary amine groups on the polyethyleneimine chain form a five-membered or six-membered ring complex structure with copper ions, thereby avoiding competition with polyethyleneimine for complexing copper ions.

[0015] As a preferred technical solution, in the enrichment stage, the electrochemically activated membrane module described in S2 applies a reducing electric field with the membrane as the cathode, and the energizing time is set according to the total copper concentration in the influent: when the total copper concentration is greater than 100 mg / L, the energizing time is 20 min to 40 min; when the total copper concentration is 50 mg / L to 100 mg / L, the energizing time is 10 min to 20 min; when the total copper concentration is less than 50 mg / L, the energizing time is 5 min to 10 min. When the rate of change of transmembrane pressure difference is greater than 5 kPa / min, the energizing time is extended by 30% to 50%; when the rate of change of transmembrane pressure difference is less than 1 kPa / min, the energizing time is shortened by 20% to 40%.

[0016] As a preferred technical solution, in the S2 enrichment stage, when the complex formed by the heavy collector and copper ions reaches saturation at a local concentration on the membrane surface, a sol-gel phase transition occurs due to the hydrophobic interaction between polyacrylic acid segments and the self-assembly behavior between β-cyclodextrin cavities, forming a loose and porous gel layer in situ on the membrane surface; the thickness of the gel layer is 50μm to 200μm, and the porosity is 60% to 80%.

[0017] A membrane-coupled complexed copper wastewater treatment system includes: The inlet of the pre-oxidation and complex-breaking reactor is connected to the inlet pipeline of the complexed copper wastewater; The complexation-membrane separation enrichment unit has its inlet connected to the outlet of the pre-oxidation complex-breaking reactor. The complexation-membrane separation enrichment unit includes a membrane separation device, which is equipped with an electrochemically activated membrane assembly. An acid release unit has its inlet connected to the concentrate outlet of the complexation-membrane separation enrichment unit, and the outlet of the acid release unit is connected to the inlet of the membrane separation device. The deep complex-breaking unit has its inlet connected to the permeate outlet of the membrane separation device; A copper recovery unit, the inlet of which is connected to the outlet of the deep breaking unit; The re-collector reuse pipeline is connected at its starting end to the re-collector retention side of the membrane separation device and at its end to the inlet of the complexation-membrane separation enrichment unit. The control system is connected to the pre-oxidation complex-breaking reactor, the membrane separation device, the acid decomposition and release unit, the deep complex-breaking unit, and the copper recovery unit.

[0018] Preferably, it also includes a concentrate reflux regulating unit, the inlet of which is connected to the concentrate outlet of the complexation-membrane separation enrichment unit, and the outlet of which is connected to the inlet of the pre-oxidation complex-breaking reactor.

[0019] The advantages and beneficial effects of this invention are as follows: By constructing a multi-stage coupled process and introducing an electrochemically activated membrane module, this invention achieves efficient treatment and copper resource recovery of complexed copper wastewater. Fenton or Fenton-like reagents are used to initially disrupt the complex structure. A large molecular complex is formed between the re-collector and copper ions. Combined with the electrochemically activated membrane module, a reducing electric field is applied using the membrane as the cathode. On the one hand, high-concentration of copper is achieved through membrane separation; on the other hand, free radicals generated in situ on the membrane surface are used to deeply disrupt the residual complex. Simultaneously, the cathode reducing environment promotes the activation of the Fenton reagent, increasing the comprehensive utilization rate of the Fenton reagent to over 85%, reducing the reagent dosage by 30%–50% compared to conventional processes. A graft copolymer or terpolymer of polyacrylic acid and β-cyclodextrin is used as the re-collector. The β-cyclodextrin cavity can encapsulate aromatic complexing agents, reducing competitive interference. The primary amine groups of polyethyleneimine form a stable complex structure with copper ions, and the recycling rate of the re-collector reaches over 75%.

[0020] During the enrichment process, the heavy collector-copper complex undergoes a sol-gel phase transition when the local concentration on the membrane surface reaches saturation, forming a loose and porous gel layer in situ. This layer naturally peels off under cross-flow shear force, achieving dynamic self-cleaning of the membrane surface and extending the membrane cleaning cycle by 2-3 times. The S3 acidification and release stage utilizes the same membrane system to complete the reuse of the heavy collector and the release of copper ions, simplifying the process. The purity of the copper product recovered through chemical deposition separation reaches over 98%, or the copper content of copper sulfide reaches over 55%. The overall process achieves a total removal rate of over 99.5% for complexed copper, with a total copper concentration in the effluent below 0.3 mg / L, while simultaneously reducing iron-containing sludge production by over 40%. Attached Figure Description

[0021] Figure 1 This is a block diagram of the system shown in this invention. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0023] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] The membrane-coupled copper wastewater treatment system provided in this application mainly includes a pre-oxidation and complex-breaking reactor, a complexation-membrane separation and enrichment unit, an acid decomposition and release unit, a deep complex-breaking unit, a copper recovery unit, and a control system.

[0026] The inlet of the pre-oxidation complex-breaking reactor is connected to the inlet pipeline of the copper complexation wastewater for preliminary oxidation and complex-breaking treatment. The inlet of the complexation-membrane separation enrichment unit is connected to the outlet of the pre-oxidation complex-breaking reactor. The core of this unit is the membrane separation device, which is equipped with an electrochemically activated membrane module. The inlet of the acid desorption / release unit is connected to the concentrate outlet of the complexation-membrane separation enrichment unit, and the outlet of the acid desorption / release unit is connected to the inlet of the membrane separation device, enabling the same membrane separation device to be used in both the enrichment and acidification / release stages. The inlet of the deep complex-breaking unit is connected to the permeate outlet of the membrane separation device, and the inlet of the copper recovery unit is connected to the outlet of the deep complex-breaking unit. The starting end of the heavy collector reuse pipeline is connected to the heavy collector retention side of the membrane separation device, and the terminal end is connected to the inlet of the complexation-membrane separation enrichment unit, for returning the recovered heavy collector to the system for recycling. The control system is connected to the pre-oxidation complex-breaking reactor, membrane separation device, acid desorption / release unit, deep complex-breaking unit, and copper recovery unit to achieve fully automated control of the entire process.

[0027] The membrane separation device is preferably made of conductive ceramic membrane, conductive carbon-based membrane, or metal-based membrane, with a pore size of 20 nm to 200 nm. It operates as a cross-flow filtration system and is equipped with a periodic pulse backwash system. To further optimize system operation, a concentrate reflux adjustment unit can be installed. Its inlet is connected to the concentrate outlet of the complexation-membrane separation enrichment unit, and its outlet is connected to the inlet of the pre-oxidation complex-breaking reactor. This unit is used to adjust the system load and improve complex-breaking efficiency when the copper concentration in the influent is low.

[0028] The method provided in this application includes the following steps. S1. Pump the copper-complexed wastewater into a pre-oxidation and complex-breaking reactor, adjust the pH to 3.0–5.0, add Fenton's reagent or a Fenton-like catalyst, and control the redox potential between 200mV and 400mV. The hydroxyl radicals generated by the Fenton reaction attack the ligand structure in the copper-complexed molecules, causing partial oxidative chain scission of complexing agents such as EDTA, citric acid, and tartaric acid, reducing the stability of the complex and releasing some copper ions. Simultaneously, this step also degrades some organic matter in the wastewater, reducing the organic pollution load on the subsequent membrane separation unit. The dosage of Fenton's reagent should not be too high to control the amount of iron sludge produced, and the iron ions can be recycled through subsequent electrochemical processes.

[0029] S2. Add a heavy collector to the wastewater treated by S1, at a dosage of 1.5 to 3.0 times the molar amount of copper, adjust the pH to 5.0 to 6.5, and perform cross-flow filtration using a membrane separation device to obtain a concentrated heavy collector-copper complex solution. The heavy collector molecular chain contains functional groups such as carboxyl and amino groups, which can form a stable coordination structure with copper ions, converting free copper and copper ions released by S1 into large molecular complexes. The membrane separation device uses cross-flow filtration to retain the large molecular weight heavy collector-copper complex, reducing the total copper concentration in the product water to below 0.5 mg / L, which can be directly reused or fed into subsequent biological treatment systems.

[0030] The membrane separation unit is equipped with an electrochemically activated membrane module. This module uses a conductive membrane as the cathode or anode, and an electric field is applied to the membrane surface to generate free radicals in situ. During the enrichment stage, a reducing electric field is applied using the membrane as the cathode, with the current density controlled between 0.5 A / m² and 5 A / m². The membrane cathode reduction reaction reduces dissolved oxygen to hydrogen peroxide, which reacts with the ferrous ions remaining from the S1 stage to form an in-situ Fenton reaction on the membrane surface, generating hydroxyl radicals. This deeply breaks down any incompletely broken complexes. The reducing electric field can also reduce Fe in the solution... 3+ Reduced to Fe 2+ First, it enables the valence state cycle of iron ions, thereby improving the utilization efficiency of Fenton's reagent. Second, the reducing electric field can suppress the excessive oxidation of the heavy collector on the membrane surface, reducing reagent loss.

[0031] S3. Adjust the pH of the concentrated solution obtained in S2 to 1.5–2.5, and perform secondary filtration using the same membrane separation device to retain the heavy collector. The permeate is an acidic solution containing free copper ions. Under acidic conditions, the heavy collector-copper complex dissociates, releasing copper ions in a free state. The heavy collector, due to its large molecular weight, is retained by the membrane. In this step, the heavy collector is separated from the copper ions, creating conditions for subsequent copper recovery and reuse of the heavy collector. In stage S3, the membrane can be switched to the anode as needed, and an oxidizing electric field can be applied with a current density controlled between 2 A / m² and 15 A / m². The hydroxyl radicals and hydrogen ions generated by the anodic oxidation reaction further enhance the degradation of organic matter attached to the surface of the heavy collector, improving the purity of the heavy collector when reused.

[0032] S4. The acidic copper-containing solution obtained in S3 is subjected to chemical deposition separation to recover copper. Chemical deposition separation can be performed using either electrochemical deposition or sulfide precipitation. For electrochemical deposition, a galvanic cell system is constructed using a MoS2 / graphite felt composite material as the cathode and a zinc or aluminum plate as the anode. The current density is controlled at 50 A / m² to 200 A / m², directly electrodepositing and recovering metallic copper, with a product purity exceeding 98%. For sulfide precipitation, the pH is adjusted to 8.0–9.0, and sodium sulfide is added at a dosage of 1.0–1.2 times the molar amount of copper, generating copper sulfide precipitate. After solid-liquid separation, the copper content in the copper sulfide can reach over 55%.

[0033] S5. The re-collecting agent retained in S3 is adjusted to pH 5.0–6.5 and then returned to S2 for recycling. The recycling rate of the re-collecting agent can reach over 75%, significantly reducing reagent costs.

[0034] The use of heavy trapping agents is an important way to achieve efficient copper enrichment in this application, and this application provides a variety of preferred heavy trapping agent schemes.

[0035] In the first preferred embodiment, the heavy collector is a graft copolymer of polyacrylic acid and β-cyclodextrin, with a grafting rate of 5%–15%. The carboxyl groups on the polyacrylic acid molecular chain can form coordination bonds with copper ions, thereby capturing them. β-cyclodextrin has a hydrophobic cavity structure, which has an inclusion effect on aromatic complexing agents (such as phthalic acid and salicylic acid) in copper-containing wastewater. It can preferentially capture and fix these aromatic complexing agents, reducing their competitive complexation of copper ions, thus improving the copper ion capture efficiency of the polyacrylic acid backbone by 20%–30%.

[0036] In the second preferred embodiment, the re-collector is a terpolymer of polyacrylic acid, β-cyclodextrin, and polyethyleneimine, wherein the mass percentage of polyethyleneimine is 10%–20%. The polyethyleneimine segments contain a large number of primary amine groups, which can form five- or six-membered ring complexes with copper ions, increasing its complexation stability constant by 1–2 orders of magnitude compared to polyacrylic acid alone. The cavity structure of β-cyclodextrin encapsulates and fixes the aromatic complexing agents in the wastewater, preventing them from competing with polyethyleneimine for copper ion complexation. These three components together increase the copper ion collection rate of the re-collector to over 99%.

[0037] In the third preferred embodiment, the re-collecting agent is a compound of polyacrylic acid and carboxymethyl chitosan, wherein the mass ratio of polyacrylic acid to carboxymethyl chitosan in the compound is 1:0.2 to 1:1. The carboxymethyl chitosan molecular chain contains both amino and carboxyl groups, and has dual coordination ability for copper ions, thus forming a complementary and synergistic effect with polyacrylic acid.

[0038] After the heavy trapping agent is added, it is mixed using an online dynamic mixer for 30-120 seconds to ensure sufficient complexation between the heavy trapping agent and copper ions before entering the membrane separation unit. The online dynamic mixer promotes the extension of the heavy trapping agent molecular chains and the exposure of functional groups through high-speed shearing, thereby increasing the kinetic rate of the complexation reaction.

[0039] This application discovered a unique dynamic self-cleaning phenomenon on the membrane surface during the S2 enrichment stage, which is related to the structural characteristics of the re-collecting agent. When a graft copolymer or terpolymer of polyacrylic acid and β-cyclodextrin is used as the re-collecting agent, when the concentration of the complex formed by the re-collecting agent and copper ions reaches saturation at the membrane surface, a sol-gel phase transition occurs due to the hydrophobic interactions between polyacrylic acid segments and the self-assembly behavior between β-cyclodextrin cavities, forming a loose and porous gel layer in situ on the membrane surface. The thickness of this gel layer is 50 μm to 200 μm, and the porosity is 60% to 80%.

[0040] During cross-flow filtration, the recapitulator-copper complex is trapped by the membrane and gradually accumulates on the membrane surface, with the local concentration continuously increasing. When the concentration reaches above the critical micelle concentration, the polyacrylic acid segments associate with each other due to hydrophobic interactions, and the β-cyclodextrin cavities form a supramolecular network structure through hydrogen bonds and hydrophobic interactions, transforming the entire system from a sol state to a gel state. This gel layer has a self-supporting structure and contains a large number of water channels, allowing solvent water molecules to permeate through the gaps between the gel layers, while the complex is further trapped.

[0041] As filtration proceeds, the gel layer thickness gradually increases. When the thickness reaches a critical value, under the action of cross-flow shear force, the gel layer naturally peels off from the membrane surface and is discharged with the concentrate, achieving dynamic self-cleaning of the membrane surface. This process requires no additional backwashing operation and does not rely on a complex control system, utilizing the phase change characteristics of the material itself to achieve self-regulation of membrane fouling. Experiments show that using this heavy collector can extend the membrane cleaning cycle by 2 to 3 times, and reduce the amount of chemical cleaning agents by 40% to 60%.

[0042] In the enrichment stage of the electrochemically activated membrane module, a reducing electric field is applied with the membrane as the cathode. The main functions of this electric field include: the cathode reduction reaction reduces dissolved oxygen to hydrogen peroxide, which forms an in-situ Fenton reaction with the ferrous ions remaining in the S1 stage, generating hydroxyl radicals on the membrane surface. This deeply oxidizes trace amounts of complexes that have penetrated the heavy collector-copper complex layer but have not yet been completely broken down, ensuring the quality of the effluent; the cathode reducing environment reduces ferric ions to ferrous ions, realizing the valence state cycle of ferric ions and improving the overall utilization rate of Fenton reagent; and the reducing electric field can inhibit the oxidative degradation of the heavy collector on the membrane surface, extending its service life.

[0043] During the backwashing or fouling control phase, the membrane is switched to the anode, and an oxidizing electric field is applied. The main functions of this electric field are as follows: First, the anodic oxidation reaction generates hydroxyl radicals, which oxidize and degrade organic matter and residual complexes adhering to the membrane surface, achieving efficient membrane cleaning; Second, anodic oxidation can modify the functional groups on the molecular chain of the heavy trapping agent, introducing highly hydrophilic groups such as sulfonic acid groups and phosphate groups, improving its complexing performance and antifouling ability after reuse; Third, the oxidizing electric field can oxidize ferrous ions in the solution, forming iron salt precipitates with phosphate or sulfate ions, which are then retained by the membrane and reused in S1 as a Fenton-like catalyst, realizing a closed-loop cycle of iron resources.

[0044] The current density and electrode polarity switching timing of the electrochemically activated membrane module can be precisely controlled by an intelligent control system. The control system monitors parameters such as total copper concentration, transmembrane pressure difference, and redox potential in the feed water in real time, and automatically adjusts operating parameters according to preset logic. For example, when the total copper concentration in the feed water is greater than 100 mg / L, the energizing time during the enrichment stage is set to 20-40 minutes; when the total copper concentration is less than 50 mg / L, the energizing time is shortened to 5-10 minutes. When the rate of change of transmembrane pressure difference is greater than 5 kPa / min, the energizing time is extended by 30%-50% to enhance the complexation breaking effect; when the rate of change of transmembrane pressure difference is less than 1 kPa / min, the energizing time is shortened by 20%-40% to save energy.

[0045] Example 1 This embodiment provides a method for treating complexed copper wastewater based on membrane coupling, including the following steps: S1. Pump the complexed copper wastewater into the pre-oxidation and complex-breaking reactor, adjust the pH to 4.0, add Fenton's reagent, and control the oxidation-reduction potential at 300mV.

[0046] S2. A heavy collector is added to the wastewater treated in S1 at a dosage 2.0 times the molar amount of copper. The pH is adjusted to 6.0, and cross-flow filtration is performed using a membrane separation device to obtain a concentrated solution of the heavy collector-copper complex. The membrane separation device is equipped with an electrochemically activated membrane module, which uses a conductive membrane as the cathode or anode. An electric field is applied to the membrane surface to generate free radicals in situ. In this embodiment, the conductive membrane is a conductive ceramic membrane with titanium oxide as the substrate and an antimony-doped tin dioxide conductive layer coated on the surface. The membrane pore size is 80 nm, and the membrane surface resistance is not greater than 100 Ω / sq. The heavy collector is a compound of polyacrylic acid and carboxymethyl chitosan, with a mass ratio of polyacrylic acid to carboxymethyl chitosan of 1:0.5. After adding the heavy collector, it is mixed using an online dynamic mixer for 60 s. The cross-flow filtration linear velocity of the membrane separation device is 3 m / s, the operating temperature is controlled at 25℃, and the concentration factor is 8 times during the enrichment stage of S2.

[0047] In S2, the redox environment on the membrane surface is differentially controlled by adjusting the electrode polarity, current density, and application time of the electrochemically activated membrane module: in the enrichment stage, the membrane is used as the cathode and a reducing electric field is applied, with the current density controlled at 2A / m²; in the backwashing or fouling control stage, the membrane is switched to the anode and an oxidizing electric field is applied, with the current density controlled at 8A / m².

[0048] S3. Adjust the pH of the concentrate obtained in S2 to 2.0, and perform secondary filtration using the same membrane separation device to retain the heavy collector. The permeate is an acidic solution containing free copper ions. In the secondary filtration stage of S3, the concentration factor is 3 times.

[0049] S4. The acidic copper-containing solution obtained in S3 is subjected to chemical deposition separation to recover copper. In this embodiment, an electrochemical deposition method is used, with MoS2 / graphite felt composite material as the cathode and zinc plate as the anode to construct a galvanic cell system, and the current density is controlled at 120 A / m. 2 , to recycle metallic copper.

[0050] S5. The heavy collector retained in S3 is adjusted to pH 6.0 and then refluxed back to S2.

[0051] The total copper concentration in the treated effluent of this embodiment was 0.25 mg / L, with a total copper removal rate of 99.4%; the recycling rate of the heavy collector was 78%; the dosage of Fenton's reagent was reduced by 42% compared to conventional processes; the amount of iron-containing sludge generated was reduced by 45%; the membrane cleaning cycle was extended by 2.5 times; and the purity of the recovered metallic copper was 98.5%.

[0052] Example 2 The difference between this embodiment and Embodiment 1 is as follows: In S1, the oxidation-reduction potential is controlled at 220mV; in S2, the heavy collector added is a graft copolymer of polyacrylic acid and β-cyclodextrin with a grafting rate of 8%, and an online dynamic mixer is not used for mixing; the cross-flow filtration linear velocity of the membrane separation device is 4m / s, the operating temperature is controlled at 18℃, and the concentration factor is 6 times in the enrichment stage of S2; in the enrichment stage of S2, the membrane is used as the cathode, and the current density of the reducing electric field is controlled at 1A / m²; in the secondary filtration stage of S3, the concentration factor is 2 times; in S4, a sulfide precipitation method is adopted, the pH is adjusted to 8.5, sodium sulfide is added, and the amount of sodium sulfide added is 1.1 times the molar amount of copper, and copper sulfide precipitate is generated and recovered.

[0053] The total copper concentration in the treated effluent of this embodiment was 0.28 mg / L, with a total copper removal rate of 99.3%; the recycling rate of the heavy collector was 76%; the dosage of Fenton's reagent was reduced by 38% compared to conventional processes; the amount of iron-containing sludge generated was reduced by 42%; the membrane cleaning cycle was extended by 2.2 times; and the copper content of the recovered copper sulfide was 56%.

[0054] Example 3 The difference between this embodiment and Embodiment 2 is as follows: In S2, the heavy collector is a terpolymer of polyacrylic acid, β-cyclodextrin, and polyethyleneimine, wherein the mass percentage of polyethyleneimine is 15%; in the enrichment stage of S2, the membrane is used as the cathode, and the current density of the reducing electric field is controlled at 4 A / m²; in S2, the energizing time is set according to the total copper concentration in the influent; in this embodiment, the total copper concentration in the influent is 120 mg / L, and the energizing time is 30 min; during operation, the transmembrane pressure difference change rate is 6 kPa / min, and the energizing time is extended by 40%; in S4, electrochemical deposition is used, and the current density is controlled at 80 A / m². 2 .

[0055] The total copper concentration in the treated effluent of this embodiment was 0.22 mg / L, with a total copper removal rate of 99.6%; the recycling rate of the heavy collector was 82%; the dosage of Fenton's reagent was reduced by 48% compared to conventional processes; the amount of iron-containing sludge generated was reduced by 52%; the membrane cleaning cycle was extended by 3.0 times; and the purity of the recovered metallic copper was 98.8%.

[0056] Example 4 The difference between this embodiment and Embodiment 3 is as follows: In S1, the oxidation-reduction potential is controlled at 380mV; in S2, the heavy precipitant is a graft copolymer of polyacrylic acid and β-cyclodextrin with a grafting rate of 12%, and is mixed using an online dynamic mixer for 100s; the cross-flow filtration linear velocity of the membrane separation device is 2.5m / s, the operating temperature is controlled at 32℃, and the concentration factor is 9 times in the enrichment stage of S2; in the enrichment stage of S2, the membrane is used as the cathode, and the current density of the reducing electric field is controlled at 0.8A / ㎡; in S2, the energizing time is set according to the total copper concentration in the influent. In this embodiment, the total copper concentration in the influent is 65mg / L, and the energizing time is 15min; the transmembrane pressure difference change rate during operation is 0.8kPa / min, and the energizing time is shortened by 25%; in the secondary filtration stage of S3, the concentration factor is 4 times; in S4, a sulfide precipitation method is used, the pH is adjusted to 8.0, and sodium sulfide is added, with the amount of sodium sulfide added being 1.0 times the molar amount of copper.

[0057] The total copper concentration in the treated effluent of this embodiment was 0.26 mg / L, with a total copper removal rate of 99.4%; the recycling rate of the heavy collector was 79%; the dosage of Fenton's reagent was reduced by 35% compared to conventional processes; the amount of iron-containing sludge generated was reduced by 44%; the membrane cleaning cycle was extended by 2.3 times; and the copper content of the recovered copper sulfide was 55%.

[0058] Example 5 The difference between this embodiment and Embodiment 1 is as follows: In S1, a Fenton-like catalyst is added. This catalyst is an iron-based supported catalyst with activated carbon as the carrier and an iron loading of 10%, using a fixed-bed reactor. In S2, the conductive membrane is a conductive ceramic membrane with tin oxide as the substrate and a fluorine-doped tin dioxide conductive layer coated on the surface; the membrane pore size is 60 nm. The re-collecting agent is a compound of polyacrylic acid and carboxymethyl chitosan, with a mass ratio of polyacrylic acid to carboxymethyl chitosan of 1:0.8. The membrane separation device... The cross-flow filtration linear velocity is 4.5 m / s, and the operating temperature is controlled at 28℃. In the enrichment stage of S2, the concentration factor is 7 times. In the enrichment stage of S2, the membrane is used as the cathode, and the current density of the reducing electric field is controlled at 3 A / ㎡. In S2, the energizing time is set according to the total copper concentration in the influent. In this embodiment, the total copper concentration in the influent is 40 mg / L, and the energizing time is 8 min. During operation, the transmembrane pressure difference change rate is 2 kPa / min, and the energizing time is not adjusted. In the secondary filtration stage of S3, the concentration factor is 3 times.

[0059] The total copper concentration in the treated effluent of this embodiment was 0.23 mg / L, with a total copper removal rate of 99.5%; the recycling rate of the heavy collector was 80%; the iron ion loss rate in the Fenton-like catalyst was less than 5%, requiring no additional iron source; the amount of iron-containing sludge generated was reduced by 48%; the membrane cleaning cycle was extended by 2.6 times; and the purity of the recovered metallic copper was 98.6%.

[0060] Comparative Example 1 This comparative example uses conventional chemical precipitation to treat copper complex wastewater. The copper complex wastewater is pumped into a reaction tank, and sodium hydroxide is added to adjust the pH to 9.0, causing copper ions to form copper hydroxide precipitate. After solid-liquid separation in a sedimentation tank, the effluent is discharged. The total copper concentration in the wastewater before treatment was 85 mg / L, and the total copper concentration in the treated effluent was 12.5 mg / L, which is still insufficient to meet national discharge standards. Furthermore, a large amount of copper-containing sludge is generated, and copper resources cannot be effectively recovered.

[0061] Comparative Example 2 This comparative example uses the conventional Fenton oxidation method to treat copper complex wastewater. The copper complex wastewater is pumped into a Fenton reactor, the pH is adjusted to 3.5, and ferrous sulfate and hydrogen peroxide are added. The amount of ferrous sulfate added is 5 times the molar amount of copper, and the amount of hydrogen peroxide added is 1.2 times the molar amount of ferrous sulfate. The reaction time is 90 minutes, followed by adjusting the pH to 9.0 for neutralization and precipitation. The total copper concentration in the wastewater before treatment was 85 mg / L, and the total copper concentration in the effluent after treatment was 2.8 mg / L. Although this meets some discharge standards, the reagent consumption is high, and the cost per ton of water treated is about 65% higher than in Example 1. It also produces a large amount of iron-containing sludge, with a sludge yield approximately 2.8 times that of Example 1, and the copper recovery product is copper-iron sludge with low value.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for treating complexed copper wastewater based on membrane coupling, characterized in that, Includes the following steps: S1. Pump the complexed copper wastewater into the pre-oxidation and complex-breaking reactor, adjust the pH to 3.0-5.0, add Fenton reagent or Fenton-like catalyst, and control the redox potential between 200mV and 400mV. S2. Add a heavy collector to the wastewater treated by S1, the dosage of which is 1.5 to 3.0 times the molar amount of copper, adjust the pH to 5.0 to 6.5, and perform cross-flow filtration using a membrane separation device to obtain a concentrated solution of heavy collector-copper complex; the membrane separation device is equipped with an electrochemically activated membrane module, which uses a conductive membrane as the cathode or anode, and applies an electric field to the membrane surface to generate free radicals in situ on the membrane surface; S3. Adjust the pH of the concentrated solution obtained in S2 to 1.5-2.5, and perform secondary filtration using the same membrane separation device to retain the heavy collector. The permeate is an acidic solution containing free copper ions. S4. The acidic copper-containing solution obtained in S3 is subjected to chemical deposition separation to recover copper; S5. The heavy collector retained in S3 is adjusted to pH 5.0-6.5 and then refluxed back to S2.

2. The method according to claim 1, characterized in that, In S2, the redox environment on the membrane surface is differentially controlled by adjusting the electrode polarity, current density and application time of the electrochemically activated membrane module: during the enrichment stage, a reducing electric field is applied with the membrane as the cathode. During the backwashing or fouling control phase, the membrane is switched to the anode, and an oxidizing electric field is applied.

3. The method according to claim 2, characterized in that, In the enrichment stage, the electrochemically activated membrane module described in S2 uses the membrane as the cathode, and the current density of the reducing electric field is controlled at 0.5 A / m² to 5 A / m². In the backwashing or fouling control stage, the membrane is switched to the anode, and the current density of the oxidizing electric field is controlled at 2 A / m² to 15 A / m².

4. The method according to claim 1, characterized in that, The conductive film described in S2 is a conductive ceramic film. The conductive ceramic film uses titanium oxide or tin oxide as the substrate and is coated with an antimony-doped tin dioxide or fluorine-doped tin dioxide conductive layer. The film pore size is 50nm to 100nm and the film surface resistance is not greater than 100Ω / sq.

5. The method according to claim 1, characterized in that, The heavy collector mentioned in S2 is any one of the following: polyacrylic acid, carboxymethyl chitosan, a compound of polyacrylic acid and carboxymethyl chitosan, a graft copolymer of polyacrylic acid and β-cyclodextrin, or a terpolymer of polyacrylic acid, β-cyclodextrin, and polyethyleneimine; after adding the heavy collector, mix for 30s to 120s.

6. The method according to claim 1, characterized in that, The cross-flow filtration linear velocity of the membrane separation devices described in S2 and S3 is 2m / s to 5m / s, and the operating temperature is controlled between 15℃ and 35℃. In the enrichment stage of S2, the concentration factor is 5 to 10 times. In the secondary filtration stage of S3, the concentration factor is 2 to 4 times.

7. The method according to claim 2, characterized in that, In the enrichment stage, the electrochemically activated membrane module described in S2 applies a reducing electric field using the membrane as the cathode. The energizing time is set according to the total copper concentration in the feed water: when the total copper concentration is greater than 100 mg / L, the energizing time is 20 min to 40 min; when the total copper concentration is 50 mg / L to 100 mg / L, the energizing time is 10 min to 20 min; when the total copper concentration is less than 50 mg / L, the energizing time is 5 min to 10 min; when the transmembrane pressure difference change rate is greater than 5 kPa / min, the energizing time is extended by 30% to 50%; when the transmembrane pressure difference change rate is less than 1 kPa / min, the energizing time is shortened by 20% to 40%.

8. The method according to claim 5, characterized in that, During the S2 enrichment stage, when the complex formed by the heavy collector and copper ions reaches local saturation on the membrane surface, a sol-gel phase transition occurs, forming a loose and porous gel layer in situ on the membrane surface; the thickness of the gel layer is 50 μm to 200 μm, and the porosity is 60% to 80%.

9. A membrane-coupled complexed copper wastewater treatment system, characterized in that, include: The inlet of the pre-oxidation and complex-breaking reactor is connected to the inlet pipeline of the complexed copper wastewater; The complexation-membrane separation enrichment unit has its inlet connected to the outlet of the pre-oxidation complex-breaking reactor. The complexation-membrane separation enrichment unit includes a membrane separation device, which is equipped with an electrochemically activated membrane assembly. The membrane separation device is a conductive ceramic membrane, a conductive carbon-based membrane, or a metal-based membrane with a pore size of 20 nm to 200 nm. It operates as a cross-flow filtration system and is equipped with a periodic pulse backwash system. An acid release unit has its inlet connected to the concentrate outlet of the complexation-membrane separation enrichment unit, and the outlet of the acid release unit is connected to the inlet of the membrane separation device. The deep complex-breaking unit has its inlet connected to the permeate outlet of the membrane separation device; A copper recovery unit, the inlet of which is connected to the outlet of the deep breaking unit; The re-collector reuse pipeline is connected at its starting end to the re-collector retention side of the membrane separation device and at its end to the inlet of the complexation-membrane separation enrichment unit. The control system is connected to the pre-oxidation complex-breaking reactor, the membrane separation device, the acid decomposition and release unit, the deep complex-breaking unit, and the copper recovery unit.

10. The system according to claim 9, characterized in that, It also includes a concentrate reflux regulating unit, whose inlet is connected to the concentrate outlet of the complexation-membrane separation enrichment unit, and whose outlet is connected to the inlet of the pre-oxidation complex-breaking reactor.

Images