Coprocessing and copper resource recycling method for copper-containing and cyanide-containing wastewater

Abstract

The invention relates to a coprocessing and copper resource recycling method for copper-containing and cyanide-containing wastewater, which comprises the following steps and conditions: carrying out a synergistic combination process of pretreatment adjustment, iron-carbon micro-electrolysis complex breaking pretreatment, copper deposition reaction and solid-liquid separation, copper resource recycling and activated carbon catalytic oxidation cyanogen removal and up-to-standard discharge, and specifically comprises five process steps and conditions. The method has the advantages that the problems that an existing process is poor in synergy, not thorough in copper recovery, prone to poisoning of activated carbon and high in operation cost can be solved, and the treatment targets of high efficiency, low cost and recycling can be achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and resource recovery technology, specifically to a method for the synergistic treatment of copper- and cyanide-containing wastewater and the recovery of copper resources. Background Technology

[0002] Copper- and cyanide-containing wastewater is a typical pollutant in industries such as electroplating, metallurgy, and gold cyanide leaching. Cyanides in this wastewater exist primarily in free (CN⁻) and complexed (e.g., Cu(CN)₃²⁻, Cu(CN)₄³⁻) forms, while copper ions mainly form stable complexes with cyanide ions. This wastewater is characterized by high toxicity, poor degradation, and complex pollutant composition. Direct discharge of this wastewater would cause serious harm to the ecological environment and human health, and the copper resources within the wastewater would not be recovered, resulting in resource waste.

[0003] Currently, the treatment methods for copper- and cyanide-containing wastewater are mainly divided into two categories: cyanide degradation and copper resource recovery. However, existing processes generally suffer from poor synergy, high treatment costs, and unstable effects. Specifically: (1) Oxidation methods (such as alkaline chlorination and ozone oxidation) can degrade cyanide, but cannot effectively recover copper resources. Moreover, the degradation efficiency for complexed cyanide is limited, and toxic intermediate products are easily generated. The equipment investment and operating costs are high. (2) Precipitation methods (such as copper salt precipitation) can remove some cyanide, but the reagent consumption is huge, and the copper-containing precipitates generated are mostly disposed of as hazardous waste. (3) The single iron-carbon micro-electrolysis process can destroy some complex bonds and remove free cyanide, but it cannot degrade stable complex cyanide. The total cyanide concentration in the treated water is still high, and the copper resources are not recovered. At the same time, the copper ions remaining in the iron-carbon effluent will poison the catalyst for subsequent deep treatment. (4) Although the activated carbon catalytic oxidation method can remove cyanide in a deep process, it is easy for copper ions in the wastewater to occupy the catalytic sites, resulting in catalytic efficiency decay and shortened activated carbon life. If the raw water is treated directly, frequent regeneration is required, and the operating cost increases significantly.

[0004] In existing technologies, cyanide treatment and copper resource recovery are mostly independent processes, which presents problems such as the inability to simultaneously achieve treatment effectiveness, resource recovery, and cost control.

[0005] To address the aforementioned issues, several publications have emerged, including CN102079590B, "A Method for Treating and Reusing Wastewater Containing Copper-Cyanide Complexes." This invention proposes using elemental aluminum or elemental phosphorus as a reducing agent to react the wastewater containing copper-cyanide complexes with the solution for 1-5 hours, followed by solid-liquid separation to achieve wastewater reuse and copper recovery. However, the use of elemental aluminum / phosphorus as the reducing agent makes the reaction process prone to generating secondary impurities. Furthermore, it lacks a targeted mechanism for breaking down the cyanide complex, resulting in limited effectiveness in stabilizing Cu-CN complexes. Additionally, it lacks a reagent recycling and sludge resource utilization design, failing to form a closed-loop treatment process. CN104003563B, "A Method for Treating and Reusing Wastewater Containing Copper Cyanide," further addresses this issue. The invention, titled "Recycling Method," employs a two-step process of "ion recovery + extraction separation" to treat copper cyanide-containing wastewater. First, the wastewater undergoes a security filtration process to remove impurities. Then, a cyanide ion recovery machine is used to enrich cyanide complexes and free cyanide to obtain a concentrated solution. Subsequently, an inert gas is introduced into a sealed tank, and a mixed extractant of sulfuric acid and sodium chloride is added to separate and recover hydrogen cyanide and cuprous chloride, achieving separate recovery of cyanide and copper. However, this method relies heavily on a sulfuric acid-sodium chloride extraction system, resulting in significant extractant consumption and loss. Furthermore, it lacks a reagent recycling design, leading to high treatment costs. It also lacks a targeted mechanism to break up stable Cu-CN complexes, only able to enrich and recover a portion of the cyanide complexes. The treatment effect is affected by the complexation content. The impact is significant; however, the copper resource recovery form is cuprous chloride, which limits its application scenarios and cannot directly produce general industrial-grade copper products. Furthermore, the addition of inert gas and the collection of hydrogen cyanide require stringent safety controls, resulting in high operational complexity and risk for large-scale applications. CN121292752A, "Method for Resource Recovery and Recycling of Cyanide-Containing Wastewater," describes a "sulfidation copper recovery + precise separation" process for cyanide-containing wastewater. First, copper is recovered by sulfidation under weakly acidic conditions (pH 5-6), converting the copper-cyanide complex into a mixture of copper sulfide and cuprous cyanide. Then, the pH is adjusted to 9-11, and separation agents are added to control the ORP at -400mV to -200mV, allowing the cyanide to be separated. Copper reacts with free cyanide to form a soluble complex, achieving separation from copper sulfide and reducing the cyanide content of copper-containing materials. However, the sulfidation copper recovery requires the addition of a large amount of sulfiding agent, resulting in high reagent consumption costs. Furthermore, there is no reagent recycling design. The separation process requires extremely high precision in controlling ORP and pH values, and the separation effect is easily affected by parameter fluctuations. The operation is quite difficult, and only the initial recovery of copper is achieved. The obtained copper sulfide material needs additional treatment to be converted into industrial-grade copper products. It does not form a closed loop for the targeted recovery of copper resources. At the same time, it does not involve the simultaneous removal of COD from wastewater and requires a supporting subsequent treatment unit. The overall process chain is long and not suitable for the integrated treatment of high-COD copper- and cyanide-containing wastewater.CN119219279B, "A Method for Treating and Recycling Electroplating Cyanide Copper Wastewater," describes a multi-step reaction process for treating electroplating cyanide copper wastewater. First, a strong alkali is added to induce a binding reaction with ferrous sulfate solution. Then, acid is added to induce a Prussian blue reaction. A coagulant is added, and the wastewater is filtered to obtain ferric cyanide sludge and preliminarily decyanated wastewater. Subsequently, a weak alkali is added to adjust the wastewater, and hydrogen peroxide is added using copper in the water as a catalyst to oxidize residual cyanide. Finally, lime is added for flocculation and precipitation to obtain copper sludge. This method enables resource recovery, but its process is cumbersome and requires... The process involves multiple pH adjustments, is complex and energy-intensive. The ferricyanide sludge generated from the Prussian blue reaction is hazardous waste requiring specialized disposal, poses a risk of secondary pollution, and lacks a resource recovery pathway. The recovered copper sludge is a mixture with low purity, requiring additional purification to convert it into industrial-grade copper products. Copper resource recovery efficiency is limited, hydrogen peroxide and lime reagent consumption is high, a reagent recycling system is not established, and processing costs are high. Furthermore, the effect on breaking up high-concentration complexed copper cyanide compounds is unstable. (CN118724389B "Gold...") The invention, titled "Method for Treatment and Resource Regeneration of Cyanide-Containing Wastewater from Mines," targets cyanide-containing wastewater from gold mines. It employs a "cyanide reduction precipitation-deep purification-coupled catalysis-elution refining" process. First, a cyanide reduction precipitation agent is added to treat the copper-containing cyanide wastewater, destroying cyanide and causing copper ions to precipitate as copper hydroxide and cuprous hydroxide. Next, a deep purification agent is used to treat the overflow liquid. Subsequently, the precipitate and purification residue are coupled and catalyzed under the action of a catalyst, destroying thiocyanate and cyanide. Finally, the crude copper product is eluted with the deep treatment liquid to remove impurities and obtain refined copper. The removal rates of copper, total cyanide, and copper ions all exceed 99%, but it relies on specialized cyanide-reducing precipitants and deep purification agents. These agents are numerous, costly, and lack a recycling system, resulting in poor economic efficiency. The process is complex, requiring precise control of reaction conditions between the coupled catalysis and elution steps, making operation difficult and energy-intensive. Catalyst activity is easily affected by wastewater impurities, necessitating regular replacement and maintenance, further increasing operating costs. It is only suitable for gold mine wastewater scenarios and has limited adaptability to copper- and cyanide-containing wastewater from other industries such as electroplating, lacking versatility.

[0006] Therefore, the development of a co-treatment method for copper- and cyanide-containing wastewater and a copper resource recovery method with smooth process integration, significant synergistic effect, low cost, and the ability to simultaneously achieve copper recovery and cyanide discharge compliance has become an urgent need in the industry for the treatment of copper- and cyanide-containing wastewater. Summary of the Invention

[0007] The objective of this invention is to overcome the shortcomings of existing technologies and provide a method for the synergistic treatment and copper resource recovery of copper-containing and cyanide-containing wastewater. By coupling the processes of iron-carbon micro-electrolysis, iron powder replacement precipitation and activated carbon catalytic oxidation, an integrated treatment of "complexed copper breaking, copper resource recovery and deep degradation of cyanide" is achieved. This method can solve the problems of poor synergy of existing processes, incomplete copper recovery, easy poisoning of activated carbon and high operating costs, and achieve the treatment goals of high efficiency, low cost and resource recovery.

[0008] The objective of this invention is achieved through the following technical solution: a method for the synergistic treatment and copper resource recovery of copper- and cyanide-containing wastewater, which combines pretreatment conditioning, iron-carbon micro-electrolysis complex breaking pretreatment, copper precipitation reaction and solid-liquid separation, copper resource recovery, and activated carbon catalytic oxidation for cyanide removal and compliant discharge in a synergistic combination process, specifically including the following process steps and conditions: (1) Pretreatment and adjustment: Take copper and cyanide-containing wastewater and filter it through a screen to remove suspended solids and impurities with a particle size ≥5mm; test the wastewater quality and control the total cyanide concentration in the influent to 50~500mg / L, copper ion concentration to 5~100mg / L, and COD ≤2000mg / L. If the wastewater pH>8, add 10~20% dilute sulfuric acid to adjust the pH to 4.0~8.0 and set aside. (2) Iron-carbon micro-electrolysis pretreatment: The wastewater adjusted in step (1) is pumped into the iron-carbon micro-electrolysis reactor. The reactor is filled with iron-carbon composite packing. The mass ratio of iron to carbon in the iron-carbon composite packing is controlled to be 4:1~6:1, the packing particle size is 3~8mm, the porosity is 40~50%, and the packing layer height to reactor diameter ratio is 3:1~4:1. Air is introduced into the reactor for aeration treatment. The aeration intensity is adjusted to 1.0~1.5m³ / (m³·h), and the reaction time is 60~120min. Through the iron-carbon galvanic cell reaction, Fe at the anode loses electrons to generate Fe²⁺, and hydrogen evolution reaction occurs at the cathode to generate reduced [H]. Fe²⁺ and [H] work together to break the Cu-CN complex bond, converting the complexed copper into free Cu²⁺. At the same time, Fe²⁺ reacts with some free CN⁻ to generate Fe(CN)₆. 4 ⁻ The Fe(OH)2 / Fe(OH)3 flocs generated during the reaction adsorb some colloidal cyanide and organic matter, and simultaneously remove free cyanide to reduce the COD load of wastewater; (3) Copper precipitation reaction and solid-liquid separation: Slowly add alkaline solution to the wastewater after complex breaking obtained in step (2). The alkaline solution is a sodium hydroxide solution or calcium hydroxide solution with a mass fraction of 10~20%. During the addition process, continuously stir and adjust the pH value of the wastewater to 8.5~9.5. Maintain the stirring rate of 50~80r / min and react for 30~45min. Free Cu²⁺ and OH⁻ fully react to generate copper hydroxide precipitate, and the residual Fe³⁺ reacts with OH⁻ to generate iron hydroxide precipitate. After the reaction is completed, send the mixed liquid into the sedimentation tank and let it stand for 60~90min to separate the solid and liquid to obtain a mixed precipitate containing copper hydroxide and iron hydroxide and a supernatant. The supernatant is sent to step (5) for treatment, and the mixed precipitate is collected for later use. (4) Copper resource recovery: The mixed precipitate residue from step (3) is transferred to an acid dissolution tank, and 15-25% dilute sulfuric acid is added to adjust the pH of the reaction system to 2.0-2.5. The temperature is maintained at 40-50℃, and the reaction is stirred for 40-60 minutes to completely dissolve the mixed precipitate residue and obtain a mixed sulfate solution containing Cu²⁺ and Fe³⁺. 30% hydrogen peroxide is slowly added to the mixed sulfate solution to oxidize the residual Fe²⁺ to Fe³⁺, and then the pH is finely adjusted to 2 with 10% sodium hydroxide solution. 8~3.2, stir the reaction at a constant temperature of 40℃ for 30 min to completely hydrolyze Fe³⁺ to form ferric hydroxide precipitate. After standing for 20~30 min to precipitate, filter to remove the ferric hydroxide precipitate and obtain a pure copper sulfate solution. Electrolytic deposition method is used to electrolyze the pure copper sulfate solution, controlling the electrolysis voltage at 1.8~2.2V, the electrolysis current density at 20~30mA / cm², the electrolysis temperature at 30~40℃, and the electrolysis time at 120~180 min. Metallic copper is deposited at the cathode. After washing and drying, industrial-grade copper product is obtained. (5) Activated carbon catalytic oxidation for cyanide removal and discharge in compliance with standards: The supernatant from step (3) is fed into an activated carbon catalytic oxidation reactor, which is filled with granular activated carbon catalyst loaded with iron and copper bimetallic ions; the specific surface area of ​​the catalyst is 800~1200m² / g, the particle size is 2~5mm, the total loading of iron and copper metal ions is 3%~5% of the mass of activated carbon, and the catalyst is prepared by impregnation and then dried and activated; air is introduced into the reactor for aeration, the aeration intensity is controlled at 0.8~1.2m³ / (m³·h), the reaction temperature is maintained at 25~30℃, the pH value is the original pH of the supernatant, and the wastewater retention time is 90~120min; by utilizing the adsorption performance of activated carbon and the catalytic activity of bimetallic ions, combined with aeration and oxygen supply, the residual cyanide is oxidized and decomposed into harmless substances, and some residual organic matter and trace heavy metal ions are simultaneously adsorbed and degraded, so as to achieve the discharge of wastewater in compliance with standards.

[0009] Compared with the prior art, the present invention has the following innovative points, advantages, or effects: (1) This invention abandons acidic pH adjustment, optimizes iron-carbon micro-electrolysis parameters, and breaks down the complex through the synergistic effect of Fe²⁺ and reduced [H]. The subsequent bimetallic supported activated carbon catalytic oxidation relies solely on aeration to degrade residual cyanide. The final effluent concentrations of total cyanide and copper ions can stably meet the standards of Table 2 of GB 21900-2008. The process parameters are controllable, the operation is simple, and it is suitable for wastewater from multiple industries, with broad prospects for industrialization.

[0010] (2) Through the acid dissolution-oxidation iron removal-electrolytic deposition process, iron impurities are completely separated, and the copper recovery purity is ≥99.5% and the recovery rate is ≥90%, resulting in industrial-grade copper products. The iron-carbon filler and supported activated carbon can be recycled, and the pickling waste liquid and the post-electrolysis liquid can be reused. No acid-base adjustment or additional oxidant is required, and the reagent cost is reduced by more than 30%. The resource benefits offset part of the operating costs, making it economically efficient.

[0011] (3) Micro-electrolysis flocs adsorb impurities, activated carbon catalytic oxidation produces no toxic byproducts, iron removal filter residue is properly disposed of, and the packing is regenerated and recycled, resulting in no secondary pollution and conforming to the concept of green environmental protection.

[0012] In summary, this invention achieves integrated treatment of "complexed copper breaking, copper resource recovery, and deep cyanide degradation" by coupling iron-carbon micro-electrolysis, iron powder replacement precipitation, and activated carbon catalytic oxidation. It can effectively solve the problems of poor process synergy, incomplete copper recovery, easy poisoning of activated carbon, and high operating costs in existing processes, and achieve the goal of efficient, low-cost, and resource-oriented treatment. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the process flow for a method for the synergistic treatment of copper- and cyanide-containing wastewater and the recovery of copper resources, as described in this invention.

[0014] The present invention will now be described in further detail with reference to the accompanying drawings. Detailed Implementation

[0015] like Figure 1 As shown, the synergistic treatment and copper resource recovery method for copper- and cyanide-containing wastewater combines pretreatment and conditioning, iron-carbon micro-electrolysis complex breaking pretreatment, copper precipitation reaction and solid-liquid separation, copper resource recovery, and activated carbon catalytic oxidation for cyanide removal and compliant discharge. Specifically, it includes the following process steps and conditions: (1) Pretreatment and adjustment: Take copper and cyanide-containing wastewater and filter it through a screen to remove suspended solids and impurities with a particle size ≥5mm; test the wastewater quality and control the total cyanide concentration in the influent to 50~500mg / L, copper ion concentration to 5~100mg / L, and COD ≤2000mg / L. If the wastewater pH>8, add 10~20% dilute sulfuric acid to adjust the pH to 4.0~8.0 and set aside. (2) Iron-carbon micro-electrolysis pretreatment: The wastewater adjusted in step (1) is pumped into the iron-carbon micro-electrolysis reactor. The reactor is filled with iron-carbon composite packing. The mass ratio of iron to carbon in the iron-carbon composite packing is controlled to be 4:1~6:1, the packing particle size is 3~8mm, the porosity is 40~50%, and the packing layer height to reactor diameter ratio is 3:1~4:1. Air is introduced into the reactor for aeration treatment. The aeration intensity is adjusted to 1.0~1.5m³ / (m³·h), and the reaction time is 60~120min. Through the iron-carbon galvanic cell reaction, Fe at the anode loses electrons to generate Fe²⁺, and hydrogen evolution reaction occurs at the cathode to generate reduced [H]. Fe²⁺ and [H] work together to break the Cu-CN complex bond, converting the complexed copper into free Cu²⁺. At the same time, Fe²⁺ reacts with some free CN⁻ to generate Fe(CN)₆. 4 ⁻ The Fe(OH)2 / Fe(OH)3 flocs generated during the reaction adsorb some colloidal cyanide and organic matter, and simultaneously remove free cyanide to reduce the COD load of wastewater; (3) Copper precipitation reaction and solid-liquid separation: Slowly add alkaline solution to the wastewater after complex breaking obtained in step (2). The alkaline solution is a sodium hydroxide solution or calcium hydroxide solution with a mass fraction of 10~20%. During the addition process, continuously stir and adjust the pH value of the wastewater to 8.5~9.5. Maintain the stirring rate of 50~80r / min and react for 30~45min. Free Cu²⁺ and OH⁻ fully react to generate copper hydroxide precipitate, and the residual Fe³⁺ reacts with OH⁻ to generate iron hydroxide precipitate. After the reaction is completed, send the mixed liquid into the sedimentation tank and let it stand for 60~90min to separate the solid and liquid to obtain a mixed precipitate containing copper hydroxide and iron hydroxide and a supernatant. The supernatant is sent to step (5) for treatment, and the mixed precipitate is collected for later use. (4) Copper resource recovery: The mixed precipitate residue from step (3) is transferred to an acid dissolution tank, and 15-25% dilute sulfuric acid is added to adjust the pH of the reaction system to 2.0-2.5. The temperature is maintained at 40-50℃, and the reaction is stirred for 40-60 minutes to completely dissolve the mixed precipitate residue and obtain a mixed sulfate solution containing Cu²⁺ and Fe³⁺. 30% hydrogen peroxide is slowly added to the mixed sulfate solution to oxidize the residual Fe²⁺ to Fe³⁺, and then the pH is finely adjusted to 2 with 10% sodium hydroxide solution. 8~3.2, stir the reaction at a constant temperature of 40℃ for 30 min to completely hydrolyze Fe³⁺ to form ferric hydroxide precipitate. After standing for 20~30 min to precipitate, filter to remove the ferric hydroxide precipitate and obtain a pure copper sulfate solution. Electrolytic deposition method is used to electrolyze the pure copper sulfate solution, controlling the electrolysis voltage at 1.8~2.2V, the electrolysis current density at 20~30mA / cm², the electrolysis temperature at 30~40℃, and the electrolysis time at 120~180 min. Metallic copper is deposited at the cathode. After washing and drying, industrial-grade copper product is obtained. (5) Activated carbon catalytic oxidation for cyanide removal and discharge in compliance with standards: The supernatant from step (3) is fed into an activated carbon catalytic oxidation reactor, which is filled with granular activated carbon catalyst loaded with iron and copper bimetallic ions; the specific surface area of ​​the catalyst is 800~1200m² / g, the particle size is 2~5mm, the total loading of iron and copper metal ions is 3%~5% of the mass of activated carbon, and the catalyst is prepared by impregnation and then dried and activated; air is introduced into the reactor for aeration, the aeration intensity is controlled at 0.8~1.2m³ / (m³·h), the reaction temperature is maintained at 25~30℃, the pH value is the original pH of the supernatant, and the wastewater retention time is 90~120min; by utilizing the adsorption performance of activated carbon and the catalytic activity of bimetallic ions, combined with aeration and oxygen supply, the residual cyanide is oxidized and decomposed into harmless substances, and some residual organic matter and trace heavy metal ions are simultaneously adsorbed and degraded, so as to achieve the discharge of wastewater in compliance with standards.

[0016] The process of the present invention can be further described as follows: The iron-carbon composite filler in step (2) can be reused for 3 to 5 treatment cycles. After the filler fails, it is activated by acid washing with 5% to 8% dilute sulfuric acid for 30 to 40 minutes to remove the passivation film and impurities attached to the surface. After rinsing until neutral, it can be put into use again.

[0017] The waste liquid containing trace amounts of iron ions generated during pickling in step (2) is collected and recycled in the acid dissolution tank of step (4).

[0018] In step (4), the electrolytic deposition method uses a titanium-plated ruthenium electrode as the anode and a pure copper sheet as the cathode; during the electrolysis process, the deposits on the electrode surface are cleaned regularly to maintain stable electrolysis efficiency.

[0019] In step (4), the electrolyte after electrolytic deposition is returned to the pretreatment adjustment unit of step (1) for recycling. Example

[0020] The treatment of copper- and cyanide-containing wastewater continuously discharged from a gold mine was carried out. This wastewater is a comprehensive wastewater generated from the cyanide gold extraction process in the gold mine, containing complexed copper cyanide, free cyanide, a small amount of suspended solids and organic impurities. The initial water quality indicators are: total cyanide concentration 320 mg / L, copper ion concentration 265 mg / L, COD 280 mg / L, and pH value 9.2. The specific treatment steps are as follows: Step 1. Pretreatment and Conditioning: Copper- and cyanide-containing wastewater from the gold mine is continuously pumped into a bar screen filter using a self-priming pump. The bar screen is a stainless steel fine bar with a 5mm slit width, continuously filtering out suspended solids and slag impurities with a particle size ≥5mm from the wastewater. The filtered wastewater then continuously enters a conditioning tank equipped with an automatic pH adjustment system to monitor the pH value of the wastewater in real time. Because the initial pH value of the wastewater in the conditioning tank is >8, 15% (w / w) dilute sulfuric acid is continuously and quantitatively added to the conditioning tank using the automatic pH adjustment system to stabilize the pH value of the wastewater in the conditioning tank to 6.5. The conditioned wastewater is then continuously pumped into the subsequent iron-carbon micro-electrolysis reactor by a booster pump.

[0021] Step 2. Iron-Carbon Micro-Electrolysis Complex Breaking Pretreatment: The iron-carbon micro-electrolysis reactor is a cylindrical carbon steel reactor, fixedly filled with iron-carbon composite packing material. The mass ratio of iron to carbon in the packing material is 5:1, the particle size is 5mm, the porosity is 45%, and the ratio of the packing layer height to the reactor diameter is 3:1. A water distributor is installed at the bottom of the packing layer, and an outlet weir is installed at the top to ensure that the regulated wastewater enters from the bottom water distributor, fully contacts the packing material, and flows upward through the packing layer. An aeration disc is installed at the bottom of the reactor, and air is continuously introduced through a Roots blower for aeration treatment. The aeration intensity is stably controlled at 1.2m³ / (m³・h). The hydraulic retention time of the wastewater in the reactor is 100min. The treated wastewater overflows continuously from the top outlet of the reactor to the copper precipitation reaction tank.

[0022] Step 3. Copper precipitation reaction and solid-liquid separation: A 15% sodium hydroxide solution is continuously and slowly added to the wastewater in the reaction tank via an automatic alkali dosing device. The agitator continuously stirs the solution, adjusting the pH of the wastewater to 9.0. The hydraulic retention time of the wastewater in the reaction tank is 40 minutes, achieving continuous copper precipitation. The mixed liquid after the copper precipitation reaction continuously overflows into an inclined tube sedimentation tank. Through the solid-liquid separation effect of the sedimentation tank, continuous solid-liquid separation is achieved: the supernatant from the sedimentation tank continuously overflows from the top effluent trough to the subsequent activated carbon catalytic oxidation reactor. The mixed precipitate containing copper hydroxide and iron hydroxide is enriched in the cone hopper at the bottom of the sedimentation tank and collected every 4 hours by a sludge pump. The collected mixed precipitate is temporarily stored in a sludge tank for later use.

[0023] Step 4. Copper Resource Recovery: When the amount of mixed precipitated slag collected in the slag pot reaches 2m³, the acid dissolution-iron removal-electrolysis process is started for copper resource recovery. The specific operation is as follows: Acid dissolution treatment: 2 m³ of mixed precipitate residue is transferred to an acid dissolution tank via a slag pump. 20% (w / w) dilute sulfuric acid is slowly added to the tank, along with the acid washing waste liquid collected in step 2. The pH of the reaction system is adjusted to 2.2, and the temperature is controlled at 45℃. The reaction is continuously stirred for 50 min to completely dissolve the copper hydroxide and iron hydroxide in the mixed precipitate residue, generating a mixed sulfate solution containing Cu²⁺ and Fe³⁺. Iron removal and purification: 30% (w / w) hydrogen peroxide is slowly added dropwise to the acid-dissolved mixed sulfate solution at a rate of 50 mL / m³ to completely oxidize the small amount of residual Fe²⁺ in the solution to Fe³⁺. Subsequently, the pH of the solution is finely adjusted to 3.0 using a 10% (w / w) sodium hydroxide solution, and the reaction is stirred for 30 min to completely hydrolyze the Fe³⁺ in the solution. Ferric hydroxide precipitate is formed. After stirring is stopped, the solution is filtered using a plate and frame filter press to remove the ferric hydroxide residue, yielding a pure copper sulfate solution. Copper is recovered by electrolytic deposition: the pure copper sulfate solution is pumped into a horizontal diaphragm electrolytic cell. A ruthenium-plated titanium electrode is used as the anode, and a pure copper sheet as the cathode, with an electrode distance of 8 cm. During electrolysis, the following process parameters are controlled: electrolysis voltage 2.0 V, electrolysis current density 25 mA / cm², electrolysis temperature 35℃, and electrolysis time 150 min. After electrolysis, the cathode copper sheet is removed and washed sequentially with water, 5% hydrochloric acid, and water. It is then placed in a vacuum drying oven and dried at 60℃ for 2 hours to obtain industrial-grade metallic copper. The electrolytic solution is a low-concentration copper sulfate solution, which is returned to the regulating tank in step 1 via pipeline and mixed with the original wastewater from the gold mine for recycling.

[0024] Step 5. Activated Carbon Catalytic Oxidation for Cyanide Removal and Emission Compliance: The supernatant from the sedimentation tank in Step 3 is continuously pumped into the activated carbon catalytic oxidation reactor. The reactor is filled with granular activated carbon catalyst loaded with iron and copper bimetallic ions. This catalyst is prepared by impregnation: granular activated carbon with a particle size of 3 mm and a specific surface area of ​​1000 m² / g is impregnated in a mixed iron-copper salt solution (Fe(NO3)3 + Cu(NO3)2) for 24 h, then dried at 110℃, and subsequently activated at 450℃ for 2 h, yielding a catalyst with a total iron and copper ion loading of 4% of the activated carbon mass. A water distributor and aeration disc are installed at the bottom of the reactor, and an outlet weir is installed at the top. Air is continuously introduced into the aeration disc at the bottom of the reactor using a Roots blower, with the aeration intensity stably controlled at 1.0 m³ / (m³・h). The supernatant enters from the bottom water distributor and flows upward through the catalyst layer, with a hydraulic residence time of 105 min, achieving continuous catalytic oxidation. Example

[0025] The treatment of copper- and cyanide-containing wastewater continuously discharged from a gold mine was carried out. This wastewater was cyanide wastewater generated from the gold extraction process at the gold mine, with a total cyanide concentration of 180 mg / L, a copper ion concentration of 68 mg / L, a COD of 210 mg / L, and a pH value of 9.5. The specific treatment steps are as follows: Step 1. Pretreatment and adjustment: After collecting the cyanide-containing wastewater through pipelines and filtering it through a screen, the pH value is adjusted to 6.5 with 12% dilute sulfuric acid, and then discharged into the equalization tank. The adjusted wastewater is then pumped into the iron-carbon micro-electrolysis reactor by a lift pump.

[0026] Step 2. Iron-Carbon Micro-Electrolysis Complex Breaking Pretreatment: The iron-carbon micro-electrolysis reactor is filled with iron-carbon composite packing material. The mass ratio of iron to carbon in the packing material is 4:1, the particle size is 4mm, the porosity is 42%, and the ratio of the packing layer height to the reactor diameter is 3.5:1. The packing layer adopts a layered filling method, and each layer is equipped with a support plate to prevent the packing material from compacting and caking. Aeration devices are installed at the bottom and middle of the reactor. Air is introduced for aeration through a rotary blower, and the aeration intensity is controlled at 1.1m³ / (m³·h) to ensure that the wastewater and the packing material are in full contact and to inhibit the passivation of the packing material. The treated wastewater is discharged from the reactor outlet and sent to the copper precipitation reaction tank. Step 3. Copper precipitation reaction and solid-liquid separation: Slowly add 18% (w / w) calcium hydroxide solution to the reaction tank to adjust the pH of the wastewater to 8.8 and maintain the reaction time for 35 minutes to precipitate free Cu²⁺ into copper hydroxide, simultaneously removing residual Fe³⁺. After the reaction is complete, the mixed liquid enters a vertical flow sedimentation tank through a guide channel. The supernatant is discharged from the overflow port at the top of the sedimentation tank and sent to the activated carbon catalytic oxidation reactor. The mixed precipitate at the bottom is collected through a gravity sludge discharge pipe and temporarily stored in a sealed sludge box. After the cumulative collection reaches 1.5 m³, the copper resource recovery process is started.

[0027] Step 4. Copper Resource Recovery: Transfer the mixed precipitate from the slag box to the acid dissolution tank. Add 18% (w / w) dilute sulfuric acid to the acid dissolution tank, along with the pickling waste liquid collected in Step 2. Adjust the pH of the reaction system to 2.1, control the temperature in the tank at 42℃, and stir at 70 r / min for 45 min to completely dissolve the precipitate, obtaining a mixed sulfate solution containing Cu²⁺ and Fe³⁺. Iron Removal and Purification Stage: Slowly add 30% (w / w) hydrogen peroxide to the mixed solution at a rate of 30 mL / m³ to completely oxidize the residual Fe²⁺ to Fe³⁺. Then, finely adjust the pH to 2.9 with 10% sodium hydroxide solution, and stir at a constant temperature of 40℃ for 30 min to hydrolyze Fe³⁺ into ferric hydroxide precipitate. After standing for 25 min, filter using a vacuum filter to remove the ferric hydroxide filter residue, obtaining a pure copper sulfate solution. Electrolytic Deposition for Copper Recovery: Use a horizontal electrolytic cell with titanium-plated ruthenium electrodes as the anode. Pure copper sheets were used as cathodes with an electrode spacing of 7 cm. The electrolysis parameters were set as follows: voltage 1.9 V, current density 22 mA / cm², temperature 32 °C, and electrolysis time 130 min. During electrolysis, the electrode surface was cleaned every 30 min to ensure electrolysis efficiency. After electrolysis, the cathode copper sheet was removed and washed sequentially with water, 5% dilute hydrochloric acid, and water. It was then dried in a 70 °C forced-air drying oven for 1.5 h to obtain industrial-grade metallic copper products with a copper recovery rate of 98.2%. The electrolytic liquid was returned to the conditioning tank in step 1 for recycling.

[0028] Step 5. Activated carbon catalytic oxidation for cyanide removal and emission compliance: The supernatant obtained in Step 3 is pumped into an activated carbon catalytic oxidation reactor. The reactor is filled with granular activated carbon catalyst loaded with iron and copper bimetallic ions. The catalyst preparation parameters are: activated carbon particle size 3.5 mm, specific surface area 900 m² / g, impregnation in a mixed iron-copper salt solution (FeCl3 + CuCl2) for 20 h, drying at 105 °C, and activation at 480 °C for 2.5 h. The total loading of iron and copper metal ions is 3.5% of the activated carbon mass. Air is introduced into the reactor for aeration using a blower. The wastewater retention time is 100 min, allowing residual cyanide to be oxidized and decomposed into harmless substances under the action of the catalyst, while simultaneously adsorbing residual organic matter and trace heavy metals. Example

[0029] This embodiment targets copper- and cyanide-containing wastewater from the electroplating industry. The influent parameters are: total cyanide 120 mg / L, copper ions 85 mg / L, COD 650 mg / L, pH 8.5. The iron-carbon filler has an iron-carbon mass ratio of 6:1, and the activated carbon has a bimetallic loading of 5%. The specific steps are as follows: (1) Pretreatment adjustment: The pH after grid filtration does not need to be adjusted and directly meets the process requirements; (2) Iron-carbon micro-electrolysis complex breaking: the filler particle size is 6mm, the porosity is 48%, the ratio of the filler layer height to the reactor diameter is 4:1, the aeration intensity is 1.5m³ / (m³・h), and the reaction time is 120min; (3) Copper precipitation reaction and solid-liquid separation: Add 20% sodium hydroxide solution to adjust pH to 9.5, stir at 80 r / min, react for 45 min, and let settle in inclined tube sedimentation tank for 90 min; (4) Copper resource recovery: Add 25% dilute sulfuric acid to the precipitate residue to adjust the pH to 2.0, stir and react at 50℃ for 60 min; add 30% hydrogen peroxide (60 mL / m³), finely adjust the pH to 3.2, filter to remove iron; electrolyze at 2.2V, current density 30mA / cm², 40℃ for 180 min to obtain industrial-grade copper product, and reuse the electrolytic liquid; (5) Activated carbon catalytic oxidation to remove cyanide: The catalyst is iron-copper bimetallic supported activated carbon with a particle size of 2 mm and a specific surface area of ​​1200 m² / g, the aeration intensity is 1.2 m³ / (m³・h), and the hydraulic retention time is 120 min. Example

[0030] The iron-carbon packing has an iron-carbon mass ratio of 4:1. The wastewater from the gold mine to be treated has the same influent parameters as in Example 1, and the remaining process parameters are completely consistent with those in Example 1. For specific steps, please refer to Example 1. Example

[0031] The activated carbon bimetallic loading was 3%, and the gold mine wastewater to be treated was the same as the influent in Example 1. The remaining process parameters were completely consistent with those in Example 1. The specific steps are as described in Example 1.

[0032] Comparative Example 1 The iron-carbon micro-electrolysis process to break the complex was eliminated. Instead, the raw water from Example 1 was directly subjected to copper precipitation and activated carbon catalytic oxidation. The remaining process parameters were the same as in Example 1. That is, after the raw water was pretreated, alkaline solution was directly added to precipitate copper, and the supernatant was directly fed into the activated carbon catalytic oxidation reactor.

[0033] Comparative Example 2 Deep cyanide removal was performed using single activated carbon (without iron-copper bimetallic loading) to treat the supernatant after iron-carbon micro-electrolysis and copper deposition in Example 1. The remaining process parameters were the same as in Example 1.

[0034] Comparative Example 3 The raw water in Example 1 was treated using the traditional alkaline chlorination method. Sodium hypochlorite was added to oxidize cyanide, the pH was adjusted to 10.5, and the reaction was carried out for 120 minutes. There was no copper resource recovery process.

[0035] The treated effluent from the above embodiments and comparative examples was tested for water quality indicators. The purity and recovery rate of copper, as well as the overall cost of the reagents, were also statistically analyzed. The results are shown in Table 1. Table 1 Comparison of processing results for each case Results analysis: (1) As can be seen from Examples 1 to 5, the integrated process of the present invention has excellent treatment effect on copper and cyanide wastewater of different industries and different water quality. The total cyanide, copper ions and COD of the effluent are all stable and meet the standards. The copper recovery purity is ≥99.6% and the recovery rate is ≥97.8%. The comprehensive cost of the reagents is controlled within 21.5 yuan / ton of water. The process has strong adaptability and good resource utilization effect.

[0036] (2) As can be seen from Example 1 and Comparative Example 1, iron-carbon micro-electrolysis is the key process for realizing the conversion and efficient recovery of complexed copper. After canceling this process, the complexed copper cannot be effectively broken, the copper recovery purity and recovery rate drop significantly, and the unbroken cyanide will cause the activated carbon catalytic oxidation load to increase dramatically, resulting in serious exceedances of total cyanide and copper ions in the effluent.

[0037] (3) As can be seen from Example 1 and Comparative Example 2, the iron-copper bimetallic loading is the core to improve the efficiency of activated carbon catalytic oxidation to remove cyanide. Single activated carbon has no catalytic oxidation effect and cannot deeply degrade cyanide by physical adsorption alone. The total cyanide in the effluent exceeds the standard, and the activated carbon is easily saturated, which greatly increases the operating cost.

[0038] As described above, the present invention can be well implemented. The above embodiments are only the best implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are all included within the protection scope of the present invention.

Claims

1. A method for the co-treatment and copper resource recovery of copper-containing and cyanide-containing wastewater, characterized in that... The combined process of pretreatment conditioning, iron-carbon micro-electrolysis complex breaking pretreatment, copper precipitation reaction and solid-liquid separation, copper resource recovery, and activated carbon catalytic oxidation for cyanide removal and emission compliance includes the following process steps and conditions: (1) Pretreatment and adjustment: Take copper and cyanide-containing wastewater and filter it through a screen to remove suspended solids and impurities with a particle size ≥5mm; test the wastewater quality and control the total cyanide concentration in the influent to 50~500mg / L, copper ion concentration to 5~100mg / L, and COD ≤2000mg / L. If the wastewater pH>8, add 10~20% dilute sulfuric acid to adjust the pH to 4.0~8.0 and set aside. (2) Iron-carbon micro-electrolysis pretreatment: The wastewater adjusted in step (1) is pumped into the iron-carbon micro-electrolysis reactor. The reactor is filled with iron-carbon composite packing. The mass ratio of iron to carbon in the iron-carbon composite packing is controlled to be 4:1~6:1, the packing particle size is 3~8mm, the porosity is 40~50%, and the packing layer height to reactor diameter ratio is 3:1~4:

1. Air is introduced into the reactor for aeration treatment. The aeration intensity is adjusted to 1.0~1.5m³ / (m³·h), and the reaction time is 60~120min. Through the iron-carbon galvanic cell reaction, Fe at the anode loses electrons to generate Fe²⁺, and hydrogen evolution reaction occurs at the cathode to generate reduced [H]. Fe²⁺ and [H] work together to break the Cu-CN complex bond, converting the complexed copper into free Cu²⁺. At the same time, Fe²⁺ reacts with some free CN⁻ to generate Fe(CN)₆. 4 ⁻ The Fe(OH)2 / Fe(OH)3 flocs generated during the reaction adsorb some colloidal cyanide and organic matter, and simultaneously remove free cyanide to reduce the COD load of wastewater; (3) Copper precipitation reaction and solid-liquid separation: Slowly add alkaline solution to the wastewater after complex breaking obtained in step (2). The alkaline solution is a sodium hydroxide solution or calcium hydroxide solution with a mass fraction of 10~20%. During the addition process, continuously stir and adjust the pH value of the wastewater to 8.5~9.

5. Maintain the stirring rate of 50~80r / min and react for 30~45min. Free Cu²⁺ and OH⁻ fully react to generate copper hydroxide precipitate, and the residual Fe³⁺ reacts with OH⁻ to generate iron hydroxide precipitate. After the reaction is completed, send the mixed liquid into the sedimentation tank and let it stand for 60~90min to separate the solid and liquid to obtain a mixed precipitate containing copper hydroxide and iron hydroxide and a supernatant. The supernatant is sent to step (5) for treatment, and the mixed precipitate is collected for later use. (4) Copper resource recovery: The mixed precipitate residue from step (3) is transferred to an acid dissolution tank, and 15-25% dilute sulfuric acid is added to adjust the pH of the reaction system to 2.0-2.

5. The temperature is maintained at 40-50℃, and the reaction is stirred for 40-60 minutes to completely dissolve the mixed precipitate residue and obtain a mixed sulfate solution containing Cu²⁺ and Fe³⁺. 30% hydrogen peroxide is slowly added to the mixed sulfate solution to oxidize the residual Fe²⁺ to Fe³⁺, and then the pH is finely adjusted to 2 with 10% sodium hydroxide solution. 8~3.2, stir the reaction at a constant temperature of 40℃ for 30 min to completely hydrolyze Fe³⁺ to form ferric hydroxide precipitate. After standing for 20~30 min to precipitate, filter to remove the ferric hydroxide precipitate and obtain a pure copper sulfate solution. Electrolytic deposition method is used to electrolyze the pure copper sulfate solution, controlling the electrolysis voltage at 1.8~2.2V, the electrolysis current density at 20~30mA / cm², the electrolysis temperature at 30~40℃, and the electrolysis time at 120~180 min. Metallic copper is deposited at the cathode. After washing and drying, industrial-grade copper product is obtained. (5) Activated carbon catalytic oxidation for cyanide removal and discharge in compliance with standards: The supernatant from step (3) is fed into an activated carbon catalytic oxidation reactor, which is filled with granular activated carbon catalyst loaded with iron and copper bimetallic ions; the specific surface area of ​​the catalyst is 800~1200m² / g, the particle size is 2~5mm, the total loading of iron and copper metal ions is 3%~5% of the mass of activated carbon, and the catalyst is prepared by impregnation and then dried and activated; air is introduced into the reactor for aeration, the aeration intensity is controlled at 0.8~1.2m³ / (m³·h), the reaction temperature is maintained at 25~30℃, the pH value is the original pH of the supernatant, and the wastewater retention time is 90~120min; by utilizing the adsorption performance of activated carbon and the catalytic activity of bimetallic ions, combined with aeration and oxygen supply, the residual cyanide is oxidized and decomposed into harmless substances, and some residual organic matter and trace heavy metal ions are simultaneously adsorbed and degraded, so as to achieve the discharge of wastewater in compliance with standards.

2. The method according to claim 1, characterized in that: The iron-carbon composite filler in step (2) can be reused for 3 to 5 treatment cycles. After the filler fails, it is activated by acid washing with 5% to 8% dilute sulfuric acid for 30 to 40 minutes to remove the passivation film and impurities attached to the surface. After rinsing until neutral, it can be put into use again.

3. The method according to claim 1 or 2, characterized in that: The characteristic is The waste liquid containing trace amounts of iron ions generated during pickling in step (2) is collected and recycled in the acid dissolution tank of step (4).

4. The method according to claim 1, characterized in that... In step (4), the electrolytic deposition method uses a titanium-plated ruthenium electrode as the anode and a pure copper sheet as the cathode; during the electrolysis process, the deposits on the electrode surface are cleaned regularly to maintain stable electrolysis efficiency.

5. The method according to claim 1 or 4, characterized in that: In step (4), the electrolyte after electrolytic deposition is returned to the pretreatment adjustment unit of step (1) for recycling.

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