A method for preparing copper sulphide concentrate from copper mine acidic wastewater

Abstract

The application discloses a method for preparing copper sulfide concentrate from copper mine acidic wastewater, and belongs to the technical field of wastewater resource utilization. The copper mine acidic wastewater is used as raw material, sodium hydrosulfide is used as a sulfidation agent, a stable sulfidation reaction system is constructed through precise control of pH and ORP, and the generation of by-products is inhibited. After the wastewater is subjected to sulfidation reaction, closed gravity sedimentation, water washing and impurity removal and low-temperature drying, the copper sulfide concentrate is prepared. The application solves the problems of large fluctuation of traditional process parameters, low copper recovery rate and poor concentrate quality, and has stable process, can be mass-produced, has environmental protection and economic value, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater resource utilization and heavy metal enrichment and recovery technology, specifically to a method for preparing copper sulfide concentrate from acidic copper mine wastewater. Background Technology

[0002] During copper mining, a large amount of acidic wastewater with low concentrations of copper ions is continuously generated. This type of wastewater is characterized by high acidity, low copper ion content, and large fluctuations in water volume. It also contains trace amounts of impurities such as iron and zinc. If it is discharged directly, it will cause serious heavy metal pollution of water bodies and damage the ecological environment. If conventional treatment processes are used to meet discharge standards, it will result in a large loss of low-grade copper resources and extremely low resource utilization, which does not meet the development requirements of green, low-carbon, and resource recycling in industry.

[0003] Currently, commonly used heavy metal recovery technologies include membrane osmosis, ion exchange, solvent extraction, adsorption, and sulfidation. Among membrane osmosis methods, reverse osmosis membranes are easily fouled or damaged, resulting in a short lifespan; they also require frequent replacement, leading to high power consumption and operating costs. Ion exchange is a mature process with stable water quality, good impurity removal, low corrosivity, and a relatively good operating environment. However, after the ion exchange resin enriches metal ions in the wastewater, these ions still need to be further recovered using other methods. Solvent extraction offers advantages such as high selectivity, high recovery rate, simple process, continuous operation, and automation. However, the extractant is easily lost during extraction and needs frequent replenishment. Multi-stage extraction and back-extraction involve the addition of substances such as kerosene, extractant, and sulfuric acid, resulting in high downstream water treatment costs. Adsorption can effectively remove copper ions and other heavy metal ions from acidic copper mine wastewater, but its selectivity is poor, and recovery is relatively complicated. For example, CN119951466A discloses a composite material for treating acidic copper mine wastewater that can adsorb copper ions, but it does not explain how to subsequently recover and reuse the adsorbed copper ions. The sulfidation method only requires the addition of a sulfiding agent, resulting in low downstream water treatment costs. However, current conventional sulfidation precipitation methods simply add a sulfiding agent without precisely controlling the pH and redox potential (ORP) of the reaction system. This leads to significant fluctuations in the acid-base and redox environments during the reaction, easily generating byproducts such as copper hydroxide and other metal sulfides. Therefore, it is often necessary to remove other metals before precipitating copper sulfide. For example, CN103145267A discloses a process that first recovers iron hydroxide and then recovers copper sulfide, which is quite complex. Direct copper recovery not only results in high impurity content in the generated copper sulfide precipitate and low concentrate grade, but also incomplete copper ion precipitation, low copper resource recovery rate, poor process stability and repeatability, making it impossible to stably produce copper sulfide concentrate industrially.

[0004] Addressing the technical bottlenecks of existing technologies, such as low copper resource recovery rate, poor product purity, weak process controllability, and numerous by-products, this invention precisely controls the pH and ORP values ​​of the reaction system to effectively suppress side reactions, achieve efficient recovery of copper ions from acidic copper mine wastewater, stably prepare copper sulfide concentrate, and simultaneously address both the harmless treatment of wastewater and the high-value utilization of copper resources. Summary of the Invention

[0005] This invention addresses the shortcomings of existing copper mine acidic wastewater treatment processes by providing a method for preparing copper sulfide concentrate from copper mine acidic wastewater. This method solves the problems of low copper recovery rate, poor purity of copper sulfide concentrate, large fluctuations in process parameters, complex by-products, and weak industrial applicability of traditional processes, thereby achieving the harmless treatment of low-value industrial copper mine acidic wastewater and the efficient and high-value recovery of copper resources.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing copper sulfide concentrate from acidic copper mine wastewater includes the following steps: (1) Raw material pretreatment: Obtain acidic copper mine wastewater with a copper ion concentration of 20-120 mg / L and an initial pH of 2.0-3.0. Remove suspended large particulate impurities from the water and let it stand for later use. (2) Directional sulfidation reaction: The pretreated acidic wastewater is sent into the copper reaction tank, and sodium hydrosulfide aqueous solution is added to the reaction tank as a sulfiding agent. The pH and ORP redox potential of the reaction system are adjusted. The reaction is carried out under constant temperature and stirring conditions for 25 to 35 minutes, so that the copper ions in the wastewater react to form copper sulfide suspended precipitate. The ORP value is adjusted from -240mV to -190mV by replacing dissolved oxygen with a small amount of nitrogen gas. (3) Gravity thickening and settling: The solid-liquid mixture after the reaction is transported to a thickening tank and allowed to settle and settle at room temperature to achieve stable solid-liquid stratification of the slurry. (4) Concentrate collection and preparation: The clear liquid on the upper layer of the thickening pool is separated and removed, and the sediment at the bottom of the pool is collected. After washing, dehydration and drying, copper sulfide concentrate is obtained.

[0007] Preferably, in step (2), the sodium hydrosulfide is industrial grade sodium hydrosulfide with a purity ≥98%, and the mass fraction of the sodium hydrosulfide aqueous solution is 10%.

[0008] Preferably, in step (2), the molar equivalent of sodium hydrosulfide added is 1.0 to 1.05 times the molar content of copper ions in the wastewater.

[0009] Preferably, in step (2), the stirring speed is 300 r / min and the reaction constant temperature is 25℃±2℃.

[0010] Preferably, in step (4), the collected bottom slag is washed with water to remove impurities, and then dehydrated and dried to further improve the purity of copper sulfide concentrate.

[0011] Preferably, in step (2), the pH of the reaction system is adjusted by adding dilute hydrochloric acid or dilute sodium hydroxide solution dropwise, with real-time feedback from an online pH monitor, to maintain the pH of the reaction system at 3.8-6.2.

[0012] Preferably, in step (2), the nitrogen aeration replacement flow rate is 0.1 to 0.3 m³ / h.

[0013] Preferably, in step (2), sodium hydrosulfide is added in a gradient manner, in two equal amounts, with an interval of 10 to 15 minutes between each addition.

[0014] Preferably, in step (3), the thickening tank sedimentation process is kept in a closed and static state throughout.

[0015] Preferably, in step (4), the drying temperature is controlled at 60-80℃.

[0016] This invention constructs a reaction system for copper ions and hydrosulfide ions by precisely controlling the weakly acidic environment and the moderately strong reducing potential environment of the reaction system, thus avoiding side reactions. Sodium hydrosulfide dissociates in water to generate HS-H2O. - It reacts with Cu²⁺ in wastewater to undergo a sulfidation reaction, the chemical equation being: Cu²⁺ + HS⁻ = CuS↓ + H⁺. Copper sulfide has a low solubility product and can rapidly and completely crystallize out of the water, forming a copper sulfide precipitate.

[0017] Compared with the prior art, the present invention has the following significant advantages: (1) Dual-parameter fixed-point precise control, high product purity: This invention differs from traditional methods by using pH and ORP precise control to construct a stable sulfidation reaction environment, which can inhibit the generation of by-products such as copper hydroxide and other metal sulfides, greatly improving the purity of copper sulfide concentrate and ensuring stable product quality. (2) High copper resource recovery rate: For acidic wastewater with low concentration of copper ions, it can achieve efficient precipitation and removal of copper ions, with a copper ion removal rate of ≥98%, improving the recovery and utilization rate of low-grade copper resources and turning waste into treasure; the gradient dosing process avoids waste of reagents, and the utilization rate of reagents is greatly improved compared with the traditional single dosing. (3) The process is highly stable and repeatable: it is suitable for the slight fluctuations in the water quality of industrial wastewater, and is simple to operate and highly controllable, meeting the needs of continuous and large-scale stable industrial production. (4) Environmental protection and economic benefits: It realizes the harmless treatment of acidic wastewater from copper mines, eliminates the risk of heavy metal pollution, and produces high-value-added copper sulfide concentrate, reduces the cost of wastewater treatment and maintenance and the cost of reagent consumption, and improves the overall benefits of industrial production. Detailed Implementation

[0018] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] Unless otherwise specified, all experimental groups used the same baseline process conditions: 50L wastewater treatment capacity per group, 300r / min stirring speed, 4h settling time in the thickening tank, 25℃±2℃ constant temperature for reaction, and 10% sodium hydrosulfide solution by mass.

[0020] The parameter control methods are as follows: pH value is adjusted by micro-addition of 0.5mol / L dilute hydrochloric acid and dilute sodium hydroxide solution, and monitored in real time by an online pH monitor; ORP value is finely adjusted by micro-adjustment of 0.2m³ / h low-flow nitrogen aeration, and the value is monitored in real time.

[0021] Example 1: Industrial acidic wastewater with a copper ion concentration of 95 mg / L and an initial pH of 2.6 was selected, filtered to remove suspended impurities, and then fed into a copper reaction tank. Sodium hydrosulfide solution was added at 1.0 times the copper ion molar equivalent. The system pH was adjusted to 4.2 and ORP to -190 mV, and the reaction was carried out at a constant temperature with stirring for 30 min. After the reaction was completed, the mixed slurry was sent to a closed thickening tank for settling for 4 h. The supernatant was separated, and the bottom slag was collected. After washing, dehydration, and drying, copper sulfide concentrate was obtained.

[0022] Example 2: Industrial acidic wastewater with a copper ion concentration of 95 mg / L and an initial pH of 2.6 was selected, filtered to remove suspended impurities, and then fed into a copper reaction tank. Sodium hydrosulfide solution was added at 1.05 times the copper ion molar equivalent. The system pH was adjusted to 5.2 and ORP to -230 mV, and the reaction was carried out at a constant temperature with stirring for 35 min. After the reaction was completed, the mixed slurry was sent to a closed thickening tank for settling for 3.5 h. The supernatant was separated, and the bottom slag was collected. After washing, dehydration, and drying, copper sulfide concentrate was obtained.

[0023] Example 3: Industrial acidic wastewater with a copper ion concentration of 95 mg / L and an initial pH of 2.6 was selected, filtered to remove suspended impurities, and then fed into a copper reaction tank. Sodium hydrosulfide solution was added at 1.0 times the copper ion molar equivalent. The system pH was adjusted to 6.2 and ORP to -200 mV, and the reaction was carried out at a constant temperature with stirring for 38 min. After the reaction was completed, the mixed slurry was sent to a closed thickening tank for settling for 3 h. The supernatant was separated, and the bottom slag was collected. After washing, dehydration, and drying, copper sulfide concentrate was obtained.

[0024] Example 4: Industrial acidic wastewater with a copper ion concentration of 95 mg / L and an initial pH of 2.6 was selected, filtered to remove suspended impurities, and then fed into a copper reaction tank. Sodium hydrosulfide solution was added at 1.02 times the copper ion molar equivalent. The system pH was adjusted to 3.8 and ORP to -240 mV, and the reaction was carried out at a constant temperature with stirring for 25 min. After the reaction was completed, the mixed slurry was sent to a closed thickening tank for settling for 4 h. The supernatant was separated, and the bottom slag was collected. After washing, dehydration, and drying, copper sulfide concentrate was obtained.

[0025] Example 5: Industrial acidic wastewater with a copper ion concentration of 95 mg / L and an initial pH of 2.6 was selected, filtered to remove suspended impurities, and then fed into a copper reaction tank. Sodium hydrosulfide solution was added at 1.03 times the copper ion molar equivalent. The system pH was adjusted to 5.8 and ORP to -220 mV, and the reaction was carried out at a constant temperature with stirring for 32 min. After the reaction was completed, the mixed slurry was sent to a closed thickening tank for settling for 4 h. The supernatant was separated, and the bottom slag was collected. After washing, dehydration, and drying, copper sulfide concentrate was obtained.

[0026] Comparative Example 1: The results were essentially the same as in Example 5, except that the pH was adjusted to 5.8 and no precise ORP fine-tuning was performed. The measured ORP was -130mV.

[0027] Comparative Example 2: It is basically the same as Example 5, except that: the ORP is adjusted to -220mV and the pH is not adjusted, and the pH of the system is naturally stable.

[0028] Comparative Example 3: It is basically the same as Example 5, except that the pH is adjusted to 7.8 and the ORP is adjusted to -160mV.

[0029] Comparative Example 4: It is basically the same as Example 5, except that the pH is adjusted to 3.2 and the ORP is adjusted to -170mV.

[0030] Method for determining copper ion removal rate: The concentration of copper ions in the water sample before and after treatment was detected using a flame atomic absorption spectrophotometer. Samples were taken and filtered to a fixed volume. The initial concentration of copper ions in the raw water and the residual concentration of copper ions in the treated effluent were determined according to GB / T 7475-1987 "Determination of Copper, Zinc, Lead and Cadmium in Water - Atomic Absorption Spectrophotometry". The formula for calculating the copper ion removal rate is: Removal rate = (Initial copper ion concentration - Effluent copper ion concentration) / Initial copper ion concentration × 100%.

[0031] Method for determining the grade of copper sulfide concentrate: Referring to GB / T 3884.1-2025 "Chemical Analysis Methods for Copper Concentrates Part 1: Determination of Copper Content by Iodometric and Electrolytic Methods", the dried copper sulfide concentrate sample is ground and pulverized, uniformly sampled, and after acid dissolution, digestion, and volume adjustment pretreatment, the pure copper content in the sample is determined by titration with sodium thiosulfate standard solution. The final conversion yields the mass percentage of copper sulfide, which is the grade of copper sulfide concentrate.

[0032] The test results for each embodiment and comparative example are shown in the table below.

[0033]

[0034] As shown in the table above, the present invention employs a precise, point-based control process using both pH and ORP parameters. All five examples achieved excellent results, with a copper ion removal rate ≥98% and a copper sulfide concentrate grade ≥60%, demonstrating excellent process stability and repeatability. In contrast, the comparative examples, due to deviations of single or dual parameter point values ​​from the protected system of the present invention, exhibited a significant decrease in copper recovery rate and a substantial reduction in concentrate grade.

[0035] Among these factors, ORP failure alone leads to insufficient reducing atmosphere in the system, incomplete sulfidation reaction, and the generation of byproducts; pH failure alone leads to strong acid inhibiting the reaction and increased side reactions in an alkaline environment; and simultaneous failure of both parameters leads to complete imbalance of the reaction system and complete product failure. This fully demonstrates that the fixed-point pH and ORP parameters and the corresponding fine-tuning process specified in this invention are not conventionally preferred, but are the core key to achieving efficient preparation of copper sulfide concentrate from acidic copper mine wastewater.

[0036] Those skilled in the art should understand that the above embodiments are merely exemplary embodiments, and various changes, substitutions, and modifications can be made without departing from the spirit and scope of this application.

Claims

1. A method for preparing copper sulfide concentrate from acidic copper mine wastewater, characterized in that, Includes the following steps: (1) Raw material pretreatment: Obtain acidic copper mine wastewater with a copper ion concentration of 20-120 mg / L and an initial pH of 2.0-3.

0. Remove suspended large particulate impurities from the water and let it stand for later use. (2) Directional sulfidation reaction: The pretreated acidic wastewater is sent into the copper reaction tank, and sodium hydrosulfide aqueous solution is added to the reaction tank as a sulfiding agent. The pH and redox potential (ORP) of the reaction system are adjusted. The reaction is carried out under constant temperature and stirring conditions for 25 to 35 minutes, so that the copper ions in the wastewater react to form copper sulfide suspended precipitate. Among them, the ORP value is adjusted from -240mV to -190mV by replacing dissolved oxygen with a small amount of nitrogen gas. (3) Gravity thickening and settling: The solid-liquid mixture after the reaction is transported to a thickening tank and allowed to settle and settle at room temperature to achieve stable solid-liquid stratification of the slurry. (4) Concentrate collection and preparation: the clear liquid on the upper layer of the thickening pool is separated and removed, the sediment at the bottom of the pool is collected, and after dehydration and drying, copper sulfide concentrate product is obtained.

2. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (2), the sodium hydrosulfide is industrial grade sodium hydrosulfide with a purity of ≥98%, and the mass fraction of the sodium hydrosulfide aqueous solution is 10%.

3. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 2, characterized in that, In step (2), the molar equivalent of sodium hydrosulfide added is 1.0 to 1.05 times the molar content of copper ions in the wastewater.

4. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (2), the stirring speed is 300 r / min and the reaction constant temperature is 25℃±2℃.

5. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (4), the collected bottom slag is washed with water to remove impurities, and then dehydrated and dried to further improve the purity of copper sulfide concentrate.

6. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (2), the pH of the reaction system is adjusted by adding dilute hydrochloric acid or dilute sodium hydroxide solution dropwise, with real-time feedback from an online pH monitor, to maintain the pH of the reaction system at 3.8-6.

2.

7. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (2), the nitrogen aeration replacement flow rate is 0.1 to 0.3 m³ / h.

8. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (2), sodium hydrosulfide is added in a gradient manner, in two equal amounts, with an interval of 10 to 15 minutes between each addition.

9. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (3), the thickening tank sedimentation process is kept in a closed and static state throughout.

10. The method for preparing copper sulfide concentrate from acidic copper mine wastewater according to claim 1, characterized in that, In step (4), the drying temperature is controlled at 60-80℃.

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