Integrated slow-release sulfidation device for separating copper and arsenic in strong acidic wastewater and method thereof

Abstract

The application provides an integrated slow-release sulfidation device and method for copper-arsenic separation in strong acidic wastewater, which comprises an integrated slow-release sulfidation platform, a high-concentration sodium sulfide storage pool and a CO2 gas tank. The integrated slow-release sulfidation platform is internally provided with a tubular hydrophobic microporous membrane. CO2 gas is introduced through an aeration head and reacts with the circulating Na2S solution before entering the tubular hydrophobic microporous membrane, thereby generating H2S in situ. The Na2S solution containing H2S then enters the membrane inside channel. H2S diffuses across the membrane driven by the concentration difference and reacts with Cu 2+ , As 3+ in the strong acidic wastewater to generate CuS and As2S3 precipitates. The application integrates CO2 acidification gas production, H2S transmembrane diffusion and heavy metal sulfidation reaction in the same platform. The passive diffusion is driven by the H2S concentration difference on both sides of the membrane, without the need for an external control loop. The sulfide ion replenishment rate is matched with the reaction consumption rate in real time, effectively avoiding the copper-arsenic coprecipitation problem. Meanwhile, there is no H2S escape and no introduction of sodium salt in the whole process.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an integrated slow-release sulfidation device and method for separating copper and arsenic in strongly acidic wastewater. Background Technology

[0002] Copper- and arsenic-containing wastewater generated by industries such as non-ferrous smelting, chemical synthesis, and electroplating often uses sulfuric acid as the acidic medium. Copper and arsenic ions coexist and their concentrations fluctuate greatly, with daily treatment volumes frequently reaching hundreds to thousands of tons. Copper is a valuable metal resource, while arsenic is a highly toxic carcinogen. Therefore, simultaneously achieving efficient copper recovery and deep removal of arsenic toxicity is a core requirement for treating this type of wastewater, ensuring both economic benefits and environmental compliance.

[0003] Sulfide precipitation is a mainstream industrial technology for treating strongly acidic copper and arsenic-containing wastewater. It utilizes the order-of-magnitude difference in the solubility products (Ksp) of copper and arsenic sulfides to achieve selective, staged precipitation. Under strongly acidic conditions, this method can directly remove impurities such as arsenic from wastewater in situ, reducing arsenic slag by 95% compared to neutralization. The residual arsenic concentration in the treated acid solution can be as low as tens of ppb. Based on the different electrode potentials of the copper and arsenic redox reactions, by controlling the different redox potentials (ORP) values ​​of the two-stage sulfide reactions, copper sulfide and arsenic sulfide can be precipitated in stages.

[0004] However, traditional sulfide precipitation methods face a series of prominent problems in practical engineering applications. First, the traditional sulfide agent dissociates too rapidly in strong acids, leading to a massive, instantaneous release of sulfur ions, causing copper-arsenic co-precipitation, reduced copper slag grade, and incomplete arsenic removal. Second, conventional constant-rate feeding devices lack online closed-loop control modules, making it impossible to adjust the dosing rate in real time according to dynamic changes in wastewater acidity and ion concentration. Third, traditional aeration methods struggle to control gas-liquid flow rates, easily generating numerous bubbles that result in excessively high local gas concentrations, uneven reactions, and the escape of large amounts of unreacted H2S gas, causing reagent loss, exhaust gas pollution, and safety hazards. Fourth, the equipment has weak resistance to strong acid corrosion, making it difficult to adapt to complex operating conditions.

[0005] To address the aforementioned issues, existing technologies incorporate hydrophobic microporous membranes into the sulfidation reaction system. Hydrophobic microporous membranes are a class of functional separation materials possessing interfacial selectivity and chemical stability, with polytetrafluoroethylene (PTFE) hydrophobic microporous membranes exhibiting the most outstanding comprehensive performance. These membrane materials possess excellent chemical stability, capable of long-term stable operation in strongly acidic (pH < 1), strongly alkaline (pH > 13), high-salt, and strongly oxidizing systems. Simultaneously, their surface water contact angle can reach over 120°, exhibiting extremely strong hydrophobicity. Under conditions below the liquid ingress pressure, the membrane pores can maintain a gaseous state, allowing only neutral gas molecules (such as H₂S) to selectively diffuse across the membrane based on concentration gradients, while H₂S... + Cu 2+Hydrated ions are completely blocked by the gas-liquid interface. This characteristic gives PTFE hydrophobic microporous membranes unique technical advantages in scenarios such as controllable mass transfer, selective isolation, and gas-phase transport.

[0006] However, existing membrane-based sulfidation schemes still remain at the single-function level of "using the membrane as a gas distributor," that is, externally purchased H2S gas is introduced into one side of the membrane, and the gas is dispersed by the membrane pores and then sent into the wastewater for reaction. This technical route has inherent limitations: (1) H2S gas still needs to be stored and transported externally, and the storage and transportation of highly toxic gases is always a major safety hazard; (2) The supply rate of H2S depends on the manual setting of the cylinder pressure reducing valve and flow meter, and cannot automatically respond to changes in wastewater conditions, which is still an open-loop control; (3) The acidification and conversion of the sulfiding agent, the generation and transmembrane diffusion of H2S gas, and the liquid-phase reaction of H2S with heavy metal ions are the three core links dispersed in different unit equipment, making the system lengthy, occupying a large area, and having many control nodes.

[0007] Based on this, the present invention proposes an integrated slow-release sulfidation device and method for the separation of copper and arsenic in strongly acidic wastewater. The aim is to use a hydrophobic microporous membrane as the core function to highly integrate three functions: CO2 acidification gas generation of Na2S, transmembrane diffusion driven by the concentration difference of H2S, and selective sulfidation precipitation of copper and arsenic in strongly acidic wastewater into the same device. This constructs a compact integrated reaction platform that integrates "intra-membrane gas generation - membrane mass transfer - extra-membrane reaction" to achieve self-stabilized replenishment of sulfide ions and stable slow release at low concentrations. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an integrated slow-release sulfidation device and method for separating copper and arsenic in strongly acidic wastewater, in order to address the shortcomings of the prior art mentioned above.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In the first aspect, an integrated slow-release sulfidation device for separating copper and arsenic in highly acidic wastewater includes an integrated slow-release sulfidation platform, a high-concentration sodium sulfide storage tank, a CO2 gas supply system, a wastewater conveying system, a precipitation separation system, and an alkaline absorption tower.

[0010] The integrated slow-release sulfidation platform is internally equipped with a tubular hydrophobic microporous membrane module, which divides the integrated slow-release sulfidation platform into an inner membrane flow channel and a multi-metal wastewater reaction zone. The inner membrane flow channel serves as a circulation channel for Na2S solution and also as a CO2 acidification and gas generation zone; the multi-metal wastewater reaction zone serves as a flow channel for strongly acidic wastewater and also as a reaction zone for H2S and heavy metal ions.

[0011] The high-concentration sodium sulfide storage tank is connected to the inner flow channel of the membrane via a circulation pipeline, forming a closed circulation loop. The high-concentration sodium sulfide storage tank is equipped with a fresh Na2S solution replenishment port and an aging solution discharge port. A pH monitor is installed inside the high-concentration sodium sulfide storage tank to monitor the pH value of the circulating liquid in real time to control the CO2 injection rate and the fresh Na2S replenishment rate. A circulation pump is installed on the circulation pipeline to drive the Na2S solution to circulate within the closed loop.

[0012] As a further explanation of the present invention, the inlet front end of the circulating pump is provided with a gas-liquid separator to separate residual CO2 bubbles entrained in the circulating liquid and prevent cavitation of the circulating pump.

[0013] As a further explanation of the present invention, the CO2 gas supply system includes a CO2 gas tank and a gas delivery pipeline. One end of the gas delivery pipeline is connected to the CO2 gas tank, and the other end is connected to a CO2 aerator installed in the inlet channel of the sodium sulfide solution. CO2 gas is introduced into the inlet channel of the sodium sulfide solution through the CO2 aerator, and reacts with the Na2S solution about to enter the tubular hydrophobic microporous membrane at the membrane front end, i.e., in situ, generating H2S gas. The H2S-containing Na2S solution then enters the inner channel of the membrane, and H2S molecules diffuse across the membrane to the multi-metal wastewater reaction zone due to the concentration gradient.

[0014] As a further explanation of the present invention, the outlet pipeline of the CO2 gas tank is equipped with a pressure reducing valve and a mass flow controller for precisely adjusting the inlet flow rate of CO2.

[0015] As a further explanation of the present invention, the wastewater conveying system includes a wastewater inlet pipeline and a wastewater outlet pipeline. The wastewater inlet pipeline is connected to a multi-metal wastewater inlet located at the bottom of the integrated slow-release sulfidation platform, and the wastewater outlet pipeline is connected to a multi-metal wastewater outlet located on the opposite side of the top of the integrated slow-release sulfidation platform. A wastewater conveying pump is provided on the wastewater inlet pipeline for continuously pumping strongly acidic copper-arsenic-containing wastewater into the multi-metal wastewater reaction zone from bottom to top. The flow direction of the wastewater in the multi-metal wastewater reaction zone (from bottom to top) is opposite to the flow direction of the Na2S solution in the inner channel of the membrane (from top to bottom), forming a countercurrent contact.

[0016] As a further explanation of the present invention, the sedimentation separation system includes a sludge separation tank. The inlet of the sludge separation tank is connected to the wastewater output pipeline, the bottom of the sludge separation tank is provided with a sludge discharge port and connected to a sludge storage tank, and the upper part of the sludge separation tank is provided with a supernatant outlet.

[0017] As a further explanation of the present invention, the integrated slow-release sulfurization platform is provided with a gas outlet at the top, which is connected to the alkaline absorption tower via a pipeline. The gas outlet is used to discharge unreacted CO2 and any trace amounts of H2S that may escape, eliminating the need for exhaust gas via the sludge separation tank.

[0018] As a further explanation of the present invention, the tubular hydrophobic microporous membrane module is a polytetrafluoroethylene (PTFE) hollow fiber membrane module with a pore size of 0.1–0.45 μm and a hydrophobic contact angle of not less than 120°. The pores of the tubular hydrophobic microporous membrane are always kept in a gas phase state, allowing only neutral H₂S molecules to diffuse from the inner channel of the membrane to the multi-metal wastewater reaction zone due to the concentration gradient, while H₂S… + Na + Cu 2+ Hydrated ions are completely blocked by the gas-liquid interface.

[0019] As a further explanation of the present invention, preferably, the tubular hydrophobic microporous membrane module is configured to operate in multiple parallel groups, with each membrane module connected to the inner flow channel of the membrane and the multi-metal wastewater reaction zone, forming a multi-point drug delivery layout.

[0020] As a further explanation of the present invention, the effective volume of the high-concentration sodium sulfide storage tank is 1.5 to 3 times the total volume of the circulation pipeline, and the pH monitor is set within the range of 10.5 to 13.0.

[0021] As a further explanation of the present invention, the alkaline absorption tower is filled with 2% to 5% NaOH solution.

[0022] Secondly, a method for an integrated slow-release sulfidation device for separating copper and arsenic in strongly acidic wastewater includes the following steps: The Na2S solution in the high-concentration sodium sulfide storage tank is driven by a circulation pump and enters the sodium sulfide solution inlet channel of the integrated slow-release sulfide platform through a circulation pipeline. Inside the inlet channel, CO2 gas is introduced into the Na2S solution in the form of microbubbles through a CO2 aerator. The CO2 dissolves in the solution to form carbonic acid, releasing H2O. + , with S 2- The reaction produces H2S. The Na2S solution containing H2S then enters the inner channel of the membrane, flowing downwards along the inner cavity of the tubular hydrophobic microporous membrane, and then returns to the high-concentration sodium sulfide storage tank via the sodium sulfide solution outlet, forming a closed loop. The above-mentioned CO2 acidification and gas generation process is completed before the Na2S solution enters the inner channel of the membrane; H2S enters the inner channel with the solution flow.

[0023] Strongly acidic copper- and arsenic-containing wastewater is continuously pumped into the multi-metal wastewater reaction zone through a multi-metal wastewater inlet located at the bottom of the platform, flowing upwards. Driven by the concentration gradient, H2S molecules in the inner channel of the membrane diffuse through the pores of the tubular hydrophobic microporous membrane into the multi-metal wastewater reaction zone. The Cu in the wastewater... 2+ And As 3+ Under strongly acidic conditions, it reacts rapidly with H2S to form CuS and As2S3 precipitates. The Na2S solution flows downwards while the wastewater flows upwards, creating a countercurrent contact that maintains a stable mass transfer driving force along the length of the membrane tube. The resulting suspension is discharged from the integrated slow-release sulfidation platform through a multi-metal wastewater outlet located on the opposite side of the platform's top.

[0024] The four stages described above—CO2 acidification and gas generation in the inlet channel, H2S-containing solution entering the membrane inner channel, H2S reverse transmembrane diffusion, and heavy metal sulfidation reaction—are completed synergistically within the integrated slow-release sulfidation platform. Unreacted CO2 and any trace amounts of H2S that may escape enter the alkaline absorption tower through the gas outlet at the top of the integrated slow-release sulfidation platform, where they are absorbed by NaOH solution and discharged harmlessly. The resulting suspension enters the sludge separation tank via the wastewater outlet pipeline. CuS and As2S3 precipitate in the sludge separation tank, and the precipitate is discharged into the sludge storage tank through the sludge discharge port. The supernatant is discharged from the supernatant outlet. The Na2CO3 generated in the membrane inner reaction is returned to the high-concentration sodium sulfide storage tank with the circulating liquid. The pH value in the tank is monitored by a pH monitor. When the pH value is lower than the set range, concentrated Na2S solution is added through the fresh Na2S solution replenishment port, while an equal amount of aging liquid is discharged through the aging liquid discharge port to maintain the effective concentration of Na2S in the circulating liquid.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: Functional integration and compact device structure: This invention uses a hydrophobic microporous membrane as its core function, highly integrating three functions—Na2S CO2 acidification and gas generation, H2S concentration-driven transmembrane diffusion, and selective sulfidation precipitation of copper and arsenic in strongly acidic wastewater—that are dispersed in different unit devices in traditional processes, into a single membrane contact reactor. The inner flow channel of the membrane simultaneously undertakes the functions of acidification and gas generation and Na2S recycling and regeneration, while the outer flow channel simultaneously undertakes the functions of H2S reception and heavy metal sulfidation reaction. The hydrophobic membrane interface simultaneously undertakes the functions of gas phase mass transfer and ion isolation. The three stages are completed synchronously in a single device, shortening the gas phase mass transfer path to the membrane thickness scale (hundreds of micrometers), fundamentally avoiding the loss of H2S due to long-distance transport in traditional series systems.

[0026] Controllable and slow release of sulfur ions, and excellent selective separation of copper and arsenic: This invention abandons the traditional method of direct addition of sulfurizing agents. Instead, it controls the generation rate of H2S by controlling the dissolution and mass transfer rate of CO2 on the inner side of the membrane. H2S then passively diffuses across the membrane into the wastewater side driven by the concentration difference. Throughout the process, the release rate of sulfur ions is controlled by a single variable: the CO2 gas supply flow rate. This achieves truly stable and slow release at low concentrations, effectively avoiding the copper and arsenic co-precipitation caused by the instantaneous release of large amounts of sulfur ions in traditional processes. This ensures the high grade of the copper sulfide slag and the deep removal of arsenic.

[0027] No sodium salt is introduced, reducing the burden of subsequent processing: In this invention, Na + The gas-liquid interface of the hydrophobic membrane completely blocks the flow in the inner channel of the membrane, preventing it from penetrating the membrane pores and entering the wastewater side. Heavy metal ions in the wastewater react with H2S to form sulfide precipitates. No sodium salts are introduced during the reaction, and the salinity of the wastewater does not increase after treatment, significantly reducing the difficulty and cost of subsequent advanced treatment.

[0028] Replacing strong acid with CO2, safe and mild: This invention uses CO2 as an acidifying agent, utilizing the weak acidity of CO2 dissolving in water to form carbonic acid, to gently transfer sulfuric acid to the inner side of the membrane. 2- The CO2 is converted into H2S. Compared to the traditional method of directly adding strong acids such as sulfuric acid and hydrochloric acid, the CO2 acidification reaction is gradual, has no risk of local overheating, and does not produce corrosive byproducts. Moreover, CO2 is a common industrial gas with mature and safe storage and transportation standards. H2S is produced and used immediately on the inside of the membrane, requiring no external storage or transportation, thus completely eliminating major safety hazards in the storage and transportation of highly toxic gases.

[0029] Rapid response and stable reliability: In this invention, the transmembrane diffusion of H2S is driven by the concentration difference across the membrane. The faster the H2S consumption rate on the wastewater side, the greater the partial pressure difference across the membrane, and the faster the H2S diffusion flux automatically increases; conversely, when the consumption rate on the wastewater side slows down, the diffusion flux automatically slows down. This passive diffusion mechanism based on concentration difference achieves real-time automatic matching between the sulfide ion supply rate and the heavy metal reaction consumption rate, without the need for an external feedback control loop, resulting in high system stability.

[0030] Countercurrent contact design enhances mass transfer efficiency: The Na2S solution flows from top to bottom while the wastewater flows from bottom to top, forming a countercurrent contact. This maintains a consistently high H2S concentration difference across the membrane along its length, effectively strengthening the driving force for transmembrane mass transfer. Simultaneously, the upward flow of wastewater washes against the outer membrane wall, inhibiting sediment adhesion. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 This is a schematic diagram of the integrated slow-release sulfurization platform in this invention.

[0032] Explanation of reference numerals in the attached figures: 1. High-concentration sodium sulfide storage tank; 2. pH monitor; 3. Integrated slow-release sulfide platform; 4. CO2 gas tank; 5. Sludge separation tank; 6. Sludge storage tank; 7. Alkaline absorption tower; 8. Sodium sulfide solution outlet; 9. Sodium sulfide solution inlet; 10. Polymetallic wastewater outlet; 11. Polymetallic wastewater inlet; 12. Polymetallic wastewater inlet; 13. Tubular hydrophobic microporous membrane; 14. Polymetallic wastewater reaction zone; 15. CO2 aerator; 16. Gas outlet. Detailed Implementation

[0033] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the described embodiments are only a part of the embodiments of this application, not all of them. The specific embodiments described herein are only used to explain the invention and are not intended to limit the invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] like Figure 1 As shown, the present invention provides a technical solution: a slow-release sulfidation and sulfide ion self-stabilizing replenishment device for the separation of copper and arsenic in strongly acidic wastewater, including an integrated slow-release sulfidation platform 3, a high-concentration sodium sulfide storage tank 1, a CO2 gas tank 4, a sludge separation tank 5, a sludge storage tank 6, and an alkaline absorption tower 7. The integrated slow-release sulfurization platform 3 is the core functional unit of this system. It contains a tubular hydrophobic microporous membrane 13, which divides the integrated slow-release sulfurization platform 3 into an inner membrane channel and a multi-metal wastewater reaction zone 14. The inner membrane channel serves as a circulation channel for Na2S solution and also as a CO2 acidification and gas generation zone. The multi-metal wastewater reaction zone 14 serves as a flow channel for strongly acidic wastewater and also as a reaction zone for H2S and heavy metal ions.

[0035] The high-concentration sodium sulfide storage tank 1 is connected to the sodium sulfide solution inlet 9 of the integrated slow-release sulfide platform 3 via a pipeline. A CO2 aerator 15 is installed within the flow channel of the sodium sulfide solution inlet 9, and the CO2 gas tank 4 is connected to the CO2 aerator 15 via a pipeline. CO2 gas is introduced into the sodium sulfide solution inlet flow channel in the form of microbubbles through the CO2 aerator 15, reacting with the Na2S solution before it enters the tubular hydrophobic microporous membrane 13, generating H2S in situ. The H2S-containing Na2S solution then enters the inner flow channel of the membrane, flowing from top to bottom along the inner cavity of the tubular hydrophobic microporous membrane 13, and returns to the high-concentration sodium sulfide storage tank 1 via the sodium sulfide solution outlet 8, forming a closed loop for the Na2S solution.

[0036] The polymetallic wastewater reaction zone 14 has a polymetallic wastewater inlet 12 at its bottom and a polymetallic wastewater outlet 10 on the opposite side of its top. Strongly acidic copper- and arsenic-containing wastewater is continuously pumped into the polymetallic wastewater reaction zone 14 through the polymetallic wastewater inlet 12 by a wastewater transfer pump. It flows upwards through the outer wall of the tubular hydrophobic microporous membrane 13, reacts with H2S gas diffused across the membrane, and is then discharged through the polymetallic wastewater outlet 10. The upward flow direction of the wastewater is opposite to the downward flow direction of the Na2S solution, forming a countercurrent contact.

[0037] The integrated slow-release sulfurization platform 3 is provided with a gas outlet 16 at the top, which is connected to the alkaline absorption tower 7 through a pipeline to discharge unreacted CO2 and trace amounts of H2S that may escape.

[0038] The polymetallic wastewater outlet 10 is connected to the inlet of the sludge separation tank 5 via a pipeline, the sludge discharge outlet of the sludge separation tank 5 is connected to the sludge storage tank 6, and the supernatant outlet of the sludge separation tank 5 is connected to the discharge pipeline.

[0039] The sludge separation tank 5 is equipped with a gas outlet at the top, which is connected to the alkaline absorption tower 7 via a pipeline.

[0040] In one possible embodiment of the present invention, the tubular hydrophobic microporous membrane 13 is a polytetrafluoroethylene (PTFE) hollow fiber membrane with a pore size of 0.1–0.45 μm and a hydrophobic contact angle of not less than 120°. The pores of the tubular hydrophobic microporous membrane 13 are always kept in a gaseous state, allowing only neutral H2S molecules to diffuse from the inner channel of the membrane to the multi-metal wastewater reaction zone 14 based on the concentration gradient, while H… + Na + Cu 2+ Hydrated ions are completely blocked by the gas-liquid interface.

[0041] As one possible implementation of the present invention, the outlet pipeline of the CO2 tank 4 is equipped with a pressure reducing valve and a mass flow controller for precisely adjusting the CO2 inlet flow rate.

[0042] As one possible implementation of the present invention, a circulation pump is provided on the connecting pipeline between the high-concentration sodium sulfide storage tank 1 and the integrated slow-release sulfide platform 3 to drive the Na2S solution to circulate in a closed loop.

[0043] As one possible embodiment of the present invention, the alkaline absorption tower 7 is filled with 2% to 5% NaOH solution for absorbing unreacted CO2 and trace amounts of H2S that may escape.

[0044] As one possible implementation of the present invention, the tubular hydrophobic microporous membrane 13 can be configured as multiple membrane modules operating in parallel, with each membrane module connected to the inner flow channel of the membrane and the multi-metal wastewater reaction zone 14, forming a multi-point drug delivery layout.

[0045] In one possible implementation of the present invention, the effective volume of the high-concentration sodium sulfide storage tank 1 is 1.5 to 3 times the total volume of the circulation pipeline, and the pH monitor 2 is set within the range of 10.5 to 13.0.

[0046] In practical use, the Na2S solution stored in the high-concentration sodium sulfide storage tank 1, with a concentration of 0.3–0.8 mol / L, flows into the inlet channel of the integrated slow-release sulfidation platform 3 through the sodium sulfide solution inlet 9, driven by a circulation pump. Inside the inlet channel, CO2 gas from the CO2 tank 4 is reduced to 0.05–0.1 MPa by a pressure reducing valve, and then adjusted to a set flow rate of 80–150 mL / min by a mass flow controller. This flow is then introduced into the Na2S solution as microbubbles through the CO2 aeration head 15.

[0047] CO2 dissolves in Na2S solution to form carbonic acid and release H2S. + , with S 2- The reaction generates H2S molecules. The Na2S solution containing H2S then enters the inner channel of the membrane, flowing downwards along the inner cavity of the tubular hydrophobic microporous membrane 13, and returning to the high-concentration sodium sulfide storage tank 1 via the sodium sulfide solution outlet 8, forming a closed loop. The Na2CO3 generated in the reaction inside the membrane flows back to the high-concentration sodium sulfide storage tank 1 with the circulating liquid. The pH value in the tank is monitored by a pH monitor 2. When the pH value falls below the set range of 10.5–11.0, fresh concentrated Na2S solution is added to the high-concentration sodium sulfide storage tank 1, while an equal amount of aging solution is discharged to maintain the effective concentration of Na2S in the circulating liquid.

[0048] H2S molecules in the inner channel of the membrane are driven by the concentration difference to diffuse through the membrane pores of the tubular hydrophobic microporous membrane 13 and diffuse from the inner channel of the membrane to the multi-metal wastewater reaction zone 14.

[0049] In this invention, the Na2S solution flows from top to bottom in the inner channel of the membrane, while the wastewater in the multi-metal wastewater reaction zone 14 flows from bottom to top, forming a countercurrent contact. Specifically, the Na2S solution enters the inlet channel from the sodium sulfide solution inlet 9, is aerated with CO2, and then enters the inner channel of the membrane. It flows from top to bottom along the inner cavity of the tubular hydrophobic microporous membrane 13 and exits from the sodium sulfide solution outlet 8. Meanwhile, the multi-metal wastewater enters the reaction zone 14 from the multi-metal wastewater inlet 12 located at the bottom of the platform, flows from bottom to top along the outer wall of the tubular hydrophobic microporous membrane 13, and exits from the multi-metal wastewater outlet 10 located on the opposite side of the top of the platform. The opposite flow directions of the two phases ensure that the concentration difference of H2S on both sides of the membrane from top to bottom along the length of the membrane tube maintains a high driving force, thereby enhancing the transmembrane mass transfer efficiency of H2S.

[0050] Meanwhile, the upward flow of wastewater continuously scours the outer wall of the tubular hydrophobic microporous membrane 13, effectively preventing the CuS and As2S3 particles generated by the reaction from adhering and depositing on the membrane surface, thus extending the operating cycle of the membrane module.

[0051] Strongly acidic copper and arsenic-containing wastewater continuously flows into the multi-metal wastewater reaction zone 14 through the multi-metal wastewater inlet 12, where it comes into contact with H2S gas permeating through the tubular hydrophobic microporous membrane 13. Because H2S is continuously supplied in a low-concentration, slow-release manner, the sulfur ion concentration in the wastewater remains at a low level, leading to preferential precipitation of CuS and effective suppression of As2S3 co-precipitation.

[0052] The resulting suspension is discharged from the integrated slow-release sulfidation platform 3 via the multi-metal wastewater outlet 10 located on the opposite side of the platform top. Unreacted CO2 and any trace amounts of H2S that may escape enter the alkaline absorption tower 7 via the gas outlet 16 at the top of the integrated slow-release sulfidation platform 3, where they are absorbed by NaOH solution and discharged harmlessly. The resulting suspension then enters the sludge separation tank 5 for solid-liquid separation. The precipitate is discharged into the sludge storage tank 6, while the supernatant is discharged after meeting standards or undergoes further treatment.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] In this embodiment, the Na2S solution stored in the high-concentration sodium sulfide storage tank 1 has a concentration of 0.5 mol / L. The outlet pressure of the CO2 gas tank 4 is adjusted to 0.08 MPa via a pressure reducing valve, and the flow rate of the mass flow controller is set to 100 mL / min. The CO2 aeration head 15 is a titanium microporous aeration head with a pore size of 15 μm, and is installed in the flow channel of the sodium sulfide solution inlet 9.

[0055] The integrated slow-release sulfurization platform 3 uses an inner tubular hydrophobic microporous membrane 13 with an effective area of ​​0.1 m². 2The PTFE hollow fiber membrane module has a pore size of 0.22 μm. A high-concentration sodium sulfide storage tank 1 has an effective volume of 3 L. Initially, 2 L of 0.5 mol / L Na₂S solution is added, and the pH in the tank is controlled at 10.5–11.0 using a pH monitor 2. A circulation pump drives the Na₂S solution to circulate in a closed loop at a flow rate of 50 mL / min, with the solution flowing downwards through the inner channel of the membrane.

[0056] The effective volume of the polymetallic wastewater reaction zone 14 is 5 L. Initially, Cu-containing wastewater is added. 2+ 0.01 mol / L (approximately 635 mg / L), As 3+ Simulated wastewater at a concentration of 0.01 mol / L (approximately 750 mg / L) (pH adjusted to 1.0 ± 0.2 with sulfuric acid) was continuously pumped into the multi-metal wastewater reaction zone 14 from the multi-metal wastewater inlet 12 at the bottom of the platform at a flow rate of 100 mL / min, flowing upwards and forming a countercurrent contact with the Na₂S solution. The alkaline absorption tower 7 contained 2 L of 2% NaOH solution.

[0057] The top gas outlet 16 of the integrated slow-release sulfurization platform 3 is connected to the alkaline absorption tower 7 for collecting unreacted gases.

[0058] During operation, CO2 is introduced into the Na2S solution through the aeration head 15 in the inlet channel, where an acidification reaction generates H2S. The H2S-containing solution then enters the inner channel of the membrane. H2S diffuses across the membrane to the multi-metal wastewater reaction zone 14 due to the concentration gradient, where it reacts with Cu in the wastewater. 2+ And As 3+ The reaction produces sulfide precipitates. The resulting suspension is continuously discharged into the sludge separation tank 5 via the multi-metal wastewater outlet 10 on the opposite side of the platform top for solid-liquid separation.

[0059] After 5 hours of continuous operation, Cu in the effluent from the multi-metal wastewater reaction zone 14 2+ The concentration decreased from the initial 635 mg / L to 21 mg / L, and the copper recovery rate reached 95.1%; As 3+ The concentration decreased from an initial 750 mg / L to 673 mg / L, with an arsenic removal rate of 10.3%; the calculated copper-arsenic separation coefficient was approximately 164.7. No H2S emissions were detected at the outlet of alkaline absorption tower 7 throughout the entire process.

[0060] It should be further noted that the accompanying drawings and embodiments of the present invention mainly describe the concept of the present invention. Based on this concept, some specific forms and arrangements of connection relationships, positional relationships, power mechanisms, power supply systems, hydraulic systems and control systems may not be fully described. However, under the premise that those skilled in the art understand the concept of the present invention, they can implement the above-mentioned specific forms and arrangements in a well-known manner.

[0061] When a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0062] The directional terms "inner" and "outer" refer to the inner and outer sides relative to the outline of each component itself. The terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," or "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0063] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, and the spatial relative descriptions used herein will be interpreted accordingly.

[0064] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, and "several" means one or more, unless otherwise explicitly specified.

[0065] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated slow-release sulfidation device for the separation of copper and arsenic in strongly acidic wastewater, characterized in that, It includes an integrated slow-release sulfidation platform (3), a high-concentration sodium sulfide storage tank (1), a CO2 gas tank (4), a sludge separation tank (5), a sludge storage tank (6), and an alkaline absorption tower (7). The integrated slow-release sulfidation platform (3) is equipped with a tubular hydrophobic microporous membrane (13). The tubular hydrophobic microporous membrane (13) divides the integrated slow-release sulfidation platform (3) into an inner membrane flow channel and a multi-metal wastewater reaction zone (14). The inner membrane flow channel is a circulation channel for Na2S solution and also serves as a CO2 acidification gas generation zone. The multi-metal wastewater reaction zone (14) is a flow channel for strongly acidic wastewater and also serves as a reaction zone for H2S and heavy metal ions. The high-concentration sodium sulfide storage tank (1) is connected to the sodium sulfide solution inlet (9) of the integrated slow-release sulfide platform (3) through a pipeline, and the sodium sulfide solution outlet (8) of the integrated slow-release sulfide platform (3) returns to the high-concentration sodium sulfide storage tank (1) through a pipeline, forming a closed loop of Na2S solution. The sodium sulfide solution inlet (9) is provided with a CO2 aerator (15) in the flow channel. The CO2 gas tank (4) is connected to the CO2 aerator (15) through a pipeline. CO2 gas is introduced into the sodium sulfide solution inlet flow channel through the CO2 aerator (15) and reacts with the Na2S solution before entering the tubular hydrophobic microporous membrane (13) to generate H2S in situ. The bottom of the polymetallic wastewater reaction zone (14) is provided with a polymetallic wastewater inlet (12) and the top opposite side is provided with a polymetallic wastewater outlet (10). Strongly acidic copper and arsenic-containing wastewater flows into the polymetallic wastewater reaction zone (14) from bottom to top through the polymetallic wastewater inlet (12) and is discharged through the polymetallic wastewater outlet (10). The integrated slow-release sulfurization platform (3) is provided with a gas outlet (16) at the top, and the gas outlet (16) is connected to the alkaline absorption tower (7) through a pipeline. The polymetallic wastewater outlet (10) is connected to the inlet of the sludge separation tank (5) via a pipeline, and the sludge discharge outlet of the sludge separation tank (5) is connected to the sludge storage tank (6).

2. The integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The tubular hydrophobic microporous membrane (13) is made of polytetrafluoroethylene hollow fiber membrane with a pore size of 0.1 to 0.45 μm and a hydrophobic contact angle of not less than 120°.

3. The integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The tubular hydrophobic microporous membrane (13) always maintains a gas phase state inside the membrane pores, allowing neutral H2S molecules to diffuse from the inner channel of the membrane to the multi-metal wastewater reaction zone (14) by means of the concentration difference, while hydrated ions are completely blocked by the gas-liquid interface.

4. The integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The high-concentration sodium sulfide storage tank (1) is equipped with a pH monitor (2), the outlet pipeline of the CO2 gas tank (4) is equipped with a pressure reducing valve and a mass flow controller, and the connecting pipeline between the high-concentration sodium sulfide storage tank (1) and the integrated slow-release sulfide platform (3) is equipped with a circulation pump.

5. An integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The alkaline absorption tower (7) contains 2% to 5% NaOH solution.

6. An integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The tubular hydrophobic microporous membrane (13) is configured to operate in parallel with multiple membrane modules. Each membrane module is connected to the inner flow channel of the membrane and the multi-metal wastewater reaction zone (14) to form a multi-point drug delivery layout.

7. An integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The effective volume of the high-concentration sodium sulfide storage tank (1) is 1.5 to 3 times the total volume of the circulation pipeline.

8. An integrated slow-release sulfidation device for copper and arsenic separation in strongly acidic wastewater according to claim 1, characterized in that, The Na2S solution flows from top to bottom in the inner channel of the membrane, while the wastewater in the multi-metal wastewater reaction zone (14) flows from bottom to top. The two phases form a countercurrent contact, which is used to enhance the H2S transmembrane mass transfer efficiency.

9. A method for an integrated slow-release sulfidation device for separating copper and arsenic in strongly acidic wastewater according to any one of claims 1-8, characterized in that, Includes the following steps: The Na2S solution stored in the high-concentration sodium sulfide storage tank (1) is driven by a circulating pump and flows into the inlet channel of the integrated slow-release sulfide platform (3) through the sodium sulfide solution inlet (9). In the inlet channel, the CO2 gas in the CO2 gas tank (4) is reduced to 0.05-0.1 MPa by a pressure reducing valve, and then adjusted to the set flow rate by a mass flow controller. It is then introduced into the Na2S solution in the form of microbubbles through the CO2 aeration head (15). The CO2 dissolves in the Na2S solution to generate carbonic acid and release H2O. + , with S 2- The reaction generates H2S molecules, and the Na2S solution containing H2S then enters the inner channel of the membrane, flows from top to bottom along the inner cavity of the tubular hydrophobic microporous membrane (13), and returns to the high-concentration sodium sulfide storage tank (1) through the sodium sulfide solution outlet (8), forming a closed loop; The Na2CO3 generated by the reaction inside the membrane is returned to the high-concentration sodium sulfide storage tank (1) with the circulating liquid. The pH value in the tank is monitored by the pH monitor (2). When the pH value is lower than the set range, fresh concentrated Na2S solution is added to the high-concentration sodium sulfide storage tank (1), and an equal amount of aging liquid is discharged at the same time to maintain the effective concentration of Na2S in the circulating liquid. The H2S molecules in the inner channel of the membrane are driven by the concentration difference, pass through the membrane pores of the tubular hydrophobic microporous membrane (13), and diffuse from the inner channel of the membrane to the multi-metal wastewater reaction zone (14). The suspension after reaction is discharged from the integrated slow-release sulfidation platform (3) through the multi-metal wastewater outlet (10) located on the opposite side of the top of the platform. Unreacted CO2 and trace amounts of H2S escaped from the gas outlet (10) at the top of the integrated slow-release sulfidation platform (3) enter the alkaline absorption tower (7), are absorbed by the NaOH solution and discharged harmlessly. The suspension after the reaction enters the sludge separation tank (5) for solid-liquid separation. The precipitate is discharged into the sludge storage tank (6), and the supernatant is discharged in compliance with standards or further treated.

10. The method of an integrated slow-release sulfidation device for separating copper and arsenic in strongly acidic wastewater according to claim 9, characterized in that, The Na2S solution flows from top to bottom in the inner channel of the membrane, while the wastewater in the multi-metal wastewater reaction zone (14) flows from bottom to top, forming a countercurrent contact. That is, the Na2S solution enters the inlet channel from the sodium sulfide solution inlet (9), is aerated with CO2, and then enters the inner channel of the membrane. It flows from top to bottom along the inner cavity of the tubular hydrophobic microporous membrane (13) and flows out from the sodium sulfide solution outlet (8). The polymetallic wastewater enters the polymetallic wastewater reaction zone (14) from the polymetallic wastewater inlet (12) set at the bottom of the platform, flows from bottom to top along the outer wall of the tubular hydrophobic microporous membrane (13), and flows out from the polymetallic wastewater outlet (10) set on the opposite side of the top of the platform. The opposite flow directions of the two phases ensure that the concentration difference of H2S on both sides of the membrane along the membrane tube from top to bottom always maintains a high driving force, thereby enhancing the transmembrane mass transfer efficiency of H2S.

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