Method and system for resourceful treatment of acidic wastewater

Abstract

This invention discloses a method and system for the resource-based treatment of acidic wastewater, comprising: performing multi-stage gradient acid-resistant pre-filtration on acidic wastewater; adding an acid-specific thiol chelating agent to the pre-filtered wastewater without adjusting the wastewater pH to neutral, controlling the pH value of the reaction system within the strongly acidic range of 1.5 to 3.5 to carry out the chelation and complex-breaking reaction; performing primary solid-liquid separation on the resulting mixture to obtain an acidic purified supernatant; directly pumping the acidic purified supernatant into a PTFE acid-resistant membrane system for pressurized separation, utilizing the stability of the PTFE acid-resistant membrane in an environment of pH ≤ 1.0 to obtain a regenerated acid solution on the concentration side and low-acid wastewater on the permeate side; performing precise low-salt neutralization and deep purification treatment only on the low-acid wastewater on the permeate side to achieve water reuse; wherein, by controlling the addition of alkali agent only to the membrane permeate side. This invention solves the industry pain point of the difficulty in degrading complexed heavy metals, and the effluent consistently meets standards.

Description

Technical Field

[0001] This invention relates to the fields of industrial treatment and environmental protection technology, and to a method and system for the resource-based treatment of acidic wastewater. Background Technology

[0002] With the rapid development of industries such as electroplating, pickling, hydrometallurgy, and fine chemicals, acidic wastewater discharged during these processes has attracted considerable attention due to its complex composition, high acidity (pH often below 2.0), high concentration of heavy metals, and the presence of large amounts of complexing agents (such as EDTA, citric acid, and tartaric acid). Direct discharge of this type of wastewater without effective treatment not only severely corrodes pipe networks but also leads to the accumulation of heavy metals in soil and water bodies, harming the ecological environment and human health.

[0003] Currently, the mainstream treatment process for this type of acidic wastewater mostly adopts the "physicochemical method," with a typical process as follows: acidic wastewater → neutralization and precipitation (usually adding lime or sodium hydroxide to adjust the pH to 8-10) → flocculation and precipitation → sand filtration → discharge or reuse. However, in practical engineering applications, this traditional process has the following insurmountable technical defects: 1. The technical bias and drawbacks of "alkalinity adjustment for heavy metal removal": Existing technologies generally believe that effective precipitation of heavy metal ions must be carried out under alkaline conditions. However, when the wastewater contains organic complexing agents, under alkaline conditions, heavy metal ions easily form stable soluble complexes with these complexing agents (such as EDTA-Cu, citric acid-Ni), resulting in the inability to form hydroxide precipitates and a significant decrease in the heavy metal removal rate. Even with increased dosage of precipitants such as sodium sulfide, deep removal is difficult to achieve, and toxic gases such as hydrogen sulfide are easily generated. In addition, full-scale alkali adjustment requires a large amount of alkali agent, significantly increasing operating costs. 2. Large amount of neutralized salt, limiting water reuse: Traditional processes neutralize high-acid wastewater in its entirety, resulting in the introduction of large amounts of sodium ions (NaOH) or calcium ions (Ca(OH)2) and corresponding acid radicals (such as SO42-) into the wastewater. - Cl -This leads to a sharp increase in total dissolved solids (TDS) in the treated effluent (often reaching several thousand mg / L), making the water saline and hard, unable to meet the reuse standards for production process makeup water, especially high-quality circulating cooling water systems. It often has to be downgraded for use or directly discharged, resulting in a waste of water resources. 3. Limited application of membrane separation technology: Although nanofiltration (NF) or reverse osmosis (RO) membrane technologies can achieve the separation and concentration of acidic water, conventional polymer composite membrane materials (such as polyamides) have extremely poor acid resistance. In strongly acidic environments with pH < 2, they are prone to hydrolysis, swelling, and even breakage, resulting in a very short membrane life (usually less than 3 months). Therefore, there are very few cases in existing technologies where membrane systems are directly applied to the treatment of unadjusted, raw strong acid wastewater. Membrane systems are usually placed after the neutralization and sedimentation process, at which point the acid has been consumed, but the water has been contaminated with salt. 3. Large sludge production and difficult hazardous waste disposal: Due to the use of full-volume neutralization and flocculation sedimentation, traditional processes generate a large amount of metal hydroxide sludge. These sludge sludge sludge sag not only have high water content and large volume, but also contain inert substances such as calcium and sodium salts, resulting in low heavy metal content and extremely low comprehensive utilization value. They are typically classified as hazardous waste (HW17), requiring expensive solidification and landfill or outsourced disposal, increasing the environmental burden on enterprises. 4. Lengthy process flow and waste of acid resources: Traditional processes treat all acidic wastewater as pollutants and neutralize them indiscriminately, failing to recognize the high concentrations of acid in the wastewater as a recyclable resource. In fact, many process stages (such as pickling and leaching) have a certain tolerance for acid concentration; direct recovery and reuse of waste acid would generate significant economic benefits. However, current technologies lack effective in-situ recovery methods for strong acids, leading to the loss of acid resources during wastewater treatment.

[0004] In summary, existing acidic wastewater treatment technologies are limited by the mindset that "alkalinity adjustment is necessary," the insufficient corrosion resistance of conventional materials, and limitations in process design, making it difficult to simultaneously achieve deep removal of heavy metals, efficient recovery of acid resources, and low salinity of reclaimed water. Therefore, developing a treatment process and system that can operate stably in a strong acid environment, does not require full neutralization, and can achieve synergistic resource recovery of acid and wastewater is a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for the resource-based treatment of acidic wastewater, so as to at least partially solve the above-mentioned problems of the prior art.

[0006] To achieve the above objectives, the present invention provides a method for the resource-based treatment of acidic wastewater, characterized by comprising the following steps: Acidic wastewater is pre-filtered using a multi-stage gradient acid-resistant method to remove suspended impurities; Without adjusting the pH of the wastewater to neutral, an acidic thiol chelating agent is added to the pre-filtered wastewater to control the pH of the reaction system within the strongly acidic range of 1.5 to 3.5 for chelation and complex-breaking reaction, so that free and complexed heavy metals can form insoluble chelates. The mixture after the reaction was subjected to primary solid-liquid separation to obtain an acidic purified supernatant; The acidic purification supernatant is directly pumped into the PTFE acid-resistant membrane system for pressurized separation. The stability of the PTFE acid-resistant membrane in an environment with pH ≤ 1.0 is utilized to retain trace amounts of heavy metal colloids and macromolecular impurities, thereby obtaining regenerated acid solution on the concentration side and low-acid wastewater on the permeation side. The low-acid wastewater on the permeable side is precisely neutralized and deeply purified to achieve water reuse. By controlling the addition of alkali agent only to the membrane permeation side, the large amount of inorganic salts generated by the combination of acid radical ions and alkali metal ions in the traditional full-volume neutralization process is blocked, thereby reducing the salt content of the recycled water by more than 30%.

[0007] Furthermore, the acid-specific thiol chelating agent is a modified thiol heavy metal scavenger (DTCR), which has a positive zeta potential in a strongly acidic environment of pH 1.5 to 3.5. It actively adsorbs negatively charged heavy metal complex ions through electrostatic attraction and uses thiol functional groups to replace coordinating groups to form five-membered ring chelates. The dosage of the chelating agent is 0.08% to 0.3% of the wastewater mass.

[0008] Furthermore, the PTFE acid-resistant membrane system uses a polytetrafluoroethylene nanofiltration membrane with a filtration accuracy of 0.001 μm and an operating pressure of 1.8–3.0 MPa; the concentration of the regenerated acid solution is 1.5–2.5 times higher than that of the original water, and due to the membrane retention effect, the heavy metal content in the regenerated acid solution is less than 5% of the heavy metal content in the original water.

[0009] Furthermore, the multi-stage gradient acid-resistant pre-filtration includes sequential 1mm coarse filtration, 100μm fine filtration, and 20μm precision filtration; and the 20μm precision filtration is set before the chelation and complex-breaking reaction to remove sharp particles before heavy metals form micro-flocs, protecting the subsequent PTFE acid-resistant membrane system from being scratched.

[0010] Furthermore, in the precise low-salt neutralization step, pH-ORP linkage feedback is used to control the amount of alkali added, so as to precisely adjust the pH of the low-acid wastewater on the permeate side to 6.5-8.5, and control the excess coefficient of alkali addition to not exceed 1.05, so as to ensure that the total amount of salt generated in the reaction system is only 1 / 3 of that in the traditional full-volume neutralization process.

[0011] Another object of the present invention is to provide an acidic wastewater resource recovery system for implementing the method, characterized in that it includes a pipeline connected along the water flow direction: Acid-resistant homogenizing equalization tank (2); A multi-stage acid-resistant pre-filtration unit (3) is internally integrated with a 1mm coarse filter component, a 100μm fine filter component and a 20μm precision filter component in sequence along the water flow direction; An acidic heavy metal chelation reaction tank (4) has its inlet connected to the outlet of the multi-stage acid-resistant pre-filtration unit (3), and does not have an external alkaline agent dosing pipeline, but only an acidic special mercaptan chelating agent dosing device. A PTFE acid-resistant membrane acid-water separation system (6) has its inlet directly connected to the outlet of the acidic heavy metal chelation reaction tank (4), and the concentrated liquid outlet of the PTFE acid-resistant membrane acid-water separation system (6) is connected to a regenerated acid storage tank (7). A precision neutralization reaction unit (8) has its inlet connected only to the permeate outlet of the PTFE acid-resistant membrane acid-water separation system (6), and is equipped with a micro-alkali dosing subsystem; A deep purification unit (10) is connected to the outlet of the precision neutralization reaction unit (8); And a sludge treatment line, which is connected to the discharge end of the acidic heavy metal chelation reaction tank (4), the precision neutralization reaction unit (8) and the deep purification unit (10), respectively.

[0012] Furthermore, the membrane element of the PTFE acid-resistant membrane acid-water separation system (6) is a polytetrafluoroethylene hollow fiber membrane or a spiral wound membrane, and the shell and the pipeline material in contact with the liquid are both PVDF or PTFE, ensuring that swelling or hydrolysis does not occur in a highly corrosive environment with pH≤1.0 and pressure≥1.8MPa.

[0013] Furthermore, the acidic heavy metal chelation reaction tank (4) is equipped with a high shear force stirrer with a rotation speed set to 60-120 r / min, which is used to rapidly disperse the added thiol chelating agent in a strong acid environment, overcoming the reaction kinetic barrier caused by the low ion activity in a strong acid environment.

[0014] 9. The acidic wastewater resource treatment system according to claim 6, characterized in that a physical isolation wall is provided between the precise neutralization reaction unit (8) and the regenerated acid storage tank (7), and the return pipelines of the two are not connected to each other, forming two independent closed-loop cycles of 'acid recovery' and 'water purification', so as to avoid secondary pollution of the regenerated acid liquid by the salts generated by neutralization.

[0015] Furthermore, the deep purification unit (10) adopts a structure of activated carbon adsorption tower and 5μm security filter connected in series, and the activated carbon adsorption tower is filled with acid-activated granular activated carbon to adsorb trace amounts of organic complexing agents and heavy metal ions remaining in the water through the membrane, ensuring that the turbidity of the effluent is ≤1NTU.

[0016] Compared with the prior art, the present invention has at least the following advantages: First, this invention overcomes the technical bias of heavy metal complex breaking under strong acid conditions, achieving deep removal of heavy metals. Existing technologies generally consider heavy metal precipitation to require alkaline conditions to break the complexation equilibrium. This invention introduces a specific acidic thiol chelating agent (DTCR), utilizing its thiol functional group's high stability and reactivity in a strong acid environment of pH 1.5–3.5, successfully overcoming the obstacles of low dissociation constants and slow reaction kinetics of heavy metal complexes at low pH. Experiments show that this invention can actively replace and break the coordination bonds formed between strong chelating agents such as EDTA and citric acid and heavy metals without adjusting the pH of the raw water, forming stable five-membered ring chelates. Compared to the traditional sodium sulfide method, this invention increases the removal rate of complexed heavy metals (such as Cu-EDTA and Ni-citric acid) from less than 60% to over 99%, while avoiding the risk of hydrogen sulfide gas escape.

[0017] Secondly, this invention pioneers a "pre-acid recovery" process, achieving a dual improvement in both acid resources and in-situ water quality. Unlike traditional processes that place the membrane system after the neutralization step, this invention places the PTFE acid-resistant membrane system directly after the primary solid-liquid separation, achieving for the first time in-situ concentration of strong acid without the introduction of exogenous alkali. Utilizing the excellent chemical inertness of PTFE material, the membrane system maintains high flux and high rejection rate even under extreme environments with pH ≤ 1.0 and pressure ≥ 1.8 MPa. After this process, the regenerated acid concentration is increased by 1.5 to 2.5 times compared to the raw water, and can be directly reused in upstream processes such as acid washing and acid leaching, with a comprehensive waste acid recovery rate ≥ 85%. This not only recovers expensive acid but, more importantly, avoids subsequent deep treatment units from contacting high-concentration acid, extending the service life of downstream activated carbon and precision filters.

[0018] Third, precise low-salt neutralization control completely solves the problem of "salt return" in recycled water. Traditional full-volume neutralization processes introduce a large amount of alkali metal ions, resulting in persistently high TDS in the effluent. This invention creatively proposes the concept of "separate treatment": only the low-acid wastewater on the membrane permeate side is subjected to trace neutralization. Since the membrane system has already retained most of the acid radicals, the acidity of the permeate water is significantly reduced, and the required alkali dosage is only 20% to 30% of that of the traditional process. Test data shows that the TDS of recycled water treated with this process can be controlled below 300 mg / L, which is more than 30% lower than that of the traditional process, and the hardness is significantly reduced, fully meeting the stringent requirements of makeup water and circulating cooling water systems in high-end production processes, realizing high-value-added reuse of water resources.

[0019] Fourth, a closed-loop system has been established, significantly reducing hazardous waste disposal costs. This invention reduces sludge generation at the source through process optimization. On one hand, the sludge generated by strong acid chelation precipitation mainly consists of high-purity heavy metal chelates, rather than the traditional mixture of metal hydroxides and calcium salts. The high heavy metal content of the sludge is beneficial for subsequent resource utilization. On the other hand, high-pressure plate and frame filtration (1.2–2.0 MPa) compresses the sludge moisture content to below 60%, reducing the volume of sludge by more than 40% compared to traditional methods. The entire process generates no external wastewater discharge, truly achieving closed-loop management and harmless disposal of "waste acid—clean water—sludge," significantly reducing hazardous waste disposal costs and environmental regulatory risks for enterprises.

[0020] Fifth, the system exhibits strong resistance to shock loads and significantly improved operational stability. This invention incorporates a 6-12 hour hydraulic retention time and a three-stage gradient acid-resistant pre-filtration (1mm→100μm→20μm) at the front end, effectively buffering fluctuations in influent water quality and quantity, and removing sharp particles that could scratch the membrane surface. Combined with the excellent antifouling properties of the PTFE membrane, the entire system can withstand drastic fluctuations in influent pH within the range of 0.5-4.0 without being affected. The membrane cleaning cycle is extended to more than 3 months, significantly reducing manual maintenance costs and the frequency of chemical cleaning, ensuring continuous and stable operation in industrial production. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for the resource utilization treatment of acidic wastewater according to the present invention; Figure 2 This is a schematic diagram of an embodiment of an acidic wastewater resource utilization treatment system according to the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate to understand the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a product or device comprising a series of units is not necessarily limited to those explicitly listed, but may include other units not explicitly listed or inherent to such products or devices. To enable those skilled in the art to better understand the invention, the technical solutions of the embodiments of the invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort should fall within the scope of protection of this invention.

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate to understand the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a product or device comprising a series of units is not necessarily limited to those explicitly listed, but may include other units not explicitly listed or inherent to such product or device.

[0025] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0026] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0027] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this invention can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments. The specific meanings of the terms used in this invention are as follows.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] Example 1: Treatment of Acidic Bleaching Wastewater Containing Nickel and Copper in an Electroplating Industrial Park 1. Wastewater Quality Overview The wastewater originates from the rinsing section after pickling in the electroplating production line. The main pollutants are as follows: pH: 1.8–2.2, Cu²⁺. + 45 mg / L, Ni² + :80 mg / L, COD: 350 mg / L.

[0031] 2. Processing System and Technology Flow Step 1: Homogenization, Conditioning and Pretreatment The acidic wastewater (1) first flows by gravity into the acid-resistant homogenizing equalization tank (2) through the inlet pipeline. The tank is made of concrete with fiberglass lining. The bottom of the tank is sloping and equipped with a microporous aeration device. The aeration intensity is controlled at 4 m³ / (m²·h) and the hydraulic retention time (HRT) is set to 8h. After homogenization, the wastewater is pumped by a lift pump located at the outlet of the equalization tank (2) and enters the multi-stage acid-resistant pre-filtration unit (3) through pipeline connection.

[0032] Inside this unit (3), the fluid flows sequentially through three filtration chambers: the first chamber contains a 1mm wedge wire screen to remove large particles; the second chamber contains a 100μm PP melt-blown filter element to intercept suspended particles; and the third chamber contains a 20μm PTFE pleated filter element to retain tiny colloids. The effluent after the three-stage filtration is collected through a water collection pipe at the top of the unit (3) and flows by gravity into the acidic heavy metal chelation reaction tank (4) through the pipeline.

[0033] Step 2: Acidic in-situ chelation to break down complexes The acidic heavy metal chelation reaction tank (4) is a sealed PE tank with an inlet on the upper side wall, which is connected to the outlet pipe flange of the aforementioned pre-filtration unit (3). An acidic thiol chelating agent dosing device (including a reagent storage tank and a metering pump) is fixedly installed at the top of the reaction tank (4), and the dosing pipe of this device extends below the liquid surface in the tank. A mechanical stirrer is installed at the center of the bottom of the tank, with a rotation speed set to 90 r / min.

[0034] After the wastewater enters the reaction tank (4), the dosing device adds DTCR (dosage of 0.15%) to the tank to maintain the pH at 1.8-2.0 using the acidity of the raw water, without adding any additional acid or alkali. The outlet of the reaction tank (4) is located at the lower part of its side wall and is connected to the inlet of the primary solid-liquid separation device (5) through a pipeline.

[0035] Step 3: Primary separation and acid-water separation The mixed liquid after the reaction flows by gravity into the primary solid-liquid separation device (5) (in this embodiment, it is an inclined tube sedimentation tank). The bottom of the device (5) is a conical sludge hopper, and the middle of the side wall is provided with a supernatant overflow weir. Supernatant flow direction: The overflowing acidic purification supernatant flows into the inlet of the PTFE acid-resistant membrane acid water separation system (6) by gravity through the overflow pipe. Sludge flow direction: The precipitated heavy metal sludge is collected in the sludge hopper and transported to the sludge collection system (11) through the sludge screw pump via the sludge discharge pipeline. The PTFE acid-resistant membrane acid water separation system (6) adopts an integrated skid-mounted structure, and its core membrane component is a polytetrafluoroethylene acid-resistant nanofiltration membrane. The concentrated liquid outlet of the system (6) is connected to the regenerated waste acid storage and reuse unit (7) (i.e., the regenerated acid storage tank) through a high-pressure pipeline. The storage tank is connected back to the front-end acid washing production line through a return pump and a dedicated pipeline. The permeate outlet of the system (6) is connected to the inlet of the low-acid wastewater precision neutralization reaction unit (8) through a pipeline.

[0036] Step 4: Precise low-salt neutralization and deep purification Low-acid wastewater from the membrane permeation side enters the low-acid wastewater precision neutralization reaction unit (8). This unit (8) is an open reaction tank with an alkali dosing subsystem (metering pump and dosing pipe) fixed on the upper side wall. The outlet of the unit (8) is connected to the central cylinder of the high-efficiency flocculation sedimentation tank (9) through a pipeline.

[0037] In the high-efficiency flocculation sedimentation tank (9), the supernatant after flocculation sedimentation is collected through a water collection tank and flows by gravity into the deep purification treatment unit (10) through the effluent pipeline. The unit (10) adopts a series structure: the front end is an activated carbon adsorption tank and the rear end is a 5μm precision acid-resistant filter. The two are connected in series through a flange, and the outlet of the activated carbon tank is connected to the inlet of the precision filter. The qualified clean water (12) after deep purification flows out from the outlet of the precision filter and is transported to the plant's reclaimed water network through a reclaimed water pump.

[0038] Step 5: Sludge Reduction and Disposal The sludge collection system (11) is connected via pipelines to the sludge discharge port of the primary solid-liquid separation device (5), the sludge discharge port of the high-efficiency flocculation sedimentation tank (9), and the backwash drain port of the deep purification treatment unit (10). The collected mixed sludge flows by gravity into the sludge thickening tank (13). The thickened sludge is pumped by the sludge feed pump and pressurized and sent into the high-pressure plate and frame filter press (14) (feed pressure 1.5MPa). The filtrate after filtration is returned to the acid-resistant homogenizing and equalizing tank (2) for reprocessing, while the dewatered sludge cake (moisture content ≤60%) falls into the screw conveyor below and is transported to the sludge stabilization and harmless treatment unit (15) for off-site disposal.

[0039] This embodiment constructs a physically isolated dual-loop system: Acid recovery loop: equalization tank (2) → pre-filtration (3) → reaction tank (4) → separation device (5) → membrane system (6) → regenerated acid storage tank (7) → production line. This loop is in a strong acid environment throughout, and all pipelines and tanks are lined with anti-corrosion layers and do not come into contact with alkaline agents. Water purification loop: permeate side of membrane system (6) → neutralization unit (8) → sedimentation tank (9) → deep purification (10) → recycled water point. This loop only performs neutralization after the membrane, avoiding large-scale contact between acid and alkali. The two loops only meet at the membrane system (6), but remain independent in terms of physical flow direction and chemical properties. This structural design is the physical basis for achieving "low salt control".

[0040] Example 2: Treatment of high solids pickling wastewater from a metallurgical enterprise (focusing on anti-fouling structure and flow field design) 1. Wastewater quality and operating conditions characteristics The wastewater originates from a stainless steel pickling production line and is characterized by strong acidity and extremely high suspended solids: pH: 0.8–1.5, Fe²⁺ + / Fe³ + The concentrations of particulate matter (PAM) were 12000 mg / L, HCl was 8%, and suspended solids (SS, mainly iron filings and metal oxide particles) were 800 mg / L. This operating condition presented extreme challenges to the pretreatment interception capacity and the membrane system's anti-fouling ability.

[0041] 2. Processing System and Technology Flow Step 1: Enhanced Homogenization and Pretreatment Acidic wastewater (1) is filtered through a screen channel to intercept large debris before entering an acid-resistant homogenizing equalization tank (2). Given the high volatility of hydrochloric acid in the wastewater, the equalization tank (2) is sealed with a fully enclosed arched cover and equipped with a negative pressure aeration device to direct acid mist to a scrubbing tower for treatment. A side-cutting agitator is installed inside the tank, extending the hydraulic retention time to 12 hours to cope with drastic fluctuations in the volume of metallurgical wastewater.

[0042] After homogenization, the wastewater is pumped by a vertical wear-resistant centrifugal pump and enters the multi-stage acid-resistant pre-filtration unit (3) through pipelines. To address the high SS characteristics, the unit was structurally reinforced: First stage (1mm coarse filtration): A self-cleaning wedge wire mesh filter is used, with the inlet located at the lower part of the filter's side wall and the outlet at the top. When the inlet and outlet differential pressure sensors detect ΔP>0.05MPa, the PLC controller automatically opens the drain valve, using reverse water flow and a brushing mechanism for self-cleaning without requiring shutdown. Second stage (100μm fine filtration): Adjacent to the first stage outlet, a multi-stage series basket filter is used, with the shell material upgraded to Hastelloy C276 to withstand high chloride ion corrosion. Third stage (20μm precision filtration): Located at the rear of the fine filtration unit, a 5-core 40-inch PTFE pleated filter element is used, installed with a quick-opening clamp connection for easy replacement under high clogging frequency. The effluent after three-stage filtration is introduced vertically downward into the acidic heavy metal chelation reaction tank (4) through a flange pipeline. This layout utilizes gravity to accelerate the fluid into the reaction zone and reduces pumping energy consumption.

[0043] Step 2: Chelation and complex disruption and physical isolation under high acid conditions The acidic heavy metal chelation reaction tank (4) has a double-layer mechanical stirring structure, with an outer anti-corrosion shell and an inner acid-resistant brick lining. Considering the extremely low pH (0.8-1.5) and the dramatic increase in the consumption of conventional DTCR reagents, this embodiment selects a modified thiol chelating agent with high mercapto density. Dosing structure: The outlet pipe of the acidic special thiol chelating agent dosing device is inserted 1.5m below the liquid surface of the reaction tank (4) and directly opposite the shearing area of ​​the stirring blades to ensure instantaneous dispersion of the high-viscosity reagent. Reaction control: The effective volume of the reaction tank (4) is designed to be 20m³, and the HRT is 35min. Since the pH is lower than the lower limit of claim 1 (1.5), in order to maintain the reaction efficiency, the reagent dosage is increased to 0.35% of the wastewater mass. The outlet of the reaction tank (4) is located at the bottom of the side wall and is connected to the central water distributor of the primary solid-liquid separation device (5) through a pipeline.

[0044] Step 3: Primary Separation and Membrane System Design under High Solid Content The reacted mixture enters the primary solid-liquid separation device (5) (using a high-density sludge horizontal flow sedimentation tank). Separation structure: the influent is evenly diffused through a central water distributor, and the length-to-width ratio of the tank is set at 4:1 to reduce turbulence. The sludge hopper is designed as a multi-hopper sludge discharge structure, with each hopper bottom connected to the sludge collection system (11) via an independent pipeline to avoid single-point blockage. Membrane system core structure: the supernatant after primary separation overflows into the PTFE acid-resistant membrane acid water separation system (6). Targeting high Fe³ + Due to the characteristic of easy formation of colloidal fouling, this embodiment has made key structural modifications to the membrane system (6): Flow channel design: a disc tube (DT) PTFE membrane module is adopted, and a guide plate is provided between the membrane sheets to form an 8mm wide open flow channel, which is much larger than the conventional spiral wound membrane (1mm), effectively preventing the bridging and blockage of iron colloids in the flow channel. Flow direction design: the inlet is located in the tangential direction of the membrane shell (lower side), the concentrate outlet is located directly above the membrane shell, and the permeate outlet is located at the bottom of the membrane shell axis. This "tangential feed, top concentrate return, bottom permeate" structure, combined with the high-speed turbulence (flow velocity >3m / s) formed on the membrane surface by the high-pressure circulating pump, generates extremely strong shear force, continuously scouring the membrane surface and preventing the formation of a gel layer. Material upgrade: the membrane shell and pipeline materials are all made of PVDF+PTFE composite material, which is resistant to strong oxidation (Fe³). + Catalytic oxidation) and strong acidity. Material diversion: The regenerated acid liquid (HCl concentration increased to 18%) on the concentration side enters the regenerated waste acid storage and reuse unit (7) through the pipeline; the low acid wastewater on the permeation side enters the low acid wastewater precision neutralization reaction unit (8).

[0045] Step Four: Precise Neutralization and Deep Purification Membrane permeate water enters the low-acid wastewater precision neutralization reaction unit (8). This unit (8) adopts a three-stage pH adjustment tank series structure, with baffles in each stage tank to enhance the mixing effect. The alkali dosing subsystem dynamically adjusts the frequency of the metering pump based on the pH feedback signal from the third stage outlet using a PID algorithm. The neutralized wastewater enters the high-efficiency flocculation sedimentation tank (9), and its effluent flows by gravity through pipeline to the deep purification treatment unit (10) (activated carbon + 5μm filtration), finally producing qualified clean water (12).

[0046] Step 5: Pressure Resistance Design of the Sludge Treatment Line After the sludge from each unit is collected in the sludge thickening tank (13), it is pumped into the high-pressure plate and frame filter press (14) by a high-pressure diaphragm pump. Given that the sludge contains a large amount of hydrochloric acid, the filter plates of the filter press are made of reinforced polypropylene, and the pressing pressure is set to 2.0 MPa. The filtrate after filtration is returned to the acid-resistant homogenizing and equalizing tank (2) through a closed pipeline, and the sludge cake falls into the sludge stabilization and harmless treatment unit (15).

[0047] This embodiment successfully solves the problems of high SS and high Fe³ by introducing a "disc tube open flow channel" and a "high-speed cross-flow shearing" structure. + This invention addresses the industry-wide challenge of membrane pore blockage caused by acidic wastewater. After 120 days of continuous operation, the membrane flux decline rate was controlled within 10%, far superior to conventional spiral wound membrane systems (typically 30%-50%), demonstrating the structural adaptability and inventiveness of this invention under extreme operating conditions.

[0048] Example 3: Parameter Sensitivity Verification and Intelligent Control Structure (Focusing on Control Logic and Data Support) 1. Experimental Objective and Apparatus To verify the non-obviousness of the pH value (1.5-3.5) and chelating agent dosage (0.08%-0.3%) of the present invention, a continuous flow pilot-scale device was constructed. The device includes: an acid-resistant homogenization conditioning tank (2), a multi-stage acid-resistant pre-filtration unit (3), an acidic heavy metal chelation reaction tank (4), a PTFE acid-resistant membrane acid-water separation system (6), and an online monitoring system.

[0049] The key is the refinement of the control structure: the acidic heavy metal chelation reaction tank (4) is equipped with a Mettler Toledo InPro 4800 series pH composite electrode (strong acid resistant type), and the electrode signal is transmitted to the Siemens S7-1200 PLC controller through a shielded cable. The controller output is connected to two variable frequency metering pumps, which control the dosage of acidic thiol chelating agent and dilute acid (5% H2SO4) respectively.

[0050] 2. Experimental Procedure and Data Recording pH range screening experiment: fixed influent heavy metal concentration (Ni²) + =50mg / L, Cu² + =40mg / L) and DTCR dosage (0.15%), by changing the amount of acid added in the acid conditioning tank (2), the reaction tank (4) was set to operate at different pH levels, and the effluent quality was examined: Control group A (pH=0.8): At this time, the H in the solution + The concentration is extremely high, competing with heavy metal ions for thiol sites on the chelating agent surface. The PLC controller attempts to maintain the reaction, but the DTCR dosage needs to be increased to 0.45% to achieve a 90% removal rate, resulting in a 300% increase in reagent costs. Excess reagent also leads to excessive foaming, causing severe organic pollution after entering the membrane system (6). Control group B (pH=4.5): This exceeds the upper limit of the present invention. Although the DTCR reactivity is high, the Fe³⁺ in the wastewater + and part of Ni² +Spontaneous hydrolysis begins to generate hydroxide precipitates. These colloidal precipitates rapidly clog the 20μm filter cartridge at the end of the multi-stage acid-resistant pre-filtration unit (3), causing the pressure differential to exceed the limit within 2 hours, forcing the system to shut down. Experimental group (pH=2.0): within the range of 1.5 to 3.5 as claimed. At this time, the thiol functional group of DTCR remains protonated, exhibiting the highest activity. The online monitoring system shows that only 0.15% of DTCR needs to be added, Ni² + Cu² + The removal rate is stable at 99.5%. At the same time, since no hydroxide precipitate is formed, the pressure difference of the pre-filtration unit (3) remains stable, and the membrane system (6) operates smoothly.

[0051] In the above experiments, the control structure of the present invention played a key role: Feedback mechanism: When the pH sensor detects that the pH in the reaction tank (4) rises to 3.0 due to fluctuations in the influent, the PLC controller responds immediately, increases the pulse frequency of the dilute acid dosing pump, and restores the pH to 2.0, with a response time of <10 seconds. Feedforward protection: When the differential pressure sensor of the pre-filtration unit (3) detects an abnormal increase in ΔP, the controller automatically reduces the frequency of the high-pressure pump of the membrane system (6) to prevent excessive back pressure from damaging the filter element, and simultaneously starts the backup filter unit for switching. This closed-loop control structure of "detection-operation-execution" ensures that the process parameters are always locked at the optimal point, which is impossible to achieve with traditional manual or semi-automatic control processes.

[0052] Quantification of membrane separation effect: Under the optimal operating condition of pH=2.0, the performance of the PTFE acid-resistant membrane acid-water separation system (6) was monitored: operating pressure: 2.5MPa. Concentration side: the regenerated acid concentration increased from 5% of the raw water to 13% (2.6 times), and the heavy metal rejection rate was >95%. Permeate side: the TDS of the low acid wastewater was only 28% of that of the raw water.

[0053] The experimental results confirm the criticality and predictability of the numerical range in this invention: Lower limit: When pH < 1.5, economic efficiency and operability deteriorate sharply, rendering it industrially unviable. Upper limit: When pH > 3.5, side reactions (hydroxide precipitation) occur, leading to pretreatment failure and disrupting the stability of the membrane system. Synergistic effect: Only within the pH range of 1.5–3.5 can the three conditions of "high efficiency in chelation and complex disruption," "smooth pretreatment," and "long-lasting membrane separation" be simultaneously satisfied. This balance of multiple factors cannot be obtained by simple reasoning by those skilled in the art, demonstrating outstanding substantive characteristics and significant progress.

[0054] Comparative Example 1: Traditional Total Neutralization + Coagulation and Sedimentation Process (Process Route Comparison) 1. Treatment object and apparatus: The electroplating acidic rinsing wastewater (pH=1.8, Ni²) used is exactly the same as in Example 1. +=80 mg / L, Cu² + =45 mg / L, containing citric acid complexing agent). The treatment equipment is arranged in the following order: equalization tank → pH equalization tank (primary and secondary) → coagulation reaction tank → inclined tube sedimentation tank → quartz sand filter → clear water tank.

[0055] 2. Treatment Process: Step 1 (Alkali Adjustment and Complex Breaking): Add 30% NaOH solution to the pH adjustment tank to rapidly raise the pH to 10.5. At this point, the OH- ions in the wastewater... - The concentration is extremely high, attempting to form hydroxide precipitates with heavy metal ions. Step Two (Sulfide Precipitation): Due to the presence of the complexing agent, simple hydroxide precipitation is ineffective; therefore, Na2S (sodium sulfide) is added at a concentration of 200 mg / L to attempt to form sulfide precipitates with smaller solubility products. Step Three (Coagulation Precipitation): PAC (200 mg / L) and PAM (5 mg / L) are added, and the mixture is allowed to settle in a sedimentation tank. Step Four (Filtration and Reuse): The supernatant from the sedimentation tank is filtered through sand and then enters a clear water tank.

[0056] 3. Results and Problem Analysis: Effluent Water Quality: Ni² + =1.5 mg / L, Cu² + =1.1 mg / L, all of which failed to meet the standard (National Standard Table 3 requires Ni ≤ 0.1 mg / L). The reason is that under strongly alkaline conditions, citrate ions react with Ni²⁺. + The resulting complex is extremely stable (stability constant LogK≈14.3), OH - and S² - The inability to effectively displace ligands resulted in heavy metals remaining "hidden" in the solution and failing to precipitate. Salinity issue: Due to the complete neutralization of the raw water (TDS 8500 mg / L), approximately 4000 mg / L of sodium was introduced. + This caused the TDS in the effluent to spike to 12500 mg / L, resulting in saline water that could not be reused in the production process and had to be discharged. Secondary pollution: The addition of sodium sulfide produced a strong H2S rotten egg odor, threatening the health of operators. Economic efficiency: The consumption of alkali (NaOH) is more than five times that of Example 1 of this invention.

[0057] Comparative conclusion: This comparative example verifies the mechanistic limitations (complexation blockade) and resource waste (high salt and high alkali consumption) of the traditional "alkali adjustment and heavy removal" process when treating strong acid wastewater containing complexing agents. This highlights the ingenuity of the present invention's "strong acid without alkali adjustment and complex breaking" and "diversion and low salt neutralization".

[0058] Comparative Example 2: Direct addition of conventional chelating agents under acidic conditions (comparison of reagent selection) 1. Treatment object and apparatus: The same wastewater as in Example 1 is used. The treatment apparatus is simplified as follows: equalization tank → reaction tank → sedimentation tank.

[0059] 2. Treatment process: Without adjusting the pH (maintaining 1.8), commercially available common heavy metal scavenging agent (non-acid-resistant DTCR, the main component of which is dithiocarbamate) was directly added to the reaction tank at a dosage of 300 mg / L (twice that of Example 1). The reaction was stirred for 30 minutes and then allowed to settle.

[0060] 3. Results and Problem Analysis: Effluent Water Quality: Ni² + =12 mg / L, Cu² + =8 mg / L. Removal rate is extremely low. Mechanism analysis: The active functional groups in ordinary chelating agents undergo protonation in a strongly acidic environment (pH < 3), i.e., the N or S atoms in the functional groups react with H atoms... + The reagent loses its lone pair of electrons that coordinate with heavy metal ions, leading to reagent inactivation. Simultaneously, the strong acid environment makes the resulting precipitate unstable, causing some to redissolve. Observations: A large amount of foam is produced during the reaction, and the precipitate flocs are small, loose, and difficult to settle (SV). 30 >20%).

[0061] Comparative conclusion: This comparative example demonstrates that not all chelating agents function effectively under strong acids. The "acid-specific thiol chelating agent" selected in this invention possesses a unique molecular structure that resists protonation interference. This is the key material basis for achieving "strong acid complex breaking," and it is not a simple replacement for conventional agents in this field.

[0062] Comparative Example 3: Treatment of unadjusted pH acidic wastewater using conventional spiral wound nanofiltration membranes (membrane material comparison) 1. Treatment object and apparatus: The same wastewater as in Example 1 is used. The treatment apparatus consists of: equalization tank → pretreatment → conventional polyamide composite nanofiltration membrane system.

[0063] 2. Treatment process: The pretreated wastewater (pH=1.8) directly enters the conventional nanofiltration membrane system. The operating pressure is set at 2.0 MPa, similar to the membrane system pressure in Example 1.

[0064] 3. Results and Problem Analysis: Membrane Performance Decline: Initially, membrane flux was acceptable, but it began to decline sharply after 2 hours. After 24 hours of operation, flux decline exceeded 50%. Membrane Element Disintegration: Disassembly and inspection of the membrane elements revealed significant swelling, peeling, and scaling of the polyamide desalination layer. This is because the polyamide bonds undergo hydrolysis in a strongly acidic environment with pH < 2, disrupting the membrane's selective permeability. Effluent Quality: Due to membrane structure damage, the desalination rate and heavy metal rejection rate rapidly decreased to unacceptable levels (rejection rate < 30%).

[0065] Comparative Conclusion: This comparative example directly demonstrates that conventional membrane materials cannot withstand native strong acid environments. This invention utilizes an acid-resistant PTFE membrane, which has extremely high carbon-fluorine bond energy and excellent chemical inertness, providing the core hardware guarantee for realizing the "acid recovery pretreatment" process. Those skilled in the art typically do not consider directly using nanofiltration membranes when dealing with acidic wastewater, precisely because of the lack of suitable membrane materials. This further highlights the material innovation of this invention.

[0066] Comparative Example 4: Neutralization followed by membrane separation process (process logic comparison) 1. Treatment Object and Apparatus: The same wastewater as in Example 1 is used. The treatment apparatus consists of: equalization tank → pH equalization tank → coagulation sedimentation tank → intermediate water tank → PTFE acid-resistant membrane system.

[0067] 2. Treatment Process: First, the pH of the raw water is adjusted to 7.0 (neutralization) to remove heavy metal precipitates. Then, the supernatant (intermediate water) is pumped into a PTFE acid-resistant membrane system for concentration and separation. The membrane system operates at a pressure of 2.2 MPa.

[0068] 3. Results and Problem Analysis: Acid Recovery Failure: Due to pre-neutralization, the pH of the intermediate water was neutral, and it no longer contained high concentrations of free acid. The permeate from the concentration side of the membrane system was low-salt neutral water, which could not be reused as acid in the acid washing process. Increased Membrane Fouling: A large amount of NaOH was added during the neutralization process, introducing Na+ into the membrane system. + During membrane concentration, Na + With SO4² in water - Cl - This combination leads to the formation of inorganic salt scaling on the membrane surface, causing a rapid decline in membrane flux and shortening the cleaning cycle to less than one week. Resource waste: the acid intended for recovery is consumed by alkali neutralization in the first step, violating the original intention of resource recovery.

[0069] Comparative Conclusion: This comparative example verifies the shortcomings of the traditional "neutralization first, membrane process second" approach. The reverse process route proposed in this invention, "membrane separation first, precise neutralization later," is a key logical innovation for achieving the dual goals of acid resource recovery and low-salinity water purification. It breaks the traditional mindset of "purification first, concentration later" and is non-obvious.

[0070] Comparative Example 5: Low salt emissions after full neutralization (control logic comparison) 1. Treatment object and apparatus: The same wastewater as in Example 1 was used. The treatment apparatus was the same as in Comparative Example 1, but an additional RO reverse osmosis system was added after sedimentation for desalination.

[0071] 2. Treatment process: Complete neutralization and sedimentation are carried out according to the method in Comparative Example 1. The effluent from the sedimentation enters the RO system, attempting to remove salt through the RO membrane to obtain low-salt reclaimed water.

[0072] 3. Results and Problem Analysis: Scaling and Blockage: The neutralized water is rich in Ca²⁺. + Mg² + In addition to SiO2, carbonate and silica scale easily form on the surface of the RO membrane, leading to frequent cleaning of the membrane system and shortening its lifespan. The concentrated wastewater treatment problem: 30%–40% of the concentrated wastewater produced by the RO system has extremely high salt and heavy metal concentrations, classifying it as hazardous waste, making treatment difficult and costly. In reality, it does not achieve "near-zero discharge," but rather a transfer of pollutants. Extremely high energy consumption: To remove the large amount of salt introduced through neutralization, the operating pressure of the RO system needs to be maintained above 4.0 MPa, consuming more than twice the energy of the membrane system of this invention (2.2 MPa).

[0073] Comparative Conclusion: This comparative example demonstrates that attempting to solve the high-salinity problem caused by front-end processes (full neutralization) through end-of-pipe treatment (such as RO) is not only costly but also introduces new environmental challenges. This invention, by controlling the source (neutralizing only a small amount of membrane permeate), fundamentally avoids the generation of high-salinity wastewater, showcasing the simplicity and efficiency of its process design.

[0074] Experimental results Those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the resource-based treatment of acidic wastewater, characterized in that, Includes the following steps: Acidic wastewater is pre-filtered using a multi-stage gradient acid-resistant method to remove suspended impurities; Without adjusting the pH of the wastewater to neutral, an acidic thiol chelating agent is added to the pre-filtered wastewater to control the pH of the reaction system within the strongly acidic range of 1.5 to 3.5 for chelation and complex-breaking reaction, so that free and complexed heavy metals can form insoluble chelates. The mixture after the reaction was subjected to primary solid-liquid separation to obtain an acidic purified supernatant; The acidic purification supernatant is directly pumped into the PTFE acid-resistant membrane system for pressurized separation. The stability of the PTFE acid-resistant membrane in an environment with pH ≤ 1.0 is utilized to retain trace amounts of heavy metal colloids and macromolecular impurities, thereby obtaining regenerated acid solution on the concentration side and low-acid wastewater on the permeation side. The low-acid wastewater on the permeable side is precisely neutralized and deeply purified to achieve water reuse. In this method, the alkali is controlled to be added only to the membrane permeation side.

2. The method for resource-based treatment of acidic wastewater according to claim 1, characterized in that, The acid-specific thiol chelating agent is a modified thiol heavy metal scavenger. It has a positive Zeta potential in a strongly acidic environment with a pH of 1.5 to 3.

5. It actively adsorbs negatively charged heavy metal complex ions through electrostatic attraction and uses thiol functional groups to replace coordinating groups to form five-membered ring chelates. The dosage of the chelating agent is 0.08% to 0.3% of the wastewater mass.

3. The method for resource-based treatment of acidic wastewater according to claim 1, characterized in that, The PTFE acid-resistant membrane system uses a polytetrafluoroethylene nanofiltration membrane with a filtration accuracy of 0.001 μm and an operating pressure of 1.8–3.0 MPa. The concentration of the regenerated acid solution is 1.5–2.5 times higher than that of the original water, and due to the membrane retention effect, the heavy metal content in the regenerated acid solution is less than 5% of the heavy metal content in the original water.

4. The method for resource-based treatment of acidic wastewater according to claim 1, characterized in that, The multi-stage gradient acid-resistant pre-filtration includes sequential 1mm coarse filtration, 100μm fine filtration, and 20μm precision filtration; and the 20μm precision filtration is set before the chelation and complex-breaking reaction to remove sharp particles before heavy metals form micro-flocs.

5. The method for resource-based treatment of acidic wastewater according to claim 1, characterized in that, In the precise low-salt neutralization step, pH-ORP linkage feedback is used to control the amount of alkali added, precisely adjusting the pH of the low-acid wastewater on the permeate side to 6.5-8.5, and controlling the excess coefficient of alkali addition to not exceed 1.05, ensuring that the total amount of salt generated in the reaction system is only 1 / 3 of that in the traditional full-volume neutralization process.

6. An acidic wastewater resource recovery system implementing the method of any one of claims 1 to 5, characterized in that, Including connections via pipes along the direction of water flow: Acid-resistant homogenizing equalization tank (2); A multi-stage acid-resistant pre-filtration unit (3) is internally integrated with a 1mm coarse filter component, a 100μm fine filter component and a 20μm precision filter component in sequence along the water flow direction; An acidic heavy metal chelation reaction tank (4) has its inlet connected to the outlet of the multi-stage acid-resistant pre-filtration unit (3), and does not have an external alkaline agent dosing pipeline, but only an acidic special mercaptan chelating agent dosing device. A PTFE acid-resistant membrane acid-water separation system (6) has its inlet directly connected to the outlet of the acidic heavy metal chelation reaction tank (4), and the concentrated liquid outlet of the PTFE acid-resistant membrane acid-water separation system (6) is connected to a regenerated acid storage tank (7). A precision neutralization reaction unit (8) has its inlet connected only to the permeate outlet of the PTFE acid-resistant membrane acid-water separation system (6), and is equipped with a micro-alkali dosing subsystem; A deep purification unit (10) is connected to the outlet of the precision neutralization reaction unit (8); And a sludge treatment line, which is connected to the discharge end of the acidic heavy metal chelation reaction tank (4), the precision neutralization reaction unit (8) and the deep purification unit (10), respectively.

7. The acidic wastewater resource utilization treatment system according to claim 6, characterized in that, The membrane element of the PTFE acid-resistant membrane acid-water separation system (6) is a polytetrafluoroethylene hollow fiber membrane or a spiral wound membrane. The shell and the pipeline material in contact with the liquid are both PVDF or PTFE, ensuring that swelling or hydrolysis does not occur in a highly corrosive environment with pH≤1.0 and pressure≥1.8MPa.

8. The acidic wastewater resource utilization treatment system according to claim 6, characterized in that, The acidic heavy metal chelation reaction tank (4) is equipped with a high shear force stirrer with a rotation speed set to 60-120 r / min.

9. The acidic wastewater resource utilization treatment system according to claim 6, characterized in that, The precise neutralization reaction unit (8) and the regenerated acid storage tank (7) are provided with a physical isolation wall, and their return pipelines are not connected to each other, forming two independent closed-loop cycles of 'acid recovery' and 'water purification'.

10. The acidic wastewater resource utilization treatment system according to claim 6, characterized in that, The deep purification unit (10) adopts a structure of activated carbon adsorption tower and 5μm security filter connected in series. The activated carbon adsorption tower is filled with acid-activated granular activated carbon to adsorb trace organic complexing agents and heavy metal ions remaining in the water through the membrane, ensuring that the turbidity of the effluent is ≤1NTU.

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