A treatment method for recycling hydrochloric acid in high-salinity acidic wastewater in the rare earth industry

Abstract

This invention discloses a method for treating highly hydrochloric acid wastewater from the rare earth industry by recycling hydrochloric acid, belonging to the field of rare earth metallurgical wastewater treatment and resource recovery technology. The method includes the following steps: first, homogenizing the wastewater, followed by primary membrane filtration to remove the extractant and secondary membrane filtration to remove impurities; then, tertiary membrane forced circulation for extractant-water separation; and finally, deep purification through ion exchange to complete the treatment. This invention provides a method for treating highly hydrochloric acid wastewater from the rare earth industry by recycling hydrochloric acid. This method has strong acid resistance and adaptability, requires no reagent adjustment, achieves thorough extractant and impurity removal, has a high resource recycling rate, achieves zero discharge, has strong process stability, good shock resistance, and high industrial adaptability, enabling large-scale industrial application. It solves the problems of high reagent consumption, incomplete hydrochloric acid recovery, easy membrane and resin fouling, waste of extractant resources, and easy secondary pollution in existing treatments of highly hydrochloric acid wastewater from the rare earth industry.

Description

Technical Field

[0001] This invention relates to the field of rare earth metallurgical wastewater treatment and resource recycling technology, specifically to a method for treating highly hydrochloric acid wastewater from the rare earth industry by recycling hydrochloric acid. Background Technology

[0002] The rare earth industry generates large amounts of highly hydrochloric acid wastewater during production. This type of wastewater has significant characteristics: extremely high acidity (pH≤2), high salt content, and complex composition. It not only contains recyclable hydrochloric acid but also oily contaminants (extract), suspended particles, colloidal impurities, as well as metal ions such as Fe, As, Ca, Al, and Mg, and SO4. 2- Anionic. Currently, the industry faces numerous technical bottlenecks in the treatment of this type of wastewater: Traditional neutralization treatment: The acidity of wastewater can be reduced by adding alkaline solution to adjust the pH. However, this method requires a large amount of neutralizing agent and generates a large amount of solid waste. This not only increases the disposal cost but also causes a complete waste of hydrochloric acid resources. At the same time, it introduces new impurity ions, resulting in a high risk of secondary pollution.

[0003] Conventional membrane separation technology: Existing membrane modules have insufficient acid resistance and are prone to aging and failure under strong acid conditions with pH ≤ 2. Furthermore, single membrane filtration cannot simultaneously achieve efficient removal of oils, suspended impurities, and trace metal ions, resulting in substandard purity of subsequently recovered hydrochloric acid, which cannot be reused in production.

[0004] Existing recycling processes have several drawbacks: some processes require adjusting the pH of the wastewater before treatment, which not only increases reagent consumption and water quality disturbance but may also lead to salt crystallization, clogging equipment and pipelines; metal ion removal is incomplete, especially harmful ions such as As and Fe, making it difficult to meet industrial hydrochloric acid reuse standards; oil pollutants easily cause membrane fouling and resin poisoning, affecting process stability, and the low recovery rate of extractants easily leads to resource waste.

[0005] Resource recycling and environmental protection shortcomings: Existing technologies mostly focus on achieving standard wastewater discharge, without forming a closed-loop recycling system of "hydrochloric acid-extractant-water resources". The hydrochloric acid recovery rate is low, and extractant pollutants are easily discharged, causing environmental pollution, which does not conform to the industry development trend of "zero discharge" and comprehensive resource utilization.

[0006] Based on the shortcomings of the existing technologies, there is an urgent need to develop a recycling treatment method that is suitable for the characteristics of high hydrochloric acid wastewater in the rare earth industry, requires no pH adjustment, has strong acid resistance, high hydrochloric acid recovery rate, stable operation, and significant environmental benefits. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a method for treating high-hydrochloric acid wastewater from the rare earth industry by recycling hydrochloric acid, thereby resolving issues such as high reagent consumption, incomplete hydrochloric acid recovery, easy fouling of membranes and resins, waste of extractant resources, and easy generation of secondary pollution in existing high-hydrochloric acid wastewater treatment methods in the rare earth industry.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A first aspect of the present invention provides a method for treating highly hydrochloric acidic wastewater from the rare earth industry and recycling hydrochloric acid, comprising the following steps: S1, Primary membrane filtration to remove extractant: The homogenized high-acid wastewater from the rare earth industry is filtered through a first-stage acid-resistant, hydrophilic, and extractant-repellent ultrafiltration membrane filtration device to obtain first-stage membrane filtration permeate and extractant-type pollutants. S2, Secondary membrane filtration for impurity removal: The primary membrane filtration permeate obtained from S1 is introduced into a secondary acid-resistant high-precision nanofiltration membrane filtration device to obtain secondary membrane filtration permeate and concentrate. S3, Three-stage membrane extractant water separation: The extractant-type pollutants obtained from S1 are introduced into a three-stage acid-resistant and extractant-resistant composite membrane filtration device for extractant-water separation to obtain an acid solution and recovered extractant-type substances. S4, Loop processing: The concentrated water obtained from S2 and the acid solution obtained from S3 are introduced into the high-salt acid wastewater from the rare earth industry in S1 for three-stage membrane separation (S1-S3) to achieve recycling treatment. S5, Ion exchange treatment: The permeate from the secondary membrane filtration obtained in S2 is sequentially introduced into an acid-resistant cation exchanger and an acid-resistant anion exchanger for ion exchange treatment to obtain recovered hydrochloric acid.

[0009] The beneficial effects of this invention are as follows: This invention provides a method for treating high-hydrochloric acid wastewater in the rare earth industry by recycling hydrochloric acid. This method has strong acid resistance and adaptability, requires no reagent adjustment, has a thorough oil and impurity removal effect, a high resource recycling rate, achieves zero discharge, has strong process stability, good impact resistance, and high industrial adaptability, and can realize large-scale industrial application.

[0010] Furthermore, the homogenization stirring rate in S1 is 60-100 rpm.

[0011] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: the present invention ensures that the water quality of high hydrochloric acid wastewater is uniform and stable by stirring in the raw water pretreatment device, providing continuous and stable feeding conditions for the subsequent membrane filtration process, and does not require pH adjustment of the raw water, directly adapting to the strong acid conditions of the raw water.

[0012] Furthermore, the membrane material of the primary acid-resistant hydrophilic and oleophobic ultrafiltration membrane filtration device in S1 is polyceramic, the shell is glass fiber reinforced plastic (FRP), the molecular weight cutoff is 50-100 kDa, the operating pressure is 0.3-0.5 MPa, and the temperature is 25-35℃.

[0013] Preferably, the molecular weight cutoff of the first-stage acid-resistant hydrophilic and oleophobic ultrafiltration membrane filtration device in S1 is 70 kDa, the operating pressure is 0.4 MPa, and the temperature is 30°C.

[0014] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: The present invention uses a first-stage acid-resistant hydrophilic and oleophobic ultrafiltration membrane for filtration, which specifically intercepts oil pollutants (extract), suspended particles and colloidal impurities in wastewater. The removal rate of extractants is ≥90%, and the wastewater is initially purified to protect the subsequent membrane modules.

[0015] Furthermore, the membrane material of the secondary acid-resistant high-precision nanofiltration membrane filtration device in S2 is polyceramic, the shell is glass fiber reinforced plastic, the molecular weight cutoff is 400-600 Da, the operating pressure is 0.6-0.8 MPa, and the temperature is 25-35℃.

[0016] Preferably, the molecular weight cutoff of the secondary acid-resistant high-precision nanofiltration membrane filtration device in S2 is 500 Da, the operating pressure is 0.7 MPa, and the temperature is 30°C.

[0017] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The present invention uses a two-stage acid-resistant high-precision nanofiltration membrane to filter the water produced by the first-stage membrane filtration, further removing fine suspended particles, fine oil droplets retained by the first-stage membrane, and some metal ions from the water. The removal rate of suspended solids is ≥99%, and the removal rate of extractants is ≥95%, ensuring that the produced water meets the influent requirements for the subsequent ion exchange resin and avoiding resin contamination and poisoning.

[0018] Furthermore, the membrane surface flow velocity of the three-stage acid- and oil-resistant composite membrane filtration device in S3 is 1.5-2.0 m / s.

[0019] Furthermore, in S3, the membrane surface flow rate is increased to 1.5-2.0 m / s by a forced circulation pump.

[0020] Furthermore, the shell material of the three-stage acid and oil resistant composite membrane filter device in S3 is glass fiber reinforced polypropylene (FRPP).

[0021] The beneficial effects of adopting the above-mentioned further technical solution are as follows: This invention introduces extractant-type pollutants after primary membrane filtration into a three-stage acid-resistant and extractant-resistant composite membrane filtration device. Through high membrane surface flow rate, the oil-water separation effect is enhanced, achieving complete separation of extractant-type substances and acid solutions. The separated extractant-type substances are collected into a collection tank through a dedicated acid-resistant and oil-resistant pipeline and returned to the rare earth production system for recycling. The separated acid solution is returned to the raw water and re-enters the treatment system for recycling, ensuring that no extractant-type substances are discharged.

[0022] Furthermore, the filtration devices in S1-S3 adopt a cross-flow filtration design and are backwashed every 0.5-1 hour, with a backwash time of 1 minute.

[0023] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: The membrane system of the present invention adopts a cross-flow filtration design and is equipped with a backwash pump, which reduces the risk of membrane fouling and extends the service life of the membrane module.

[0024] Furthermore, in S4, the acid-resistant cation exchanger uses a phosphoric acid-based strong acid cation exchange resin; the strong base-based anion exchanger uses a styrene-based acid-resistant anion exchange resin.

[0025] The beneficial effects of adopting the above-mentioned further technical solution are as follows: This invention passes the permeate from the secondary membrane filtration process sequentially through an acid-resistant cation exchanger and an acid-resistant anion exchanger. The cation exchanger specifically removes metal ions such as Fe, As, Ca, Al, and Mg, while the anion exchanger specifically removes SO4. 2- Anions are used to ensure that the content of impurity ions in the acid solution meets the industrial hydrochloric acid recovery standards.

[0026] Furthermore, the working exchange capacity of the phosphate-based acid-resistant cation exchange resin is ≥1.8 mmol / g; the working exchange capacity of the styrene-based acid-resistant anion exchange resin is ≥1.2 mmol / g.

[0027] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By strictly limiting the type of ion exchange resin and the working exchange capacity, the present invention ensures the efficient removal of target impurity ions.

[0028] Furthermore, when the ion exchange resin reaches adsorption saturation, it can be regenerated using an ion exchange regeneration device.

[0029] Furthermore, the ion exchange regeneration device (the shell is made of FRP and includes a regenerated water pump and an ejector).

[0030] Furthermore, the wastewater generated during the regeneration process is introduced into a regeneration wastewater tank, neutralized, and then sent to the sewage treatment system for treatment to meet standards, thus avoiding secondary pollution.

[0031] Furthermore, the equipment and pipelines involved in the above treatment method are all designed to be acid and oil resistant: the tank material is PE / FRP / FRPP, the pipeline material is UPVC / PTFE, and the pump and valve material is PTFE-lined / SS316L+PTFE sealed.

[0032] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By strictly controlling the materials of equipment and pipelines, this invention is adapted to working conditions where strong acids and extractants coexist, thus avoiding the risk of leakage.

[0033] Furthermore, a fully automated control mode using PLC and touchscreen is adopted to detect and process the workflow.

[0034] The beneficial effects of adopting the above-mentioned further technical solutions are: key parameters such as pressure, flow rate and liquid level can be monitored in real time through the fully automatic control mode, which is easy to operate and requires little maintenance.

[0035] Furthermore, the finished can is made of PE.

[0036] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: the recovered hydrochloric acid obtained by the present invention can be directly transported to the rare earth production recycling point and directly reused in the rare earth production process. The concentration of hydrochloric acid is kept consistent with the concentration of the raw material liquid, and no additional concentration is required (if concentration is required for production, the concentration can be increased by subsequent coupling of the permeation vaporization membrane).

[0037] Furthermore, acid-resistant pipelines (made of UPVC) are used when transporting recycled hydrochloric acid to rare earth production recycling points.

[0038] A second aspect of the present invention provides an application apparatus for the above-described treatment method, comprising a raw water pretreatment apparatus, a membrane separation apparatus, and an ion exchange apparatus; Membrane separation devices include primary separation membrane devices, secondary separation membrane devices, and tertiary separation membrane devices; The primary separation membrane unit is connected to the raw water pretreatment unit and receives the raw water delivered by the raw water pretreatment unit; The secondary membrane separation unit is connected to the primary membrane separation unit and the raw water pretreatment unit respectively. It receives the permeate after treatment by the primary membrane separation unit and transports the concentrated water separated and retained by the secondary membrane separation unit to the raw water pretreatment unit. The three-stage membrane separation unit is connected to the first-stage membrane separation unit and the raw water pretreatment unit respectively. It receives the extractant pollutants separated and retained by the first-stage membrane separation unit and transports the treated water from the three-stage membrane separation unit to the raw water pretreatment unit. Ion exchange devices include cation exchangers and anion exchangers; The cation exchanger is connected to the secondary separation membrane unit and receives the permeate water treated by the secondary separation membrane unit. The anion exchanger is connected to the cation exchanger and receives the permeate water treated by the cation exchanger.

[0039] The beneficial effects of the present invention are as follows: The present invention provides an application device based on the above-mentioned treatment method. The equipment involved in the device are all conventional chemical equipment, with a small footprint, low power load, low utility requirements, and simple operation. It can directly provide technical basis and operating parameters for large-scale projects, and can realize low-cost and high-efficiency recycling treatment of high hydrochloric acid wastewater in the rare earth industry.

[0040] Furthermore, an acid-resistant stirring device is installed inside the raw water pretreatment unit.

[0041] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: the raw water treatment device of the present invention only needs to set up a simple acid-resistant stirring device for wastewater homogenization treatment, ensuring that the wastewater quality is uniform and stable, reducing the impact on the system, and ensuring the subsequent membrane filtration process. No additional pH adjustment or other treatment processes are required, and it can be directly adapted to the strong acid conditions of raw water.

[0042] Furthermore, the primary separation membrane device is an acid-resistant, hydrophilic, and oleophobic ultrafiltration membrane filtration device. The membrane material is polyceramic, the shell is glass fiber reinforced plastic, and the molecular weight cutoff is 50-100 kDa.

[0043] Preferably, the molecular weight cutoff of the primary separation membrane device is 70 kDa.

[0044] Furthermore, the secondary separation membrane device is an acid-resistant, high-precision nanofiltration membrane filtration device. The membrane material is polyceramic, the shell is glass fiber reinforced plastic, and the molecular weight cutoff is 400-600 Da.

[0045] Preferably, the molecular weight cutoff of the secondary separation membrane device is 500 Da.

[0046] Furthermore, the three-stage separation membrane device is an acid- and oil-resistant composite membrane filtration device, and the shell is made of glass fiber reinforced polypropylene.

[0047] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The present invention treats high-acid wastewater through a three-stage separation membrane device, gradually removing extractant pollutants, suspended particles, colloidal impurities, etc. from the wastewater, achieving complete separation of extractant from acid solution, and achieving 100% recovery of extractant substances with no waste extractant discharge.

[0048] Furthermore, the membrane separation unit is equipped with a backwash pump.

[0049] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By equipping the membrane separation device with a backwash pump, the present invention performs backwashing with product water after a period of operation, which effectively reduces the risk of membrane fouling and extends the life of the membrane module.

[0050] Furthermore, an ion exchange regeneration device is provided in the ion exchange device.

[0051] Furthermore, the shell of the ion exchange regeneration device is made of FRP and includes a regenerated water pump and an ejector.

[0052] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By setting a regeneration device in the ion exchange device, the present invention performs regeneration treatment after the ion exchange resin reaches adsorption saturation, thereby improving process stability and shock resistance.

[0053] Furthermore, the cation exchanger uses a phosphoric acid-based strong acid cation exchange resin, and the anion exchanger uses a styrene-based strong base anion exchange resin.

[0054] Furthermore, it also includes a wastewater treatment device for reclaimed water.

[0055] Furthermore, the regenerated wastewater treatment device is connected to a cation exchanger and an anion exchanger to receive the regenerated wastewater treated by the cation exchanger and anion exchanger.

[0056] Furthermore, the regenerated wastewater treatment unit also receives regenerated wastewater generated from the ion exchange regeneration unit.

[0057] Furthermore, all equipment and pipelines involved in the application device are designed to be acid and oil resistant: the tank material is PE / FRP / FRPP, the pipeline material is UPVC / PTFE, and the pump and valve material is PTFE-lined / SS316L+PTFE sealed.

[0058] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: By strictly controlling the materials of the equipment and pipelines involved, the present invention enables the application device to be adapted to working conditions where strong acids and extractants coexist, without the risk of leakage.

[0059] Furthermore, the application device also includes a fully automatic control module.

[0060] Furthermore, the fully automatic control module adopts a PLC + touch screen fully automatic control mode.

[0061] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: the present invention can monitor key parameters such as pressure, flow rate and liquid level in real time through a fully automatic control module, which is easy to operate and requires little maintenance.

[0062] The present invention has the following beneficial effects: 1. Strong acid resistance and adaptability, no chemical adjustment required. The core equipment and pipelines involved in the method of this invention are all made of acid-resistant materials, which can be directly adapted to the strong acid conditions of raw water with pH≤2. There is no need to add neutralizing agents or demulsifiers, avoiding chemical consumption and water quality disturbance, reducing operating costs and secondary pollution.

[0063] 2. Thorough removal of impurities such as extractants. Through a combination of "three-stage membrane filtration + forced circulation," the removal rate of extractants is ≥95%, and the removal rate of suspended solids is ≥99%. Combined with acid-resistant special ion exchange resin, the content of metal ions such as Fe, As, and Ca after removal is ≤5mg / L, ≤1mg / L, and ≤5mg / L, respectively, and SO42- is also removed. 2- ≤20mg / L, fully compliant with the GB320-2023 standard for industrial hydrochloric acid.

[0064] 3. High resource recycling rate, achieving zero emissions. Hydrochloric acid recovery rate ≥98%, directly reused in production after treatment, reducing the cost of purchasing fresh hydrochloric acid; oil pollutants (extract) recycling rate 100%, with no waste extractant discharged; regenerated wastewater meets discharge standards after neutralization treatment, the entire system achieves "zero emissions" of pollutants, with significant environmental and economic benefits.

[0065] 4. Strong industrial stability and good shock resistance. The multi-stage treatment units work together to adapt to fluctuations in raw water extractant content and suspended solids concentration within ±20%. The membrane system has a low backwashing frequency and a long regeneration cycle for the ion exchange resin. Pilot tests have shown that it can operate continuously and stably for ≥30 days without equipment corrosion, leakage, or membrane module failure.

[0066] 5. High industrial adaptability. All equipment consists of conventional chemical equipment, occupying only 90 square meters. 2 (10 m × 9 m), power load 60 kW (380 V, 50 Hz, three-phase five-wire), low utility requirements (only 1 m of power is needed for a single regeneration cycle). 3 Pure water), easy to operate, can directly provide technical basis and operating parameters for large-scale projects. Attached Figure Description

[0067] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0068] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0069] The example uses high-hydrochloric acid wastewater from a rare earth group limited company. The wastewater quality is as follows: pH=1.8, hydrochloric acid concentration is the original concentration of the production process, total salt content ≥5%, extractant pollutant content ≤50mg / L, suspended solids content ≤100 mg / L, metal ion and anion content: Fe≤3000 mg / L, As≤100 mg / L, Ca≤500 mg / L, Mg≤100 mg / L, SO42- 2- ≤100 mg / L. The pilot-scale equipment has a processing capacity of 1 m³. 3 / h.

[0070] Example: A method for treating highly hydrochloric acid wastewater from the rare earth industry and recycling hydrochloric acid includes the following steps: S1, Raw Water Homogenization Buffer The aforementioned highly hydrochloric acid wastewater was directly introduced into a PE-material raw water conditioning tank (1000 L capacity). An acid-resistant stirring device was started (stirring speed 80 r / min). The homogenized wastewater was then pumped through a PTFE-lined raw water lift pump (Q=2 m³ / h). 3 (H=15 m, P=1.1kW) is transported to the primary membrane filtration unit.

[0071] S2, primary membrane filtration for oil removal The first-stage ultrafiltration membrane unit (membrane material: ceramic, shell: FRP, molecular weight cutoff: 70 kDa) operates at a pressure of 0.4 MPa and a temperature of 30°C. The content of extractant in the filtered permeate is ≤5 mg / L, and the content of suspended particles is ≤10 mg / L. The retained extractant and large particulate impurities are temporarily stored with a small amount of concentrate for subsequent treatment.

[0072] S3, Secondary membrane filtration for impurity removal The permeate from the primary membrane enters the secondary nanofiltration membrane unit (membrane material: ceramic, shell: FRP, molecular weight cutoff: 500 Da), operating pressure: 0.7 MPa, temperature: 30℃. The suspended solids content in the permeate is ≤1 mg / L, the extractant content is ≤0.5 mg / L, and some trace metal ions are retained. The permeate quality meets the requirements for ion exchange resin feed water. The retained concentrate is returned to the raw water conditioning tank in S1.

[0073] S4, Three-stage membrane forced circulation extractant water separation The concentrated water produced by the primary membrane filtration is introduced into the tertiary acid-resistant and extractant-resistant composite membrane device (shell FRPP). The forced circulation pump is started to increase the flow velocity on the membrane surface to 1.8 m / s. After separation, the extractant substances are collected in the FRP material oil-water separation unit (volume 500 L). After separation by the oil skimming device, it is returned to the production system for reuse through the DN25 acid-resistant and oil-resistant pipeline. The separated acid solution is returned to the raw water regulating tank for recycling.

[0074] S5, Ion Exchange Deep Purification The permeate from the tertiary membrane system sequentially passes through two FRP (0.5 m in diameter) ion exchangers. First, it passes through a cation exchanger (filled with phosphate-based acid-resistant cation exchange resin, with a working exchange capacity of 2.0 mmol / g) to remove metal ions such as Fe, As, and Ca. Then, it passes through an anion exchanger (filled with styrene-based acid-resistant anion exchange resin, with a working exchange capacity of 1.5 mmol / g) to remove SO4. 2- The flow rate of the iso-anion exchanger is controlled at 12 m / h.

[0075] S6, Hydrochloric acid recycling The hydrochloric acid solution obtained after deep purification through ion exchange is introduced into a PE finished product tank (1000 L volume) and transported to the rare earth production recycling point via a DN25 UPVC acid-resistant pipeline. Testing shows that the hydrochloric acid concentration is consistent with the raw material solution: Fe=3.2 mg / L, As=0.8 mg / L, Ca=4.1 mg / L, Mg=3.5 mg / L, SO42- 2- =15 mg / L, which meets the standard of GB 320-2023 "Industrial Hydrochloric Acid".

[0076] S7. Resin Regeneration and Wastewater Treatment After the ion exchange resin has been running continuously for 72 hours, the regeneration device is started. The cation exchange resin is regenerated with hydrochloric acid solution and the anion exchange resin is regenerated with sodium hydroxide solution. The regeneration wastewater is collected in the regeneration wastewater tank, neutralized and adjusted to pH 6-8, and then sent to the sewage treatment system for discharge in compliance with standards.

[0077] After 30 days of continuous operation, the results of this embodiment are as follows: the equipment operates stably without corrosion, leakage or other malfunctions; the hydrochloric acid recovery rate is 98.5%, and all indicators of the recycled hydrochloric acid meet production requirements; the recycling rate of extractant pollutants is 100%, and there is no waste extractant discharge; the unit wastewater treatment cost (including energy consumption, resin regeneration costs, and membrane cleaning agent costs) is reduced by more than 60% compared with traditional treatment methods, the resource recovery benefits are significant, and it fully meets the needs of industrial promotion.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating highly hydrochloric acidic wastewater from the rare earth industry by recycling hydrochloric acid, characterized in that, Includes the following steps: S1, Primary membrane filtration to remove extractant: First, the strong acid wastewater with pH ≤ 2 is homogenized without adding neutralizing agents or demulsifiers, and without adjusting the pH value. Then, the homogenized high-salt acid wastewater from the rare earth industry is filtered through a first-stage acid-resistant hydrophilic and oleophobic ultrafiltration membrane filtration device to remove the extract, suspended particles and colloidal impurities in the wastewater, thus obtaining the first-stage membrane filtration product water and extractant pollutants. S2, Secondary membrane filtration for impurity removal: The first-stage membrane filtration permeate obtained from S1 is introduced into a second-stage acid-resistant high-precision nanofiltration membrane filtration device to filter out fine suspended particles, fine oil droplets not retained by the first-stage membrane, and some metal ions, thus obtaining the second-stage membrane filtration permeate and concentrate. S3, Three-stage membrane oil-water separation: The extractant pollutants obtained from S1 are introduced into a three-stage acid and oil resistant composite membrane filtration device for oil-water separation, achieving complete separation of the extractant and acid solution, and obtaining acid solution and recovered extractant substances; S4, Loop processing: The concentrated water obtained from S2 and the acid solution obtained from S3 are introduced into the high-salt acid wastewater from the rare earth industry in S1 for three-stage membrane separation (S1-S3) to achieve recycling treatment. S5, Ion exchange treatment: The permeate obtained from the secondary membrane filtration in S2 is sequentially introduced into an acid-resistant cation exchanger and an acid-resistant anion exchanger for ion exchange treatment to obtain recovered hydrochloric acid. The molecular weight cutoff of the first-stage acid-resistant hydrophilic and oleophobic ultrafiltration membrane filtration device is 50-100 kDa. The molecular weight cutoff of the secondary acid-resistant high-precision nanofiltration membrane filtration device is 400-600 Da. The membrane material of the primary acid-resistant hydrophilic and oleophobic ultrafiltration membrane filtration device in S1 is polyceramic, the shell is glass fiber reinforced plastic, the operating pressure is 0.3-0.5 MPa, and the temperature is 5-60℃. The membrane material of the secondary acid-resistant high-precision nanofiltration membrane filtration device in S2 is polyceramic, the shell is glass fiber reinforced plastic, the operating pressure is 0.6-0.8 MPa, and the temperature is 5-60℃. The membrane surface flow velocity of the three-stage acid and oil resistant composite membrane filtration device in S3 is 1.5-2.0 m / s; The acid-resistant cation exchanger in S4 uses a phosphoric acid-based strong acid cation exchange resin; the acid-resistant anion exchanger uses a styrene-based strong base anion exchange resin.

2. The method for treating high-acid wastewater from the rare earth industry by recycling hydrochloric acid according to claim 1, characterized in that, The filtration devices in S1-S3 adopt a cross-flow filtration design and are backwashed once every 0.5-1 hours, with a backwash time of 1 minute.

3. An application apparatus for the processing method according to claim 1 or 2, characterized in that, This includes raw water pretreatment equipment, membrane separation equipment, and ion exchange equipment; The membrane separation device includes a primary separation membrane device, a secondary separation membrane device, and a tertiary separation membrane device; The primary separation membrane device is connected to the raw water pretreatment device and receives the raw water delivered by the raw water pretreatment device; The secondary separation membrane device is connected to the primary separation membrane device and the raw water pretreatment device, respectively. It receives the product water treated by the primary separation membrane device and transports the concentrated water separated and retained by the secondary separation membrane device to the raw water pretreatment device. The three-stage separation membrane device is connected to the first-stage separation membrane device and the raw water pretreatment device, respectively. It receives the extractant pollutants separated and retained by the first-stage separation membrane device and transports the treated water from the three-stage separation membrane device to the raw water pretreatment device. The ion exchange device includes a cation exchanger and an anion exchanger; The cation exchanger is connected to the secondary separation membrane device and receives the permeate water treated by the secondary separation membrane device. The anion exchanger is connected to the cation exchanger and receives the permeate water treated by the cation exchanger.

4. The application device according to claim 3, characterized in that, The raw water pretreatment device is equipped with an acid-resistant stirring device. The primary separation membrane device is an acid-resistant, hydrophilic, and oleophobic ultrafiltration membrane filtration device. The membrane material is polyceramic, the shell is glass fiber reinforced plastic, and the molecular weight cutoff is 50-100 kDa. The secondary separation membrane device is an acid-resistant, high-precision nanofiltration membrane filtration device. The membrane material is polyceramic, the shell is glass fiber reinforced plastic, and the molecular weight cutoff is 400-600 Da. The three-stage separation membrane device is an acid- and oil-resistant composite membrane filtration device, and the shell is made of glass fiber reinforced polypropylene. The membrane separation device is equipped with a backwash pump.

5. The application device according to claim 3, characterized in that, The ion exchange device is equipped with an ion exchange regeneration device; The cation exchanger uses a phosphoric acid-based strong acid cation exchange resin, and the anion exchanger uses a styrene-based strong base anion exchange resin.

6. The application device according to claim 3, characterized in that, It also includes wastewater regeneration treatment equipment; The regenerated wastewater treatment device is connected to the cation exchanger and the anion exchanger, and receives the regenerated wastewater treated by the cation exchanger and the anion exchanger.

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