Method for separating and purifying waste boric acid liquid in formed foil waste liquid and concentrating boric acid

Abstract

The invention relates to a method for separating and purifying waste boric acid liquid in formed foil waste liquid and concentrating boric acid, which comprises the following steps: adding ammonia water into the boric acid waste liquid to promote the waste liquid to separate out aluminum hydroxide precipitate, and separating the aluminum hydroxide precipitate from the waste liquid to obtain primary separated liquid; carrying out ultrafiltration on the primary separated liquid, adding boric acid or citric acid, and promoting ammonium pentaborate in the primary separated liquid to be hydrolyzed into boric acid, so as to obtain acidizing fluid; freezing and crystallizing the acidizing fluid until solid boric acid is separated out; and carrying out solid-liquid separation on the precipitated boric acid solid mixed solution, and carrying out vacuum drying or normal-pressure drying on the boric acid solid for recycling. According to the treatment method and system, aluminum and ammonium radicals can be efficiently separated from the aging waste liquid, ammonium pentaborate is converted into boric acid to be efficiently recycled, the environment can be better protected, the purity of the recycled boric acid product and recycling of the recycled boric acid product in the formed foil industry are guaranteed, and the operation cost of an enterprise is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of producing aluminum foil from chemical foil, and in particular to a method for separating and purifying boric acid liquid in chemical foil waste liquid and concentrating boric acid. Background Art

[0002] With the rapid development of the electronics industry, capacitors are increasingly being used. In the chemical foil industry for the production of capacitor aluminum foil, medium and high voltage chemical formation requires the use of a large amount of boric acid of capacitor grade purity as the chemical bath solution. Ammonia or ammonium pentaborate is generally added to the preparation of the bath solution to adjust the pH value. During the production process of chemical foil, a small amount of aluminum on the aluminum foil will continuously dissolve into the bath solution, which will eventually lead to a decrease in chemical efficiency and a decrease in product quality, that is, the bath solution is aged. When the aged bath solution can no longer be used, a new chemical bath solution needs to be prepared, and the aged bath solution can only be treated as waste liquid. However, the aged waste liquid contains a large amount of boric acid and some aluminum ions, which will cause natural water pollution and environmental damage when discharged from the factory, so it is best to separate the relevant substances in the waste liquid for recycling and reuse.

[0003] However, the previous treatment method is to directly heat the boric acid waste liquid to boiling, wait for the boric acid to precipitate after cooling, and then filter the waste liquid to separate and dry it to obtain the boric acid. The disadvantages of the traditional method are: 1. The aluminum and ammonium pentaborate in the waste liquid are not removed, not only the aluminum and ammonium pentaborate cannot be collected and recycled, but also the filtrate will still damage the environment; 2. The ammonium pentaborate in the waste liquid is not separated, resulting in the recovered boric acid being not pure enough due to the residual ammonium pentaborate. The recovered boric acid cannot be recycled in the chemical foil industry, and the treatment is still a big problem; 3. The heating and evaporation cost of the traditional treatment method is too high, which is not economically feasible.

[0004] In view of the above-mentioned deficiencies, a method is urgently needed in the industry to effectively solve the problems of the inability to fully utilize organic matter and aluminum ions in the separation of waste boric acid liquid from waste foil in the traditional method, pollution problems in the production process, and high economic costs. Summary of the invention

[0005] Based on the above analysis, the purpose of the present invention is to provide a method for separating and purifying waste boric acid liquid and concentrating boric acid in aluminum foil waste liquid, which solves the problems of high aluminum content and high organic content in aluminum foil aluminum foil boric acid waste liquid, and realizes closed-loop clean production of aluminum foil. The method uses ultrafiltration membrane to separate aluminum ions and macromolecular organic matter, nanofiltration membrane to separate small molecular organic matter and dialyze dilute boric acid at the same time, uses nanofiltration membrane to dialyze dilute boric acid, and reverse osmosis membrane to concentrate dilute boric acid, and simultaneously obtains purified boric acid concentrated solution. In the process, the reverse osmosis membrane filtrate is recycled, forming a closed-loop clean production process for aluminum foil.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for separating and purifying waste boric acid liquid in chemical foil waste liquid and concentrating boric acid, comprising the following steps:

[0008] S1. Pre-treating the waste boric acid stock solution of the formed foil, and filtering the waste boric acid stock solution through a bag filter to remove the residual solids and insoluble impurities in the liquid;

[0009] S2. The effluent after slag removal is sent to CMF equipment for clarification and filtration to remove bacteria, microorganisms and other impurities in the feed liquid to ensure the suspended matter and turbidity index of the membrane system inlet water;

[0010] The clarified liquid obtained from S3 and S2 is fed into the CUF1 device to remove and intercept macromolecular organic matter to prevent the macromolecular organic matter from affecting the boric acid product;

[0011] S4, adding ammonia water to the CUF1 permeable water to promote the precipitation of aluminum hydroxide precipitate from the waste liquid, and the precipitate containing the aluminum hydroxide precipitate mixed solution enters the CUF2 equipment and separates the aluminum hydroxide precipitate from the waste liquid to obtain the primary liquid separation;

[0012] S5, using the initial fractionated liquid as the comprehensive inlet liquid of nanofiltration system 1, controlling the inlet pressure at 2.5-3.5 MPa and the temperature at 25-40°C, obtaining the dilute liquid of nanofiltration system 1 and the concentrated liquid of nanofiltration system 1, transferring the concentrated liquid of nanofiltration system 1 to nanofiltration system 2 for purification, obtaining the purified dilute liquid of nanofiltration system 2 and the concentrated liquid of nanofiltration system 2, and returning the concentrated liquid of nanofiltration system 2 to S4 for continuous circulation and impurity removal;

[0013] S6, according to the preset concentration concentration of the system, the inlet pressure and temperature are adjusted, and the light liquid of the nanofiltration system 2 and the purified boric acid light liquid in S5 are passed through the primary reverse osmosis pre-concentration system to obtain the primary reverse osmosis concentrated liquid and the primary reverse osmosis light liquid, and the effluent is controlled to meet the internal circulation water standard, and the effluent is returned to the nanofiltration system 2 through the water storage tank for water replenishment in the dialysis process;

[0014] S7, adjusting the liquid inlet pressure to 3.5-5.5Mpa and the temperature to 30-45°C, allowing the primary reverse osmosis concentrated solution to enter the secondary reverse osmosis system for concentration, obtaining a secondary reverse osmosis dilute solution and a secondary reverse osmosis concentrated solution, freezing and crystallizing the secondary reverse osmosis concentrated solution until solid boric acid is precipitated, centrifuging the precipitated solid boric acid mixed solution, vacuum drying or drying at normal pressure, and recycling the boric acid solid for reuse;

[0015] S8. Mix the S6 dilute liquid and the S7 dilute liquid and return them to the comprehensive liquid inlet storage tank as the comprehensive liquid inlet of the three-stage reverse osmosis system for circulating separation water to recover residual boric acid. The concentrated liquid returns to the S6 raw liquid tank, and the dilute liquid is used as the dialysate water replenishment of the nanofiltration system 2 or returned to the enterprise to make ultrapure water.

[0016] Furthermore, the comprehensive inlet liquid of the nanofiltration system 1 is a mixture of a small amount of aluminum, boric acid, ammonium pentaborate, water, etc.; the dialysate of the nanofiltration system 2 is a boric acid solution, and the concentrated solution is a mixture of a small amount of aluminum, a small amount of boric acid, ammonium pentaborate, water, etc.; the reverse osmosis concentrated solution is a solution mainly composed of boric acid, and the concentrated solution of the secondary reverse osmosis system is a 5%-8% boric acid solution.

[0017] Furthermore, the membrane system comprises: a raw liquid storage tank (1), a bag filtration system (2), a filtration collection tank (3), a CMF system (4), a CMF collection tank (5), a CUF1 system (6), a CUF1 concentrated liquid collection tank (7), a CUF1 dilute liquid collection tank (8), a CUF2 system (9), a CUF2 concentrated and dilute liquid collection tank (10), a first-stage nanofiltration system (11), a second-stage nanofiltration system (12), a first-stage nanofiltration system concentrated liquid collection tank (13), a first-stage nanofiltration system dilute liquid collection tank (14), a first-stage pre-concentration reverse osmosis system (15), a first-stage pre-concentration reverse osmosis system concentrated liquid collection tank (16), a first-stage pre-concentration reverse osmosis system dilute liquid collection tank (17), a second-stage ultra-high pressure concentration reverse osmosis system (18), a second-stage ultra-high pressure concentration reverse osmosis system concentrated liquid collection tank (19), a third-stage reverse osmosis system (20), and a reverse osmosis concentrated and dilute liquid collection pipe storage tank.

[0018] Furthermore, the raw liquid storage tank (1) is connected to the bag filter system (2), and the bag filter system (2) includes a centrifugal pump, a regulating valve a, a sensor a, and a flow element a connected by pipelines; the filter collection tank (3) is connected to the CMF system (4), and the CMF system (4) includes a centrifugal pump, a regulating valve b, a sensor b, and a flow element b connected by pipelines; the CMF collection tank (5) is connected to the CUF1 system (6) and the CUF2 system (9), and the CUF1 system (6) and the CUF2 system (9) include a centrifugal pump, a regulating valve c, a sensor c, and a flow element c connected by pipelines; the CUF2 dilute liquid collection tank is connected to the nanofiltration system 1, and the nanofiltration system 1 includes a power pump, a regulating valve d, a sensor d, a flow element d, a nanofiltration membrane of the nanofiltration system 1, a concentrated liquid storage tank of the nanofiltration system 1, and a dilute liquid storage tank of the nanofiltration system 1; the concentrated liquid storage tank of the nanofiltration system 1 is connected to the nanofiltration system 2, and the nanofiltration system (2 includes a A power pump, a regulating valve e, a sensor e, a flow element e, a nanofiltration system 2 nanofiltration membrane, a concentrated liquid storage tank of the nanofiltration system 2, and a dilute liquid storage tank of the nanofiltration system 2; the first-level reverse osmosis pre-concentration system is connected to the filtrate storage tank of the nanofiltration system 1, and the first-level reverse osmosis pre-concentration system includes a power pump, a regulating valve f, a sensor f, a flow element f, a high-pressure reverse osmosis membrane, a first-level reverse osmosis pre-concentrated liquid storage tank, and a water storage tank connected by pipelines; the second-level reverse osmosis ultra-high pressure concentration system is connected to the first-level reverse osmosis pre-concentrated liquid storage tank, and the second-level reverse osmosis ultra-high pressure concentration system includes a power pump, a regulating valve g, a sensor g, a flow element g, an ultra-high pressure reverse osmosis membrane, a second-level reverse osmosis concentrated liquid storage tank, and a water storage tank connected by pipelines; the third-level reverse osmosis purification system is connected to the water storage tank, and the third-level reverse osmosis purification system includes a power pump, a regulating valve h, a sensor h, a flow element h, a high-pressure reverse osmosis membrane, a third-level reverse osmosis concentrated liquid storage tank, and a pure water tank 17 connected by pipelines, and the pure water tank is also connected to the nanofiltration system 2.

[0019] Furthermore, the sensors a~c include: temperature sensors a~c, pressure sensors a~c, PH meters a~c, conductivity meters a~c, and liquid level meters a~c; the sensors d and e include: temperature sensors d and e, pressure sensors d and e, conductivity meters d and e, and liquid level meters d and e; the sensors f~h include: temperature sensors f~h, pressure sensors f~h, PH meters f~h, conductivity meters f~h, and liquid level meters f~h; the sensors a~h, regulating valves a~h, and flow elements a~h are electrically connected to the control system.

[0020] Furthermore, the ultrafiltration membrane used in the CUF system adopts an online cleaning method, the working temperature is 10-60°C, the working pressure is less than 60bar, and the molecular retention capacity of the ultrafiltration membrane is 5000-30000Da.

[0021] Furthermore, the reverse osmosis membrane used in the membrane system is an acid-resistant high-pressure reverse osmosis membrane, and the nanofiltration membrane of the nanofiltration system 1 and the nanofiltration membrane of the nanofiltration system 2 are acid-resistant high-pressure nanofiltration membranes.

[0022] Furthermore, when the nanofiltration system 1 is used for separation and purification of the boric acid solution by dialysis, the inlet pressure is 2.5-3.5 MPa and the temperature is 25-40°C.

[0023] Furthermore, when the nanofiltration system 2 is used for boric acid purification and dialysis purification, the inlet pressure is 3.5-5.5 MPa and the temperature is 30-45°C.

[0024] Furthermore, when the first-stage reverse osmosis pre-concentration system is used for pre-concentration of boric acid, the inlet pressure is 3.5-5.5 MPa and the temperature is 25-40°C.

[0025] Furthermore, when the boric acid is concentrated using a two-stage reverse osmosis ultra-high pressure concentration system, the inlet pressure is 4.5-8.5 MPa and the temperature is 35-45°C.

[0026] Furthermore, when the three-stage reverse osmosis purification system is used to purify and concentrate the dilute liquid, the inlet pressure is 2.5-4.5Mpa and the temperature is 25-35°C.

[0027] Furthermore, the boric acid content in the boric acid solution obtained in step S5 is greater than 11.5 g / l.

[0028] Furthermore, the boric acid solution obtained in step S7 has a concentration of 103.9 g / l or more.

[0029] The beneficial effects of the present invention are:

[0030] (1) The membrane technology can be used to separate organic matter and reduce the aluminum ion content in the boric acid of the formed foil. During the concentration process, the boric acid will be separated from the water permeable side, and the concentration of the concentrated boric acid will increase less. Then, the water-adding dialysis method can be used to further separate the aluminum ions and boric acid without reducing the boric acid content, thereby achieving the purpose of concentrating aluminum, organic matter and separating boric acid.

[0031] (2) The membrane treatment system in the process of the present invention is customized in scale according to the production line and can be matched with continuous industrial production. The system process is simple and the treatment efficiency is high. The system adopts integrated intelligent control; integrated control method: each system is an independent skid-mounted unit. By controlling the programming logic of the CPU and monitoring the feedback values ​​such as pressure, flow, temperature, pH, concentration, pump frequency, valve opening, etc., the system program automatically controls and adjusts the real-time operating value according to the set target value to achieve the production target; the system has a high degree of control automation and precise automatic adjustment, and realizes paperless office and unattended operation in the workshop.

[0032] (3) The permeate in the nanofiltration system 1 and 2 process uses a multi-stage reverse osmosis system to concentrate boric acid to a boric acid content of 103.9 g / l, thereby achieving the purpose of recovering boric acid. The concentrated permeate can be directly reused in the nanofiltration dialysis process section, thereby improving the utilization rate of water resources, purifying water resources for reuse, achieving zero discharge of the project, and generating good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a schematic diagram of the system structure, wherein: a raw liquid storage tank (1), a bag filter system (2), a filter collection tank (3), a CMF system (4), a CMF collection tank (5), a CUF1 system (6), a CUF1 concentrated liquid collection tank (7), a CUF1 dilute liquid collection tank (8), a CUF2 system (9), a CUF2 concentrated and dilute liquid collection tank (10), a first-stage nanofiltration system (11), a second-stage nanofiltration system (12), a first-stage nanofiltration system concentrated liquid collection tank (13), a first-stage nanofiltration system dilute liquid collection tank (14), a first-stage pre-concentration reverse osmosis system (15), a first-stage pre-concentration reverse osmosis system concentrated liquid collection tank (16), a first-stage pre-concentration reverse osmosis system dilute liquid collection tank (17), a second-stage ultra-high pressure concentration reverse osmosis system (18), a second-stage ultra-high pressure concentration reverse osmosis system concentrated liquid collection tank (19), and a third-stage reverse osmosis system (20). DETAILED DESCRIPTION

[0034] As shown in the figure, the membrane system includes a raw liquid storage tank, a bag filtration system, a filtration collection tank, a CMF system, a CMF collection tank, a CUF1 system, a CUF1 concentrated and thin liquid collection tank, a CUF2 system, a CUF2 concentrated and thin liquid collection tank, a nanofiltration system 1, a nanofiltration system 2, a nanofiltration system concentrated and thin liquid collection tank, a first-level pre-concentration reverse osmosis system, a second-level ultra-high pressure concentration reverse osmosis system, a third-level reverse osmosis system, and a reverse osmosis concentrated and thin liquid collection pipe storage tank; the raw liquid storage tank is connected to the bag filtration system, and the bag filtration system includes a centrifugal pump connected by a pipeline, a regulating valve a, a sensor a, Flow element a; the filtration collection tank is connected to the CMF system, and the CMF system includes a centrifugal pump, a regulating valve b, a sensor b, and a flow element b connected by pipelines; the CMF collection tank is connected to the CUF1 and CUF2 systems, and the CUF1 and CUF2 systems include a centrifugal pump, a regulating valve c, a sensor c, and a flow element c connected by pipelines; the CUF2 dilute liquid collection tank is connected to the nanofiltration system 1, and the nanofiltration system 1 includes a power pump, a regulating valve d, a sensor d, a flow element d, a nanofiltration membrane, and a nanofiltration system 1 connected by pipelines. A concentrated liquid storage tank and a dilute liquid storage tank of the nanofiltration system 1; the concentrated liquid storage tank of the nanofiltration system 1 is connected to the nanofiltration system 2, and the nanofiltration system 2 includes a power pump, a regulating valve e, a sensor e, a flow element e, a nanofiltration membrane of the nanofiltration system 2, a concentrated liquid storage tank of the nanofiltration system 2, and a dilute liquid storage tank of the nanofiltration system 2 connected by pipelines; the primary reverse osmosis pre-concentration system is connected to the filtrate storage tank of the nanofiltration system 1, and the primary reverse osmosis pre-concentration system includes a power pump, a regulating valve f, a sensor f, a flow element f, a high-pressure reverse osmosis membrane, a primary reverse osmosis pre-concentrated liquid storage tank, and a water storage tank connected by pipelines ; The secondary reverse osmosis ultra-high pressure concentration system is connected to the primary reverse osmosis pre-concentrated liquid storage tank, and the secondary reverse osmosis ultra-high pressure concentration system includes a power pump, a regulating valve g, a sensor g, a flow element g, an ultra-high pressure reverse osmosis membrane, a secondary reverse osmosis concentrated liquid storage tank, and a water storage tank connected by pipelines; the tertiary reverse osmosis purification system is connected to the water storage tank, and the tertiary reverse osmosis purification system includes a power pump, a regulating valve h, a sensor h, a flow element h, a high pressure reverse osmosis membrane, a tertiary reverse osmosis concentrated liquid storage tank, and a pure water tank connected by pipelines, and the pure water tank is also connected to the nanofiltration system 2.

[0035] The present invention provides a method for separating and purifying waste boric acid liquid in chemical foil waste liquid and concentrating boric acid, comprising the following steps:

[0036] S1. Pre-treating the waste boric acid stock solution of the formed foil, and filtering the waste boric acid stock solution through a bag filter to remove the residual solids and insoluble impurities in the liquid;

[0037] S2. The effluent after slag removal is sent to CMF equipment for clarification and filtration to remove bacteria, microorganisms and other impurities in the feed liquid to ensure the suspended solids and turbidity index of the membrane system influent water, turbidity <0.1NTU;

[0038] S3, the clarified liquid enters CUF1 equipment to remove and intercept macromolecular organic matter to prevent the influence of macromolecular organic matter on the boric acid product. The online cleaning method is adopted, the working temperature is 10-60℃, the working pressure is less than 60bar, and the ultrafiltration membrane molecular retention capacity is 5000-30000Da;

[0039] S4, adding ammonia water to the CUF1 permeable water to promote the precipitation of aluminum hydroxide precipitate in the waste liquid, the precipitate containing aluminum hydroxide precipitate mixed solution enters CUF2 and separates aluminum hydroxide precipitate from the waste liquid to obtain primary liquid separation, adopting online cleaning method, working temperature of 10-60°C, working pressure <60bar, ultrafiltration membrane molecular retention capacity of 5000-30000Da;

[0040] S5, taking the initial fractionated liquid as the comprehensive inlet liquid of nanofiltration system 1, controlling the inlet liquid pressure and temperature, obtaining the dilute liquid of nanofiltration system 1 and the concentrated liquid of nanofiltration system 1, allowing the concentrated liquid of nanofiltration system 1 to enter nanofiltration system 2 for purification, obtaining the purified dilute liquid of nanofiltration system 2 and the concentrated liquid of nanofiltration system 2, and the concentrated liquid of nanofiltration system 2 returns to S4 for continuous circulation and impurity removal, with an operating pressure of 2.5-5.5Mpa and a temperature of 25-45°C;

[0041] S6, according to the preset concentration of the system, adjust the inlet pressure and temperature, and pass the dialysate of the nanofiltration system 2 and the purified boric acid dilute liquid in S5 through the primary reverse osmosis pre-concentration system to obtain the primary reverse osmosis concentrate and the primary reverse osmosis dilute liquid, and control the effluent to meet the internal circulation water standard and return to the nanofiltration system 2 dialysis process through the water storage tank for water replenishment, with an operating pressure of 2.5-8.5Mpa and a temperature of 25-45°C;

[0042] S7, adjusting the inlet pressure and temperature, so that the primary reverse osmosis concentrated solution enters the secondary reverse osmosis system for concentration, and obtains the secondary reverse osmosis dilute solution and the secondary reverse osmosis concentrated solution, and the secondary reverse osmosis concentrated solution is subjected to freeze crystallization until solid boric acid is precipitated, and the precipitated solid boric acid mixed solution is centrifuged, and the boric acid solid is vacuum dried or dried at normal pressure, and recycled for reuse, with an operating pressure of 2.5-8.5Mpa and a temperature of 25-45°C;

[0043] S8. Mix the S6 dilute liquid and S7 dilute liquid and return them to the comprehensive liquid inlet storage tank as the comprehensive liquid inlet of the three-stage reverse osmosis system for circulating separation of water to recover residual boric acid. The concentrated liquid returns to the S6 original liquid tank, and the dilute liquid is used as the dialysate water for the nanofiltration system 2 or returned to the company to make ultrapure water. The operating pressure is 2.5-8.5Mpa and the temperature is 25-45℃.

[0044] The ultrafiltration membrane involved in this process uses 5000-30000Da imported membrane components.

[0045] This process involves membrane concentration and membrane purification systems using imported acid-resistant high-pressure nanofiltration membranes and imported ultra-high-pressure reverse osmosis membrane elements.

[0046] Example 1

[0047] S1. Pre-treat the waste boric acid stock solution of the foil, and the waste boric acid stock solution enters the bag filter for slag removal and filtration to remove the residual solids and insoluble impurities in the liquid, with a filtration accuracy of 0.45-5um;

[0048] S2. The effluent after slag removal is sent to CMF equipment for clarification and filtration to remove bacteria, microorganisms and other impurities in the feed liquid to ensure the suspended solids and turbidity index of the membrane system influent water, turbidity <0.1NTU;

[0049] S3, the clarified liquid enters CUF1 equipment to remove and intercept macromolecular organic matter to prevent the influence of macromolecular organic matter on the boric acid product. The online cleaning method is adopted, the working temperature is 10-60℃, the working pressure is less than 60bar, and the ultrafiltration membrane molecular retention capacity is 20000Da;

[0050] S4, adding ammonia water to the CUF1 permeate, pH = 7.01, to promote the precipitation of aluminum hydroxide precipitate in the waste liquid, the precipitate containing aluminum hydroxide precipitate mixed solution enters CUF2 and separates aluminum hydroxide precipitate from the waste liquid to obtain the primary separation liquid, the ultrafiltration membrane molecular retention capacity is 5000Da;

[0051] S5, taking the initial fractionated liquid as the comprehensive inlet liquid of nanofiltration system 1, controlling the inlet pressure and temperature, obtaining the dilute liquid of nanofiltration system 1 and the concentrated liquid of nanofiltration system 1, making the concentrated liquid of nanofiltration system 1 enter nanofiltration system 2 for purification, obtaining the purified dilute liquid of nanofiltration system 2 and the concentrated liquid of nanofiltration system 2, and the concentrated liquid of nanofiltration system 2 returns to S4 for continuous circulation and impurity removal, with an operating pressure of 2.6 MPa and a temperature of 25-40°C;

[0052] S6, according to the preset concentration of the system, adjust the inlet pressure and temperature, and pass the dialysate of the nanofiltration system 2 and the purified boric acid dilute liquid in S5 through the primary reverse osmosis pre-concentration system to obtain the primary reverse osmosis concentrate and the primary reverse osmosis dilute liquid, and control the effluent to meet the internal circulation water standard and return to the nanofiltration system 2 dialysis process through the water storage tank for water replenishment, with an operating pressure of 4.0Mpa and a temperature of 30-45°C;

[0053] S7, adjusting the inlet pressure and temperature, so that the primary reverse osmosis concentrated solution enters the secondary reverse osmosis system for concentration, and obtains the secondary reverse osmosis dilute solution and the secondary reverse osmosis concentrated solution, and the secondary reverse osmosis concentrated solution is subjected to freeze crystallization until solid boric acid is precipitated, and the precipitated solid boric acid mixed solution is centrifuged, and the boric acid solid is vacuum dried or dried at normal pressure, and recycled for reuse, with an operating pressure of 6.3 MPa and a temperature of 35-45° C.;

[0054] S8. Mix the S6 dilute liquid and S7 dilute liquid and return them to the comprehensive liquid inlet storage tank as the comprehensive liquid inlet of the three-stage reverse osmosis system for circulating separation water to recover residual boric acid. The concentrated liquid returns to the S6 original liquid tank, and the dilute liquid is used as the dialysate replenishment of the nanofiltration system 2 or returned to the company to make ultrapure water. The operating pressure is 2.5Mpa and the temperature is 25-35℃.

[0055] Example 2

[0056] S1. Pre-treat the waste boric acid stock solution of the foil, and the waste boric acid stock solution enters the bag filter for slag removal and filtration to remove the residual solids and insoluble impurities in the liquid, with a filtration accuracy of 0.45-5um;

[0057] S2. The effluent after slag removal is sent to CMF equipment for clarification and filtration to remove bacteria, microorganisms and other impurities in the feed liquid to ensure the suspended solids and turbidity index of the membrane system influent water, turbidity <0.1NTU;

[0058] S3, the clarified liquid enters CUF1 equipment to remove and intercept macromolecular organic matter to prevent the influence of macromolecular organic matter on the boric acid product. The online cleaning method is adopted, the working temperature is 10-60℃, the working pressure is less than 60bar, and the ultrafiltration membrane molecular retention capacity is 10000Da;

[0059] S4, adding ammonia water to the CUF1 permeate, pH = 6.8, to promote the precipitation of aluminum hydroxide precipitate in the waste liquid, the precipitate containing aluminum hydroxide precipitate mixed solution enters CUF2 and separates aluminum hydroxide precipitate from the waste liquid to obtain the primary separation liquid, the ultrafiltration membrane molecular retention capacity is 8000Da;

[0060] S5, taking the initial fractionated liquid as the comprehensive inlet liquid of nanofiltration system 1, controlling the inlet pressure and temperature, obtaining the dilute liquid of nanofiltration system 1 and the concentrated liquid of nanofiltration system 1, allowing the concentrated liquid of nanofiltration system 1 to enter nanofiltration system 2 for purification, obtaining the purified dilute liquid of nanofiltration system 2 and the concentrated liquid of nanofiltration system 2, and the concentrated liquid of nanofiltration system 2 returns to S4 for continuous circulation and impurity removal, with an operating pressure of 3.0 MPa and a temperature of 25-40°C;

[0061] S6, according to the preset concentration of the system, adjust the inlet pressure and temperature, and pass the dialysate of the nanofiltration system 2 and the purified boric acid dilute liquid in S5 through the primary reverse osmosis pre-concentration system to obtain the primary reverse osmosis concentrate and the primary reverse osmosis dilute liquid, and control the effluent to meet the internal circulation water standard and return to the nanofiltration system 2 dialysis process through the water storage tank for water replenishment, with an operating pressure of 5.0Mpa and a temperature of 30-45°C;

[0062] S7, adjusting the inlet pressure and temperature, so that the primary reverse osmosis concentrated solution enters the secondary reverse osmosis system for concentration, and obtains the secondary reverse osmosis dilute solution and the secondary reverse osmosis concentrated solution, and the secondary reverse osmosis concentrated solution is subjected to freeze crystallization until solid boric acid is precipitated, and the precipitated solid boric acid mixed solution is centrifuged, and the boric acid solid is vacuum dried or dried at normal pressure, and recovered for reuse, with an operating pressure of 8.0 MPa and a temperature of 35-45° C.;

[0063] S8. Mix the S6 dilute liquid and S7 dilute liquid and return them to the comprehensive liquid inlet storage tank as the comprehensive liquid inlet of the three-stage reverse osmosis system for circulating separation water to recover residual boric acid. The concentrated liquid returns to the S6 raw liquid tank, and the dilute liquid is used as the dialysate water for the nanofiltration system 2 or returned to the company to make ultrapure water. The operating pressure is 3.0Mpa and the temperature is 25-35℃.

[0064] Example 3

[0065] S1. Pre-treat the waste boric acid stock solution of the foil, and the waste boric acid stock solution enters the bag filter for slag removal and filtration to remove the residual solids and insoluble impurities in the liquid, with a filtration accuracy of 0.45-5um;

[0066] S2. The effluent after slag removal is sent to CMF equipment for clarification and filtration to remove bacteria, microorganisms and other impurities in the feed liquid to ensure the suspended solids and turbidity index of the membrane system influent water, turbidity <0.1NTU;

[0067] S3, the clarified liquid enters CUF1 equipment to remove and intercept macromolecular organic matter to prevent the influence of macromolecular organic matter on the boric acid product. The online cleaning method is adopted, the working temperature is 10-60℃, the working pressure is less than 60bar, and the ultrafiltration membrane molecular retention capacity is 30000Da;

[0068] S4, adding ammonia water to the CUF1 permeate, pH = 7.4, to promote the precipitation of aluminum hydroxide precipitate in the waste liquid, the precipitate containing aluminum hydroxide precipitate mixed solution enters CUF2 and separates aluminum hydroxide precipitate from the waste liquid to obtain the primary separation liquid, the ultrafiltration membrane molecular retention capacity is 6000Da;

[0069] S5, taking the initial fractionated liquid as the comprehensive inlet liquid of nanofiltration system 1, controlling the inlet pressure and temperature, obtaining the dilute liquid of nanofiltration system 1 and the concentrated liquid of nanofiltration system 1, allowing the concentrated liquid of nanofiltration system 1 to enter nanofiltration system 2 for purification, obtaining the purified dilute liquid of nanofiltration system 2 and the concentrated liquid of nanofiltration system 2, and the concentrated liquid of nanofiltration system 2 returns to S4 for continuous circulation and impurity removal, with an operating pressure of 2.7 MPa and a temperature of 25-40°C;

[0070] S6, according to the preset concentration of the system, adjust the inlet pressure and temperature, and pass the dialysate of the nanofiltration system 2 and the purified boric acid dilute liquid in S5 through the primary reverse osmosis pre-concentration system to obtain the primary reverse osmosis concentrate and the primary reverse osmosis dilute liquid, and control the effluent to meet the internal circulation water standard and return to the nanofiltration system 2 dialysis process through the water storage tank for water replenishment, with an operating pressure of 3.5Mpa and a temperature of 30-45°C;

[0071] S7, adjusting the inlet pressure and temperature, so that the primary reverse osmosis concentrated solution enters the secondary reverse osmosis system for concentration, and obtains the secondary reverse osmosis dilute solution and the secondary reverse osmosis concentrated solution, and the secondary reverse osmosis concentrated solution is subjected to freeze crystallization until solid boric acid is precipitated, and the precipitated solid boric acid mixed solution is centrifuged, and the boric acid solid is vacuum dried or dried at normal pressure, and recycled for reuse, with an operating pressure of 7.5 MPa and a temperature of 35-45° C.;

[0072] S8. Mix the S6 dilute liquid and S7 dilute liquid and return them to the comprehensive liquid inlet storage tank as the comprehensive liquid inlet of the three-stage reverse osmosis system for circulating separation water to recover residual boric acid. The concentrated liquid returns to the S6 original liquid tank, and the dilute liquid is used as the dialysate water for the nanofiltration system 2 or returned to the company to make ultrapure water. The operating pressure is 4.0Mpa and the temperature is 25-35℃.

[0073] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for separating and purifying waste boric acid liquid in chemical foil waste liquid and concentrating boric acid, comprising: S1, pre-treating the waste boric acid stock solution of the foil, and the waste boric acid stock solution enters the bag filter for slag removal and filtration to remove impurities in the feed liquid; S2. The effluent after slag removal is sent to CMF equipment for clarification and filtration to remove bacteria and microorganisms in the feed liquid, ensuring that the suspended solids and turbidity of the membrane system influent water are less than 0.1NTU; S3, the clarified liquid enters the CUF1 equipment to remove and intercept macromolecular organic matter, and obtains CUF1 permeable water; S4, adding ammonia water to the permeable water of CUF1, the mixed solution containing aluminum hydroxide precipitate in the precipitate enters the CUF2 equipment and separates the aluminum hydroxide precipitate from the waste liquid to obtain the primary separation liquid; S5, using the initial fractionated liquid as the comprehensive inlet liquid of nanofiltration system 1, controlling the inlet pressure at 2.5-3.5 MPa and the temperature at 25-40°C, obtaining the dilute liquid of nanofiltration system 1 and the concentrated liquid of nanofiltration system 1, transferring the concentrated liquid of nanofiltration system 1 to nanofiltration system 2 for purification, obtaining the purified dilute liquid of nanofiltration system 2 and the concentrated liquid of nanofiltration system 2, and returning the concentrated liquid of nanofiltration system 2 to S4 for continuous circulation and impurity removal; S6, according to the preset concentration concentration of the system, the inlet pressure and temperature are adjusted, and the light liquid of the nanofiltration system 2 and the purified boric acid light liquid in S5 are passed through the primary reverse osmosis pre-concentration system to obtain the primary reverse osmosis concentrated liquid and the primary reverse osmosis light liquid, and the effluent is controlled to meet the internal circulation water standard, and the effluent is returned to the nanofiltration system 2 through the water storage tank for water replenishment in the dialysis process; S7, adjusting the liquid inlet pressure to 3.5-5.5Mpa and the temperature to 30-45°C, allowing the primary reverse osmosis concentrate to enter the secondary reverse osmosis system for concentration, obtaining a secondary reverse osmosis dilute solution and a secondary reverse osmosis concentrate, freezing and crystallizing the secondary reverse osmosis concentrate until solid boric acid is precipitated, centrifuging the precipitated solid boric acid mixed solution, vacuum drying or drying at normal pressure, and recycling the boric acid solid for reuse; S8. Mix the S6 dilute liquid and the S7 dilute liquid and return them to the comprehensive liquid inlet storage tank as the comprehensive liquid inlet of the three-stage reverse osmosis system for circulating separation water to recover residual boric acid. The concentrated liquid returns to the S6 raw liquid tank, and the dilute liquid is used as the dialysate water replenishment of the nanofiltration system 2 or returned to the enterprise to make ultrapure water.

2. The method according to claim 1, wherein: The nanofiltration system 1 has a comprehensive influent comprising a mixed solution of aluminum, boric acid, ammonium pentaborate and water; The dialysate of the nanofiltration system 2 is boric acid solution; The concentrated solution comprises: a mixture of aluminum, boric acid, ammonium pentaborate and water; The reverse osmosis concentrate comprises: a boric acid solution; The concentrated solution of the secondary reverse osmosis system is a 5%-8% boric acid solution.

3. The method according to claim 1, wherein: The membrane system comprises: a raw liquid storage tank (1), a bag filtration system (2), a filtration collection tank (3), a CMF system (4), a CMF collection tank (5), a CUF1 system (6), a CUF1 concentrated liquid collection tank (7), a CUF1 dilute liquid collection tank (8), a CUF2 system (9), a CUF2 concentrated and dilute liquid collection tank (10), a first-stage nanofiltration system (11), a second-stage nanofiltration system (12), a first-stage nanofiltration system concentrated liquid collection tank (13), a first-stage nanofiltration system dilute liquid collection tank (14), a first-stage pre-concentration reverse osmosis system (15), a first-stage pre-concentration reverse osmosis system concentrated liquid collection tank (16), a first-stage pre-concentration reverse osmosis system dilute liquid collection tank (17), a second-stage ultra-high pressure concentration reverse osmosis system (18), a second-stage ultra-high pressure concentration reverse osmosis system concentrated liquid collection tank (19), a third-stage reverse osmosis system (20), and a reverse osmosis concentrated and dilute liquid collection pipe storage tank.

4. The method according to claim 3, wherein: The raw liquid storage tank (1) is connected to the bag filter system (2); The bag filter system (2) comprises a centrifugal pump, a regulating valve a, a sensor a, and a flow element a connected by pipelines; the filter collection tank (3) is connected to the CMF system (4), and the CMF system (4) comprises a centrifugal pump, a regulating valve b, a sensor b, and a flow element b connected by pipelines; The CMF collection tank (5) is connected to the CUF1 system (6) and the CUF2 system (9); The CUF1 system (6) and the CUF2 system (9) include a centrifugal pump, a regulating valve c, a sensor c, and a flow element c connected by pipelines; The CUF2 dilute liquid collection tank is connected to the nanofiltration system 1, and the nanofiltration system 1 includes a power pump, a regulating valve d, a sensor d, a flow element d, a nanofiltration membrane of the nanofiltration system 1, a concentrated liquid storage tank of the nanofiltration system 1, and a dilute liquid storage tank of the nanofiltration system 1 connected by pipelines; The concentrated liquid storage tank of the nanofiltration system 1 is connected to the nanofiltration system 2, and the nanofiltration system 2 includes a power pump, a regulating valve e, a sensor e, a flow element e, a nanofiltration membrane of the nanofiltration system 2, a concentrated liquid storage tank of the nanofiltration system 2, and a dilute liquid storage tank of the nanofiltration system 2 connected by pipelines; The primary reverse osmosis pre-concentration system is connected to the filtrate storage tank of the nanofiltration system 1; The primary reverse osmosis pre-concentration system includes a power pump, a regulating valve f, a sensor f, a flow element f, a high-pressure reverse osmosis membrane, a primary reverse osmosis pre-concentrated liquid storage tank, and a water storage tank connected by pipelines; The secondary reverse osmosis ultra-high pressure concentration system is connected to the primary reverse osmosis pre-concentrated liquid storage tank, and the secondary reverse osmosis ultra-high pressure concentration system includes a power pump, a regulating valve g, a sensor g, a flow element g, an ultra-high pressure reverse osmosis membrane, a secondary reverse osmosis concentrated liquid storage tank, and a water storage tank connected by pipelines; The three-stage reverse osmosis purification system is connected to the water storage tank, and the three-stage reverse osmosis purification system includes a power pump, a regulating valve h, a sensor h, a flow element h, a high-pressure reverse osmosis membrane, a three-stage reverse osmosis concentrate storage tank, and a pure water tank 17 connected by pipelines; The pure water tank is also connected to the nanofiltration system 2.

5. The method according to claim 4, wherein: The sensors a~c include: temperature sensors a~c, pressure sensors a~c, PH meters a~c, conductivity meters a~c, and liquid level meters a~c; The sensors d and e include: temperature sensors d and e, pressure sensors d and e, conductivity meters d and e, and liquid level meters d and e; The sensors f~h include: temperature sensors f~h, pressure sensors f~h, PH meters f~h, conductivity meters f~h, and liquid level meters f~h; The sensors a~h, regulating valves a~h, and flow elements a~h are electrically connected to the control system.

6. The method according to claim 3, wherein: The ultrafiltration membrane used in the CUF system adopts an online cleaning method, with an operating temperature of 10-60°C, an operating pressure of <60bar, and an ultrafiltration membrane molecular retention capacity of 5000-30000Da; The reverse osmosis membrane used in the membrane system is an acid-resistant high-pressure reverse osmosis membrane, and the nanofiltration membranes of the nanofiltration system 1 and the nanofiltration membranes of the nanofiltration system 2 are acid-resistant high-pressure nanofiltration membranes.

7. The method according to claim 3, wherein: When the nanofiltration system 1 is used for boric acid solution separation and dialysis purification, the liquid inlet pressure is 2.5-3.5Mpa and the temperature is 25-40°C; when the nanofiltration system 2 is used for boric acid purification and dialysis purification, the liquid inlet pressure is 3.5-5.5Mpa and the temperature is 30-45°C; when the first-stage reverse osmosis pre-concentration system is used for boric acid pre-concentration, the liquid inlet pressure is 3.5-5.5Mpa and the temperature is 25-40°C; when the second-stage reverse osmosis ultra-high pressure concentration system is used for boric acid concentration, the liquid inlet pressure is 4.5-8.5Mpa and the temperature is 35-45°C; when the third-stage reverse osmosis purification system is used for dilute liquid purification and concentration, the liquid inlet pressure is 2.5-4.5Mpa and the temperature is 25-35°C.

8. The method according to claim 1, wherein: The boric acid content in the boric acid solution obtained in step S5 reaches above 11.5 g / l.

9. The method according to claim 1, wherein: The concentration of the boric acid solution obtained in step S7 reaches above 103.9 g / l.

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