Integrated membrane separation device

Abstract

The utility model belongs to the field of valuable metal recovery, and relates to an integrated membrane separation device capable of improving the valuable metal recovery rate and an operation method. Monovalent and multivalent cations are separated through a selectively separated semi-permeable membrane, meanwhile, in the process of concentrating a monovalent valuable metal solution by using an acid-permeable reverse osmosis membrane, acid-containing water flows back to a front-end process in a water permeation stage to realize recycling of acid and water, and meanwhile, the high recovery rate of monovalent valuable metal or cations is ensured; therefore, high recovery rate, stable operation and recycling of acid and water of the whole membrane system are realized.

Description

Technical Field

[0001] The utility model relates to the field of valuable metal recovery, and particularly to an integrated membrane separation device and an operation method thereof which can be used to improve the recovery rate of valuable metals. Background Art

[0002] In material separation, membrane separation technology has been increasingly widely used in the field of water treatment due to its characteristics of high efficiency, energy conservation, simple equipment, convenient operation, etc. The main membrane types in the current market are microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, etc. These membranes can be applied in processes such as seawater desalination, brackish water treatment, filtering drinking water from water containing harmful substances, manufacturing industrial ultrapure water, wastewater treatment, valuable substance recovery, etc.

[0003] Most of the currently commercially available reverse osmosis membranes and nanofiltration membranes are composite semi-permeable membranes. The composite semi-permeable membrane generally includes a substrate, a porous support layer provided on the substrate, and a separation functional layer provided on the porous support layer.

[0004] Due to the advantages of nanofiltration membranes such as the selective separation of monovalent and divalent ions, their application scope has been expanding year by year. With the development of new energy vehicles in China, the usage of lithium batteries is increasing, and the required amount of lithium is also increasing year by year. Therefore, the application projects of nanofiltration membranes in the extraction of valuable metals such as lithium extraction from salt lakes are also increasing. At the same time, with the increase in the usage of batteries, the amount of waste batteries is also increasing year by year, and the treatment of waste batteries has gradually become an important issue. The current waste battery recycling process mainly uses the extraction method. For example, patent document (CN114085996B) discloses a method for co-processing and recovering nickel and cobalt from nickel-cobalt materials. After extracting nickel and cobalt from nickel-cobalt materials or each positive electrode black powder, the raffinate is then used for lithium precipitation to prepare lithium carbonate. This method has a long process, complex refining, easy lithium loss resulting in a low overall lithium recovery rate. At the same time, due to the use of chemical methods and the need to add various agents in the middle, the amount of agent used is large and the environmental load is high.

[0005] Due to the characteristics of nanofiltration membranes in separating monovalent and divalent ions, there are more and more application studies in lithium battery recycling. Patent document (CN109234524B) discloses a method and system for comprehensively recovering valuable metals from waste ternary lithium batteries, which uses a combined method of ultrafiltration-nanofiltration-reverse osmosis to separate and concentrate lithium and nickel, cobalt, and manganese therein. However, due to the high concentration of the positive electrode acid leaching solution of waste ternary lithium batteries, the conventional continuous operation method will cause high ion concentration and too high osmotic pressure on the concentrated water side of the nanofiltration membrane during high-recovery operation, which is not conducive to operation. If operating at a low recovery rate, although the increase in osmotic pressure is inhibited to some extent, in a binary acid system such as sulfuric acid, the permeation rate of the nanofiltration membrane for lithium cannot reach 100%, resulting in a low overall lithium recovery rate and affecting the separation and recovery effect.

[0006] Therefore, the present application provides a membrane integration process and device for efficiently separating monovalent and polyvalent valuable metals. At the same time, by designing the membrane operation process and device to address the problems in membrane operation, the operation stability and the recovery rate of monovalent cations are improved, the overall chemical consumption is reduced, the environmental load and chemical cost are lowered, which is of great significance in the recovery of valuable metals. Summary of the Utility Model

[0007] The technical problem to be solved by the present utility model is:

[0008] Aiming at the problems of poor operation stability and low recovery rate of valuable metals in the membrane system in the field of valuable metal recovery, a membrane integration process and device are provided. Through the design and improvement of the operation method, on the premise of ensuring stable operation, the recovery rate of monovalent valuable metals is increased, the chemical consumption is reduced, and the effects of saving chemicals, high recovery rate, and stable operation of the system are achieved.

[0009] The means for solving the foregoing technical problems of the present utility model are:

[0010] After repeated research, the inventor of the present utility model found that the integrated membrane separation process and device through batch operation can effectively improve the recovery rate of monovalent metals or cations. During the operation process, since hydrogen ions and water can permeate through the nanofiltration membrane, as the operation progresses, the increase in pH and concentration in the raw water tank of the nanofiltration membrane due to the loss of hydrogen ions and water will affect the separation effect and osmotic pressure of the nanofiltration membrane. In this application, a reverse osmosis membrane with a high hydrogen ion permeability is used to concentrate monovalent metals or cations in the permeate water of the nanofiltration membrane, and at the same time, the reverse osmosis permeate water with hydrogen ions can be supplied to the raw water tank of the nanofiltration membrane to ensure the stability of the ion concentration and pH in the raw water tank of the nanofiltration membrane, thus ensuring the separation effect and operation stability of the nanofiltration membrane, reducing the external acid addition amount, and having the beneficial effects of reducing chemical consumption, increasing the recovery rate of monovalent valuable metals or cations, and operation stability.

[0011] The aforementioned integrated membrane separation device includes n separation devices a and separation device b. The separation device contains a separation member that is a semi-permeable membrane or a semi-permeable membrane element, a pressure supply device, a raw water tank, a permeate water pipeline, and a concentrate water pipeline. It is characterized in that: the n separation devices a are connected in sequence, the concentrate water pipelines of each stage in the n separation devices a are connected to the raw water tank of the corresponding stage separation device, and the permeate water pipeline is connected to the raw water tank of the next-stage separation device; wherein, n≥1; the permeate water pipeline of the last stage in the n separation devices a is connected to the raw water tank of separation device b; the concentrate water pipeline of separation device b is connected to the raw water tank of separation device b, and the permeate water of separation device b is connected to the raw water tank of separation device a.

[0012] The aforementioned separating member includes one or more semipermeable membranes or semipermeable membrane elements. The semipermeable membrane includes a substrate, a porous support layer, and a separation functional layer. The semipermeable membrane element is formed by winding one or more raw water side flow path materials, a semipermeable membrane, and a permeate side flow path material arranged in sequence around a permeate water collecting pipe. There is no limit to the size of the semipermeable membrane and the semipermeable membrane element. It can be an 8-inch or 4-inch membrane element commonly used in the current industry, or a 3-inch, 2.5-inch, or 2-inch membrane element, or flat membranes of various shapes or areas. In actual engineering applications, the semipermeable membrane element system will adopt a two-stage or three-stage structure to ensure the membrane surface flow rate and overall recovery rate. In each stage, a 6-core or 7-core structure will be adopted. The meaning of 6-core or 7-core is the number of membrane elements connected in series in a single membrane housing of the system. Two-stage means that the concentrated water of one-stage membrane elements is used as the supply water for the two-stage membrane elements for reprocessing. The supply pressure on the supply water side is the supply water pressure of the first element in the first stage, and the supply pressure on the concentrated water side is the concentrated water side pressure of the last element at the end. During continuous operation, as the permeate water continuously flows out, the ion concentration and osmotic pressure on the concentrated water side of the system increase, and the supply pressure required for the last element at the end increases. Especially in the case of high recovery rates, here the recovery rate is the permeate water volume / total supply water volume. A high recovery rate means a large permeate water volume and a small concentrated water volume, which also means a high concentration multiple of the concentrated water, an increase in ion concentration, and a large increase in osmotic pressure. Especially in the field of recycling waste lithium batteries, the concentration of the acid leaching solution of the positive electrode is very high itself, and the ion concentration is even greater than 100 g / L. Assuming a traditional two-stage 6-core and continuous operation mode, in the case of low recovery rates, the concentrated water volume is large and the permeate water volume is small. Although the increase in osmotic pressure is not obvious, due to the small permeate water volume, the permeation rate of monovalent metals or cations is limited, and there are still some monovalent metals or cations remaining in the concentrated water, resulting in a low overall monovalent metal or cation recovery rate. If the recovery rate is increased, the concentrated water volume decreases and the permeate water volume increases. Although the recovery rate of the monovalent supply water increases, the osmotic pressure on the concentrated water side increases significantly, resulting in problems with difficult operation.

[0013] The utility model discloses an integrated membrane separation device. The permeate water of separation device b is connected to the raw water tank of separation device a to reduce the risk of increased osmotic pressure caused by the increasing concentration in the raw water tank of separation device a during operation, thereby ensuring the stable operation of the system.

[0014] At the same time, since there is also a possibility that the concentrated water contains monovalent metals or cations, by connecting the concentrated water pipeline of the separation device to the raw water tank of this stage of the separation device, the monovalent and polyvalent metals in the raw water tank are continuously filtered and separated to improve the overall monovalent metal recovery rate.

[0015] The separation device a cannot achieve 100% separation of monovalent and polyvalent cations. As the monovalent cations pass through the separation device a, inevitably, some polyvalent cations will also pass through the separation device a. Therefore, in order to increase the separation of monovalent and polyvalent cations and improve the purity of monovalent cations, n separation devices a are selected to be connected in series, where n≥1.

[0016] To concentrate the separated monovalent metal or cations, the concentrated water pipeline of the separation device b is connected to the original water tank of the separation device b.

[0017] Preferably, for the aforementioned integrated membrane separation device, the separation element of the separation device a is a nanofiltration membrane, and the separation element of the separation device b is a reverse osmosis membrane. The separation of monovalent and polyvalent cations is carried out through the nanofiltration membrane in n separation devices. At the same time, the monovalent cations are concentrated through the reverse osmosis membrane of the separation device b, and the permeate water of the reverse osmosis is returned to the original water tank of the separation device a to reduce the risk of increased osmotic pressure and difficult operation caused by the increase in concentration during the operation of the separation device a. The aforementioned separation device b includes one or more reverse osmosis membranes or reverse osmosis membrane elements, which are connected in series, that is, the concentrated water of the previous stage reverse osmosis enters the next stage reverse osmosis for concentration, and the final concentrated water is returned to the original water tank of the separation device b to improve the overall concentration efficiency. The permeate water pipeline of the last stage of the separation device a is connected to the original water tank of the first separation device b.

[0018] Preferably, for the aforementioned integrated membrane separation device, under the conditions of pH 7, supply pressure of 0.5 MPa, and water temperature of 25 °C, the salt rejection rate of the nanofiltration membrane in a 2000 mg / L NaCl aqueous solution is A, and the salt rejection rate in a 2000 mg / L MgSO 4 aqueous solution is B, and A / B>80. The aforementioned limitation is to better reflect the separation performance of the nanofiltration membrane for monovalent and polyvalent cations. When A / B is smaller, it means that the NaCl salt rejection rate is smaller and the MgSO4 salt rejection rate is larger, that is, the separation of monovalent and divalent cations is lower, the monovalent rejection rate is low, the divalent rejection rate is high, and there is relatively less monovalent and relatively more divalent in the permeate water of the separation device a. To achieve the separation purpose, the number n of the separation device a required increases and the cost increases. When A / B is larger, the monovalent rejection rate is high and the divalent rejection rate is low, that is, there is relatively more monovalent and relatively less divalent in the permeate water of the separation device a, and the separation efficiency increases. Under the premise of achieving the same separation effect, the number n of the separation device a can be reduced. Therefore, preferably A / B>80, and more preferably A / B>150.

[0019] Preferably, for the aforementioned integrated membrane separation device, the H + permeation rate and Na +The ratio of the transmittance is above 100. The above limitation is for better reflecting the separation performance of the reverse osmosis membrane for H + and Na + . The higher the ratio, the easier it means for H + to pass through the reverse osmosis membrane while monovalent cations other than hydrogen are not easy to pass through the reverse osmosis membrane, which is more conducive to the concentration of monovalent metals or cations. At the same time, the high transmittance of H + is beneficial to the pH stability of the solution in separation device a, thus improving the operation stability of separation device a. At the same time, on the premise of ensuring the same operation stability, it can play the beneficial effect of reducing the dosage of chemicals. Therefore, it is preferred that the ratio of the H + transmittance of the reverse osmosis membrane to the Na + transmittance is above 100, and more preferably above 150.

[0020] The above integrated membrane separation device is preferably such that the H + transmittance of the reverse osmosis membrane in a solution of pH 3 and 2000 mg / L NaCl is ≥50%, and more preferably ≥100%. The above limitation is for better reflecting the H + transmission performance of the reverse osmosis membrane. A high hydrogen transmittance can recover more acid solution, and the increase in the hydrogen ion concentration and osmotic pressure on the permeate side can reduce the osmotic pressure difference during the operation of the reverse osmosis membrane, that is, reduce the supply pressure, having the effect of energy saving and consumption reduction. At the same time, it can also reduce the subsequent treatment difficulty and cost of the concentrated monovalent metal or cation solution. The concentrated monovalent solution usually undergoes a process of precipitation by adding sodium carbonate subsequently. The higher the hydrogen ion transmittance, the less the residual hydrogen ions in the reverse osmosis concentrate, the higher the pH, the less sodium carbonate needs to be added, having the beneficial effect of reducing the chemical dosage and thus reducing the cost.

[0021] Preferably, there is a switching supply device between the permeate water pipeline of the separation device b and the raw water tank of the separation device a in the aforementioned integrated membrane separation device. The concentrated water pipeline of the separation device b is connected to the raw water tank of the separation device b, which is a continuous concentration process. As the concentration progresses, the concentration of monovalent metal or cation in the raw water tank increases. Even if the permeation rate of reverse osmosis remains unchanged, the concentration of monovalent metal or cation in the permeate water of reverse osmosis will increase and then flow back to the raw water tank of the separation device a for re-filtration and separation, which will reduce the overall separation efficiency. Moreover, if the concentration of monovalent metal or cation in the reverse osmosis permeate water is greater than the concentration of monovalent metal or cation in the raw water tank of the separation device a at the same time, the yield of monovalent metal or cation in the whole system will not only not increase but may even decrease. Furthermore, preferably, there is a switching supply device between the permeate water pipeline of the separation device b and the raw water tank of the separation device a to switch the permeate water containing relatively low concentration of monovalent metal or cation and the permeate water containing relatively high concentration of monovalent metal or cation. The monovalent metal or cation mentioned here is the metal or cation to be recovered.

[0022] Preferably, the switching supply device in the aforementioned integrated membrane separation device includes two or more water storage tanks. The two or more water storage tanks are used to store the permeate water containing relatively low concentration of monovalent metal or cation and the permeate water containing relatively high concentration of monovalent metal or cation. The concentration of monovalent metal or cation in the reverse osmosis permeate water is set as relatively low concentration A1 and relatively high concentration A2, and the concentration of monovalent metal or cation in the raw water tank of the separation device a is set as relatively low concentration B1 and relatively high concentration B2. When the operation starts in batch operation and the concentration of the reverse osmosis permeate water A1 < the concentration of the raw water tank B2, the reverse osmosis permeate water flows back to the raw water tank of the separation device a; as the operation continues, the concentration of the reverse osmosis permeate water becomes A2, and the concentration of the raw water tank of the separation device a becomes B1. When A2 > B1, it is stored for use and used to flow back to the initial raw water tank after replacing the raw water batch, that is, the raw water tank containing relatively high concentration B2 of monovalent metal or cation.

[0023] Preferably, the stored water in the water storage tank in the switching supply device of the aforementioned integrated membrane separation device is sourced from the permeate water of the separation device b or external addition. The aforementioned limitation is to better ensure the operation stability of the separation device a. When the reverse osmosis permeate water is used for storage and the operation of the separation device a continues, water can be externally added to ensure the concentration and pH value of the stock solution in the separation device a, thereby ensuring the stable operation of the separation device a.

[0024] Preferably, the separation device b of the aforementioned integrated membrane separation device includes two or more permeate water outlets. The above limitation is to better ensure the switching of the permeate water of the separation device b. Through the design of two or more permeate water outlets, the permeate water from each part of the separation device b, that is, the permeate water with a relatively low concentration of monovalent metal or cation on the feed water side and the permeate water with a relatively high concentration of monovalent metal or cation on the concentrate water side, can be separately collected and stored, so as to achieve the purpose of ensuring the stable operation of the separation device a through the reflux of the permeate water without reducing the overall recovery rate of monovalent metal or cation. The permeate water outlet can be set at the permeate water outlet position of each stage of reverse osmosis membrane or reverse osmosis membrane element, or at the permeate water outlet position of each single membrane element or membrane housing.

[0025] The present invention also discloses an operation method of an integrated membrane separation device. The separation devices a are connected in sequence from 1a to na, the concentrate water is refluxed respectively, the permeate water of the previous stage enters the next stage in sequence, the permeate water of the separation device na enters the separation device b, the permeate water of the separation device b is refluxed to the separation devices 1a - na, and the concentrate water of the separation device b is refluxed to the original water tank of the separation device b. The separation efficiency and the purity of monovalent metal or cation in the permeate water are improved by connecting n separation devices a in sequence for treatment. The purity of monovalent metal or cation refers to the ratio of the concentration of the monovalent metal or cation to be recovered in the aqueous solution to the total concentration of the monovalent metal or cation plus the polyvalent metal or cation. The recovery rate of monovalent metal or cation is increased by refluxing the concentrate water of the separation device a respectively. The reflux of the concentrate water of the separation device b can ensure the concentration degree of the monovalent metal or cation solution, and the reflux of the permeate water of the separation device b to the separation device a is used to ensure the stability of the original solution concentration and pH in the separation device a, thereby ensuring the stable operation of the entire separation device a.

[0026] Preferably, the permeate water of the separation device b is supplied to the separation device a in stages in the aforementioned operation method. Since the composition of the permeate water of the separation device b is different in each stage, the permeate water with a relatively low concentration of monovalent metal or cation is directly supplied to the separation device a, and the permeate water with a relatively high concentration of monovalent metal or cation is stored for later use and then supplied to the separation device a during the treatment of another batch. In this way, the stable operation of the separation device a is ensured without reducing the overall recovery rate of monovalent metal or cation.

[0027] Preferably, the permeate water of the separation device b is separately collected in the aforementioned operation method. There are no restrictions on the conditions for separately collecting the permeate water of the separation device b. It can be collected at different times or the permeate water from each part can be separately collected at the same time. Both can achieve the purpose of separately collecting and storing the permeate water with a relatively low concentration of monovalent metal or cation and the permeate water with a relatively high concentration of monovalent metal or cation.

[0028] The above-mentioned operation method preferably has the pH of the solution in the raw water tank of separation device a ≤ 3. This method is applicable to the separation of monovalent metals or cations and polyvalent metals or cations under acidic conditions. Under relatively low pH conditions, due to reasons such as changes in the membrane surface charge and the valence states of the constituent ions in the solution, the separation performance of the membrane for monovalent and polyvalent substances will increase. Therefore, it is preferred that the pH of the solution in the raw water tank of separation device a ≤ 3, and more preferably pH ≤ 2.

[0029] There is no limitation on the types of anions in the stock solution, which can be conventional polyvalent sulfate ions, phosphate ions, or monovalent chloride ions, fluoride ions, nitrate ions, etc., and can even be organic acid ions, such as acetate ions, etc.

[0030] The above-mentioned operation method preferably has the amount of monovalent metal or cation in separation device a entering separation device b ≥ 90%. The specific calculation method is the ratio of the amount of monovalent metal or cation contained in the raw water tank of separation device b at the end of the operation to the amount of monovalent metal or cation contained in the raw water tank of separation device a at the beginning of the operation, that is, the above-mentioned yield of monovalent metal or cation. The above-mentioned monovalent metal or cation is the target metal or cation to be recovered or extracted. For example, lithium or other valuable cations, and polyvalent cations can be magnesium, calcium, nickel, cobalt, manganese, iron, aluminum, copper, or other polyvalent elements.

[0031] Through the above-mentioned device and method, it can be ensured that a large amount of the target monovalent metal or cation enters separation device b, thereby greatly increasing the separation from polyvalent cations. At the same time, by setting the reflux of the permeated water at each stage of separation device b, the loss of the target monovalent metal or cation is effectively reduced and the recycling efficiency is improved, and the overall yield of the target monovalent metal or cation is increased.

[0032] The above-mentioned operation method preferably has the ratio of monovalent metal or cation to the total amount of cations in the solution in separation device b ≥ 80%. The above-mentioned limitation is to better represent the purity of the target monovalent metal or cation after separation. The above-mentioned monovalent metal or cation is the target metal or cation to be recovered or extracted, and the total amount of cations in the above-mentioned solution is the sum of the above-mentioned monovalent metal or cation and other polyvalent metals or cations. Through the highly selective nanofiltration membranes of the above-mentioned n separation devices a, the purity of the target monovalent metal or cation can be effectively improved.

[0033] The specific effects are as follows:

[0034] The purity of the target monovalent metal or cation is improved by n highly selective separation devices a, and at the same time, the yield of the target monovalent metal or cation is increased by continuously circulating and filtering through the concentrated water reflux of separation device a. At the same time, high H +During the process of concentrating the target monovalent metal or cation, the separation device b for transmittance returns the permeate water containing hydrogen ions to the raw water tank of the separation device a for water and acid recovery, thereby ensuring the stability of the concentration and pH of the raw water tank of the separation device a and further ensuring the stable operation of the separation device a. In view of the adverse phenomenon that part of the target monovalent metal or cation generated at the end of the operation is refluxed to the raw water tank of the separation device a, resulting in the inability to increase the yield, by setting the reflux of the permeate water at different stages of the separation device b, on the basis of ensuring the overall stable operation, the yield of the monovalent metal or cation is increased, and at the same time, the operation efficiency is improved. Description of the Drawings

[0035] Figure 1 A composition of the integrated membrane separation device in the present application

[0036] Figure 2 Another composition of the integrated membrane separation device in the present application

[0037] Among them, 1-n separation devices a, 2-separation device b, 3-switching supply device, 4-separation device a, 5-separation device na, 6-raw water tank a, 7-raw water tank na, 8-raw water tank b, 9-water storage tank A, 10-water storage tank B, 11-separation member a, 12-separation member na, 13-separation member b, 14-permeate water outlet 1, 15-permeate water outlet 2 Detailed Description of the Invention

[0038] The present utility model will be further described below in conjunction with the drawings and specific embodiments, but it shall not be construed as a limitation of the present utility model.

[0039] The test conditions, test methods and meanings of the parameters in the embodiments are as follows:

[0040] B-Magnesium sulfate salt transmittance: The evaluation water adjusted to a temperature of 25 ± 1°C, pH 6.5 - 7.5, and magnesium sulfate concentration of 2000 mg / L is supplied to the semi-permeable membrane element at an operating pressure of 0.5 MPa, and membrane filtration treatment is carried out for 1 hour under the condition of a recovery rate of 15%. The conductivity meters manufactured by HACH Company of the United States are used to measure the conductivity of the supply water and the permeate water to obtain their respective actual salinity, that is, the magnesium sulfate concentration. Based on the obtained magnesium sulfate concentration and the following formula, the magnesium sulfate salt transmittance is calculated.

[0041] Magnesium sulfate salt transmittance (%) = [(Magnesium sulfate concentration in the permeate water) / (Magnesium sulfate concentration in the supply water)] × 100.

[0042] A - Sodium chloride salt rejection: Feed the evaluation water adjusted to a temperature of 25 ± 1 °C, pH 6.5 - 7.5, and sodium chloride concentration of 2000 mg / L to the semi - permeable membrane element at an operating pressure of 0.5 MPa, and conduct membrane filtration treatment for 1 hour under the condition of a recovery rate of 15%. Use a conductivity meter manufactured by HACH Company, USA, to measure the conductivity of the feed water and the permeate water, and obtain the actual salinity, that is, the sodium chloride concentration of each. Based on the obtained sodium chloride concentration and the following formula, calculate the sodium chloride salt rejection.

[0043] Sodium chloride salt rejection (%) = [(Sodium chloride concentration in the permeate water) / (Sodium chloride concentration in the feed water)] × 100.

[0044] A / B = Sodium chloride salt rejection / Magnesium sulfate salt rejection.

[0045] H + Rejection and Na + Rejection: Feed the evaluation water adjusted to a temperature of 25 ± 1 °C, pH 2.9 - 3.1, and sodium chloride concentration of 2000 mg / L to the semi - permeable membrane element at an operating pressure of 0.5 MPa, and conduct membrane filtration treatment for 1 hour under the condition of a recovery rate of 15%. Use a pH meter manufactured by the Ganges Company of Japan to measure the pH of the feed water and the permeate water, and obtain the pH value, that is, the H + concentration. Use ion chromatography from Metrohm to measure Na + in the feed water and the permeate water, and obtain the Na + concentration of each. Based on the obtained hydrogen ion concentration, sodium ion concentration and the following formula, calculate the H + rejection and Na + rejection and their ratio.

[0046] H + Rejection (%) = [(H + concentration in the permeate water) / (H + concentration in the feed water)] × 100.

[0047] Na + Rejection (%) = [(Na + concentration in the permeate water) / (Na + concentration in the feed water)] × 100.

[0048] H + Ratio of rejection to Na + rejection = the above - mentioned H + rejection / the above - mentioned Na + rejection.

[0049] Membrane element operating recovery rate: The permeate water volume V P within a specified time and the feed water flow rate VF The ratio is calculated according to V P / V F × 100.

[0050] Target monovalent metal or cation yield: the amount of the target monovalent metal or cation in separation device a that enters separation device b. The specific calculation method is (the amount of the target monovalent metal or cation contained in the raw water tank of separation device b at the end of operation) / (the amount of the target monovalent metal or cation contained in the raw water tank of separation device a at the start of operation) × 100%.

[0051] Target monovalent metal or cation purity: (the target monovalent metal or cation in separation device b) / (the sum of the target monovalent metal or cation and other polyvalent cations in the raw water tank solution of separation device b) × 100%.

[0052] The relevant data calculation method in the present utility model is to calculate by taking the average value of 10 test data. Considering the test errors of instruments, operating conditions, etc., ±10% is within the defined range.

[0053] In order to better illustrate the comparison results of each system, the specific composition and operating conditions of the raw water are defined. In fact, the applicable scope of this device and method includes but is not limited to the embodiments.

[0054] Comparative Example 1

[0055] The integrated membrane system has one separation device containing a nanofiltration membrane element, i.e., separation device a, and a separation device containing a reverse osmosis membrane element, i.e., separation device b. Both separation device a and separation device b adopt the continuous operation mode of traditional water treatment, that is, the feed water enters the integrated membrane system and is treated into concentrated water and permeate water and discharged from the system. The permeate water of separation device a enters separation device b. The operating recovery rates of both separation device a and separation device b are 85% ± 5%. More than 90% of the total mass of anions in the raw water is sulfate ions. The cations include lithium ions, cobalt ions, nickel ions, manganese ions, etc. The mass ratio of the total amount of lithium ions and polyvalent ions is 1:8. The pH of the raw water is 2.5 - 3. The A / B of the nanofiltration membrane element in separation device a is 69. The H⁺ permeation rate of separation device b is 3%. The H⁺ permeation rate / Na⁺ permeation rate is 28. There is no switching supply device. The permeate water of separation device b does not flow back and is directly discharged from the membrane system, and there is no reflux setting. The supply pressure during constant flow operation is set to 1x, and it does not involve the amount of acid added to the raw water tank a - na of separation device a except for the stock solution, that is, no addition. The target monovalent metal or cation yield of this integrated membrane system is 64.7%, and the target monovalent metal or cation purity is 58.2%.

[0056] Comparative Example 2

[0057] The integrated membrane system has two separation devices containing nanofiltration membrane elements, namely separation device a and separation device 2a, and a separation device b containing reverse osmosis membrane elements. Both separation device a and separation device b adopt the continuous operation mode of traditional water treatment, that is, the feed water enters the integrated membrane system and is processed into concentrated water and permeate water and discharged from the system. The permeate water of separation device a enters separation device 2a, and the permeate water of separation device 2a enters separation device b. The operating recovery rates of separation device a, 2a, and separation device b are all 85% ± 5%. More than 90% of the total mass of anions in the raw water is sulfate ions. The cations include lithium ions, cobalt ions, nickel ions, manganese ions, etc. The mass ratio of the total amount of lithium ions and polyvalent ions is 1:8, and the pH of the raw water is 2.5 - 3. The A / B of the nanofiltration membrane element in separation device a is 69. The H+ permeation rate of separation device b is 3%, and the H+ permeation rate / Na+ permeation rate is 28. There is no switching supply device, and the permeate water of separation device b is directly discharged from the membrane system without reflux, and there is no reflux setting. When operating at a constant flow rate, the supply pressure is set to 1x, and there is no addition of acid to the raw water tank a - na of separation device a except for the stock solution. The target monovalent metal or cation recovery rate of this integrated membrane system is 64.7%, and the target monovalent metal or cation purity is 90.8%.

[0058] Example 1

[0059] The integrated membrane system has one separation device containing a nanofiltration membrane element, namely separation device a, and a separation device b containing a reverse osmosis membrane element. The concentrated water of both separation device a and separation device b is refluxed to their respective raw water tanks. The permeate water of separation device a enters separation device b, and the permeate water of separation device b is refluxed to the raw water tank of separation device a. The operating recovery rates of separation device a and separation device b are both 15 ± 5%. More than 90% of the total mass of anions in the raw water is sulfate ions. The cations include lithium ions, cobalt ions, nickel ions, manganese ions, etc. The mass ratio of the total amount of lithium ions and polyvalent ions is 1:8, and the pH of the raw water is 2.5 - 3. The A / B of the nanofiltration membrane element in separation device a is 69. The H+ permeation rate of separation device b is 3%, and the H+ permeation rate / Na+ permeation rate is 28. There is no switching supply device, and the permeate water of separation device b is refluxed to the raw water tank of separation device a. When operating at a constant flow rate (the same flow rate as in the comparative example), the supply pressure is 0.2x. To ensure the stability of the pH in the nanofiltration raw water tank, the additional amount of acid added to the nanofiltration raw water tank is 1y. The target monovalent metal or cation recovery rate of this integrated membrane system is 90.0%, and the target monovalent metal or cation purity is 58.2%.

[0060] Example 2

[0061] The integrated membrane system has two separation devices containing nanofiltration membrane elements, namely separation device a and separation device 2a, and a separation device b containing reverse osmosis membrane elements. The concentrated water of separation device a and separation device b is refluxed to their respective original water tanks. The permeate water of separation device a enters separation device 2a, the permeate water of separation device 2a enters separation device b, and the permeate water of separation device b is refluxed to the original water tanks of separation device a and 2a. The operating recovery rates of separation device a, 2a, and separation device b are all 15 ± 5%. More than 90% of the total mass of anions in the raw water is sulfate ions. The cations include lithium ions, cobalt ions, nickel ions, manganese ions, etc. The mass ratio of the total amount of lithium ions to polyvalent ions is 1:8, and the pH of the raw water is 2.5 - 3. The A / B of the nanofiltration membrane element in separation device a is 69, the H+ permeation rate of separation device b is 3%, and the H+ permeation rate / Na+ permeation rate is 28. There is no switching supply device, and the permeate water of separation device b is refluxed to the original water tanks of separation device a and 2a. The ratio of the supply pressure during constant flow (the same flow rate as in the comparative example) operation to the supply pressure in the comparative example is 0.2x. To ensure the stability of the pH in the nanofiltration original water tank, the additional amount of acid added to the nanofiltration original water tank is 1.4y. The target monovalent metal or cation recovery rate through this integrated membrane system is 90.0%, and the target monovalent metal or cation purity is 90.8%.

[0062] Example 3

[0063] Compared with Comparative Example 2, there are 3 separation devices a containing nanofiltration membrane elements in the integrated membrane system. To ensure the stability of the pH in the nanofiltration original water tank, the additional amount of acid added to the nanofiltration original water tank is 2y. The target monovalent metal or cation purity through this integrated membrane system is 94.5%. Other parameters are the same, and the specific values are shown in Table 1.

[0064] Example 4

[0065] Compared with Comparative Example 2, the A / B in Example 4 is 86, and the target monovalent metal or cation purity is 93.1%. Other parameters are the same, and the specific values are shown in Table 1.

[0066] Example 5

[0067] Compared with Comparative Example 2, the A / B in Example 5 is 158, and the target monovalent metal or cation purity is 95.3%. Other parameters are the same, and the specific values are shown in Table 1.

[0068] Example 6

[0069] Compared with Comparative Example 5, the H+ permeation rate in Example 6 is 50%, and the additional amount of acid added to the nanofiltration original water tank is 0.7y. Other parameters are the same, and the specific values are shown in Table 1.

[0070] Example 7

[0071] Compared with Comparative Example 5, the H⁺ permeation rate in Example 7 is 170%, the amount of acid additionally added to the nanofiltration raw water tank is 0.1y, and other parameters are the same. The specific values are shown in Table 1.

[0072] Example 8

[0073] Compared with Comparative Example 7, the H⁺ permeation rate / Na⁺ permeation rate in Example 8 is 113, and the yield of the target monovalent metal or cation is 92.8%. Other parameters are the same. The specific values are shown in Table 1.

[0074] Example 9

[0075] Compared with Comparative Example 7, the H⁺ permeation rate / Na⁺ permeation rate in Example 9 is 349, and the yield of the target monovalent metal or cation is 95.2%. Other parameters are the same. The specific values are shown in Table 1.

[0076] Example 10

[0077] Compared with Example 9, in Example 10, there is a switching supply device. The permeate water with a relatively low initial concentration of the target monovalent metal or cation in Separation Device b is refluxed to the raw water tanks of Separation Devices a and 2a, and the permeate water with a relatively high concentration of the target monovalent metal or cation in Separation Device b at the end of operation is stored for later use. During the storage period, since nanofiltration is still operating, as the permeate water is continuously produced, the concentration in the nanofiltration raw water tank continuously increases, the osmotic pressure increases, and the supply pressure increases. Therefore, the supply pressure during constant flow (the same flow rate as in the comparative example) operation is 0.2x, and at the end it is 0.8x. The permeate water with a relatively high concentration of the target monovalent metal or cation in Separation Device b at the end does not reflux to the nanofiltration raw water tank. Although the increase in pH in the raw water tank will cause a decrease in the overall yield, under the combined action of the two, the overall yield of the target monovalent metal or cation in the system increases to 96.2%. Other parameters are the same. The specific values are shown in Table 1.

[0078] Example 11

[0079] Compared with Example 10, the permeate water with a relatively low initial concentration of the target monovalent metal or cation in Separation Device b is refluxed to the raw water tanks of Separation Devices a and 2a. At the end of the operation, the permeate water with a relatively high concentration of the target monovalent metal or cation in Separation Device b is stored for future use. During the storage period, water containing hydrogen ions is externally added to ensure the stability of the solution concentration and pH in the nanofiltration raw water tank. Therefore, the supply pressure during the constant flow rate (the same flow rate as in the comparative example) operation is 0.2x. However, due to the external addition of pure water containing hydrogen ions, the additional amount of acid added to the nanofiltration raw water tank is 0.3y. The permeate water with a relatively high concentration of the target monovalent metal or cation in Separation Device b at the end does not reflux to the nanofiltration raw water tank, and at the same time, the pH in the raw water tank is stable. Under the combined action of the two, the overall target monovalent metal or cation recovery rate of the system increases to 96.5%. Other parameters are the same, and their specific values are shown in Table 1.

[0080] Example 12

[0081] Compared with Example 11, the permeate water with a relatively low initial concentration of the target monovalent metal or cation in Separation Device b is refluxed to the raw water tanks of Separation Devices a and 2a. At the same time, Separation Device b has two permeate water outlets. At the end of the operation, the reverse osmosis permeate water with a relatively low concentration of the target monovalent metal or cation at the front end passes through Outlet 1 and is refluxed to the nanofiltration raw water tank, and the reverse osmosis permeate water with a relatively high concentration of the target monovalent metal or cation at the back end passes through Outlet 2 and flows out to the storage tank for future use. During the period when part of the reverse osmosis permeate water is stored for future use, since part of the reverse osmosis permeate water is still refluxed, the solution concentration and pH in the nanofiltration raw water tank can still be ensured to be stable. At the same time, since the reverse osmosis permeate water with a relatively high concentration of the target monovalent metal or cation is stored for future use through Outlet 2 and does not reflux, the overall target monovalent metal or cation recovery rate can also be ensured. Therefore, the additional amount of acid added to the raw water tank is 0.1y, and other parameters are the same, and their specific values are shown in Table 1.

[0082] Example 13

[0083] Compared with Example 11, in Example 13, the pH of the raw water is 2 ± 0.2. The target monovalent metal or cation recovery rate achieved by the same device within the same operation time is 97.3%, and the purity of the target monovalent metal or cation is 97.5%. Since the pH of the stock solution is relatively low, the additional amount of acid added to the raw water tank increases to 3y, and other parameters are the same, and their specific values are shown in Table 1.

[0084] Example 14

[0085] Compared with Comparative Example 13, the pH of the raw water in Example 14 is 1 ± 0.2. For the same device within the same operation time, the yield of the target monovalent metal or cation achieved is 98.4%, and the purity of the target monovalent metal or cation is 97.8%. Since the pH of the stock solution is relatively low, the amount of acid additionally added to the raw water tank increases to 30y, and other parameters are the same. The specific values are shown in Table 1.

[0086] [Table 1]

[0087]

[0088] As described above, in Example 1, the method of returning reverse osmosis water can effectively improve the yield of the target monovalent metal or cation of the overall system; in Examples 2 and 3, the purity of the target monovalent metal or cation of the overall system is improved by increasing the number of separation devices a; in Examples 4 and 5, the use of a nanofiltration membrane with high selective separation performance can effectively improve the purity of the target monovalent metal or cation; in Examples 6 and 7, by using a reverse osmosis membrane with high H+ permeability, the amount of acid additionally added externally can be effectively reduced, and the consumption of chemicals and costs can be decreased; in Examples 8 and 9, by returning the permeate of a reverse osmosis membrane with a relatively high ratio of H+ permeability / Na+ permeability, the loss of the target monovalent metal or cation caused by the return can be reduced, and the yield of the target monovalent metal or cation can be improved. In Example 10, by storing the reverse osmosis permeate containing a relatively high relative concentration of the target monovalent metal or cation at the end for future use, the loss caused by the return can be effectively reduced, thereby improving the yield of the target monovalent metal or cation. In Example 11, the problem of the increased osmotic pressure at the end brought about by Example 10 is solved by an external addition method, thereby improving the yield and reducing the operating pressure, and improving the overall operating stability. In Example 12, by partially returning the reverse osmosis permeate, the problem of the increased osmotic pressure caused by non-returning in Example 10 and the problem of the increased acid addition amount caused by the external addition in Example 11 are both solved. In Examples 13 and 14, by setting the pH value of the raw water, the separation effect of the nanofiltration membrane is effectively improved, thereby improving the yield and purity of the target monovalent metal or cation. Compared with the devices and methods of the comparative examples, the structure of the present utility model can effectively improve the yield and purity of the target monovalent metal or cation, while reducing the amount of acid added externally and the operating pressure, improving the operating stability, and having the beneficial effects of energy conservation and chemical agent saving.

Claims

1. An integrated membrane separation device, comprising n separation devices a and separation devices b, wherein the separation devices comprise a separation element which is a semipermeable membrane or a semipermeable membrane element, a pressure supply device, a raw water tank, a permeate water pipeline and a concentrated water pipeline, characterized in that: The n separation devices a are connected in sequence, the concentrated water pipeline of each stage in the n separation devices a is connected to the raw water tank of the separation device of that stage, and the permeate water pipeline is connected to the raw water tank of the separation device of the next stage; wherein, n≥1; the permeate water pipeline of the last stage in the n separation devices a is connected to the raw water tank of separation device b; the concentrated water pipeline of separation device b is connected to the raw water tank of separation device b, and the permeate water of separation device b is connected to the raw water tank of separation device a.

2. The integrated membrane separation device according to claim 1, characterized in that: The separation element of the separation device a is a nanofiltration membrane, and the separation element of the separation device b is a reverse osmosis membrane.

3. The integrated membrane separation device according to claim 2, characterized in that: Under the conditions of pH 7, supply pressure 0.5 MPa and water temperature 25°C, the salt permeability of the nanofiltration membrane in a 2000 mg / L NaCl aqueous solution is A, and the salt permeability in a 2000 mg / L MgSO4 aqueous solution is B, and A / B>80.

4. The integrated membrane separation device according to claim 2, characterized in that: The ratio of the H+ permeability to the Na+ permeability of the reverse osmosis membrane in a solution of pH 3 and a NaCl concentration of 2000 mg / L is greater than 100.

5. The integrated membrane separation device according to claim 2 or 4, characterized in that: The H+ permeability of the reverse osmosis membrane in a solution of pH 3 and a NaCl concentration of 2000 mg / L is ≥50%.

6. The integrated membrane separation device according to claim 1 or 2, characterized in that: A switching supply device is provided between the permeate water pipeline of the separation device b and the raw water tank of the separation device a.

7. The integrated membrane separation device according to claim 6, characterized in that: The switching supply device includes more than two water storage tanks.

8. The integrated membrane separation device according to claim 6, characterized in that: The water stored in the water storage tank in the switching supply device comes from the permeated water of the separation device b or external addition.

9. The integrated membrane separation device according to claim 7, characterized in that: The water stored in the water storage tank in the switching supply device comes from the permeated water of the separation device b or external addition.

10. The integrated membrane separation device according to claim 1 or 2, characterized in that: The separation device b comprises two or more permeate water outlets.

Images