Method and device for synchronously separating multiple metals through metal coordination coupling solar driven electrodialysis

Abstract

The invention belongs to the technical field of metal separation, and particularly relates to a method and device for synchronously separating multiple metals through metal coordination coupling solar driven electrodialysis. In the electrodialysis separation process, a ligand is added into a to-be-separated feed liquid rich in various valuable metal ions, and the ligand is controlled to be coordinated with at least one to-be-separated metal ion to form an anion complex; in the coordination reaction process, under the driving of an electric field obtained by solar energy, anion complexes and uncoordinated metal cations are respectively transmitted in opposite directions, the anion complexes realize transmission and separation through a polymer coating film, and the uncoordinated metal cations realize transmission and separation of single metal ions through a cation selective composite film. Further, coordinated and non-coordinated multi-ions are separated. Renewable energy sources such as solar energy are used as driving force, synchronous separation of multiple metal ions can still be achieved, energy is saved, and consumption is reduced. The method can be widely applied to the fields of valuable metal separation and recovery of waste lithium ion batteries and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal separation, and in particular relates to a method and a device for synchronously separating multiple metals by metal coordination coupling and solar-driven electrodialysis. Background Art

[0002] With the booming development of the electronics industry, the markets for electronic appliances, lithium-ion batteries (LIBs), etc. are growing rapidly, and the resulting electronic waste, circuit boards, and waste batteries are gradually increasing. However, electronic devices contain a large amount of valuable metals, and their wanton discharge not only causes waste of resources, but also damages the ecological environment. From the perspective of circular economy and sustainable development, recycling valuable metals such as lithium, cobalt, nickel, and manganese from electronic waste not only helps stabilize the supply chain, but also protects the environment, and is a focus of attention in today's world. In the LIBs valuable metal recovery technology, hydrometallurgy is a mature method that can extract metal ions in the positive electrode material from the solid phase to the liquid phase. However, due to the similar physicochemical properties of metal ions, the downstream metal ion separation process is extremely challenging.

[0003] As an efficient membrane separation technology, electrodialysis allows anions and cations to be transported across the membrane in opposite directions under the action of an electric field, thereby achieving ion separation. However, due to the same charge properties of metal cations, it is difficult to achieve effective separation of metal ions by relying on traditional electrodialysis. At present, the separation of binary metal ions such as lithium and cobalt can be achieved by introducing extractants into polymer membrane matrices to develop polymer-coated membranes, and organically combining them with electrodialysis technology (Zhang Yang, Liu Yang, Tan Ming, Wang Yuzhen, Wang Pengfei, Wang Xin, A method for separating multiple valuable metals in one step from secondary resource leachate, application number: 202211181291.X; Zhang Yang, Liu Yang, Tan Ming, Wang Yuzhen, Jiang Jiaxin, Li Zheng, A method for separating molybdenum and vanadium with high-efficiency membranes, application number: 202 211611824.3; Jiang Heqing, Wang Baoying, Liang Wenyuan, a metal ion membrane separation device and method thereof, application number: 202110532543.8; Zhang Zongliang, Li Bingqin, Liu Siliang, Jia Ming, Jiang Liangxing, Liu Fangyang, a method and device for extracting lithium from brine or seawater based on the principle of electrodialysis, application number 202211056141.6), but most studies are limited to the separation of two metal ions, and it is difficult to achieve the separation of multiple metal ions. However, with the rapid upgrading of LIBs, the positive electrode materials contain multiple metals such as lithium, cobalt, nickel, and manganese at the same time. Therefore, how to achieve the simultaneous separation of multiple metal ions in one step is crucial.

[0004] The formation of anionic complexes between metal ions and ligands is a way to generate metal complexes through reversible coordination reactions. Currently, most of them are widely used in catalysis, adsorption, material synthesis, separation and other fields. In the field of catalysis, the combination of metal centers and ligands can change the catalyst morphology and improve the catalytic activity. For the separation field, by constructing metal complexes on the membrane surface, the adsorption effect of the membrane on the target molecules / ions can be increased, thereby improving the separation performance. However, the above separation is only applicable to pressure-driven membrane separation, and in the electrodialysis process, to achieve good separation, the target object and the functional groups / components in the membrane need to be transferred in the form of ion exchange. Therefore, since the above composite membrane only constructs metal complexes on the membrane surface, its interaction with the target object only occurs on the surface, which is not suitable for the field of electrodialysis separation. Therefore, it is urgent to develop a new separation technology that is efficient and energy-saving and can simultaneously realize multiple metal ions. Summary of the invention

[0005] The object of the present invention is to provide a method and device for synchronously separating multiple metals by metal coordination coupling solar energy driven electrodialysis.

[0006] To achieve the above purpose, the present invention adopts the following technical solution:

[0007] A method for synchronous separation of multiple metals by metal coordination-coupled solar-driven electrodialysis. In the electrodialysis separation process, a ligand is added to a feed solution rich in multiple valuable metal ions to be separated, and the ligand is controlled to coordinate with at least one metal ion to be separated to form an anion complex. During the coordination reaction, driven by the electric field obtained by solar energy, the anion complex and the uncoordinated metal cation are respectively transmitted in opposite directions, the anion complex is transmitted and separated through a polymer coating membrane, and the uncoordinated metal cation is transmitted and separated as a single metal ion through a cation-selective composite membrane, thereby separating the coordinated and uncoordinated multiple ions.

[0008] Specifically, the feed solution to be separated and rich in multiple valuable metal ions is first tested for the types and concentrations of ions contained therein, and after the metal ions to be separated are determined, a ligand is added to the feed solution, and the ligand is controlled to coordinate with at least one metal ion to be separated to form an anion complex; during the coordination reaction, driven by an electric field, the anion complex and the uncoordinated metal cation are transported in opposite directions respectively, the anion complex is transported and separated by a polymer coating membrane, and the uncoordinated metal cation is transported and separated as a single metal ion by a cation selective composite membrane, thereby separating the coordinated and uncoordinated multiple ions; the cation selective composite membrane is a cation exchange membrane, a specific cation selective composite membrane, or a monovalent / multivalent selective cation exchange membrane.

[0009] The uncoordinated metal cations are one or more than two;

[0010] If the uncoordinated metal is one, it is transported to the cathode under the drive of the electric field and separated from the feed liquid through the cation exchange membrane;

[0011] If there are two or more uncoordinated metals and they contain metals of the same valence, they are transported to the cathode under the drive of the electric field, and a certain metal ion that interacts with the membrane is separated from the feed liquid through a specific cation selective composite membrane, and then separated one by one according to the metal properties until each ion is separated individually;

[0012] If there are more than two uncoordinated metals and they contain metals of different valence states, they are transported to the cathode under the drive of the electric field, and the monovalent metal ions are separated from the feed liquid through the monovalent / multivalent selective cation exchange membrane, and then separated one by one according to the metal properties until each ion is separated individually.

[0013] If the uncoordinated metal is one, it is transported toward the cathode under the drive of the electric field and separated from the feed liquid through the cation exchange membrane;

[0014] If there are two or more uncoordinated metals and they contain metals of the same valence, they are transported to the cathode under the drive of the electric field, and a certain metal ion that interacts with the membrane is separated from the feed liquid through a specific cation selective composite membrane, and then separated one by one according to the metal properties until each ion is separated individually;

[0015] If there are more than two uncoordinated metals and they contain metals of different valence states, they are transported to the cathode under the drive of the electric field, and the monovalent metal ions are separated from the feed liquid through the monovalent / multivalent selective cation exchange membrane, and then separated one by one according to the metal properties until each ion is separated individually.

[0016] The cation selective composite membrane is a cation exchange membrane, a specific cation selective composite membrane or a monovalent / multivalent cation exchange membrane;

[0017] The cation exchange membrane is a polymer membrane containing at least one negatively charged group; the negatively charged group is one or more of sulfonic acid, phosphoric acid, carboxylic acid, phenolic acid, arsenic acid and selenic acid; for example, polystyrene sulfonate membrane, perfluorosulfonic acid membrane.

[0018] The specific cation selective composite membrane has components or groups in the membrane that interact with specific metals, including one or more of crown ether and EDTA modified polymer membranes; for example, crown ether modified polyamide membrane and EDTA modified polysulfone membrane.

[0019] The monovalent cation exchange membrane is a polymer-coated membrane with at least one negatively charged group inside and a positively charged surface; the negatively charged group is one or more of sulfonic acid, phosphoric acid, carboxylic acid, phenolic acid, arsenic acid and selenic acid. For example, CIMS provided by ASTOM of Japan.

[0020] The ligand coordinates with a metal ion to be separated to form an anion complex; during the coordination reaction, the anion complex is driven by an electric field and transported toward the anode, and the anion complex is separated from the feed through the polymer coating membrane;

[0021] If the ligand coordinates with two or more metal ions to be separated to form an anion complex; during the coordination reaction, under the driving force of the electric field, the anion complex is transported toward the anode, and the anion complex is separated from the feed through the polymer coating membrane; then the ligand is added to the separated two or more metal ions to form an anion complex, and the above electric field driving effect is repeated to separate different metal ions one by one until a single metal ion is separated.

[0022] The multiple valuable metal ions in the feed liquid to be separated are Li + 、Co 2+ 、Ni 2+ , Mn 2+ , Cu 2+ 、Zn 2+ 、Cd 2+ , Pb 2 + ;

[0023] The ligand is one or more of NH4SCN, KSCN, NaSCN, HCl, NaCN, ethylenediaminetetraacetic acid, and HF;

[0024] The polymer coating film is one or more polymer composite films containing trihexyltetradecylphosphonium chloride, methyltrioctyl, ammonium chloride and trioctylamine.

[0025] The addition amount of the ligand is 5wt%-70wt%, and the pH of the system after adding the ligand is 1-7;

[0026] The electric field voltage is 0.01-30V; the current density is 1-50mA / cm 2 .

[0027] A device used in the method, the device is composed of a photovoltaic unit and an electrodialysis unit; the anode and cathode of the photovoltaic unit are respectively arranged on both sides of the electrodialysis unit, and the electrodialysis unit is divided into different chambers by a membrane according to the number of separated ions, and the two chambers adjacent to the cathode and the anode are electrode chambers, in which electrode liquid is added; the feed liquid to be separated is injected into the chamber relatively in the center of the electrodialysis unit. The other chambers in the electrodialysis unit are all concentration chambers, and corresponding concentrated liquid is added according to the different separated ions.

[0028] The photovoltaic unit is powered by the sun.

[0029] An application of the method, application of the method in metal separation.

[0030] The method is applied in separation and recovery of valuable metals in waste lithium-ion batteries and separation of metals in waste electronic components.

[0031] The above device and method are used to treat Li + 、Co 2+ 、Ni 2+ The three metal liquids are separated and processed:

[0032] Before the electrodialysis operation, a solution containing 40 mg / L Li + , 100mg / L Co 2+ , 100mg / L Ni 2+ NH4SCN was added to the mixed solution to make its concentration 0.1 mol / L. 2+ Priority with SCN - Coordination to form Co(SCN)4 2- complex, and Li + and Ni 2+ Not with SCN - Coordination. Under the action of electric field, Co(SCN)4 2- Transmission separation into concentrate 1, Li + Through the monovalent cation exchange membrane into the concentrate 2, while Ni 2+ Retained in the raw material solution, so as to achieve the synchronous separation of the three metal ions. At the same time, a sample is taken from the raw material solution, concentrated solution 1 and concentrated solution 2 at regular intervals to analyze the metal ion concentration in the solution and calculate the ion transmission flux and metal ion purity.

[0033] Furthermore, by controlling the ligand concentration and current density in the system and adjusting the ion concentration in the feed solution to meet the requirements, the simultaneous separation of multiple metal ions can be achieved in combination with the device, with high separation efficiency.

[0034] The specific ion selective composite membrane 1 (polymer coated membrane) and composite membrane 2 (cation selective composite membrane) are selective for coordinated anion complexes and monovalent metal cations, respectively;

[0035] The polymer coating membrane can be one or more of the polymer composite membranes containing trihexyltetradecylphosphonium chloride, methyltrioctyl, ammonium chloride, and trioctylamine. The monovalent cation selective membrane is CIMS provided by ASTOM of Japan.

[0036] Preferably, the polymer coating film is obtained by the following preparation method: a certain amount of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and trioctylamine (TOA) are added to tetrahydrofuran solvent, and stirred at 45° C. for 5 hours to form a uniform casting solution. After degassing, the above solution is poured into a mold, and the solvent is evaporated for standby use.

[0037] A device for separating three kinds of ions: it is composed of a photovoltaic unit and an electrodialysis unit; the anode and cathode of the photovoltaic unit are respectively arranged on both sides of the electrodialysis unit, and the electrodialysis unit is divided into five different chambers by four membranes according to the number of separated ions into three kinds. From the anode to the cathode, the four membranes are arranged in the order of commercial cation exchange membrane, polymer coated membrane, monovalent cation exchange membrane and commercial anion exchange membrane, and the separated chambers are respectively an electrode liquid chamber, a concentrate chamber 1, a feed liquid chamber, a concentrate chamber 2 and an electrode liquid chamber.

[0038] The photovoltaic unit uses renewable energy such as solar energy and wind energy as the driving force of the electrodialysis separation process. Combined with the metal coordination strategy, it can still achieve the synchronous separation of multiple metal ions and save energy and reduce consumption.

[0039] A metal coordination coupled solar-driven electrodialysis system was established outdoors, using photovoltaic power generation to provide energy for the system. A multimeter was used to monitor the changes in current and voltage in real time. The system operation time was 8:00-16:00.

[0040] The present invention has the following advantages:

[0041] The present invention introduces metal coordination strategy into electrodialysis membrane separation technology, and further organically combines it with renewable energy sources such as solar energy to achieve synchronous separation of multiple metal ions. In the electrodialysis separation process, a coordination compound is added to a feed solution rich in multiple valuable metal ions. By controlling the type of ligand, ligand concentration, solution pH, etc., a certain metal ion is prompted to react with the ligand to form an anion complex, while other ions are not coordinated and remain in the form of cations. Under the drive of an electric field with a certain current density, the anion complex and the metal cation are respectively transmitted in opposite directions and enter different chambers of the device through a specific ion-selective composite membrane, thereby achieving synchronous separation of multiple metal ions with high separation efficiency. At the same time, this technology can further separate more metal ions. In addition, solar energy is used as a driving force to achieve synchronous separation of multiple metal ions, saving energy and reducing consumption. At the same time, the method proposed by the present invention has a small amount of chemical reagents, a simple operation process, and can achieve effective separation of multiple metal ions in one step. Furthermore, the metal coordination coupled light-driven electrodialysis technology of the present invention breaks through the bottleneck of the difficulty in synchronous separation of valuable metal ions faced by traditional electrodialysis technology, as well as the problem of high operating energy consumption. Using renewable energy as a driving force is ideally environmentally friendly and sustainable, and can promote the realization of my country's "dual carbon" goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the metal coordination coupled solar-driven electrodialysis system provided by the present invention.

[0043] Figure 2 The metal ion transmission flux under different ligand conditions provided in Example 1 of the present invention.

[0044] Figure 3 Effects of different NH4SCN concentrations on ion transport flux (a) and metal separation purity (b) provided in Example 2 of the present invention.

[0045] Figure 4 The proportions of various metal ions in the concentrated solution 2 at different current densities provided in Example 3 of the present invention.

[0046] Figure 5 (a) The proportion of corresponding metal ions in each solution and the separation purity under solar energy drive provided in Example 5 of the present invention; (b) the changes in voltage and current.

[0047] Figure 6 Schematic diagram of the metal coordination coupled solar-driven electrodialysis system for separating multi-metal ions provided in Example 6 of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. It is necessary to point out that the specific implementation cases described herein are only used to explain the present application, rather than to limit the present application.

[0049] Example 1

[0050] This embodiment is used to separate three kinds of metal ions. Figure 1 As shown, the metal coordination coupled solar-driven electrodialysis system consists of a photovoltaic unit and an electrodialysis unit; the anode and cathode of the photovoltaic unit are respectively arranged on both sides of the electrodialysis unit, and the electrodialysis unit is divided into different chambers by membranes, and the chambers adjacent to the cathode and the anode are respectively separated by corresponding ion exchange membranes to form electrode liquid chambers of each polarity; the membrane of the chamber composed of the anion exchange membrane is a cation selective composite membrane to form a concentration chamber 2; the membrane of the chamber composed of the cation selective composite membrane to form a liquid storage chamber to be separated is a polymer coated membrane, and the polymer coated membrane and the cation exchange membrane form a concentration chamber 1.

[0051] The photovoltaic unit is powered by the sun.

[0052] The above-mentioned concentrated solutions are all 0.1M sulfuric acid solutions, and the electrode solutions are all 0.1M sulfuric acid solutions.

[0053] Example 2

[0054] Separation method:

[0055] 1) Preparation of polymer coating film:

[0056] The composite membrane 1 is prepared by solvent evaporation method using polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a polymer macromolecule. The preparation according to the existing method is as follows: a certain amount of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and trioctylamine (TOA) (PVDF-HFP and TOA mass ratio is 2:3) are added to tetrahydrofuran solvent, and stirred at 45°C for 5 hours to form a uniform casting solution. After degassing, the above solution is poured into a mold, and the solvent is evaporated to obtain the result.

[0057] 2) Metal coordination coupled electrodialysis technology is used for metal ion separation:

[0058] use Figure 1 A metal coordination coupled solar-driven electrodialysis system was established. The difference is that a DC power supply is used to power the electrodialysis system. The raw material solution contains 40 mg / L Li + 、100mg / LCo 2+ 、100mg / LNi 2+ The mixed solution is 0.1M H2SO4, the concentrate 1, the concentrate 2 and the electrode solution, the composite membrane 1 is a polymer coated membrane prepared by the above method, and the composite membrane 2 is a monovalent cation selective membrane. The current density is 10mA / cm 2 Before the system was operated, 0.1 M, 0.01 M or 6 M NH4SCN, EDTA or HCl was added to the raw material solution to coordinate the metal ions with the ligand compounds in advance. Subsequently, the system was operated in constant current mode with a current density of 10 mA / cm 2 , and run for 8 hours. During this period, 1 ml samples were taken from the raw solution, concentrate 1 and concentrate 2 every 1 hour to determine the metal ion concentration and analyze the ion transfer flux.

[0059] Depend on Figure 2 It can be seen that when NH4SCN is used as a ligand, Co(SCN)4 2- The transport flux was 12.7 μmol m -2 s -1 , Li + The flux was 25 μmol m -2 s -1 , Ni 2+ The flux was only 0.03 μmol m -2 s -1 , indicating that Co(SCN)4 2- Passing through composite membrane 1 into concentrate 1 and being enriched, Li + is enriched in concentrate 2, while Ni 2+Retained in the raw liquid, thus achieving the synchronous separation of the three.

[0060] When EDTA is used as a ligand, Li + The flux was 20 μmol m -2 s -1 However, due to the strong coordination ability of EDTA, it 2+ and Ni 2+ Reacts to form Co(EDTA) 2- andNi(EDTA) 2- The transport flux of the two is close, about 10 μmol m -2 s -1 , indicating that it is difficult to achieve the simultaneous separation of the three using EDTA as a ligand.

[0061] When HCl is used as a ligand, Co 2+ With Cl - Coordination occurs to form CoCl4 2- , with a flux of 11 μmol m -2 s -1 , Ni 2+ Not with Cl - Coordination occurs, the flux is close to 0, but Li + The flux is also close to 0, indicating that in this state, Li + It is difficult to transport across the membrane, and it is difficult to achieve synchronous separation of the three.

[0062] Among them, the ion transmission flux is calculated using the formula J = (C t -C0)×V / A m / t, where C0 and C t represents the concentration of metal ions in concentrate 1 and concentrate 2 at the beginning of the experiment and time t, respectively, V represents the volume of the solution, A m is the effective membrane area.

[0063] In summary, it can be seen that the type of ligand has an important influence on the efficient separation of lithium, cobalt and nickel. Compared with EDTA and HCl, NH4SCN is an ideal ligand that can selectively bind to Co 2+ Coordination to form Co(SCN)4 2- , enriched in the concentrate 1 by the composite membrane 1, Li + is enriched in concentrate 2, while Ni 2+ Retained in the raw liquid, thus achieving the synchronous separation of the three.

[0064] Example 3

[0065] The difference from Example 2 is that the ligand is NH4SCN, and the effect of its concentration on the metal ion separation effect is investigated. The current density is 10 mA / cm 2.Depend on Figure 3 (a) It can be seen that as the concentration of NH4SCN increases, Li + The flux showed a downward trend, Co(SCN)4 2- The flux of Co(SCN)4 increases first and then stabilizes. 2- The flux was 12.7 μmol m -2 s -1 , Li + The flux was 25 μmol m -2 s -1 In addition, Figure 3 (b) It can be seen that when the NH4SCN concentration is 0.1M, the purities of cobalt, lithium and nickel in concentrate 1, concentrate 2 and feed solution are 97.5%, 97.2% and 58.3%, respectively, indicating that the efficient separation of lithium, cobalt and nickel can be achieved simultaneously through metal coordination coupled electrodialysis technology.

[0066] Example 4

[0067] The difference from Example 3 is that the ligand is NH4SCN with a concentration of 0.1 M, and the effect of current density on metal coordination and ion separation is investigated. Figure 4 It can be seen that when the current density is 3.5mA / cm 2 When the concentration of lithium in concentrate 2 is 100%, it means that only Li + Transmitted through composite membrane 2; when the current density is 10mA / cm 2 When the current density is as high as 20 mA / cm 2 , the proportion of lithium in the concentrated solution 2 dropped to 67.8%, cobalt accounted for 11.2%, and nickel accounted for 21%, indicating that under high current conditions, the electric field strength increased, and Ni2+ was transmitted across the membrane due to the strong electric field force, while affecting the coordination of Co2+ and SCN-, resulting in a large amount of Co2+ in the raw material solution. Under the action of the electric field force, it crosses the membrane into the concentrated solution 2. Therefore, the current intensity will affect the coordination of metal ions, and then affect the ion separation effect.

[0068] Example 5

[0069] The difference from Example 4 is that: + / Co 2+ The influence of ratio on metal coordination and ion separation. 2+ Priority with SCN - Coordination, and Ni 2+ Uncoordinated, under the action of electric field, Li+ and Co(SCN)4 2-As the main transport ions, the two are transported in opposite directions, forming a closed loop. When the transmission of one of the ions ends, the electrodialysis process ends. 2+ The concentration remains unchanged, and the Li content in the feed solution is adjusted + / Co 2+ The concentration ratios were 1:10, 1:5, 1:2.5 and 1:1, and the current density was 7 mA / cm 2 The test results show that with the Li + / Co 2+ The decrease in the ratio of Co(SCN)4 2- The transfer flux and the purity of cobalt in concentrate 1 remain almost unchanged, but Li + As the transmission flux increases, the purity of lithium in the concentrated solution 2 increases, while the purity of nickel in the raw solution decreases; + / Co 2+ When the ratio is 1:10, due to the Li + Less, the transmission flux is lower under the electric field; with the Li + / Co 2+ The ratio decreases, and the Li + Increase, more Li under the electric field + Through the composite membrane 2, the Li+ transport flux increases; when Li + When the content is too high, Co(SCN)4 2- The electroosmosis process is terminated after the transfer is completed, which causes some Li + It cannot be transported further and remains in the raw material solution, resulting in a decrease in the purity of nickel. Comprehensive analysis shows that the separation condition is when the Li+ / Co2+ ratio is 1:2.5. + The transport flux was 15 μmol m -2 s -1 ,Co(SCN)4 2- The transport flux is 8 μmol m -2 s -1 The purity of lithium, cobalt and nickel are 95%, ~100% and 32% respectively.

[0070] By comparing Examples 3 and 4, it is shown that starting the treatment when the metal ion concentration in the raw material liquid reaches a certain ratio under direct current and coordinating the current density has an important influence on the ion separation effect, and the coordinated regulation of the above factors can improve the separation efficiency.

[0071] Example 6

[0072] By analyzing the influencing factors of the above embodiments, specific conditions are determined, and the Figure 1 As shown, a metal coordination coupled solar-driven electrodialysis system is established outdoors to separate metal ions, and photovoltaics are used to provide electrical energy for the electrodialysis system.

[0073] The raw material solution contains 40mg / LLi + 、100mg / LCo 2+ 、100mg / LNi 2+ The mixed solution, the concentrated solution 1, the concentrated solution 2 and the electrode solution are all 0.1M H2SO4, the composite membrane 1 is the polymer coated membrane prepared in step (1) of Example 2, and the composite membrane 2 is a monovalent cation selective membrane.

[0074] Before the system is operated, NH4SCN is added to the raw material solution at a concentration of 0.1 M to make Co 2+ Pre-work with SCN - Subsequently, the system was operated under solar energy drive from 8:00 to 16:00 for 8 hours. During this period, 1 ml of samples were taken from the raw material solution, concentrate 1 and concentrate 2 every 1 hour to determine the metal ion concentration, analyze the ion transfer flux, and use a multimeter to monitor the changes in current and voltage in real time.

[0075] Depend on Figure 5 It can be seen that under the assistance of solar energy, cobalt, lithium and nickel are enriched in concentrate 1, concentrate 2 and feed solution respectively. As time goes on, the content of cobalt in concentrate 1 gradually increases, and the lithium and cobalt in the feed solution decrease significantly. Due to the small amount of nickel entering concentrates 1 and 2, its content decreases slightly, and the lithium content in concentrate 2 increases significantly. After 8 hours of continuous testing, the purity of cobalt, lithium and nickel in concentrate 1, concentrate 2 and feed solution is 100%, 94.3% and 99.2% respectively. During the test phase, the voltage range is 5-6V, the current range is 0.06-0.2A, and the corresponding current density is 3-10mA / cm 2 , indicating that even under the non-steady-state current and voltage provided by solar energy (such as Figure 5 b), the separation system proposed in the present invention can still obtain excellent separation performance, which further illustrates that the metal coordination coupled electrodialysis system can be easily combined with renewable energy sources such as solar energy and wind energy to achieve the synchronous separation of lithium, cobalt and nickel.

[0076] Example 7

[0077] The difference from Example 6 is that the number of photovoltaic panels is increased to provide a larger voltage (current). During the separation test, the voltage range is 9V-10V, the current range is 0.2A-0.5A, and the corresponding current density is 10-25mA / cm 2After 8 hours of continuous testing, the purities of cobalt, lithium and nickel in concentrate 1, concentrate 2 and feed solution were 100%, 90% and 46% respectively, indicating that the voltage (or current) provided by solar photovoltaic power generation has an important influence on the separation performance. The metal ion separation effect in the system can be improved by comprehensively adjusting the current density, the concentration ratio of metal ions in the solution, and the type and concentration of ligands.

[0078] Example 8

[0079] like Figure 1 Based on the system, the metal coordination coupled electrodialysis system is used to separate and recycle lead, copper, zinc, cadmium and sodium metal ions contained in waste circuit boards. According to the difference in the stability constants of the complexes formed by metal ions and different ligands, organic ligands are screened, and the ligand concentration (0.01-6M), current density (1-50mA / cm 2 ) and other conditions.

[0080] like Figure 6 As shown, HCl is added to the raw material solution as ligand 1 to promote the coordination reaction of lead, cadmium and zinc ions to form anionic complexes, which are transported to the anode through membrane 1 under the action of the electric field, while copper and sodium ions are not coordinated and are transported to the cathode. Since sodium ions have a smaller size, they pass through membrane 2 while copper ions remain in the raw material solution; then NH4SCN ligand 2 is added to the mixed solution of lead, cadmium and zinc ions. Since cadmium and zinc ions have stronger coordination ability, they continue to be transported to the anode through membrane 3 in the form of anionic complexes; finally, sulfosalicylic acid is added to the mixed solution of cadmium and zinc as ligand 3. Cadmium ions have stronger coordination ability and continue to be transported to the cathode through membrane 4, and the zinc ion complex dissociates into zinc ions, thereby achieving effective separation of the five metals.

[0081] The specific implementation methods described above are only used to specifically illustrate the spirit of the present invention, and the protection scope of the present invention is not limited thereto. Under the guidance of the present invention, changes made by technicians in this field within the scope covered by the purpose of the present invention are still within the protection scope of the present invention.

Claims

1. A method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis, characterized in that: In the electrodialysis separation process, a ligand is added to a feed solution rich in multiple valuable metal ions to be separated, and the ligand is controlled to coordinate with at least one metal ion to be separated to form an anion complex; during the coordination reaction, driven by the electric field obtained by solar energy, the anion complex and the uncoordinated metal cation are transported in opposite directions respectively, the anion complex is transported and separated through the polymer coating membrane, and the uncoordinated metal cation is transported and separated as a single metal ion through the cation selective composite membrane, thereby separating the coordinated and uncoordinated multiple ions.

2. The method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis according to claim 1, characterized in that: First, the feed liquid rich in multiple valuable metal ions to be separated is tested for the types and concentrations of ions contained therein, and after the metal ions to be separated are determined, a ligand is added to the feed liquid to control the ligand to coordinate with at least one metal ion to be separated to form an anion complex; during the coordination reaction, driven by an electric field, the anion complex and the uncoordinated metal cation are transported in opposite directions respectively, the anion complex is transported and separated by a polymer coating membrane, and the uncoordinated metal cation is transported and separated by a cation selective composite membrane to realize the transport and separation of a single metal ion, thereby separating the coordinated and uncoordinated multiple ions; the cation selective composite membrane is a cation exchange membrane, a specific cation selective composite membrane or a monovalent / multivalent selective cation exchange membrane.

3. The method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis according to claim 2, characterized in that: The uncoordinated metal cations are one or more than two; If the uncoordinated metal is one, it is transported to the cathode under the drive of the electric field and separated from the feed liquid through the cation exchange membrane; If there are two or more uncoordinated metals and they contain metals of the same valence, they are transported to the cathode under the drive of the electric field, and a certain metal ion that interacts with the membrane is separated from the feed liquid through a specific cation selective composite membrane, and then separated one by one according to the metal properties until each ion is separated individually; If there are more than two uncoordinated metals and they contain metals of different valence states, they are transported to the cathode under the drive of the electric field, and the monovalent metal ions are separated from the feed liquid through the monovalent / multivalent selective cation exchange membrane, and then separated one by one according to the metal properties until each ion is separated individually.

4. The method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis according to claim 3, characterized in that: The cation selective composite membrane is a cation exchange membrane, a specific cation selective composite membrane or a monovalent / multivalent selective cation exchange membrane; The cation exchange membrane is a polymer membrane containing at least one negatively charged group; the negatively charged group is one or more of a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, a phenolic group, an arsenic acid group and a selenic acid group; The specific cation selective composite membrane has components or groups in the membrane that interact with specific metals, including one or more of crown ether and EDTA modified polymer membranes; The monovalent cation exchange membrane is a polymer coating membrane with at least one negatively charged group inside and a positively charged surface; the negatively charged group is one or more of sulfonic acid group, phosphoric acid group, carboxylic acid group, phenol group, arsenic acid group and selenic acid group.

5. The method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis according to claim 2, characterized in that: The ligand coordinates with a metal ion to be separated to form an anion complex; during the coordination reaction, the anion complex is driven by an electric field and transported toward the anode, and the anion complex is separated from the feed through the polymer coating membrane; If the ligand coordinates with two or more metal ions to be separated to form an anion complex; during the coordination reaction, under the driving force of the electric field, the anion complex is transported toward the anode, and the anion complex is separated from the feed through the polymer coating membrane; then the ligand is added to the separated two or more metal ions to form an anion complex, and the above electric field driving effect is repeated to separate different metal ions one by one until a single metal ion is separated.

6. The method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis according to any one of claims 1 to 5, characterized in that: The multiple valuable metal ions in the feed liquid to be separated are Li + 、Co 2+ 、Ni 2+ , Mn 2+ , Cu 2+ 、Zn 2+ 、Cd 2+ , Pb 2+ ; The ligand is one or more of NH4SCN, KSCN, NaSCN, HCl, NaCN, ethylenediaminetetraacetic acid, and HF; The polymer coating film is one or more polymer composite films containing trihexyltetradecylphosphonium chloride, methyltrioctyl, ammonium chloride and trioctylamine.

7. The method for synchronous separation of multiple metals by metal coordination coupling solar energy driven electrodialysis according to any one of claims 1 to 5, characterized in that: The concentration of the ligand is 0.01-6M; the electric field voltage is 0.01-30V; the current density is 1-50mA / cm 2 .

8. A device used in the method of claim 1, characterized in that: The device consists of a photovoltaic unit and an electrodialysis unit; the anode and cathode of the photovoltaic unit are respectively arranged on both sides of the electrodialysis unit, and the electrodialysis unit is divided into different chambers by a membrane according to the number of separated ions. The two chambers adjacent to the cathode and the anode are electrode chambers, in which electrolyte is added; The feed solution to be separated is injected into a relatively central chamber in the electrodialysis unit.

9. The device used in the method according to claim 8, characterized in that: The photovoltaic unit is powered by the sun.

10. An application of the method according to claim 1, characterized in that: Application of the method in metal separation.

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