Method for recycling chloride solution from metal smelting separation process by means of electrolysis

Abstract

Disclosed in the present invention is a method for recycling a chloride solution from a metal smelting separation process by means of electrolysis. A metal chloride solution and a sodium chloride solution obtained from a metal smelting separation process are recovered, a sodium hydroxide solution prepared by means of an electrolysis method and hydrochloric acid are recycled for the metal smelting separation process, and CO2 generated in a roasting process is recovered and is cyclically used in a metal carbonization and precipitation process, thereby achieving the recycling of the materials from the smelting separation process. Moreover, the technique has good applicability, and solves problems common in the industry at present, such as the high energy consumption and costs of the end-of-pipe treatment of wastewater, and difficulties in material recycling.

Description

A method for electrolytic recycling of chloride solution in metal smelting separation process

[0001] Cross-referencing

[0002] This application is based on and claims priority to Chinese Patent Application No. 2024112010987, filed on August 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of hydrometallurgical technology, and in particular to a method for the electrolytic recycling of chloride solutions in metal smelting and separation processes. Background Technology

[0004] Metals are diverse and can be categorized into heavy metals (such as copper, lead, and zinc), light metals (such as aluminum and magnesium), transition metals (such as titanium, vanadium, chromium, manganese, iron, and zinc), and rare earth metals (lanthanum, cerium, praseodymium, neodymium, and yttrium). Metal smelting involves separating metallic elements from ores, concentrates, and secondary resources (such as scrap metal and smelting slag). Taking hydrometallurgy as an example, it takes place in an aqueous solution and includes leaching, liquid-solid separation, solution purification, and enrichment.

[0005] In the purification process of metal smelting solutions, hydrochloric acid can be used to dissolve and remove impurities from the obtained metal oxides, metal hydroxides, metal carbonates and basic metal carbonates, or to back-extract the loaded organic phase containing metal elements obtained after extraction, ultimately obtaining a single / high-purity metal chloride solution. Then, oxalic acid, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, etc. are used for precipitation to obtain metal oxalates and carbonates, and finally calcination is used to obtain high-purity metal oxides.

[0006] Next, we will take rare earth smelting and separation technology as an example. Global rare earth resources are mainly divided into mineral-type rare earth mines (typical examples include bastnaesite, monazite, and mixed rare earth concentrates, xenotime, and niobium phosphate) and ion-adsorption-type rare earth mines. The former are mainly distributed in China, the United States, Australia, India, Brazil, South Africa, and Canada, while the latter are mainly distributed in China, Myanmar, Malaysia, and Vietnam. Around these resources, various unique decomposition and extraction separation purification processes have been developed. Mixed rare earth concentrates are mainly smelted and separated using the sulfuric acid roasting method (third-generation acid method). After sulfuric acid roasting and decomposition followed by water leaching, a mixed sulfuric acid rare earth solution is obtained. Then, through extraction separation and hydrochloric acid back-extraction, a single or high-purity rare earth chloride solution is obtained. Bastate rare earth concentrates are generally decomposed by oxidative roasting and acid dissolution to obtain a mixed rare earth chloride solution, followed by extraction separation and hydrochloric acid back-extraction to obtain a single or high-purity rare earth chloride solution. Monazite, xenotime, and other mineral-type rare earth concentrates are mainly processed using an alkaline decomposition-acid dissolution method to obtain a mixed rare earth chloride solution. This solution is then extracted and separated using hydrochloric acid back-extraction to obtain a single or high-purity rare earth chloride solution. Ion-adsorption type rare earth mineral products include mixed rare earth chloride solutions, or mixed rare earth oxides or carbonates. Acid dissolution is used to remove impurities, resulting in a mixed rare earth chloride solution. This solution is then extracted and separated using hydrochloric acid back-extraction to obtain a single or high-purity rare earth chloride solution. The obtained single / high-purity rare earth chloride solutions are then precipitated using oxalic acid, ammonium bicarbonate, sodium carbonate, etc., to obtain rare earth oxalates and rare earth carbonates. Finally, calcination yields rare earth oxides.

[0007] The above process requires the purchase of chemical materials such as hydrochloric acid, oxalic acid, ammonium bicarbonate, sodium carbonate, and sodium bicarbonate. The precipitation process inevitably generates large amounts of oxalic acid wastewater / ammonia nitrogen wastewater / high-salt wastewater, as well as CO2 greenhouse gases produced during precipitation and roasting, placing a heavy cost and environmental burden on metal smelting and separation enterprises. Currently, the research and application of recycling and treating smelting wastewater mainly focuses on evaporation crystallization, membrane separation, stripping, and breakpoint chlorination. Evaporation crystallization is a relatively mature method, suitable for high-concentration ammonia nitrogen wastewater and saline wastewater. After evaporation and concentration to a supersaturated state, crystal nuclei are formed, gradually generating crystalline solids, producing large amounts of industrial waste salt with no market. This technology requires highly corrosion-resistant equipment, involves large investments, high energy consumption, and high operating costs. Calcium-containing sulfate systems are prone to scaling, affecting operation. Membrane separation utilizes selective permeability to separate ions, molecules, or particles in water, offering good treatment results, but it is prone to membrane fouling, has stringent requirements for wastewater quality, and still needs to be followed by evaporation concentration after concentration. Steam stripping involves direct contact between wastewater and steam, causing volatile substances in the wastewater to diffuse into the gas phase in a specific ratio, thus separating pollutants from the wastewater. It is primarily used for treating volatile pollutants. Breakpoint chlorination involves adding a certain amount of chlorine or sodium hypochlorite to the wastewater, oxidizing ammonia nitrogen to N2, thereby removing ammonia nitrogen. However, this method requires large chlorination volumes and incurs high operating costs. These methods are not end-of-pipe treatment technologies and have disadvantages such as high operating costs, large investment costs, lack of material recycling, and limitations imposed by wastewater conditions, thus restricting their industrial application. Under increasingly stringent environmental requirements, developing green and environmentally optimized smelting separation technologies is of paramount importance. Summary of the Invention

[0008] The purpose of this invention is to provide a method for the electrolytic recycling of chloride solutions obtained in the metal smelting and separation process. By recovering the metal chloride solution or sodium chloride solution obtained in the metal smelting and separation process, sodium hydroxide solution is prepared by electrolysis and recycled with hydrochloric acid for use in the metal smelting and separation process. The CO2 generated in the roasting process is recovered and recycled for the metal carbonization and precipitation process. This realizes the recycling of materials in the smelting and separation process. Moreover, this technology has good applicability and can solve the problems of high energy consumption and cost of end-of-pipe wastewater treatment, difficulty in recycling materials, and CO2 greenhouse gas emissions that are common in industry.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for the electrolytic recycling of chloride solutions in a metal smelting separation process, the method comprising the following steps:

[0010] S1: Dissolve at least one of the metal oxides, metal hydroxides, metal carbonates and basic metal carbonates obtained from the metal smelting and separation process in the recovered hydrochloric acid to obtain a metal chloride solution.

[0011] or,

[0012] The recovered hydrochloric acid is used in a metal solution extraction and separation process to obtain a metal chloride solution;

[0013] S2: The metal chloride solution obtained in S1, the recovered sodium hydroxide solution and CO2 gas are subjected to a carbonation precipitation reaction to obtain a slurry. After solid-liquid separation, metal carbonates and / or basic carbonates and sodium chloride solution are obtained.

[0014] S3: The metal chloride solution obtained in S1 and / or the sodium chloride solution obtained in S2 are subjected to ion membrane electrolysis to obtain metal hydroxide precipitate and / or sodium hydroxide solution, as well as hydrogen and chlorine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in S2. The hydrogen and chlorine are used to synthesize hydrochloric acid, which is then recycled for the dissolution or extraction separation process in S1.

[0015] or,

[0016] The sodium chloride solution obtained in S2 is subjected to bipolar membrane electrolysis to obtain sodium hydroxide solution, hydrochloric acid and dilute brine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in S2, the hydrochloric acid is recycled for the dissolution or extraction separation process in S1, and the dilute brine is recovered for diluting the sodium chloride solution obtained in S2.

[0017] S4: The metal carbonate and / or basic carbonate obtained in S2 are roasted to obtain high-purity metal oxide and CO2 gas, and the CO2 gas is recycled for the carbonization precipitation reaction in S2.

[0018] S5: The metal hydroxide precipitate obtained in S3 is calcined to obtain high-purity metal oxide and water. The water is recycled for the ion-exchange membrane electrolysis or bipolar membrane electrolysis described in S3.

[0019] Furthermore, the metal includes at least one of the following: alkaline earth metals, rare earth metals, refractory rare metals, transition metals, and main group metals;

[0020] Preferably, the alkaline earth metal includes at least one of beryllium, magnesium, calcium, and strontium; the rare earth metal includes at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium; the refractory rare metal includes at least one of zirconium, hafnium, tantalum, and niobium; the transition metal includes at least one of vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, and thorium; and the main group metal includes at least one of aluminum, gallium, indium, tin, antimony, and bismuth.

[0021] Furthermore, the ion-exchange membrane electrolysis in S3 is to perform ion-exchange membrane electrolysis on the metal chloride solution and / or the sodium chloride solution through an ion-exchange membrane electrolysis cell;

[0022] The electrolysis process parameters are as follows: current density is 1.0 kA / m 2 ~8.0kA / m 2 The electrolysis temperature is 20℃~90℃, and the cell voltage is 2.1V~5.0V;

[0023] The inter-electrode spacing is 0.1 mm to 10 mm, and preferably the inter-electrode spacing is equal to the thickness of the ion exchange membrane.

[0024] Furthermore, the membrane electrolyzer includes several ion-exchange membrane electrolysis units;

[0025] Each of the ion-exchange membrane electrolysis units includes: a cathode chamber, an anode chamber, a cathode, an anode, and a cation exchange membrane, wherein the cation exchange membrane separates the cathode chamber and the anode chamber, the anode located in the anode chamber is connected to the positive terminal of a DC power supply, and the cathode located in the cathode chamber is connected to the negative terminal of a DC power supply;

[0026] The membrane electrolyzer also includes a gas recovery and utilization unit, which includes: a hydrogen gas-liquid separator and dryer, a chlorine gas-liquid separator and dryer, and a hydrochloric acid synthesis device; the sodium hydroxide solution obtained from the hydrogen gas-liquid separation is returned to the cathode chamber, and the sodium chloride solution obtained from the chlorine gas-liquid separation is returned to the anode chamber.

[0027] Furthermore, the electrolyte in the anode chamber of the ion-exchange membrane electrolysis unit is a sodium chloride solution or / and a metal chloride solution, preferably a sodium chloride solution;

[0028] The electrolyte in the cathode chamber of the ion-exchange membrane electrolysis unit is a sodium hydroxide solution and pure water.

[0029] Furthermore, the concentration of sodium chloride and / or metal chloride solution in the electrolyte of the anode chamber is 100 g / L to 300 g / L, calculated as NaCl and / or MO, where M is a metal element;

[0030] The sodium hydroxide concentration in the cathode chamber electrolyte is 150 g / L to 350 g / L.

[0031] Furthermore, the bipolar membrane electrolysis process parameters are: current density of 0.3 kA / m 2 ~3kA / m 2 The electrolysis temperature is 5℃~50℃, and the membrane stack voltage is 10V-50V;

[0032] The membrane spacing is 0.1mm to 10mm, and the electrode spacing is 2.0-7.0cm.

[0033] Furthermore, the bipolar membrane electrolysis includes several bipolar membrane electrolysis units;

[0034] Each of the bipolar membrane electrolysis units has a four-membrane, three-compartment configuration, including: an anode, a cathode, a cation exchange membrane, an anion exchange membrane, a bipolar membrane, a cathode chamber, a salt chamber, and an anode chamber. The bipolar membrane, cation exchange membrane, and anion exchange membrane separate the cathode chamber, salt chamber, and anode chamber. The anode is connected to the positive terminal of a DC power supply, and the cathode is connected to the negative terminal of a DC power supply.

[0035] Furthermore, the electrolyte in the salt chamber of the bipolar membrane electrolysis unit is a sodium chloride solution;

[0036] The electrolyte in the acid and alkali chambers of the bipolar membrane electrolysis unit is pure water.

[0037] Furthermore, the concentration of sodium chloride raw material at the inlet of the anode chamber is 80 g / L to 150 g / L (calculated as NaCl), and the concentration of sodium chloride at the outlet is 10 g / L to 50 g / L (calculated as NaCl).

[0038] Furthermore, the cation exchange membrane is one of a perfluorosulfonic acid membrane, a perfluorocarboxylic acid membrane, or a perfluorosulfonic acid / carboxylic acid composite membrane.

[0039] Furthermore, the cation exchange membrane is a cation exchange membrane with valence selectivity obtained by surface modification through at least one of surface coating, electrodeposition, and chemical grafting.

[0040] Furthermore, the anion exchange membrane contains -NH3. + -NR2H + or PR 3+ A polymer membrane with basic active exchange groups, where R is a hydrocarbon group;

[0041] The bipolar membrane is an ion exchange membrane prepared by one of the following methods: hot pressing of anion and cation exchange membranes, adhesive molding, casting molding, and electrodeposition molding.

[0042] Furthermore, the cathode includes: a titanium metal mesh, a nickel metal mesh, an iron metal mesh, or a metal mesh with an active layer of at least one of nickel, platinum, or ruthenium electroplated on its surface;

[0043] The anode comprises: a titanium metal mesh with at least one of ruthenium, iridium, rhodium, palladium and platinum electroplated on its surface, wherein the phases of ruthenium, iridium, rhodium and platinum are oxides.

[0044] Furthermore, the carbonization precipitation reaction described in S2, involving the metal chloride solution obtained in S1, the sodium hydroxide solution obtained in S3, and the CO2 gas obtained in S4, includes:

[0045] Simultaneously, a carbonization precipitation reaction is carried out, with a pH value of 3.5 to 9.0, a pressure range of 0.1 MPa to 0.6 MPa, and a temperature range of 5℃ to 60℃. The obtained slurry is then subjected to solid-liquid separation to obtain metal carbonates and / or basic carbonates and sodium chloride solutions.

[0046] Furthermore, the carbonization precipitation reaction described in S2, involving the metal chloride solution obtained in S1, the sodium hydroxide solution obtained in S3, and the CO2 gas obtained in S4, includes:

[0047] First, the metal chloride solution obtained in S1 and the sodium hydroxide solution obtained in S3 are mixed to carry out a precipitation reaction to generate a metal hydroxide slurry. The pH value during the precipitation reaction is 3.0 to 13.0, preferably 5.0 to 11.5.

[0048] The CO2 gas obtained by S4 is then introduced into the metal hydroxide slurry to carry out a carbonization reaction, and a carbonized slurry is obtained. After solid-liquid separation, the metal carbonate and / or basic carbonate, as well as a sodium chloride solution, are obtained. The pressure range of the carbonization reaction process is 0.1 MPa to 0.6 MPa, and the temperature range is 5℃ to 60℃.

[0049] The technical solution of this invention has the following beneficial technical effects:

[0050] 1. All materials required in the entire metal smelting and separation process, such as hydrochloric acid, sodium hydroxide, sodium chloride, CO2, and water, are internally recycled, without introducing impurities or pollution. This is beneficial for metal separation and purification, and can yield metal-related products with higher purity.

[0051] 2. It has achieved internal recycling of materials such as acids, alkalis, salts, CO2 and water throughout the entire process, generating virtually no waste and significantly reducing the cost of chemical raw materials and environmental protection.

[0052] 3. When sodium chloride is used as the electrolyte in the anode chamber, by selecting a cation exchange membrane with valence state selectivity through surface modification, high-valence ions brought in by sodium chloride wastewater in the anode chamber are prevented from entering the cathode chamber and combining with hydroxide ions to form precipitates, thereby avoiding the increase in cell voltage and energy consumption and membrane damage, and ensuring continuous and stable operation of the electrolysis process;

[0053] 4. Taking rare earth as an example, the sodium chloride wastewater generated by various single rare earth element separation production lines can all share a set of equipment. The rare earth elements do not interfere with each other. The hydrochloric acid and sodium hydroxide solutions generated by electrolysis are of high purity and do not generate secondary pollution when returned to the rare earth hydrometallurgical separation system. Attached Figure Description

[0054] Figure 1 is a flowchart of the chloride solution electrolytic recycling method for metal smelting separation process provided by an embodiment of the present invention;

[0055] Figure 2 is a schematic diagram of the principle of the chloride solution ion membrane electrolysis recycling method in the rare earth metal smelting and separation process provided in the embodiment of the present invention.

[0056] Figure 3 is a schematic diagram of the principle of the bipolar membrane electrolytic recycling method for chloride solution in the rare earth metal smelting and separation process provided in the embodiment of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0058] Referring to Figure 1, this embodiment of the invention provides a method for the electrolytic recycling of chloride solutions in a metal smelting separation process, the method comprising the following steps:

[0059] S1: Dissolve at least one of the metal oxides, metal hydroxides, metal carbonates and basic metal carbonates obtained from the metal smelting and separation process in the recovered hydrochloric acid to obtain a metal chloride solution.

[0060] or,

[0061] The hydrochloric acid is applied to a metal solution extraction and separation process to obtain a metal chloride solution.

[0062] S2: The metal chloride solution obtained in S1, the recovered sodium hydroxide solution and CO2 gas are subjected to a carbonation precipitation reaction to obtain a slurry. After solid-liquid separation, metal carbonates and / or basic carbonates, as well as sodium chloride solution, are obtained.

[0063] S3: The metal chloride solution obtained in S1 and / or the sodium chloride solution obtained in S2 are subjected to ion membrane electrolysis to obtain metal hydroxide precipitate and / or sodium hydroxide solution, as well as hydrogen and chlorine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in S2. The hydrogen and chlorine are used to synthesize hydrochloric acid, which is then recycled for the dissolution or extraction separation process in S1.

[0064] or,

[0065] The sodium chloride solution obtained in S2 is subjected to bipolar membrane electrolysis to obtain sodium hydroxide solution, hydrochloric acid and dilute brine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in S2, the hydrochloric acid is recycled for the dissolution or extraction separation process in S1, and the dilute brine is recovered for diluting the sodium chloride solution obtained in S2.

[0066] S4: The metal carbonate and / or basic carbonate obtained in S2 are roasted to obtain high-purity metal oxide and CO2 gas, and the CO2 gas is recycled for the carbonization precipitation reaction in S2.

[0067] S5: The metal hydroxide precipitate obtained in S3 is calcined to obtain high-purity metal oxide and water. The water is recycled for the ion-exchange membrane electrolysis or the bipolar membrane electrolysis described in S3.

[0068] In a preferred embodiment of the present invention, in S3, the sodium chloride solution obtained in S2 is subjected to ion-exchange membrane electrolysis to obtain a sodium hydroxide solution, as well as hydrogen and chlorine. The sodium hydroxide solution is used for the carbonization precipitation reaction in S2, and the hydrogen and chlorine are used for a synthesis reaction to obtain hydrochloric acid, which is used for the dissolution or extraction separation process in S1, thereby realizing the effective recycling of materials.

[0069] or,

[0070] In step S3, the sodium chloride solution obtained in step S2 is subjected to bipolar membrane electrolysis to obtain sodium hydroxide solution, hydrochloric acid, and dilute brine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in step S2, the hydrochloric acid is recycled for the dissolution or extraction separation process in step S1, and the dilute brine is recovered to dilute the sodium chloride solution obtained in step S2, thereby achieving effective recycling of materials.

[0071] Specifically, the metals include at least one of the following: alkaline earth metals, rare earth metals, refractory rare metals, transition metals, and main group metals;

[0072] Preferably, the alkaline earth metal includes at least one of beryllium, magnesium, calcium, and strontium; the rare earth metal includes at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium; the refractory rare metal includes at least one of zirconium, hafnium, tantalum, and niobium; the transition metal includes at least one of vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, and thorium; and the main group metal includes at least one of aluminum, gallium, indium, tin, antimony, and bismuth.

[0073] In S3, ion-exchange membrane electrolysis involves electrolyzing a metal chloride solution and / or a sodium chloride solution using an ion-exchange membrane electrolytic cell. Figure 2 shows a schematic diagram of the principle of the ion-exchange membrane electrolysis recycling method for chloride solutions in the rare earth metal smelting and separation process provided in this embodiment of the invention. Referring to Figure 2, the electrolysis process parameters for ion-exchange membrane electrolysis are: current density of 1.0 kA / m 2 ~8.0kA / m 2 The electrolysis temperature is 20℃~90℃, the cell voltage is 2.1V~5.0V, and the electrode spacing is 0.1mm~10mm.

[0074] In the embodiments of the present invention, the preferred current density for the S3 ion-exchange membrane electrolysis process is 3 kA / m. 2 ~6kA / m 2 Electrolysis temperature 60℃~90℃, cell voltage 2.5V~4.0V, inter-electrode spacing ion membrane thickness.

[0075] The S3 process employs ion-exchange membrane electrolysis technology. At the cathode, a reduction reaction of water molecules produces hydrogen and hydroxide ions, while at the anode, a chloride ion oxidation reaction produces chlorine. Current density, electrolysis temperature, cell voltage, and electrode spacing all affect the electrolysis efficiency, power consumption, and acid-base recycling rate of the entire process. Therefore, in the application scenario of this invention, a current density range of 3 kA / m is preferred. 2 ~6kA / m 2 The electrolysis temperature is 60℃~90℃, the cell voltage is 2.5V~4.0V, and the electrode spacing is equal to the thickness of the ion membrane. This allows the electrolysis efficiency, alkali recycling rate, and hydrochloric acid recycling rate to reach approximately 98%, 98%, and 95%, respectively.

[0076] The membrane electrolyzer includes several ion-exchange membrane electrolysis units; each ion-exchange membrane electrolysis unit includes: a cathode chamber, an anode chamber, a cathode, an anode, and a cation exchange membrane. The cation exchange membrane separates the cathode chamber and the anode chamber. The anode in the anode chamber is connected to the positive terminal of the DC power supply, and the cathode in the cathode chamber is connected to the negative terminal of the DC power supply.

[0077] The membrane electrolyzer also includes a gas recovery and utilization unit, which comprises a hydrogen gas-liquid separator and dryer, a chlorine gas-liquid separator and dryer, and a hydrochloric acid synthesis device. The sodium hydroxide produced during electrolysis is used in the S2 carbonization precipitation process, or the metal hydroxide precipitate produced during electrolysis is directly used in the roasting process. The sodium hydroxide solution obtained from hydrogen gas-liquid separation returns to the cathode chamber, and the sodium chloride solution obtained from chlorine gas-liquid separation returns to the anode chamber. The separated and dried hydrogen and chlorine are respectively passed through a chlorine buffer tank, a chlorine flame arrester, a hydrogen buffer tank, a hydrogen flame arrester, and their respective regulating and connecting devices, and are mixed and burned in a certain ratio [chlorine to hydrogen ratio (1:1.05)~(1:1.10)] to synthesize hydrochloric acid, which is returned to S1 for use in the S1 dissolution or extraction separation process.

[0078] The electrolyte in the anode chamber of the ion-exchange membrane electrolysis unit is a sodium chloride solution and / or a metal chloride solution, preferably a sodium chloride solution;

[0079] The electrolyte in the cathode chamber of the ion-exchange membrane electrolysis unit is a sodium hydroxide solution and pure water.

[0080] The concentration of sodium chloride and / or metal chloride solution in the electrolyte of the anode chamber is 100 g / L to 300 g / L, preferably 150 g / L to 250 g / L, calculated as NaCl and / or MO, where M is a metal element;

[0081] The sodium hydroxide solution content in the cathode chamber electrolyte is 150 g / L to 350 g / L, preferably 200 g / L to 300 g / L.

[0082] In the ion-exchange membrane electrolysis described in this invention, the electrolyte concentration is closely related to the ionic strength and solution conductivity, thereby affecting the electrolysis efficiency, cell voltage, power consumption, and acid-base recycling rate. Too low a concentration will result in low ionic strength and conductivity, increased cell voltage, decreased electrolysis efficiency, increased power consumption, and decreased acid-base recycling rate. Therefore, to obtain the optimal process effect, in the application scenario of this invention, the preferred concentration range of sodium chloride and / or metal chloride solution is 150 g / L to 250 g / L, and the preferred concentration of sodium hydroxide solution in the cathode electrolyte is 200 g / L to 300 g / L, which can achieve an electrolysis efficiency, alkali recycling rate, and hydrochloric acid recycling rate of approximately 98%, 98%, and 95%, respectively.

[0083] The specific reaction equations for the electrolysis and hydrochloric acid synthesis processes are shown below:

[0084] Anode reaction: 2Cl - -2e = Cl2↑;

[0085] Cathode reaction: 2H₂O + 2e⁻ = H₂↑ + 2OH⁻ - ;

[0086] Na + +OH - =NaOH or / and M n+ +nOH - =M(OH) n ↓, M is a metallic element

[0087] Hydrochloric acid synthesis reaction: H2 + Cl2 = 2HCl;

[0088] In S3, bipolar membrane electrolysis involves electrolyzing a sodium chloride solution using a bipolar membrane stack. Figure 3 shows a schematic diagram of the principle of the bipolar membrane electrolysis recycling method for chloride solutions in the rare earth metal smelting and separation process provided in this embodiment of the invention. Referring to Figure 3, the rated process parameters of the bipolar membrane electrode are: current density of 0.3 kA / m 2 ~3kA / m 2 The electrolysis temperature is 5℃~50℃, the membrane stack voltage is 10V-50V, the membrane spacing is 0.1mm~10mm, and the electrode spacing is 2.0-7.0cm.

[0089] The bipolar membrane electrolysis comprises several bipolar membrane electrolysis units. Each bipolar membrane electrolysis unit has a four-membrane, three-compartment configuration, including: an anode, a cathode, a cation exchange membrane, an anion exchange membrane, a bipolar membrane, a cathode chamber, a salt chamber, and an anode chamber. The bipolar membrane, cation exchange membrane, and anion exchange membrane separate the cathode chamber, salt chamber, and anode chamber. The anode is connected to the positive terminal of a DC power supply, and the cathode is connected to the negative terminal of a DC power supply. Under the action of a DC electric field, water molecules are electrolyzed into H+ within the bipolar membrane. + and OH - H + OH- migrates through the bipolar membrane to the acid chamber via the cation exchange membrane. - Cl- migrates through the anion exchange membrane of the bipolar membrane to the alkali chamber. - It migrates through the anion exchange membrane to the acid chamber and reacts with H+. + Combined to form hydrochloric acid solution, Na + It enters the alkali chamber through the cation exchange membrane and combines with the alkali to form a sodium hydroxide solution.

[0090] The electrolyte in the salt chamber of the bipolar membrane electrolysis unit is a sodium chloride solution, and the electrolytes in the acid and alkali chambers of the bipolar membrane electrolysis unit are pure water.

[0091] Since the concentration of sodium chloride solution entering the salt chamber is directly related to the solution conductivity, which in turn affects the membrane stack voltage and energy consumption, in this embodiment, the preferred concentration of sodium chloride raw material at the anode chamber inlet (calculated as NaCl) is 120 g / L to 150 g / L, and the preferred concentration of sodium chloride at the outlet (calculated as NaCl) is 30 g / L to 50 g / L.

[0092] In S3 ion-exchange membrane electrolysis or bipolar membrane electrolysis, the cation exchange membrane is one of perfluorosulfonic acid membrane, perfluorocarboxylic acid membrane, or perfluorosulfonic acid / carboxylic acid composite membrane.

[0093] The cation exchange membrane is mainly composed of perfluorosulfonic acid resin, perfluorocarboxylic acid resin, polytetrafluoroethylene reinforcing mesh, and a modified hydrophilic coating. During electrolysis, the carboxylic acid layer facing the cathode chamber is thinner, repelling OH-. - For metal ions and / or Na + It exhibits high selectivity; the thicker sulfonic acid layer facing the anode chamber provides high ion permeability and low cell voltage. When the ion exchange membrane operates under the electric field generated by direct current, metal ions and / or Na+ in the brine (anolyte) are effectively absorbed. + Metal ions and / or Na migrate from one fixed negative charge to the next fixed negative charge through the ion exchange membrane. + In this way, they migrate from the anode chamber to the cathode chamber of the electrolytic cell, while Cl... - OH - Due to the repulsion of like ions, they are repelled into the anode and cathode chambers respectively, thereby achieving OH- -Without migrating from the cathode chamber to the anode chamber and thus reducing current efficiency, Cl - The product does not migrate from the anode chamber to the cathode chamber and thus contaminate it.

[0094] A cation exchange membrane is a cation exchange membrane with valence selectivity that has been modified by surface modification. Surface modification methods include at least one of the following: surface coating, electrodeposition, chemical grafting, etc.

[0095] The cation exchange membrane with valence selectivity obtained through the above surface modification can effectively control the migration process of cations in the electrolyte in the anode chamber and prevent impurity ions from entering the cathode chamber. For example, by increasing the surface charge density and / or reducing the pore size of the membrane through surface modification, only monovalent cations are allowed to pass through, while high-valence cations are retained, thereby obtaining a monovalent selective cation exchange membrane. It has the following advantages: In this invention, the monovalent selective cation exchange membrane can prevent high-valence cation impurities such as Ca, Mg, Al, and Fe in the electrolyte in the anode chamber from passing through, while retaining high-valence cations such as Na... + They are moved together into the cathode chamber to avoid combining with hydroxide ions in the cathode chamber to form precipitates, which would cause scaling on the membrane surface, increase the cell voltage, and reduce the performance of the ion exchange membrane, thus ensuring the stable operation of the electrolysis process.

[0096] The anion exchange membrane contains -NH3. + -NR2H + or PR 3+ An anion exchange membrane is a polymer membrane with alkaline active exchange groups, where R represents hydrocarbon groups. A suitable anion exchange membrane can effectively control OH- in solution. - and Cl - Selective migration reduces membrane stack voltage and energy consumption.

[0097] The bipolar membrane is an amphoteric ion exchange membrane prepared by hot pressing, bonding, casting, or electrodeposition. Under the action of a DC electric field, water molecules inside the bipolar membrane undergo electrolysis, and H+ is converted into hydrogen ions by the electric field between the anode and cathode. + Selective migration from the cation membrane to the acid chamber, OH - Selective migration from the anion exchange membrane to the alkali chamber enables efficient separation of anions and cations, providing key raw materials for subsequent acid and alkali production.

[0098] The cathode comprises: a titanium metal mesh, a nickel metal mesh, an iron metal mesh, or a metal mesh with an active layer of at least one of nickel, platinum, or ruthenium electroplated on its surface; the anode comprises: a titanium metal mesh with at least one of ruthenium, iridium, rhodium, palladium, and platinum electroplated on its surface, wherein the phases of ruthenium, iridium, rhodium, palladium, and platinum are oxides.

[0099] In the electrolytic production of sodium hydroxide, the electrodes initially used only for graphite as the anode due to the strong corrosive and oxidizing properties of chlorine gas and chlorine water. Carbon steel was sufficient for the cathode, as the operating conditions were milder. With the advent of ion-exchange membranes, titanium and nickel were used as cathode substrates to withstand the corrosiveness of high-concentration caustic soda. However, with technological advancements, the hydrogen evolution overpotential of titanium and nickel is higher than that of carbon steel. To further reduce the hydrogen evolution overpotential and achieve energy savings and increased current density, active coatings such as Raney nickel and other precious metals are plated onto nickel and titanium substrates. Graphite anodes, due to their susceptibility to deformation and detachment, have been replaced by titanium mesh coated with precious metal oxides, resulting in a lower chlorine evolution overpotential and greater resistance to chlorine gas and chlorine water corrosion. The mesh structure provides a larger contact area compared to sheet metal, which is more conducive to gas desorption.

[0100] In S2, the metal chloride solution obtained from S1, the sodium hydroxide solution obtained from S3, and the CO2 gas obtained from S4 undergo a carbonization precipitation reaction, including:

[0101] Simultaneously, a carbonization precipitation reaction is carried out, with the pH value ranging from 4.5 to 9.0, the pressure range from 0.1 MPa to 0.6 MPa, and the temperature range from 5℃ to 60℃. The resulting slurry is then separated into metal carbonates and / or basic carbonates, and sodium chloride solutions. Controlling the pH value, pressure, and temperature within the above ranges satisfies the requirements for the carbonization precipitation reaction of the metal chloride solution involved in this patent.

[0102] Taking rare earth metals as an example, the carbonization precipitation reaction equations are: 2RECl3+6NaOH+3CO2=RE2(CO3)3↓+6NaCl+3H2O; RECl3+3NaOH+CO2=RE(OH)(CO3)↓+3NaCl+H2O;

[0103] Furthermore,

[0104] In S2, the metal chloride solution obtained from S1, the sodium hydroxide solution obtained from S3, and the CO2 gas obtained from S4 undergo a carbonization precipitation reaction, including:

[0105] First, the metal chloride solution obtained in S1 and the sodium hydroxide solution obtained in S3 are mixed to carry out a precipitation reaction to generate a metal hydroxide slurry. The pH value during the precipitation reaction is 3.0 to 13.0. Controlling the pH value within the above range can meet the requirements of the metal chloride solution precipitation reaction involved in this patent, so that the CO2 recycling rate is as high as about 90%.

[0106] CO2 gas obtained by introducing S4 into a metal hydroxide slurry undergoes a carbonization reaction to obtain a carbonized slurry. After solid-liquid separation, metal carbonates and / or basic carbonates, as well as a sodium chloride solution, are obtained. The pressure range of the carbonization reaction is 0.1 MPa to 0.6 MPa, and the temperature range is 5℃ to 60℃. Controlling the pressure and temperature within the above ranges meets the requirements of the metal hydroxide carbonization precipitation reaction involved in this patent, resulting in a CO2 recycling rate of approximately 90%.

[0107] The precipitation reaction equation is MCl n +nNaOH=M(OH) n ↓+3NaCl;

[0108] M represents a metallic element, and n represents the valence state of the metal.

[0109] Taking rare earth metals as an example, the precipitation reaction equation is: RECl3 + 3NaOH = RE(OH)3↓ + 3NaCl;

[0110] The carbonization reaction equation is: 2M(OH) n +nCO2=M2(CO3) n ↓+nH2O;

[0111] Taking rare earth metals as an example, the carbonization reaction equations are: 2RE(OH)3 + 3CO2 = RE2(CO3)3↓ + 3H2O; RE(OH)3 + CO2 = RE(OH)(CO3)↓ + H2O;

[0112] The above process utilizes a recycled sodium hydroxide solution and CO2 gas with extremely low impurity content. By controlling key parameters such as pH, pressure, and temperature during the reaction, a higher metal yield (>97%) is achieved, with an optimal yield of 98.5%. Simultaneously, impurity ions are prevented from entering the precipitate, allowing for further purification during precipitation to prepare higher-purity metal-related products. Furthermore, by controlling the different carbonization precipitation reaction processes, it is possible to prepare metal carbonates and / or basic carbonates with varying product properties, resulting in products with different crystal forms, phases, particle sizes, and microstructures (plates, rods, discs, spheres, clusters, etc.), achieving a purity exceeding 99.999%.

[0113] The implementation conditions of the above technical solution are described below with reference to several embodiments and comparative examples (see Tables 1 and 2 for details of the embodiments).

[0114] Example 1

[0115] This embodiment uses praseodymium chloride-neodymium solution as raw material, and employs saponification P507 extraction to separate praseodymium and neodymium, obtaining high-purity praseodymium chloride and high-purity neodymium chloride solution. According to the process flow diagram shown in Figure 1, the method for electrolytic recycling of chloride solution in a metal smelting separation process described in this embodiment includes the following steps:

[0116] S1: The hydrochloric acid recovered by this method is used in the praseodymium-neodymium extraction and separation process to obtain praseodymium chloride and neodymium chloride solutions;

[0117] S2: The sodium hydroxide solution recovered by this method and CO2 gas are used to perform carbonation precipitation reactions on the praseodymium chloride and neodymium chloride solutions obtained in S1 to obtain a slurry. The pH value of the reaction process is 7.0 to 7.5, and the pressure range is 0.1 MPa. After solid-liquid separation of the slurry, praseodymium carbonate and neodymium carbonate solids and sodium chloride solution are obtained.

[0118] Alternatively, the sodium hydroxide solution recovered by this method can be added to praseodymium chloride and neodymium chloride solutions respectively and stirred to react and obtain praseodymium hydroxide and neodymium hydroxide slurries. The pH value during the precipitation process is 7.5-8.0. Then, the CO2 gas recovered by this method is passed into the slurries respectively and carbonization reaction is carried out under the conditions of 0.1 MPa and 35-40℃ to obtain praseodymium carbonate and neodymium carbonate slurries.

[0119] S3: The sodium chloride solution obtained in S2 is subjected to ion-exchange membrane electrolysis to obtain sodium hydroxide solution, hydrogen gas, and chlorine gas. The sodium hydroxide solution is used for the carbonization precipitation reaction in S2, and the hydrogen gas and chlorine gas are used for synthesis reaction to obtain hydrochloric acid, which is then recovered and used in the extraction and separation process of S1.

[0120] In this step, a nickel mesh is used as the cathode, a titanium mesh coated with ruthenium oxide is used as the anode, and the ion-exchange membrane is a perfluorosulfonic acid / carboxylic acid composite cation exchange membrane. The electrode spacing is equal to the thickness of the ion-exchange membrane. The electrolysis process parameters are: current density of 6.0 kA / m 2 The electrolysis temperature is 50℃, and the cell voltage is 2.3V.

[0121] The electrolyte in the anode chamber is a sodium chloride solution obtained from S2; the electrolyte in the cathode chamber is a sodium hydroxide solution and pure water. The concentration of the sodium chloride solution in the anode chamber electrolyte (calculated as NaCl) is 300 g / L; the concentration of the sodium hydroxide solution in the cathode chamber electrolyte is 300 g / L.

[0122] S4: The praseodymium carbonate and neodymium carbonate obtained in S2 are roasted separately to obtain high-purity praseodymium oxide, neodymium oxide and CO2 gas. The CO2 gas is captured and recovered for carbonization precipitation reaction in S2.

[0123] In the above steps, the sodium chloride produced in S2 is recycled by producing sodium hydroxide and hydrochloric acid through an ion-exchange membrane electrolysis process. The CO2 produced in S4 is recycled through a carbonization precipitation reaction and a roasting process, achieving a closed-loop material flow throughout the entire process. In this embodiment, the electrolysis efficiency reaches 98%, the alkali recycling rate reaches 98%, the hydrochloric acid recycling rate reaches 95%, the CO2 recycling rate reaches 87%, and the purity of praseodymium oxide and neodymium oxide products reaches 99.95% and 99.99%, respectively, with recovery rates of 98.5% and 98.4%, respectively.

[0124] Example 2

[0125] The hydrochloric acid recovered by this invention is used for praseodymium-neodymium extraction and separation to obtain praseodymium chloride and neodymium chloride solutions. The other steps are the same as in Example 1, except that the electrode spacing in the S3 electrolysis process parameters is 3 mm. Due to the increase in electrode spacing, the resistance between electrodes increases, and the cell voltage increases to 3.0 V.

[0126] In this embodiment, the electrolysis efficiency reached 96%, the alkali recycling rate reached 97%, the hydrochloric acid recycling rate reached 93%, the CO2 recycling rate reached 85%, and the purity of praseodymium oxide and neodymium oxide products reached 99.95% and 99.99%, respectively, with recovery rates of 98.1% and 98.0%, respectively.

[0127] The parameters for the other embodiments are shown in Tables 1 and 2:

[0128] Table 1. Ion-exchange membrane electrolysis conditions

[0129] Table 2 Carbonization precipitation conditions and final process evaluation indicators

[0130] Example 38

[0131] This embodiment uses praseodymium chloride-neodymium solution as raw material, and employs saponification P507 extraction to separate praseodymium and neodymium, obtaining high-purity praseodymium chloride and high-purity neodymium chloride solution. According to the process flow diagram shown in Figure 3, the method for electrolytic recycling of chloride solution in a metal smelting separation process described in this embodiment includes the following steps:

[0132] S1: The hydrochloric acid recovered by this method is used in the praseodymium-neodymium extraction and separation process to obtain praseodymium chloride and neodymium chloride solutions;

[0133] S2: The sodium hydroxide solution recovered by this method and CO2 gas are used to perform carbonation precipitation reactions on the praseodymium chloride and neodymium chloride solutions obtained in S1 to obtain a slurry. The pH value of the reaction process is 7.0 to 7.5, and the pressure range is 0.1 MPa. After solid-liquid separation of the slurry, praseodymium carbonate and neodymium carbonate solids and sodium chloride solution are obtained.

[0134] Alternatively, the sodium hydroxide solution recovered by this method can be added to praseodymium chloride and neodymium chloride solutions respectively and stirred to react and obtain praseodymium hydroxide and neodymium hydroxide slurries. The pH value during the precipitation process is 7.5-8.0. Then, the CO2 gas recovered by this method is passed into the slurries respectively and carbonization reaction is carried out under the conditions of 0.1 MPa and 35-40℃ to obtain praseodymium carbonate and neodymium carbonate slurries.

[0135] S3: The sodium chloride solution obtained in S2 is subjected to bipolar membrane electrolysis to obtain sodium hydroxide solution, hydrochloric acid and low-concentration sodium chloride solution. The sodium hydroxide solution is used for the carbonization precipitation reaction in S2, the hydrochloric acid is used for the extraction and separation process in S1, and the low-concentration sodium chloride solution is used for the sodium chloride solution obtained in S2.

[0136] In this step, a nickel mesh is used as the cathode, and a titanium mesh coated with ruthenium oxide is used as the anode. The cation exchange membrane is a perfluorosulfonic acid / carboxylic acid composite cation exchange membrane, and the anion exchange membrane is a polymer membrane containing -NH3+. The bipolar membrane is prepared by hot pressing the cation exchange membrane and the anion exchange membrane. The electrode spacing is 3 cm. The electrolysis process parameters are: current density 0.5 kA / m 2 The electrolysis temperature is 40℃ and the cell voltage is 21V.

[0137] The electrolyte in the salt chamber is obtained by diluting the sodium chloride solution from S2; the electrolytes in the acid and alkali chambers are pure water. The concentration of sodium chloride solution in the salt chamber electrolyte, expressed as NaCl, is 150 g / L.

[0138] S4: The praseodymium carbonate and neodymium carbonate obtained in S2 are roasted separately to obtain high-purity praseodymium oxide, neodymium oxide and CO2 gas. The CO2 gas is captured and recovered for carbonization precipitation reaction in S2.

[0139] In the above steps, the sodium chloride produced in S2 is recycled by producing sodium hydroxide and hydrochloric acid through an ion-exchange membrane electrolysis process. The CO2 produced in S4 is recycled through a carbonization precipitation reaction and a roasting process, achieving a closed-loop material flow throughout the entire process. In this embodiment, the electrolysis efficiency reaches 60%, the alkali recycling rate reaches 99%, the hydrochloric acid recycling rate reaches 99%, the CO2 recycling rate reaches 88%, and the purity of praseodymium oxide and neodymium oxide products reaches 99.95% and 99.99%, respectively, with recovery rates of 98.7% and 98.9%, respectively.

[0140] The parameters for the other embodiments are shown in Table 3. Since the only difference is the electrolysis method, the carbonization precipitation process remains basically the same, so the corresponding final process evaluation indicators are not listed.

[0141] Table 3. Bipolar film electrolysis process conditions

[0142] Comparative Example 1

[0143] A mixed praseodymium and neodymium rare earth chloride solution is extracted and separated by hydrochloric acid back-extraction to obtain a single or high-purity rare earth chloride solution. Excess ammonium bicarbonate is then used for precipitation to obtain rare earth carbonate precipitates, which are finally calcined to obtain rare earth oxides. Producing 1 ton of REO consumes at least 2.4 tons of hydrochloric acid and 1.7 tons of ammonium bicarbonate, generating ammonium chloride wastewater. End-of-pipe treatment methods such as evaporation crystallization, membrane separation, stripping, and breakpoint chlorination are extremely costly and difficult to meet standards.

[0144] Comparative Example 2

[0145] A mixed praseodymium-neodymium rare earth chloride solution is extracted and separated by hydrochloric acid back-extraction to obtain a single or high-purity rare earth chloride solution. Excess sodium carbonate is then used for precipitation to obtain rare earth carbonate precipitates, which are finally calcined to obtain rare earth oxides. Producing 1 ton of REO consumes at least 2.4 tons of hydrochloric acid and 1.2 tons of sodium carbonate, generating high-salt sodium chloride wastewater. End-of-pipe treatment methods such as evaporation crystallization and membrane separation are extremely costly and difficult to meet standards.

[0146] From the above, we can conclude that:

[0147] The technical solution of this invention reduces the consumption of hydrochloric acid, sodium hydroxide and other materials by more than 90% in the production of 1 ton of REO, and eliminates the need for ammonium bicarbonate, sodium carbonate and other materials, thus avoiding the generation of ammonia nitrogen wastewater from the source. It realizes the internal recycling of acid, alkali, salt, CO2 and water materials throughout the entire process, generating virtually no waste and significantly reducing the cost of chemical raw materials and environmental protection.

Claims

1. A method for the electrolytic recycling of chloride solution in a metal smelting separation process, characterized in that, The method includes the following steps: S1: Dissolve at least one of the metal oxides, metal hydroxides, metal carbonates and basic metal carbonates obtained from the metal smelting and separation process in the recovered hydrochloric acid to obtain a metal chloride solution. or, The recovered hydrochloric acid is used in a metal solution extraction and separation process to obtain a metal chloride solution; S2: The metal chloride solution obtained in S1, the recovered sodium hydroxide solution and CO2 gas are subjected to a carbonation precipitation reaction to obtain a slurry. After solid-liquid separation, metal carbonates and / or basic carbonates and sodium chloride solution are obtained. S3: The metal chloride solution obtained in S1 and / or the sodium chloride solution obtained in S2 are subjected to ion membrane electrolysis to obtain metal hydroxide precipitate and / or sodium hydroxide solution, as well as hydrogen and chlorine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in S2. The hydrogen and chlorine are used to synthesize hydrochloric acid, which is then recycled for the dissolution or extraction separation process in S1. or, The sodium chloride solution obtained in S2 is subjected to bipolar membrane electrolysis to obtain sodium hydroxide solution, hydrochloric acid and dilute brine. The sodium hydroxide solution is recycled for the carbonization precipitation reaction in S2, the hydrochloric acid is recycled for the dissolution or extraction separation process in S1, and the dilute brine is recovered for diluting the sodium chloride solution obtained in S2. S4: The metal carbonate and / or basic carbonate obtained in S2 are roasted to obtain high-purity metal oxide and CO2 gas, and the CO2 gas is recycled for the carbonization precipitation reaction in S2. S5: The metal hydroxide precipitate obtained in S3 is calcined to obtain high-purity metal oxide and water. The water is recycled for the ion-exchange membrane electrolysis or bipolar membrane electrolysis described in S3.

2. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 1, characterized in that, The metals include at least one of the following: alkaline earth metals, rare earth metals, refractory rare metals, transition metals, and main group metals. Preferably, the alkaline earth metal includes at least one of beryllium, magnesium, calcium, and strontium; the rare earth metal includes at least one of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium; the refractory rare metal includes at least one of zirconium, hafnium, tantalum, and niobium; the transition metal includes at least one of vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, and thorium; and the main group metal includes at least one of aluminum, gallium, indium, tin, antimony, and bismuth.

3. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 1, characterized in that, S3 The ion membrane electrolysis is performed by ion membrane electrolysis of the metal chloride solution and / or the sodium chloride solution through an ion membrane electrolysis cell; The electrolysis process parameters are as follows: current density is 1.0 kA / m 2 ~8.0kA / m 2 The electrolysis temperature is 20℃~90℃, and the cell voltage is 2.1V~5.0V; The inter-electrode spacing is 0.1 mm to 10 mm, and preferably the inter-electrode spacing is equal to the thickness of the ion exchange membrane.

4. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 3, characterized in that, The membrane electrolyzer includes several ion-exchange membrane electrolysis units; Each of the ion-exchange membrane electrolysis units includes: a cathode chamber, an anode chamber, a cathode, an anode, and a cation exchange membrane, wherein the cation exchange membrane separates the cathode chamber and the anode chamber, the anode located in the anode chamber is connected to the positive terminal of a DC power supply, and the cathode located in the cathode chamber is connected to the negative terminal of a DC power supply; The membrane electrolyzer also includes a gas recovery and utilization unit, which includes: a hydrogen gas-liquid separator and dryer, a chlorine gas-liquid separator and dryer, and a hydrochloric acid synthesis device; the sodium hydroxide solution obtained from the hydrogen gas-liquid separation is returned to the cathode chamber, and the sodium chloride solution obtained from the chlorine gas-liquid separation is returned to the anode chamber.

5. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 4, characterized in that, The electrolyte in the anode chamber of the ion-exchange membrane electrolysis unit is a sodium chloride solution or / and a metal chloride solution, preferably a sodium chloride solution; The electrolyte in the cathode chamber of the ion-exchange membrane electrolysis unit is a sodium hydroxide solution and pure water.

6. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 5, characterized in that, The concentration of sodium chloride and / or metal chloride solution in the electrolyte of the anode chamber is 100 g / L to 300 g / L, calculated as NaCl and / or MO. ， M is a metallic element; The sodium hydroxide concentration in the cathode chamber electrolyte is 150 g / L to 350 g / L.

7. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 1, characterized in that, The bipolar membrane electrolysis process parameters are: current density of 0.3 kA / m 2 ~3kA / m 2 The electrolysis temperature is 5℃~50℃, and the membrane stack voltage is 10V-50V; The membrane spacing is 0.1mm to 10mm, and the electrode spacing is 2.0-7.0cm.

8. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 7, characterized in that, The bipolar membrane electrolysis includes several bipolar membrane electrolysis units; Each of the bipolar membrane electrolysis units has a four-membrane, three-compartment configuration, including: an anode, a cathode, a cation exchange membrane, an anion exchange membrane, a bipolar membrane, a cathode chamber, a salt chamber, and an anode chamber. The bipolar membrane, cation exchange membrane, and anion exchange membrane separate the cathode chamber, salt chamber, and anode chamber. The anode is connected to the positive terminal of a DC power supply, and the cathode is connected to the negative terminal of a DC power supply.

9. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 8, characterized in that, The electrolyte in the salt chamber of the bipolar membrane electrolysis unit is a sodium chloride solution; The electrolyte in the acid and alkali chambers of the bipolar membrane electrolysis unit is pure water.

10. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 7, characterized in that, The concentration of sodium chloride raw material at the inlet of the anode chamber is 80 g / L to 150 g / L (calculated as NaCl), and the concentration of sodium chloride at the outlet is 10 g / L to 50 g / L (calculated as NaCl).

11. The method for electrolytic recycling of chloride solution in a metal smelting separation process according to claim 4 or 8, characterized in that, The cation exchange membrane is one of a perfluorosulfonic acid membrane, a perfluorocarboxylic acid membrane, or a perfluorosulfonic acid / carboxylic acid composite membrane.

12. The method for electrolytic recycling of chloride solution in a metal smelting separation process according to claim 4 or 8, characterized in that, The cation exchange membrane is a cation exchange membrane with valence selectivity obtained by surface modification through at least one of surface coating, electrodeposition, and chemical grafting.

13. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 8, characterized in that, The anion exchange membrane contains -NH3. + -NR2H + or PR 3+ A polymer membrane with basic active exchange groups, where R is a hydrocarbon group; The bipolar membrane is an ion exchange membrane prepared by one of the following methods: hot pressing of anion and cation exchange membranes, adhesive molding, casting molding, and electrodeposition molding.

14. The method for electrolytic recycling of chloride solution in a metal smelting separation process according to claim 4 or 8, characterized in that, The cathode includes: a titanium metal mesh, a nickel metal mesh, an iron metal mesh, or a metal mesh with an active layer of at least one of nickel, platinum, or ruthenium electroplated on its surface; The anode comprises: a titanium metal mesh with at least one of ruthenium, iridium, rhodium, palladium and platinum electroplated on its surface, wherein the phases of ruthenium, iridium, rhodium and platinum are oxides.

15. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 1, characterized in that: The carbonization precipitation reaction described in S2, involving the metal chloride solution obtained in S1, the sodium hydroxide solution obtained in S3, and the CO2 gas obtained in S4, includes: Simultaneously, a carbonization precipitation reaction is carried out, with a pH value of 3.5 to 9.0, a pressure range of 0.1 MPa to 0.6 MPa, and a temperature range of 5℃ to 60℃. The obtained slurry is then subjected to solid-liquid separation to obtain metal carbonates and / or basic carbonates and sodium chloride solutions.

16. The method for electrolytic recycling of chloride solution in metal smelting separation process according to claim 1, characterized in that: The carbonization precipitation reaction described in S2, involving the metal chloride solution obtained in S1, the sodium hydroxide solution obtained in S3, and the CO2 gas obtained in S4, includes: First, the metal chloride solution obtained in S1 and the sodium hydroxide solution obtained in S3 are mixed to carry out a precipitation reaction to generate a metal hydroxide slurry. The pH value during the precipitation reaction is 3.0 to 13.0, preferably 5.0 to 11.

5. The CO2 gas obtained by S4 is then introduced into the metal hydroxide slurry to carry out a carbonization reaction, and a carbonized slurry is obtained. After solid-liquid separation, the metal carbonate and / or basic carbonate, as well as a sodium chloride solution, are obtained. The pressure range of the carbonization reaction process is 0.1 MPa to 0.6 MPa, and the temperature range is 5℃ to 60℃.

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