A method for treating battery black powder and a wastewater treatment device

Abstract

This invention discloses a method for treating battery black powder and a wastewater treatment device, comprising: reacting battery black powder with a leaching agent to obtain a leachate containing multiple soluble metal salts, wherein the multiple soluble metal salts include lithium; separating the multiple soluble metal salts by a precipitation method to obtain a precipitate containing the separated lithium; performing a primary pretreatment on the residual wastewater; inputting the pretreated wastewater into an oxidation and hydrogen production system for oxidation treatment and electrolytic hydrogen production; performing a secondary pretreatment on the wastewater after oxidation treatment and electrolytic hydrogen production; performing lithium precipitation treatment on the pretreated wastewater; and performing post-treatment on the wastewater after lithium precipitation treatment to meet the required wastewater discharge and / or recyclable material recovery standards; wherein the oxidation and hydrogen production system includes an electrolytic cell, a DC power supply, and a hydrogen storage tank.

Description

Technical Field

[0001] The embodiments of the present invention relate to a method for treating battery black powder, wastewater treatment equipment, and wastewater treatment device. Background Technology

[0002] With the widespread use of electronic communication devices and the rapid development of the electric vehicle industry, the consumption of ternary lithium-ion batteries and lithium iron phosphate batteries has surged, while the lifespan of these batteries is typically 5-8 years. Currently, hydrometallurgical methods can be used to process battery black powder, but this method suffers from complex processes and low energy-saving and environmental benefits.

[0003] On the other hand, known electrochemical reactors for wastewater treatment mainly include electrocatalytic oxidation (ECO) reactors and electrocoagulation (EC) reactors. Their basic structures are similar, both containing an electrolytic cell and a DC power supply, with the anode and cathode of the electrolytic cell connected to the positive and negative terminals of the DC power supply, respectively. Their main differences lie in the electrode materials and their working mechanisms.

[0004] Electrocatalytic oxidation (EO) utilizes the oxidation of the anode (usually a titanium-based metal oxide coated electrode) and / or the generation of free radicals through an electric field to promote the oxidative decomposition of pollutants, thereby achieving wastewater treatment. It can be further divided into direct oxidation and indirect oxidation methods. Direct oxidation directly oxidizes pollutants on the anode surface to remove them. Indirect oxidation uses an electric field to decompose molecules, generating hydroxyl radicals and other oxidants, which then react with pollutants in the wastewater to remove them.

[0005] Electrocoagulation (EC) removes pollutants by dissolving metal ions in the wastewater at the anode (usually an aluminum or iron electrode), which then undergoes a hydrolysis reaction to form metal hydroxides. These metal hydroxides act as flocculants, coagulating suspended solids and colloids in the wastewater. Simultaneously, hydrogen ions at the cathode gain electrons and are reduced to hydrogen gas, which escapes as microbubbles, causing flocculent matter and oily substances in the wastewater to float to the surface.

[0006] Currently, electrocatalytic oxidation and electrocoagulation technologies have relatively limited functions and have not yet achieved the recovery and utilization of hydrogen. Summary of the Invention

[0007] One of the objectives of this invention is to provide an improved method for treating battery black powder and a wastewater treatment device for treating the highly polluting wastewater generated in the method. This method can effectively purify the highly polluting wastewater and also utilize the wastewater to produce hydrogen, thereby improving energy conservation and environmental protection benefits.

[0008] A second objective of this invention is to provide a wastewater treatment device that can be used in the above-mentioned battery black powder treatment method and wastewater treatment equipment, which can improve the oxidation treatment effect of the oxidation and hydrogen production system on the wastewater to be treated.

[0009] In a first aspect, a method for treating battery black powder is provided, comprising: reacting battery black powder with a leaching agent to obtain a leachate containing multiple soluble metal salts, wherein the multiple soluble metal salts include lithium; separating the multiple soluble metal salts by means of extraction, and obtaining raffinate wastewater containing the separated lithium; performing a first pretreatment on the raffinate wastewater to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater are 6-9; inputting the pretreated wastewater into an oxidation and hydrogen production system for oxidation treatment and electrolytic hydrogen production, thereby obtaining post-oxidation and post-electrolytic hydrogen production wastewater; and performing a second pretreatment on the post-oxidation and post-electrolytic hydrogen production wastewater to ensure that the post-oxidation and post-electrolytic hydrogen production wastewater is 6-9; inputting the post-oxidation and post-electrolytic hydrogen production wastewater into an oxidation and hydrogen production system for oxidation treatment and electrolytic hydrogen production, thereby obtaining post-oxidation and post-electrolytic hydrogen production wastewater; and performing a second pretreatment on the post-oxidation and post-electrolytic hydrogen production wastewater to ensure that the post-oxidation and post-electrolytic hydrogen production wastewater is 6-9 ... The total dissolved solids in the wastewater after secondary pretreatment mainly contain lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment. The wastewater after secondary pretreatment is subjected to lithium precipitation treatment to obtain lithium precipitate converted from the lithium salts and lithium precipitation wastewater. The lithium precipitation wastewater mainly contains the other soluble metal salts. The lithium precipitation wastewater is then subjected to wastewater post-treatment to meet the required wastewater discharge and / or recyclable material recovery standards. The oxidation and hydrogen production system includes an electrolytic cell, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolytic cell are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the wastewater after primary pretreatment through an anodic electrochemical reaction, and the cathode evolves hydrogen through a cathodic electrochemical reaction. The exhaust structure of the electrolytic cell is connected to the hydrogen storage tank.

[0010] According to an embodiment of the present invention, the battery black powder mainly comes from ternary lithium cathode material; the leaching agent is a sulfuric acid solution, and the multiple soluble metal salts in the leaching solution include nickel sulfate, cobalt sulfate, manganese sulfate, and lithium sulfate; the extraction method specifically includes multiple extraction and separation steps and multiple back-extraction and separation steps; the first extraction and separation step is used to obtain a first extract for obtaining manganese sulfate and a first raffinate for retaining the nickel salt and the cobalt salt from the leaching solution; the second extraction and separation step is used to obtain a second extract for obtaining cobalt sulfate and a second raffinate for retaining the nickel salt from the first raffinate; the third extraction and separation step is used to obtain a third extract for obtaining nickel sulfate and a third raffinate from the second raffinate; the first back-extraction and separation step is used to obtain a third extract for obtaining manganese sulfate from the first extract. The process includes: a first back-extraction liquid and a first back-extraction residue; a fourth extraction and separation step for obtaining a fourth extract and a fourth back-extraction residue from the first back-extraction liquid to obtain the manganese sulfate; a second back-extraction and separation step for obtaining a second back-extraction liquid and a second back-extraction residue from the second extract to obtain the cobalt sulfate, wherein the second back-extraction liquid is a cobalt sulfate solution; a third back-extraction and separation step for obtaining a third back-extraction liquid and a third back-extraction residue from the third extract to obtain the nickel sulfate, wherein the third back-extraction liquid is a nickel sulfate solution; a fourth back-extraction and separation step for obtaining a fourth back-extraction liquid and a fourth back-extraction residue from the fourth extract to obtain the manganese sulfate, wherein the fourth back-extraction liquid is a manganese sulfate solution; and obtaining the raffinate wastewater containing the separated lithium comprises: mixing the third raffinate residue and the fourth raffinate residue to form the raffinate wastewater.

[0011] According to an embodiment of the present invention, the first extraction and separation process uses P204 extractant; the second extraction and separation process uses P507 extractant; the third extraction and separation process uses P507 extractant; and the fourth extraction and separation process uses C272 extractant.

[0012] According to an embodiment of the present invention, the primary pretreatment includes sequentially subjecting the raffinate wastewater to air flotation for impurity removal, activated carbon adsorption for impurity removal, and a first solid-liquid separation and filtration for impurity removal.

[0013] According to an embodiment of the present invention, the secondary pretreatment includes sequentially subjecting the wastewater from the oxidation treatment and electrolytic hydrogen production to alkaline precipitation treatment, a second solid-liquid separation and filtration treatment, pH adjustment treatment, sodium sulfate crystallization by evaporation and concentration treatment, and a third solid-liquid separation and filtration treatment. The pH adjustment treatment is used to adjust the pH value of the wastewater to be treated to 6-7.

[0014] According to an embodiment of the present invention, the method for treating battery black powder further includes increasing the chloride ion concentration in the wastewater after the first pretreatment before performing oxidation treatment and electrolytic hydrogen production.

[0015] According to an embodiment of the present invention, by adding and mixing chloride salts, with a mass ratio of sodium chloride to the chemical oxygen demand measured in the wastewater after primary pretreatment being 1-10, the chloride ion concentration in the wastewater after primary pretreatment is increased.

[0016] Secondly, a wastewater treatment device is provided for treating residual wastewater from battery black powder leaching solution. The process of generating the residual wastewater includes: reacting battery black powder with a leaching agent to obtain a leaching solution containing multiple soluble metal salts, including lithium; separating the multiple soluble metal salts using an extraction method, and obtaining residual wastewater containing the separated lithium; the device includes: a primary pretreatment system for pretreating the residual wastewater to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater are 6-9; an oxidation and hydrogen production system for oxidizing and electrolyzing the pretreated wastewater to obtain post-oxidation and post-electrolysis hydrogen production wastewater; and a secondary pretreatment system for further pretreatment of the post-oxidation and post-electrolysis hydrogen production wastewater. The secondary pretreatment ensures that the total dissolved solids in the wastewater after the secondary pretreatment mainly contain lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment. A lithium precipitation treatment system is used to precipitate lithium from the wastewater after the secondary pretreatment to obtain lithium precipitate converted from the lithium salts and lithium-precipitated wastewater, which mainly contains the other soluble metal salts. A wastewater post-treatment system is used to treat the lithium-precipitated wastewater to meet the required wastewater discharge and / or recyclable material recovery standards. The oxidation and hydrogen production system includes an electrolytic cell, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolytic cell are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the wastewater after the primary pretreatment through an anodic electrochemical reaction, and the cathode evolves hydrogen through a cathodic electrochemical reaction. The exhaust structure of the electrolytic cell is connected to the hydrogen storage tank.

[0017] According to an embodiment of the present invention, the battery black powder mainly comes from the positive electrode material of a ternary lithium battery; the leaching agent is a sulfuric acid solution, and the multiple soluble metal salts in the leaching solution include nickel sulfate, cobalt sulfate, manganese sulfate, and lithium sulfate; the extraction method specifically includes multiple extraction and separation steps and multiple back-extraction and separation steps; the first extraction and separation step is used to obtain a first extract for obtaining manganese sulfate and a first raffinate for retaining the nickel salt and the cobalt salt from the leaching solution; the second extraction and separation step is used to obtain a second extract for obtaining cobalt sulfate and a second raffinate for retaining the nickel salt from the first raffinate; the third extraction and separation step is used to obtain a third extract for obtaining nickel sulfate and a third raffinate from the second raffinate; the first back-extraction and separation step is used to obtain the manganese sulfate from the first extract. A first back-extraction liquid and a first back-extraction residue; a fourth extraction and separation process for obtaining a fourth extract and a fourth back-extraction residue from the first back-extraction liquid to obtain the manganese sulfate; a second back-extraction and separation process for obtaining a second back-extraction liquid and a second back-extraction residue from the second extract to obtain the cobalt sulfate, wherein the second back-extraction liquid is a cobalt sulfate solution; a third back-extraction and separation process for obtaining a third back-extraction liquid and a third back-extraction residue from the third extract to obtain the nickel sulfate, wherein the third back-extraction liquid is a nickel sulfate solution; a fourth back-extraction and separation process for obtaining a fourth back-extraction liquid and a fourth back-extraction residue from the fourth extract to obtain the manganese sulfate, wherein the fourth back-extraction liquid is a manganese sulfate solution; obtaining the raffinate wastewater containing the separated lithium comprises: mixing the third raffinate residue and the fourth raffinate residue to form the raffinate wastewater.

[0018] According to an embodiment of the present invention, the oxidation and hydrogen production system includes a wastewater pretreatment module, which is used to add chloride salt to the wastewater after primary pretreatment before performing the oxidation treatment and electrolytic hydrogen production, thereby increasing the chloride ion concentration in the wastewater after primary pretreatment.

[0019] The basic technical concept of the above-mentioned battery black powder treatment method and wastewater treatment equipment is as follows: First, the various soluble metal salts are separated using an extraction method, resulting in raffinate wastewater containing the separated lithium, thus initially extracting lithium into the liquid phase (i.e., raffinate wastewater). Subsequently, the raffinate wastewater undergoes a pretreatment process to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater are 6-9. This ensures that the pretreated wastewater meets the requirements for subsequent oxidation treatment and electrolytic hydrogen production. The high chemical oxygen demand (COD content) in the raffinate wastewater originates from both the organic electrolyte in the battery and the extractant used in the extraction method. Subsequently, the pretreated wastewater is fed into an oxidation and hydrogen production system for oxidation and electrolysis to produce hydrogen. This system includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the pretreated wastewater through an anodic electrochemical reaction, while the cathode generates hydrogen through a cathodic electrochemical reaction. The exhaust system of the electrolyzer is connected to the hydrogen storage tank. Therefore, the oxidation and hydrogen production system can both oxidize the pretreated wastewater, primarily reducing its COD content, and generate hydrogen. With increasing energy conservation and emission reduction requirements, the demand for hydrogen is gradually increasing, and its applications are expanding. Therefore, using an oxidation and hydrogen production system can improve energy conservation and environmental protection benefits. Subsequently, the wastewater from the oxidation and electrolytic hydrogen production processes undergoes a second pretreatment to ensure that the total dissolved solids in the pretreated wastewater mainly consist of lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation. This helps improve the lithium recovery rate. Afterward, the pretreated wastewater undergoes lithium precipitation treatment, followed by post-treatment to meet the required wastewater discharge and / or recyclable material recovery standards. Therefore, the above-described battery black powder treatment method and wastewater treatment equipment can effectively purify the residual wastewater from battery black powder leaching solution and improve energy-saving and environmental protection benefits.

[0020] Thirdly, a method for treating battery black powder is provided, comprising: reacting battery black powder with a leaching agent to obtain a leachate containing multiple soluble metal salts, wherein the soluble metal salts contain lithium; separating the multiple soluble metal salts by precipitation to obtain a mother liquor containing the separated lithium; performing a first pretreatment on the mother liquor to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater ≤500 mg / L; inputting the pretreated wastewater into an oxidation treatment and hydrogen production system for oxidation treatment and electrolytic hydrogen production to obtain post-oxidation treatment and post-electrolytic hydrogen production wastewater; and performing a second pretreatment on the post-oxidation treatment and post-electrolytic hydrogen production wastewater to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater ≤6-9; inputting the post-oxidation treatment and post-electrolytic hydrogen production ... to obtain post-oxidation treatment and post-electrolytic hydrogen production wastewater ≤6-9; and performing a second pretreatment on the post-oxidation treatment and post-electrolytic hydrogen production wastewater to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater ≤6-9; inputting The total dissolved solids in the wastewater after secondary pretreatment mainly contain lithium salts and other soluble metal salts that can be separated from the lithium salts after subsequent lithium precipitation treatment. The wastewater after secondary pretreatment is subjected to lithium precipitation treatment to obtain lithium precipitate converted from the lithium salts and wastewater after lithium precipitation treatment. The wastewater after lithium precipitation treatment mainly contains the other soluble metal salts. The wastewater after lithium precipitation treatment is subjected to wastewater post-treatment to meet the required wastewater discharge and / or recovery standards for recyclable materials. The oxidation and hydrogen production system includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the wastewater after primary pretreatment through an anodic electrochemical reaction, and the cathode evolves hydrogen through a cathodic electrochemical reaction. The exhaust structure of the electrolyzer is connected to the hydrogen storage tank.

[0021] According to an embodiment of the present invention, the battery black powder mainly comes from lithium iron phosphate cathode material; the leaching agent is a sulfuric acid solution, and the lithium iron phosphate in the battery black powder decomposes into lithium ions, iron ions and phosphate ions in the sulfuric acid solution; the precipitation method specifically includes reacting the leaching solution with a mixed solution of sodium hydroxide and hydrogen peroxide, so that the iron ions react with the phosphate ions to generate iron phosphate precipitate; the precipitate mother liquor containing the separated lithium includes: performing solid-liquid separation on the reaction liquid after the reaction of the leaching solution with the mixed solution of sodium hydroxide and hydrogen peroxide, and using the liquid phase of the solid-liquid separation as the precipitate mother liquor.

[0022] According to an embodiment of the present invention, the precipitate containing the separated lithium further comprises: washing the iron phosphate precipitate after solid-liquid separation with water, subjecting the wash water to alkali precipitation, first solid-liquid separation filtration and reverse osmosis membrane filtration in sequence, and then mixing the concentrate produced by the reverse osmosis membrane filtration with the liquid phase as the precipitate mother liquor.

[0023] According to an embodiment of the present invention, the first pretreatment includes sequentially subjecting the precipitated mother liquor to alkaline precipitation, a second solid-liquid separation and filtration treatment, pH adjustment treatment, and evaporation and concentration treatment, wherein the pH adjustment treatment is used to adjust the pH value of the wastewater to be treated to 6-7.

[0024] According to an embodiment of the present invention, the secondary pretreatment includes sequentially subjecting the wastewater from the oxidation treatment and electrolytic hydrogen production to evaporation concentration treatment for sodium sulfate crystallization, freeze crystallization treatment for sodium sulfate crystallization, and a third solid-liquid separation and filtration treatment.

[0025] According to an embodiment of the present invention, the method further includes increasing the chloride ion concentration in the pretreated wastewater before oxidation treatment and electrolytic hydrogen production.

[0026] According to an embodiment of the present invention, by adding and mixing chloride salts, with a mass ratio of sodium chloride to the chemical oxygen demand measured in the wastewater after primary pretreatment being 1-10, the chloride ion concentration in the wastewater after primary pretreatment is increased.

[0027] Fourthly, a wastewater treatment device is provided for treating the precipitate mother liquor from battery black powder leachate. The process of generating the precipitate mother liquor from the battery black powder leachate includes: reacting battery black powder with a leaching agent to obtain a leachate containing multiple soluble metal salts, including lithium; separating the multiple soluble metal salts using a precipitation method to obtain the precipitate mother liquor containing the separated lithium; the device includes: a primary pretreatment system for pretreating the leached wastewater to ensure that the concentration of suspended solids ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and pH value of the pretreated wastewater ≤500 mg / L; an oxidation and hydrogen production system for oxidizing and electrolyzing the pretreated wastewater to obtain post-oxidation and post-electrolysis hydrogen production wastewater; and a secondary pretreatment system for further pretreating the post-oxidation and post-electrolysis hydrogen production wastewater. The secondary pretreatment ensures that the total dissolved solids in the wastewater after the secondary pretreatment mainly contain lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment. A lithium precipitation treatment system is used to precipitate lithium from the wastewater after the secondary pretreatment to obtain lithium precipitate converted from the lithium salts and lithium-precipitated wastewater, which mainly contains the other soluble metal salts. A wastewater post-treatment system is used to treat the lithium-precipitated wastewater to meet the required wastewater discharge and / or recyclable material recovery standards. The oxidation and hydrogen production system includes an electrolytic cell, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolytic cell are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the wastewater after the primary pretreatment through an anodic electrochemical reaction, and the cathode evolves hydrogen through a cathodic electrochemical reaction. The exhaust structure of the electrolytic cell is connected to the hydrogen storage tank.

[0028] According to an embodiment of the present invention, the battery black powder mainly comes from lithium iron phosphate cathode material; the leaching agent is sulfuric acid solution, and the lithium iron phosphate in the battery black powder decomposes into lithium ions, iron ions and phosphate ions in the sulfuric acid solution; the precipitation method specifically includes reacting the leaching solution with a mixed solution of sodium hydroxide and hydrogen peroxide, so that the iron ions react with the phosphate ions to generate iron phosphate precipitate; obtaining the precipitate mother liquor containing the separated lithium includes: performing solid-liquid separation on the reaction liquid after the reaction of the leaching solution with the mixed solution of sodium hydroxide and hydrogen peroxide, and using the liquid phase of the solid-liquid separation as the precipitate mother liquor; obtaining the precipitate mother liquor containing the separated lithium further includes: washing the iron phosphate precipitate after solid-liquid separation with water, and sequentially performing alkaline precipitation treatment, first solid-liquid separation filtration treatment and reverse osmosis membrane filtration treatment on the wash water, and then mixing the concentrated liquid produced by the reverse osmosis membrane filtration treatment with the liquid phase as the precipitate mother liquor.

[0029] The basic technical concept of the above-mentioned battery black powder treatment method and wastewater treatment equipment is as follows: First, the various soluble metal salts are separated using a precipitation method, resulting in a mother liquor containing the separated lithium, thus initially extracting lithium into the liquid phase (i.e., the mother liquor). Subsequently, the leached wastewater undergoes a pretreatment process to ensure that the pretreated wastewater has a suspended solids concentration ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and a pH value of 6-9. This ensures that the pretreated wastewater meets the requirements for subsequent oxidation treatment and electrolytic hydrogen production. The high chemical oxygen demand (COD content) in the mother liquor mainly originates from the organic electrolyte in the battery. Subsequently, the pretreated wastewater is fed into an oxidation and hydrogen production system for oxidation and electrolysis to produce hydrogen. This system includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the pretreated wastewater through an anodic electrochemical reaction, while the cathode generates hydrogen through a cathodic electrochemical reaction. The exhaust system of the electrolyzer is connected to the hydrogen storage tank. Therefore, the oxidation and hydrogen production system can both oxidize the pretreated wastewater, primarily reducing its COD content, and generate hydrogen. With increasing energy conservation and emission reduction requirements, the demand for hydrogen is gradually increasing, and its applications are expanding. Therefore, using an oxidation and hydrogen production system can improve energy conservation and environmental protection benefits. Subsequently, the wastewater from the oxidation and electrolytic hydrogen production processes undergoes a second pretreatment to ensure that the total dissolved solids in the pretreated wastewater mainly consist of lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation. This helps improve the lithium recovery rate. Afterward, the pretreated wastewater undergoes lithium precipitation treatment, followed by post-treatment to meet the required wastewater discharge and / or recyclable material recovery standards. Therefore, the above-described battery black powder treatment method and wastewater treatment equipment can effectively purify the mother liquor from the battery black powder leachate and improve energy-saving and environmental protection benefits.

[0030] Fifthly, a wastewater treatment device is provided, comprising: an oxidation and hydrogen production system for oxidizing and electrolyzing hydrogen from wastewater to be treated, the oxidation and hydrogen production system including a wastewater pretreatment module, an electrolyzer, a DC power supply, and a hydrogen storage tank, wherein the anode and cathode of the electrolyzer are respectively connected to the positive and negative terminals of the DC power supply, the anode oxidizes the wastewater to be treated through an anodic electrochemical reaction, the cathode evolves hydrogen through a cathodic electrochemical reaction, the exhaust structure of the electrolyzer is connected to the hydrogen storage tank, and the wastewater pretreatment module is used to add chloride salts to the wastewater to be treated before performing the oxidation and electrolysis hydrogen production to increase the chloride ion concentration in the wastewater to be treated.

[0031] According to an embodiment of the present invention, the wastewater pretreatment module includes a chloride solution preparation unit, a metering control unit, and a chloride solution delivery unit. The chloride solution preparation unit is used to prepare a chloride solution of the required concentration. The chloride solution delivery unit is used to deliver the chloride solution to the wastewater to be treated, thereby mixing the chloride solution with the wastewater. The metering control unit is used to meter and control the amount of chloride added to the wastewater to be treated.

[0032] According to an embodiment of the present invention, the metering control unit is a metering control unit used to control the amount of chloride added in the wastewater to be treated to a mass ratio of sodium chloride to the chemical oxygen demand measured in the wastewater to be treated of 1-10.

[0033] According to an embodiment of the present invention, a wastewater treatment device includes: a main cylinder, wherein an electrolysis zone and a flotation zone are arranged sequentially from bottom to top within the main cylinder; a first output port corresponding to the lower part of the electrolysis zone, an input port corresponding to the upper part of the electrolysis zone, and a second output port corresponding to the upper part of the flotation zone are respectively provided on the main cylinder; the electrolysis zone constitutes the electrolytic cell; an electrolysis device, wherein the electrolysis device includes a DC power supply and an anode and a cathode arranged at intervals in the electrolysis zone; the anode and the cathode are respectively connected to the positive and negative terminals of the DC power supply; during operation, the anode oxidizes the wastewater entering the electrolysis zone through the input port to generate oxygen through an anodic electrochemical reaction, and the cathode generates hydrogen through a cathodic electrochemical reaction; and a hydrogen recovery device, wherein the hydrogen recovery device includes a gas isolation component corresponding to each cathode; the gas isolation component is sleeved outside the corresponding cathode and has a side wall surrounding the cathode and an end cap located at the upper end of the side wall. The lower end of the sidewall is provided with an opening and / or the sidewall itself is made of a membrane material that is permeable to ions and water but not to air bubbles. The end cap is provided with an exhaust port, which is used to connect to the hydrogen storage tank through an exhaust pipe, which serves as the exhaust structure. An oxygen flotation channel is formed by the space between the anode of the electrolysis device and the hydrogen recovery device, and is used to guide the oxygen generated by the anode upward into the flotation zone. A foam cleaning mechanism is installed at the top of the flotation zone and is used to discharge the foam generated at the top of the flotation zone from the second output port. The outlet of the chloride solution delivery unit is connected to the input port and / or extends into the electrolysis zone and is in communication with the electrolysis zone. When the outlet of the chloride solution delivery unit extends into the electrolysis zone and is in communication with the electrolysis zone, the outlet of the chloride solution delivery unit is located at the upper part of the electrolysis zone and outputs chloride solution downward and / or is located at the lower part of the electrolysis zone and outputs chloride solution upward.

[0034] According to an embodiment of the present invention, a wastewater treatment device includes: a main cylinder having an electrolysis zone and a flotation zone arranged sequentially from bottom to top; a first output port corresponding to the lower part of the electrolysis zone, an input port corresponding to the upper part of the electrolysis zone, and a second output port corresponding to the upper part of the flotation zone, respectively, wherein the electrolysis zone constitutes the electrolytic cell; an electrolysis device including a DC power supply and an anode and a cathode spaced apart in the electrolysis zone, wherein the anode and the cathode are respectively connected to the positive and negative terminals of the DC power supply; during operation, the anode oxidizes the wastewater entering the electrolysis zone through the input port via an anodic electrochemical reaction, and the cathode generates hydrogen via a cathodic electrochemical reaction; and a hydrogen recovery device including a gas isolation component corresponding to each cathode, wherein the gas isolation component is sleeved outside the corresponding cathode and has a sidewall surrounding the cathode and a sidewall located on the sidewall. The sidewall has an end cap at the upper end, an opening at the lower end, and / or the sidewall itself is made of a membrane material that is permeable to ions and water but not to air bubbles. The end cap has an exhaust port for connecting to a hydrogen storage tank via an exhaust pipe, which serves as the exhaust structure. An aeration device is located between the electrolysis zone and the flotation zone for aeration within the main cylinder. A foam cleaning mechanism is installed at the top of the flotation zone to discharge foam generated at the top of the flotation zone from the second output port. The outlet of the chloride solution delivery unit is connected to the input port and / or extends into the electrolysis zone, communicating with it. When the outlet of the chloride solution delivery unit extends into the electrolysis zone and communicates with it, the outlet of the chloride solution delivery unit is located at the upper part of the electrolysis zone and outputs chloride solution downwards, and / or located at the lower part of the electrolysis zone and outputs chloride solution upwards.

[0035] According to an embodiment of the present invention, the outlet of the chloride solution delivery unit is located above the aeration device.

[0036] According to an embodiment of the present invention, the upper part of the air flotation zone is provided with a lateral partition located inside the main cylinder and spaced a certain distance from the inner wall of the main cylinder, and a bottom partition connected between the bottom of the lateral partition and the inner wall of the main cylinder. The lateral partition and the bottom partition form a notch located slightly above the side of the air flotation zone. The second output port is provided on the side wall of the main cylinder and communicates laterally with the notch. The foam cleaning mechanism is installed at the top of the air flotation zone and is used to push the foam generated at the top of the air flotation zone toward the notch.

[0037] According to an embodiment of the present invention, the electrolysis apparatus includes a plurality of anodes and a plurality of cathodes, which are arranged alternately in the electrolysis zone along a horizontal direction.

[0038] According to an embodiment of the present invention, a first water distributor is provided at the upper part of the electrolysis zone, and the water distributor inputs the wastewater to be treated from the inlet into the electrolysis zone in a manner that is evenly distributed across the cross-section of the electrolysis zone.

[0039] According to an embodiment of the present invention, the chloride solution delivery unit outputs chloride solution through a second water distributor extending into the electrolysis zone, and the second water distributor inputs the chloride solution into the main cylinder in a manner that is uniformly distributed across the cross-section of the electrolysis zone.

[0040] The aforementioned wastewater treatment device is equipped with a wastewater pretreatment module. This module adds chloride salts to the wastewater to be treated before the oxidation treatment and electrolytic hydrogen production, thereby increasing the chloride ion concentration in the wastewater. Chloride ions can react with oxygen generated at the anode during electrolysis to generate hypochlorite ions. Hypochlorite ions have a strong oxidizing effect on the organic matter in the wastewater to be treated, thereby enhancing the oxidation treatment effect of the oxidation and hydrogen production system on the wastewater to be treated and significantly reducing the COD content of the wastewater to be treated.

[0041] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice. Attached Figure Description

[0042] The accompanying drawings, which form part of this specification, are used to aid in understanding the invention. The contents provided in the drawings and their related descriptions in this specification can be used to explain the invention, but do not constitute an undue limitation of the invention.

[0043] Figure 1 This is a process flow diagram of a battery black powder processing method according to an embodiment of the present invention.

[0044] Figure 2 for Figure 1 The process flow diagram for generating residual wastewater from the leaching solution of battery black powder in the method shown is presented.

[0045] Figure 3 This is a process flow diagram of a battery black powder processing method according to an embodiment of the present invention.

[0046] Figure 4 for Figure 3 The process flow diagram for generating the mother liquor from the battery black powder leachate in the method shown is as follows.

[0047] Figure 5 This is a schematic diagram of a wastewater treatment device according to an embodiment of the present invention. Detailed Implementation

[0048] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0049] The technical solutions and features provided in the various sections, including the following description, can be combined with each other without conflict. Furthermore, where possible, these technical solutions, features, and related combinations can be given specific technical subject matter and protected by relevant patents.

[0050] The embodiments of the present invention described below are generally only some embodiments and not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of patent protection.

[0051] Regarding the terminology and units in this specification: The terms "comprising," "including," "having," and any variations thereof in this specification, the corresponding claims, and related sections are intended to cover non-exclusive inclusion. Furthermore, other related terms and units can be reasonably interpreted based on the relevant content provided in this specification.

[0052] Figure 1 This is a process flow diagram of a battery black powder processing method according to an embodiment of the present invention. Figure 2 for Figure 1 The process flow diagram for the generation of residual wastewater from the leaching solution of battery black powder in the method shown is as follows. Figures 1-2 As shown, a method for treating battery black powder includes the following steps.

[0053] Step 1: React battery black powder with a leaching agent to obtain a leachate containing a variety of soluble metal salts, including lithium.

[0054] Step 2: Separate the various soluble metal salts by means of extraction, and obtain the raffinate wastewater containing the separated lithium.

[0055] Step 3: Perform a pretreatment on the raffinate wastewater to ensure that the concentration of suspended solids in the pretreated wastewater is ≤5mg / L, the oil content is ≤5mg / L, the chemical oxygen demand is ≤500mg / L, and the pH value is 6-9.

[0056] Step 4: The pretreated wastewater is fed into the oxidation and hydrogen production system for oxidation and electrolysis to produce hydrogen, thereby obtaining post-oxidation and post-electrolysis hydrogen-producing wastewater. The oxidation and hydrogen production system includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the pretreated wastewater through an anodic electrochemical reaction, and the cathode generates hydrogen through a cathodic electrochemical reaction. The exhaust system of the electrolyzer is connected to the hydrogen storage tank.

[0057] Step 5: Perform secondary pretreatment on the wastewater after oxidation and electrolysis to ensure that the total dissolved solids in the wastewater after secondary pretreatment mainly contain lithium salts and other dissolved metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment.

[0058] Step 6: The wastewater after the secondary pretreatment is subjected to lithium precipitation treatment to obtain lithium precipitate converted from the lithium salt and wastewater after lithium precipitation treatment. The wastewater after lithium precipitation treatment mainly contains the other dissolved metal salts.

[0059] Step 7: Perform post-treatment on the wastewater after lithium precipitation to meet the required wastewater discharge and / or recycling standards.

[0060] Specifically, such as Figure 2As shown, in this embodiment, the battery black powder mainly comes from ternary lithium cathode material; the leaching agent is a sulfuric acid solution, and the various soluble metal salts in the leaching solution include nickel sulfate, cobalt sulfate, manganese sulfate, and lithium sulfate; the extraction method specifically includes multiple extraction and separation steps and multiple back-extraction and separation steps; wherein, the first extraction and separation step is used to obtain a first extract for obtaining manganese sulfate and a first raffinate for retaining the nickel salt and the cobalt salt from the leaching solution; the second extraction and separation step is used to obtain a second extract for obtaining cobalt sulfate and a second raffinate for retaining the nickel sulfate from the first raffinate; the third extraction and separation step is used to obtain a third extract for obtaining nickel sulfate and a third raffinate from the second raffinate; the first back-extraction and separation step is used to obtain manganese sulfate from the first extract. The process includes: a first back-extraction liquid and a first back-extraction residue; a fourth extraction and separation step for obtaining a fourth extract and a fourth back-extraction residue from the first back-extraction liquid to obtain the manganese sulfate; a second back-extraction and separation step for obtaining a second back-extraction liquid and a second back-extraction residue from the second extract, wherein the second back-extraction liquid is a cobalt sulfate solution; a third back-extraction and separation step for obtaining a third back-extraction liquid and a third back-extraction residue from the third extract, wherein the third back-extraction liquid is a nickel sulfate solution; a fourth back-extraction and separation step for obtaining a fourth back-extraction liquid and a fourth back-extraction residue from the fourth extract, wherein the fourth back-extraction liquid is a manganese sulfate solution; and obtaining the raffinate wastewater containing the separated lithium comprises: mixing the third raffinate residue and the fourth raffinate residue to form the raffinate wastewater.

[0061] Specifically, the first extraction and separation process uses P204 extractant; the second extraction and separation process uses P507 extractant; the third extraction and separation process uses P507 extractant; and the fourth extraction and separation process uses C272 extractant. P204, P507, and C272 extractants are existing extractants, and their names are known. These extractants introduce organic matter, thereby increasing the difficulty of treating the residual wastewater from the battery black powder leaching solution.

[0062] The following is combined with Figure 1 As shown, the method for processing battery black powder in this embodiment will be further described in detail.

[0063] In step three, the leaching wastewater (i.e., the leaching wastewater from battery black powder) first enters the dissolved air flotation (DAF) tank 11 for solid-liquid separation. The DAF tank 11 is an existing wastewater treatment device that primarily uses a large number of microbubbles to capture and adsorb fine particulate matter, causing it to float and achieving solid-liquid separation. Here, the main function of the DAF tank 11 is to remove most of the suspended solids (SS), oil, and COD from the leaching wastewater. Afterward, the leaching wastewater output from the DAF tank 11 enters the activated carbon decolorization device 12. The activated carbon decolorization device 12 uses activated carbon to adsorb impurities in the wastewater, further removing SS, oil, and COD. Then, the leaching wastewater output from the activated carbon decolorization device 12 passes through a filter press 13 and a precision filter 14 (using a microfiltration filter) to achieve solid-liquid separation, resulting in pre-treated wastewater with a suspended solids concentration ≤5 mg / L, oil content ≤5 mg / L, chemical oxygen demand ≤500 mg / L, and a pH value of 6-9.

[0064] In step four, the oxidation and hydrogen production system 21 includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the pretreated wastewater through an anodic electrochemical reaction, and the cathode generates hydrogen through a cathodic electrochemical reaction. The exhaust structure of the electrolyzer is connected to the hydrogen storage tank. The anode can be the same as or similar to that of an electrocatalytic oxidation reactor (such as a titanium-based metal oxide coated electrode), and the cathode can be the same as or similar to that of an electrocoagulation reactor (to facilitate hydrogen evolution).

[0065] In one optional embodiment, the oxidation and hydrogen production system 21 includes a wastewater pretreatment module. This module adds chloride salts to the pretreated wastewater before the oxidation and electrolytic hydrogen production process, thereby increasing the chloride ion concentration in the pretreated wastewater. Chloride ions react with oxygen generated at the anode during electrolysis to form hypochlorite ions. Hypochlorite ions have a strong oxidizing effect on organic matter in the wastewater, thus enhancing the oxidation treatment effect of the oxidation and hydrogen production system on the wastewater and significantly reducing the COD content of the wastewater.

[0066] Generally, the chloride ion concentration in the pretreated wastewater is increased by adding and mixing a chloride salt (calculated as sodium chloride) at a mass ratio of 1-10 to the measured chemical oxygen demand (COD) in the pretreated wastewater. In this embodiment, sodium chloride is used as the chloride salt, and the mass ratio of the added sodium chloride to the measured COD in the pretreated wastewater is 3.

[0067] In step five, firstly, the wastewater from the oxidation treatment and electrolytic hydrogen production enters pH adjustment tank 31. The function of pH adjustment tank 31 is to add alkali to the wastewater to increase its pH value. In this embodiment, the pH value of the wastewater from the oxidation treatment and electrolytic hydrogen production is adjusted to 11 in pH adjustment tank 31. This causes metal ions such as nickel, cobalt, manganese, and copper in the wastewater to precipitate as hydroxides. Subsequently, the wastewater from the oxidation treatment and electrolytic hydrogen production output from pH adjustment tank 31 passes through filter press 32 and precision filter 33 (using a microfiltration filter) to achieve solid-liquid separation. Then, the wastewater from the precision filter 33 enters pH adjustment tank 34, where the pH value is adjusted to 6-7 (by adding sulfuric acid) for subsequent sodium sulfate recovery. Subsequently, the wastewater from the oxidation treatment and electrolytic hydrogen production sequentially passes through an evaporator-concentrator-crystallizer 35 and a thickener 36. The evaporator-concentrator-crystallizer 35 specifically employs an MVR evaporator-concentrator-crystallizer with a concentration factor of 5, causing sodium sulfate in the wastewater to crystallize and precipitate. Afterward, it passes through a centrifuge 37 for solid-liquid separation. The resulting wastewater, with total dissolved solids (TDS) primarily containing lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment, represents a secondary pretreatment process.

[0068] In step six, the wastewater after secondary pretreatment is fed into the lithium precipitation reactor 41. The sodium carbonate added to the lithium precipitation reactor 41 reacts with the lithium ions in the wastewater to generate lithium carbonate. Then, solid-liquid separation is achieved through a centrifuge 42.

[0069] In step seven, the wastewater after lithium precipitation is acidified by mother liquor acidifier 51, and then mixed salts are obtained by drum drying.

[0070] The material balance tables for each step of the battery black powder treatment method in the above embodiment are shown in Tables 1 and 2 (the material balance tables are split into Tables 1 and 2).

[0071] Table 1:

[0072]

[0073]

[0074] Table 2:

[0075]

[0076]

[0077] Figure 3This is a process flow diagram of a battery black powder processing method according to an embodiment of the present invention. Figure 4 for Figure 3 The process flow diagram for generating the mother liquor from the battery black powder leachate in the method shown is as follows. Figures 3-4 As shown, a method for treating battery black powder includes the following steps.

[0078] Step 1: React battery black powder with a leaching agent to obtain a leachate containing a variety of soluble metal salts, among which lithium is present.

[0079] Step 2: Separate the various soluble metal salts by precipitation method, and obtain the mother liquor containing the separated lithium.

[0080] Step 3: Perform a pretreatment on the precipitated mother liquor to ensure that the concentration of suspended solids in the pretreated wastewater is ≤5mg / L, the oil content is ≤5mg / L, the chemical oxygen demand is ≤500mg / L, and the pH value is 6-9.

[0081] Step 4: The pretreated wastewater is fed into the oxidation and hydrogen production system for oxidation and electrolysis to produce hydrogen, thereby obtaining post-oxidation and post-electrolysis hydrogen production wastewater. The oxidation and hydrogen production system includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the pretreated wastewater through an anodic electrochemical reaction, and the cathode generates hydrogen through a cathodic electrochemical reaction. The exhaust system of the electrolyzer is connected to the hydrogen storage tank.

[0082] Step 5: Perform secondary pretreatment on the wastewater after oxidation and electrolysis to ensure that the total dissolved solids in the wastewater after secondary pretreatment mainly contain lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment.

[0083] Step 6: The wastewater after the secondary pretreatment is subjected to lithium precipitation treatment to obtain lithium precipitate converted from the lithium salt and wastewater after lithium precipitation treatment. The wastewater after lithium precipitation treatment mainly contains the other dissolved metal salts.

[0084] Step 7: Perform post-treatment on the wastewater after lithium precipitation to meet the required wastewater discharge and / or recycling standards.

[0085] Specifically, such as Figure 4As shown, in this embodiment, the battery black powder mainly comes from lithium iron phosphate cathode material; the leaching agent is a sulfuric acid solution, and the lithium iron phosphate in the battery black powder decomposes into lithium ions, iron ions, and phosphate ions in the sulfuric acid solution; the precipitation method specifically includes reacting the leaching solution with a mixed solution of sodium hydroxide and hydrogen peroxide, so that the iron ions react with the phosphate ions to form iron phosphate precipitate; obtaining the precipitate mother liquor containing the separated lithium includes: performing solid-liquid separation on the reaction liquid after the reaction of the leaching solution with the mixed solution of sodium hydroxide and hydrogen peroxide, and using the liquid phase of the solid-liquid separation as the precipitate mother liquor. In addition, obtaining the precipitate mother liquor containing the separated lithium also includes: washing the iron phosphate precipitate after solid-liquid separation with water, and subjecting the wash water to alkaline precipitation treatment, first solid-liquid separation filtration treatment, and reverse osmosis membrane filtration treatment in sequence, and then mixing the concentrated liquid produced by the reverse osmosis membrane filtration treatment with the liquid phase as the precipitate mother liquor. The clear liquid produced by the reverse osmosis membrane filtration treatment can be reused.

[0086] The principle by which lithium iron phosphate in the battery black powder decomposes into lithium ions, iron ions, and phosphate ions in the sulfuric acid solution can be expressed as follows:

[0087] LiFePO4 + H2SO4 → Li + +Fe 2+ +PO4 3- +SO4 2- +H20.

[0088] The principle of reacting the leachate with a mixed solution of sodium hydroxide and hydrogen peroxide to react the iron ions with the phosphate ions to form iron phosphate precipitate can be expressed as follows:

[0089] Li + +Fe 2+ +PO4 3- +SO4 2- +NaOH+H202→FeP04(s)+Na2SO4+Li2SO4+H20.

[0090] The following is combined with Figure 3 As shown, the method for processing battery black powder in this embodiment will be further described in detail.

[0091] In step three, the mother liquor first enters flocculation sedimentation system A61 and flocculation sedimentation system B63 sequentially (a filter press and a precision filter 62 are also installed between flocculation sedimentation system A61 and flocculation sedimentation system B63, the filter press is not shown in the attached diagram). Flocculation sedimentation system A61 adds sodium hydroxide, calcium hydroxide, hydrogen peroxide, and PAM flocculant to precipitate iron, aluminum, and other metal ions from the mother liquor. Flocculation sedimentation system B63 adds sodium hydroxide and PAM flocculant to precipitate magnesium, copper, and other metal ions from the mother liquor. Then, the mixture passes sequentially through a filter press (not shown in the diagram), a precision filter 64, and a pH adjustment tank 65 (to adjust the pH to approximately 6) to obtain pretreated wastewater.

[0092] In step four, the oxidation and hydrogen production system 71 includes an electrolyzer, a DC power supply, and a hydrogen storage tank. The anode and cathode of the electrolyzer are connected to the positive and negative terminals of the DC power supply, respectively. The anode oxidizes the pretreated wastewater through an anodic electrochemical reaction, and the cathode generates hydrogen through a cathodic electrochemical reaction. The exhaust structure of the electrolyzer is connected to the hydrogen storage tank. The anode can be the same as or similar to that of an electrocatalytic oxidation reactor (such as a titanium-based metal oxide coated electrode), and the cathode can be the same as or similar to that of an electrocoagulation reactor (to facilitate hydrogen evolution).

[0093] In one optional embodiment, the oxidation and hydrogen production system 71 includes a wastewater pretreatment module. This module adds chloride salts to the pretreated wastewater before the oxidation and electrolytic hydrogen production process, thereby increasing the chloride ion concentration in the pretreated wastewater. Chloride ions react with oxygen generated at the anode during electrolysis to form hypochlorite ions. Hypochlorite ions have a strong oxidizing effect on organic matter in the wastewater, thus enhancing the oxidation treatment effect of the oxidation and hydrogen production system on the wastewater and significantly reducing the COD content of the wastewater.

[0094] Generally, the chloride ion concentration in the pretreated wastewater is increased by adding and mixing a chloride salt (calculated as sodium chloride) at a mass ratio of 1-10 to the measured chemical oxygen demand (COD) in the pretreated wastewater. In this embodiment, sodium chloride is used as the chloride salt, and the mass ratio of the added sodium chloride to the measured COD in the pretreated wastewater is 3.

[0095] In step five, the wastewater from the oxidation treatment and electrolytic hydrogen production is first passed sequentially through an evaporation-concentration crystallizer 81 and a freeze crystallizer 82 for sodium sulfate crystallization via evaporation concentration and freeze crystallization. Then, solid-liquid separation is achieved via a centrifuge 83. The resulting wastewater, after secondary pretreatment, contains mainly lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment.

[0096] In step six, the wastewater after secondary pretreatment is fed into the lithium precipitation reactor 91. The sodium carbonate added to the lithium precipitation reactor 91 reacts with the lithium ions in the wastewater to generate lithium carbonate. Then, solid-liquid separation is achieved through centrifuge 92.

[0097] In step seven, the wastewater after lithium precipitation is acidified by a mother liquor acidifier, and then dried by a drum dryer to obtain mixed salts.

[0098] The material balance tables for each step of the battery black powder treatment method in the above embodiments are shown in Tables 3-5 (the material balance tables are divided into Tables 3-5).

[0099] Table 3:

[0100]

[0101]

[0102] Table 4:

[0103]

[0104]

[0105] Table 5:

[0106]

[0107]

[0108] Figure 5 This is a schematic diagram of a wastewater treatment device according to an embodiment of the present invention. This wastewater treatment device can be used in the aforementioned battery black powder treatment method and in the oxidation and hydrogen production system of wastewater treatment equipment.

[0109] The wastewater treatment device includes a main cylinder 101, an electrolysis unit 102, a hydrogen recovery unit 103, an aeration unit 107, and a foam removal mechanism 105. The main cylinder 101 contains an electrolysis zone 1011 and a flotation zone 1012 arranged sequentially from bottom to top. The main cylinder 101 is provided with a first output port 1013 corresponding to the lower part of the electrolysis zone 1011, an input port 1014 corresponding to the upper part of the electrolysis zone 1011, and an input port 1014 corresponding to the upper part of the flotation zone 1012. The upper part corresponds to the second output port 1015 that is conductive; the electrolysis device 102 includes a DC power supply 1021 and an anode 1022 and a cathode 1023 arranged at intervals in the electrolysis zone 1011. The anode 1022 and the cathode 1023 are respectively connected to the positive and negative terminals of the DC power supply 1021. During operation, the anode 1022 oxidizes the wastewater entering the electrolysis zone 1011 through the input port 1014 through an anodic electrochemical reaction, and the cathode 1023 generates hydrogen through a cathodic electrochemical reaction; the hydrogen recovery device 103 includes a gas isolation component corresponding to each cathode 1023. The gas isolation component is sleeved on the outside of the corresponding cathode 1023 and has a side wall 1031 arranged around the cathode and an end cap 1032 located at the upper end of the side wall 1031. The lower end of the side wall 1031 is provided with an opening and / or the side wall 1031 itself is made of a membrane material that is permeable to ions and water but not to bubbles (e.g., the membrane material is made of...). The membrane used in alkaline water electrolysis for hydrogen production has an exhaust port on the end cap 1032, which is connected to the hydrogen storage tank via an exhaust pipe 1033; the aeration device 107 is disposed between the electrolysis zone 1011 and the flotation zone 1012 for aeration within the main cylinder 101; and the foam cleaning mechanism 105 is installed at the top of the flotation zone 1012 for discharging the foam generated at the top of the flotation zone 1012 from the second output port 1015.

[0110] In addition, the aforementioned wastewater treatment device also includes a wastewater pretreatment module 108. This module 108 is used to add chloride salts to the wastewater to be treated before oxidation treatment and electrolytic hydrogen production, thereby increasing the chloride ion concentration in the wastewater. Specifically, the wastewater pretreatment module 108 includes a chloride salt solution preparation unit, a metering control unit, and a chloride salt solution delivery unit. The chloride salt solution preparation unit is used to prepare a chloride salt solution (e.g., sodium chloride solution) of the required concentration. The chloride salt solution delivery unit is used to deliver the chloride salt solution to the wastewater to be treated, thereby mixing the chloride salt solution with the wastewater. The metering control unit is used to meter and control the amount of chloride added to the wastewater. Typically, the metering control unit controls the amount of chloride added to the wastewater to be treated at a mass ratio of 1-10 (based on sodium chloride) to the measured chemical oxygen demand (COD) in the wastewater.

[0111] The working principle of the above-mentioned wastewater purification and hydrogen production system is as follows: the wastewater to be treated enters the main cylinder 101 through the inlet 1014. At the same time, the wastewater pretreatment module 108 adds chloride solution to the wastewater to be treated. Furthermore, the aeration device 107 (usually air aeration) generates a large number of bubbles that flow counter-currently with the wastewater entering the main cylinder 101 through the inlet 1014. These bubbles adhere to the suspended particles in the wastewater, and buoyancy causes these suspended particles to float to the surface of the flotation zone 1012, forming foam. This foam is then discharged from the second outlet 1015 by the foam cleaning mechanism 105 and can enter the defoaming device for further treatment. Aeration allows the chloride solution to be fully mixed with the wastewater. Afterward, the wastewater flows downward from the flotation zone 1012 into... When the electrolysis unit 102 is working in the electrolysis zone 1011, the anode 1022 oxidizes the wastewater entering the electrolysis zone 1011 through the input port 1014 via an anodic electrochemical reaction (the anode 1022 generates oxygen bubbles, which react with chloride ions added by the wastewater pretreatment module 108 to generate hypochlorite ions. Hypochlorite ions have a strong oxidizing effect on the organic matter in the wastewater to be treated, thereby enhancing the oxidation and hydrogen production system's effect on the wastewater to be treated and significantly reducing the COD content of the wastewater to be treated). The cathode 1023 generates hydrogen gas through a cathode electrochemical reaction. At this time, the hydrogen gas is collected through a gas isolation component and introduced into a hydrogen storage tank through an exhaust pipe 1033. The material at the bottom of the electrolysis zone 1011 (usually a mixture of water and solid slag) is discharged from the first output port 1013.

[0112] In the electrolysis device 102, the anode 1022 can be the same as or similar to that of the electrocatalytic oxidation reactor (such as a titanium-based metal oxide coated electrode), and the cathode 1023 can be the same as or similar to that of the electrocoagulation reactor (to facilitate hydrogen evolution). Generally, the electrolysis device 102 includes a plurality of anodes 1022 and a plurality of cathodes 1023, which are arranged alternately in the horizontal direction in the electrolysis zone 1011.

[0113] In one optional embodiment, the main cylinder 101 further includes a sedimentation zone 1016 located below the electrolysis zone 1011. Typically, the bottom of the sedimentation zone 1016 forms a conical discharge trough, and the slag discharge port is located at the bottom of the conical discharge trough.

[0114] The foam removal mechanism 105 can be a scraper conveyor. Furthermore, to facilitate foam handling, the upper part of the flotation zone 1012 is provided with a lateral partition located inside the main cylinder 101 and spaced a certain distance from the inner wall of the main cylinder 101, and a bottom partition connected between the bottom of the lateral partition and the inner wall of the main cylinder 101. The lateral partition and the bottom partition form a notch 1016 located slightly above the side of the flotation zone. The second output port 1015 is located on the side wall of the main cylinder 101 and communicates laterally with the notch 1016. The foam removal mechanism 105 is installed at the top of the flotation zone and is used to push the foam generated at the top of the flotation zone towards the notch 1016.

[0115] Since scum mainly contains suspended particles and air bubbles, it has poor flowability and easily clogs pipes. The above design allows the scum removed by the scum cleaning mechanism 105 (scraper conveyor) to be temporarily stored in the notch 1016. Then, the second outlet 1015 on the side of the notch 1016 serves as an overflow outlet, allowing the scum to flow naturally out of the second outlet 1015, preventing blockage. Furthermore, this design also allows the upper part of the main cylinder 101 to be completely enclosed except for the second outlet 1015, reducing noise, minimizing safety hazards, and improving the aesthetic appearance of the equipment.

[0116] In one optional embodiment, a water distributor 106 is provided on the upper part of the electrolysis zone 1011. The water distributor 106 inputs the wastewater to be treated from the inlet 1014 into the electrolysis zone 1011 in a manner that distributes it evenly across the cross-section of the electrolysis zone 1011. Specifically, the water distributor 106 has a main inlet pipe connected to the inlet 1014 and water distribution manifolds spaced apart on the main inlet pipe. The main inlet pipe is arranged horizontally, and the water distribution manifolds are arranged vertically downward.

[0117] The aeration device 107 is preferably disposed between the water distributor 106 and the electrolysis device 102. Figure 5 In this process, the aeration device 107 may have a main air inlet pipe and aeration points spaced apart on the main air inlet pipe. The main air inlet pipe is arranged in a horizontal direction and connected to an air source.

[0118] The aforementioned wastewater treatment device can also eliminate the aeration device 107, utilizing the oxygen bubbles generated by the anode 1022 during the oxidation treatment of wastewater in the electrolysis zone 1011 to achieve a similar effect to air flotation. The space between the anode of the electrolysis device and the hydrogen recovery device can form an oxygen flotation channel, thereby guiding the oxygen generated by the anode upward into the air flotation zone.

[0119] In the aforementioned wastewater treatment device, the outlet of the chloride solution conveying unit 108 can be connected to the inlet 1014 (e.g., Figure 5 (As shown) or / and extends into the electrolysis zone and is connected to the electrolysis zone 1011. When the outlet of the chloride solution conveying unit 108 extends into the electrolysis zone and is connected to the electrolysis zone, the outlet of the chloride solution conveying unit 108 can be located at the upper part of the electrolysis zone and output chloride solution downwards and / or located at the lower part of the electrolysis zone and output chloride solution upwards. When the outlet of the chloride solution conveying unit extends into the electrolysis zone and is connected to the electrolysis zone, a structure similar to the water distributor 106 described above can be adopted to input the chloride solution into the main cylinder in a manner that is uniformly distributed across the cross-section of the electrolysis zone.

[0120] The present invention has been described above. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the foregoing content of this specification without inventive effort should fall within the scope of patent protection.

Claims

1. A method for treating battery sludge, characterized by, The application relates to a method for treating wastewater generated in the process of extracting lithium from battery black powder. The method comprises the following steps: reacting battery black powder with a leaching agent to obtain a leaching solution containing a plurality of soluble metal salts, wherein the soluble metal salts contain lithium; separating the plurality of soluble metal salts by using a precipitation method to obtain a precipitate mother liquor containing the separated lithium; performing primary pretreatment on the precipitate mother liquor to ensure that the concentration of solid suspensions in the primary pretreated wastewater is less than or equal to 5 mg / L, the oil content is less than or equal to 5 mg / L, the chemical oxygen demand is less than or equal to 500 mg / L, and the pH value is 6-9; inputting the primary pretreated wastewater into an oxidation treatment and hydrogen production system to perform oxidation treatment and electrolytic hydrogen production, thereby obtaining post-oxidation treatment and electrolytic hydrogen production wastewater; performing secondary pretreatment on the post-oxidation treatment and electrolytic hydrogen production wastewater to ensure that the total dissolved solid substances in the post-secondary pretreatment wastewater mainly contain lithium salts and other soluble metal salts which can be separated from the lithium salts through subsequent lithium precipitation treatment; performing lithium precipitation treatment on the post-secondary pretreatment wastewater to obtain lithium precipitates converted from the lithium salts and post-lithium precipitation treatment wastewater mainly containing the other soluble metal salts; performing wastewater post-treatment on the post-lithium precipitation treatment wastewater to reach required wastewater discharge and / or to-be-recovered material recovery standards; wherein the oxidation and hydrogen production system comprises an electrolytic cell, a direct current power supply and a hydrogen storage tank, the anode and the cathode of the electrolytic cell are connected with the positive and negative electrodes of the direct current power supply respectively, the anode performs oxidation treatment on the primary pretreated wastewater through anode electrochemical reaction, the cathode generates hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected with the hydrogen storage tank; the battery black powder mainly comes from lithium iron phosphate positive materials; the leaching agent is a sulfuric acid solution, lithium ions, iron ions and phosphate ions are generated by decomposing lithium iron phosphate in the battery black powder in the sulfuric acid solution; the precipitation method specifically comprises the following steps: mixing the leaching solution with a sodium hydroxide and hydrogen peroxide mixed solution to make the iron ions react with the phosphate ions to generate phosphorus iron precipitates; the post-solid-liquid separation liquid phase is used as the precipitate mother liquor; the post-solid-liquid separation phosphorus iron precipitates are washed with water, the washing water is sequentially subjected to alkali precipitation treatment, first solid-liquid separation filtration treatment and reverse osmosis membrane filtration treatment, and then the concentrated solution generated by the reverse osmosis membrane filtration treatment is mixed with the liquid phase to serve as the precipitate mother liquor; the primary pretreatment comprises the following steps: sequentially performing alkali precipitation treatment, second solid-liquid separation filtration treatment and pH value readjustment treatment on the precipitate mother liquor, and the pH value readjustment treatment is used for readjusting the pH value of the wastewater to be treated to 6-7; the secondary pretreatment comprises the following steps: sequentially performing sodium sulfate crystallization evaporation concentration treatment, sodium sulfate crystallization freezing crystallization treatment and third solid-liquid separation filtration treatment on the post-oxidation treatment and electrolytic hydrogen production wastewater. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The method also comprises increasing the concentration of chloride ions in the once-pretreated wastewater before the oxidation treatment and electrolytic hydrogen production; the concentration of chloride ions in the once-pretreated wastewater is increased by adding and mixing a chlorate in the once-pretreated wastewater, wherein the mass ratio of the amount of sodium chloride added to the measured chemical oxygen demand in the once-pretreated wastewater is 1-10.

2. A wastewater treatment apparatus, characterized by: The method for treating the battery black powder of claim 1 comprises the following steps: The method comprises the following steps: a once-pretreatment system for once-pretreating the precipitation mother liquor, so that the once-pretreated wastewater obtained after the once-pretreatment has a solid suspension concentration of ≤5 mg / L, an oil content of ≤5 mg / L, a chemical oxygen demand of ≤500 mg / L, and a pH value of 6-9; an oxidation and hydrogen production system for oxidizing and electrolytically producing hydrogen from the once-pretreated wastewater, so as to obtain oxidized and electrolytically hydrogen-produced wastewater; a secondary pretreatment system for secondary-pretreating the oxidized and electrolytically hydrogen-produced wastewater, so that the secondary-pretreated wastewater obtained after the secondary pretreatment mainly contains lithium salt and other dissolved metal salts that can be separated from the lithium salt by subsequent lithium precipitation treatment; a lithium precipitation treatment system for precipitating lithium from the secondary-pretreated wastewater, so as to obtain lithium precipitates converted from the lithium salt and lithium precipitation-treated wastewater mainly containing the other dissolved metal salts; and a wastewater post-treatment system for post-treating the lithium precipitation-treated wastewater to meet the required wastewater discharge and / or recovery standards of the to-be-recovered substances; The oxidation and hydrogen production system comprises an electrolytic cell, a direct current power supply, and a hydrogen storage tank, the anode and the cathode of the electrolytic cell are connected to the positive and negative electrodes of the direct current power supply, respectively, the anode oxidizes the once-pretreated wastewater through an anode electrochemical reaction, the cathode produces hydrogen through a cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected to the hydrogen storage tank. The oxidation and hydrogen production system further comprises a wastewater pretreatment module for adding a chlorate to the once-pretreated wastewater before the oxidation treatment and electrolytic hydrogen production, so as to increase the concentration of chloride ions in the once-pretreated wastewater; the wastewater pretreatment module is configured to add and mix a chlorate in the once-pretreated wastewater, wherein the mass ratio of the amount of sodium chloride added to the measured chemical oxygen demand in the once-pretreated wastewater is 1-10.

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