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 means of extraction, and obtaining raffinate wastewater containing the separated lithium; performing a primary pretreatment on the raffinate 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 electrolyzer, a DC power supply, and a hydrogen storage tank.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to a battery black powder treatment method, a wastewater treatment device and a wastewater treatment apparatus. BACKGROUND

[0002] With the popularity of electronic communication equipment and the rapid development of the electric vehicle industry, the consumption of ternary lithium ion batteries and lithium iron phosphate batteries has increased dramatically. The service life of these batteries is usually 5-8 years, and a large number of waste batteries will be generated after the service life expires. At present, the wet metallurgical scheme can be used for waste battery black powder, but there are problems of complex process and low energy saving and environmental protection benefits.

[0003] On the other hand, the known electrochemical reactor for wastewater treatment mainly includes an electro-catalytic oxidation (ECO) reactor and an electro-coagulation (EC) reactor. Their basic structures are similar, that is, they both include an electrolytic cell and a direct current power supply, and the anode and cathode of the electrolytic cell are connected to the positive and negative electrodes of the direct current power supply, respectively. The main difference between them is that the electrode materials and working mechanisms are different.

[0004] Electro-catalytic oxidation (EO) is to use the oxidation of the anode (usually a titanium-based metal oxide coated electrode) and / or to use the electric field to generate free radicals to promote the oxidation and decomposition of pollutants, thereby achieving wastewater treatment. It can be divided into direct oxidation method and indirect oxidation method. The direct oxidation method is to directly oxidize the pollutants on the surface of the anode to achieve the purpose of removing pollution. The indirect oxidation method is to decompose water molecules by an electric field to generate oxidizing agents such as hydroxyl radicals, which react with pollutants in wastewater to remove pollution.

[0005] Electro-coagulation (EC) is to dissolve metal ions in the anode (usually aluminum electrodes or iron electrodes) into wastewater, generate metal hydroxides through hydrolysis reaction, and the metal hydroxides act as flocculants to coagulate suspended solids and colloids in wastewater, thereby achieving the purpose of removing pollution. At the same time, the hydrogen ions at the cathode are reduced to hydrogen gas after obtaining electrons, which overflow in the form of fine bubbles, which can make the flocculent and oil substances in the wastewater float to the water surface.

[0006] At present, the electro-catalytic oxidation technology and the electro-coagulation technology are relatively single in function, and the recycling of hydrogen gas has not been realized. SUMMARY

[0007] One of the purposes of the embodiments of the present application is to provide an improved battery black powder treatment method and wastewater treatment equipment for treating high-pollution wastewater generated in the method, which can effectively purify high-pollution wastewater and use high-pollution wastewater to produce hydrogen, thereby improving energy-saving and environmental protection benefits.

[0008] The second purpose of the embodiments of the present application is to provide a wastewater treatment device that can be used in the battery black powder treatment method and the 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 battery black powder treatment method is provided, comprising: reacting battery black powder with a leaching agent to obtain a leaching solution containing a plurality of soluble metal salts, the plurality of soluble metal salts containing lithium; separating the plurality of soluble metal salts, the separation using an extraction method, and obtaining raffinate wastewater containing the separated lithium; performing a first pretreatment on the raffinate wastewater to ensure that the first pretreated wastewater obtained after the first pretreatment has a solid suspended matter concentration ≤5 mg / L, an oil content ≤5 mg / L, a chemical oxygen demand ≤500 mg / L, and a pH value of 6-9; inputting the first pretreated wastewater into an oxidation and hydrogen production system for oxidation treatment and electrolytic hydrogen production, thereby obtaining oxidation and electrolytic hydrogen production wastewater; performing a second pretreatment on the oxidation and electrolytic hydrogen production wastewater to ensure that the second pretreated wastewater obtained after the second pretreatment mainly contains lithium salts and other soluble metal salts that can be separated from the lithium salts after subsequent lithium precipitation treatment; performing lithium precipitation treatment on the second pretreated wastewater to obtain lithium precipitates converted from the lithium salts and lithium precipitation treatment wastewater mainly containing the other soluble metal salts; performing wastewater post-treatment on the lithium precipitation treatment wastewater to meet the required wastewater discharge and / or recycled 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 cathode of the electrolytic cell are connected to the positive and negative electrodes of the direct current power supply, respectively, the anode performs oxidation treatment on the first pretreated wastewater through anode electrochemical reaction, the cathode generates hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected to the hydrogen storage tank.

[0010] According to the embodiment of the present application, the battery black powder is mainly from ternary lithium positive electrode material; the leaching agent is sulfuric acid solution, 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 separation processes and multiple back-extraction separation processes; the first extraction separation process is used to obtain the first extraction solution containing the manganese sulfate and the first raffinate containing the nickel salt and the cobalt salt from the leaching solution; the second extraction separation process is used to obtain the second extraction solution containing the cobalt sulfate and the second raffinate containing the nickel salt from the first raffinate; the third extraction separation process is used to obtain the third extraction solution containing the nickel sulfate and the third raffinate from the second raffinate; the first back-extraction separation process is used to obtain the first back-extraction solution containing the manganese sulfate and the first back-extraction raffinate from the first extraction solution; the fourth extraction separation process is used to obtain the fourth extraction solution containing the manganese sulfate and the fourth raffinate from the first back-extraction solution; the second back-extraction separation process is used to obtain the second back-extraction solution containing the cobalt sulfate and the second back-extraction raffinate from the second extraction solution, and the second back-extraction solution is cobalt sulfate solution; the third back-extraction separation process is used to obtain the third back-extraction solution containing the nickel sulfate and the third back-extraction raffinate from the third extraction solution, and the third back-extraction solution is nickel sulfate solution; the fourth back-extraction separation process is used to obtain the fourth back-extraction solution containing the manganese sulfate and the fourth back-extraction raffinate from the fourth extraction solution, and the fourth back-extraction solution is manganese sulfate solution; the raffinate wastewater containing the separated lithium is obtained by mixing the third raffinate and the fourth raffinate to form the raffinate wastewater.

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

[0012] According to the embodiment of the present application, the first pretreatment includes sequentially performing air floatation impurity removal treatment, activated carbon adsorption treatment and first solid-liquid separation filtration treatment on the raffinate wastewater.

[0013] According to the embodiment of the present application, the second pretreatment includes sequentially performing alkali precipitation method treatment, second solid-liquid separation filtration treatment, pH value adjustment treatment, sodium sulfate crystallization evaporation concentration treatment and third solid-liquid separation filtration treatment on the wastewater after the oxidation treatment and electrolytic hydrogen production, and the pH value adjustment treatment is used to adjust the pH value of the wastewater to be treated to 6-7.

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

[0015] According to the embodiment of the present application, the concentration of chloride ions in the once-pre-treated wastewater is increased by adding and mixing a chloride salt in the once-pre-treated wastewater, the mass ratio of the amount of the chloride salt added to the measured chemical oxygen demand in the once-pre-treated wastewater being 1-10.

[0016] In a second aspect, a wastewater treatment device for treating battery black powder leaching residue wastewater is provided, wherein the battery black powder leaching residue wastewater is generated by a process including: reacting battery black powder with a leaching agent to obtain a leaching solution containing a plurality of soluble metal salts, the plurality of soluble metal salts containing lithium; and separating the plurality of soluble metal salts by using an extraction method to obtain the lithium-containing leaching residue wastewater. The device includes: a first pretreatment system for first pretreating the leaching residue wastewater to ensure that the first pretreated wastewater has a solid suspended substance concentration of less than or equal to 5 mg / L, an oil content of less than or equal to 5 mg / L, a chemical oxygen demand of less than or equal to 500 mg / L, and a pH value of 6-9; an oxidation and hydrogen production system for oxidizing and electrolyzing the first pretreated wastewater to obtain oxidized and electrolyzed wastewater; a second pretreatment system for second pretreating the oxidized and electrolyzed wastewater to ensure that the second pretreated wastewater contains mainly lithium salts and other soluble metal salts that can be separated from the lithium salts by subsequent lithium precipitation treatment; a lithium precipitation treatment system for precipitating lithium from the second pretreated wastewater to obtain lithium precipitates converted from the lithium salts and lithium precipitation treated wastewater containing mainly the other soluble metal salts; and a wastewater post-treatment system for post-treating the lithium precipitation treated wastewater to meet required wastewater discharge and / or recycling standards. The oxidation and hydrogen production system includes an electrolytic cell, a direct current power supply, and a hydrogen storage tank, the anode and cathode of the electrolytic cell are connected to the positive and negative electrodes of the direct current power supply, respectively, the anode oxidizes the first 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.

[0017] According to the embodiment of the present application, the battery black powder mainly comes from the positive electrode material of ternary lithium battery; the leaching agent is sulfuric acid solution, 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 separation processes and multiple back-extraction separation processes; the first extraction separation process is used to obtain the first extraction solution containing the manganese sulfate and the first raffinate containing the nickel salt and the cobalt salt from the leaching solution; the second extraction separation process is used to obtain the second extraction solution containing the cobalt sulfate and the second raffinate containing the nickel salt from the first raffinate; the third extraction separation process is used to obtain the third extraction solution containing the nickel sulfate and the third raffinate from the second raffinate; the first back-extraction separation process is used to obtain the first back-extraction solution containing the manganese sulfate and the first back-extraction raffinate from the first extraction solution; the fourth extraction separation process is used to obtain the fourth extraction solution containing the manganese sulfate and the fourth raffinate from the first back-extraction solution; the second back-extraction separation process is used to obtain the second back-extraction solution containing the cobalt sulfate and the second back-extraction raffinate from the second extraction solution, and the second back-extraction solution is cobalt sulfate solution; the third back-extraction separation process is used to obtain the third back-extraction solution containing the nickel sulfate and the third back-extraction raffinate from the third extraction solution, and the third back-extraction solution is nickel sulfate solution; the fourth back-extraction separation process is used to obtain the fourth back-extraction solution containing the manganese sulfate and the fourth back-extraction raffinate from the fourth extraction solution, and the fourth back-extraction solution is manganese sulfate solution; the raffinate wastewater containing the separated lithium is obtained by mixing the third raffinate and the fourth raffinate to form the raffinate wastewater.

[0018] According to the embodiment of the present application, the oxidation and hydrogen production system includes a wastewater pretreatment module, which is used to add chloride salt to the once-pretreated wastewater to increase the concentration of chloride ions in the once-pretreated wastewater before the oxidation treatment and electrolytic hydrogen production.

[0019] The basic technical concept of the battery black powder treatment method and the wastewater treatment equipment is as follows: first, the plurality of soluble metal salts are separated by using an extraction method, and the lithium in the separated lithium is obtained in the raffinate wastewater, so that the lithium is preliminarily extracted into the liquid phase (i.e., the raffinate wastewater). Thereafter, the raffinate wastewater is subjected to a first pretreatment to ensure that the concentration of solid suspensions in the first pretreated wastewater is ≤5 mg / L, the oil content is ≤5 mg / L, the chemical oxygen demand is ≤500 mg / L, and the pH value is 6-9, so that the first pretreated wastewater meets the requirements for subsequent oxidation treatment and electrolytic hydrogen production. The chemical oxygen demand (i.e., the COD content) in the raffinate wastewater is very high, which is derived from the organic electrolyte in the battery and the extractant used in the extraction method. Thereafter, the first pretreated wastewater is input into an oxidation and hydrogen production system for oxidation treatment and electrolytic hydrogen production. Since the oxidation and hydrogen production system includes an electrolytic tank, a direct current power supply, and a hydrogen storage tank, the anode and the cathode of the electrolytic tank are connected to the positive and negative electrodes of the direct current power supply, respectively. The anode performs oxidation treatment on the first pretreated wastewater through an anode electrochemical reaction, the cathode generates hydrogen through a cathode electrochemical reaction, and the exhaust structure of the electrolytic tank is connected to the hydrogen storage tank. Therefore, the oxidation and hydrogen production system can not only perform oxidation treatment on the first pretreated wastewater to mainly reduce the COD content in the first pretreated wastewater, but also produce hydrogen. As the energy saving and emission reduction requirements improve, the demand for hydrogen gradually increases, and the application scenarios of hydrogen also increase. Therefore, using the oxidation and hydrogen production system can improve the energy saving and environmental protection benefits. Thereafter, the wastewater after oxidation treatment and electrolytic hydrogen production is subjected to a second pretreatment to ensure that the total dissolved solids in the second pretreated wastewater mainly contain lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment, which helps to improve the lithium recovery rate. Thereafter, the second pretreated wastewater is subjected to lithium precipitation treatment, and the wastewater after lithium precipitation treatment is subjected to wastewater post-treatment to meet the required wastewater discharge and / or recycled material recovery standards. It can be seen that the battery black powder treatment method and the wastewater treatment equipment can effectively purify the raffinate wastewater of the battery black powder leaching solution and improve the energy saving and environmental protection benefits.

[0020] In a third aspect, a method for treating battery black powder is provided, comprising: 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 a first pretreatment on the precipitate mother liquor to ensure that a first pretreated wastewater obtained after the first pretreatment has a solid suspended substance concentration of less than or equal to 5 mg / L, an oil content of less than or equal to 5 mg / L, a chemical oxygen demand of less than or equal to 500 mg / L, and a pH value of 6-9; inputting the first pretreated wastewater into an oxidation treatment and hydrogen production system to perform oxidation treatment and electrolytic hydrogen production, thereby obtaining an oxidation treated and electrolytic hydrogen produced wastewater; performing a second pretreatment on the oxidation treated and electrolytic hydrogen produced wastewater to ensure that a second pretreated wastewater obtained after the second pretreatment mainly contains lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment; performing lithium precipitation treatment on the second pretreated wastewater to obtain lithium precipitates converted from the lithium salts and lithium precipitation treated wastewater mainly containing the other soluble metal salts; performing wastewater post-treatment on the lithium precipitation treated wastewater to meet required wastewater discharge and / or recyclable material recycling 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 cathode of the electrolytic cell are connected to the positive and negative electrodes of the direct current power supply, the anode performs oxidation treatment on the first pretreated wastewater through anode electrochemical reaction, the cathode produces hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected to the hydrogen storage tank.

[0021] According to the embodiments of the present application, the battery black powder mainly comes from lithium iron phosphate positive electrode material; the leaching agent is a sulfuric acid solution, and the lithium iron phosphate in the battery black powder is decomposed into lithium ions, iron ions and phosphate ions in the sulfuric acid solution; the precipitation method specifically comprises reacting the leaching solution with a mixed solution of sodium hydroxide and hydrogen peroxide to make the iron ions react with the phosphate ions to generate phosphorus iron precipitates; and obtaining the precipitate mother liquor containing the separated lithium comprises: performing solid-liquid separation on the reaction solution after the leaching solution reacts 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 the embodiments of the present application, obtaining the precipitate mother liquor containing the separated lithium further comprises: washing the phosphorus iron precipitates after the solid-liquid separation with water, sequentially performing alkali precipitation method treatment, first solid-liquid separation filtration treatment and reverse osmosis membrane filtration treatment on the washing water after the washing, and then mixing the concentrated solution generated by the reverse osmosis membrane filtration treatment with the liquid phase as the precipitate mother liquor.

[0023] According to the embodiment of the present application, the first pretreatment comprises sequentially performing alkali precipitation, second solid-liquid separation, pH value adjustment and evaporation concentration on the precipitation mother liquor, and the pH value adjustment is used to adjust the pH value of the wastewater to be treated to 6-7.

[0024] According to the embodiment of the present application, the second pretreatment comprises sequentially performing evaporation concentration for sodium sulfate crystallization, freezing crystallization for sodium sulfate crystallization and third solid-liquid separation on the wastewater after the oxidation treatment and electrolytic hydrogen production.

[0025] According to the embodiment of the present application, the concentration of chloride ions in the wastewater after the first pretreatment is increased before the oxidation treatment and electrolytic hydrogen production.

[0026] According to the embodiment of the present application, the concentration of chloride ions in the wastewater after the first pretreatment is increased by adding and mixing a chloride salt in an amount of 1-10 times the mass ratio of the measured chemical oxygen demand in the wastewater after the first pretreatment.

[0027] In a fourth aspect, a wastewater treatment device for treating battery black powder leaching solution precipitate mother liquor is provided, wherein the battery black powder leaching solution precipitate mother liquor is generated by a process comprising: reacting battery black powder with a leaching agent to obtain a leaching solution containing a plurality of soluble metal salts, wherein the plurality of soluble metal salts contain lithium; and separating the plurality of soluble metal salts by a precipitation method to obtain a precipitate mother liquor containing the separated lithium; and the device comprises: a first pretreatment system for pretreating the wastewater to ensure that the first pretreated wastewater has a solid suspended substance concentration of less than or equal to 5 mg / L, an oil content of less than or equal to 5 mg / L, a chemical oxygen demand of less than or equal to 500 mg / L, and a pH value of 6-9; an oxidation and hydrogen production system for oxidizing and electrolyzing the first pretreated wastewater to obtain oxidized and electrolyzed wastewater; a second pretreatment system for pretreating the oxidized and electrolyzed wastewater to ensure that the second pretreated wastewater contains mainly lithium salts and other soluble metal salts that can be separated from the lithium salts by subsequent lithium precipitation treatment; a lithium precipitation treatment system for treating the second pretreated wastewater by lithium precipitation treatment to obtain lithium precipitates converted from the lithium salts and lithium precipitation treated wastewater containing mainly the other soluble metal salts; and a wastewater post-treatment system for treating the lithium precipitation treated wastewater by wastewater post-treatment to meet required wastewater discharge and / or recycling 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 cathode of the electrolytic cell are connected to the positive and negative electrodes of the direct current power supply, the anode oxidizes the first pretreated wastewater by anode electrochemical reaction, the cathode produces hydrogen by cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected to the hydrogen storage tank.

[0028] According to the embodiments of the present application, the battery black powder mainly comes from lithium iron phosphate positive materials; the leaching agent is a sulfuric acid solution, and the lithium iron phosphate in the battery black powder is decomposed into lithium ions, iron ions and phosphate ions in the sulfuric acid solution; the precipitation method specifically comprises reacting the leaching solution with a mixed solution of sodium hydroxide and hydrogen peroxide to make the iron ions react with the phosphate ions to generate iron phosphate precipitates; obtaining the precipitate mother liquor containing the separated lithium comprises: performing solid-liquid separation on the reaction liquid after the leaching solution reacts 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; and obtaining the precipitate mother liquor containing the separated lithium further comprises: washing the iron phosphate precipitates after the solid-liquid separation with water, sequentially performing alkali precipitation treatment, first solid-liquid separation filtration treatment and reverse osmosis membrane filtration treatment on the washing water after the washing, and then mixing the concentrated liquid generated by the reverse osmosis membrane filtration treatment with the liquid phase as the precipitate mother liquor.

[0029] The basic technical concept of the battery black powder treatment method and the wastewater treatment equipment is that: first, the lithium is preliminarily extracted into the liquid phase (i.e. the precipitate mother liquor) by separating the plurality of soluble metal salts using the precipitation method and obtaining the precipitate mother liquor containing the separated lithium. Then, the once pretreated wastewater after the pretreatment meets the requirements of subsequent oxidation treatment and electrolytic hydrogen production by ensuring that the solid suspended matter concentration of the once pretreated wastewater after the pretreatment is ≤5 mg / L, the oil content is ≤5 mg / L, the chemical oxygen demand is ≤500 mg / L, and the pH value is 6-9. The chemical oxygen demand (i.e. COD content) in the precipitate mother liquor is relatively high, mainly from the organic electrolyte in the battery. Then, the once pretreated wastewater is input into the oxidation and hydrogen production system for oxidation treatment and electrolytic hydrogen production. Since the oxidation and hydrogen production system includes an electrolytic tank, a direct current power supply, and a hydrogen storage tank, the anode and the cathode of the electrolytic tank are connected to the positive and negative electrodes of the direct current power supply, respectively. The anode performs oxidation treatment on the once pretreated wastewater through anodic electrochemical reaction, and the cathode generates hydrogen through cathodic electrochemical reaction. The exhaust structure of the electrolytic tank is connected to the hydrogen storage tank. Therefore, the oxidation and hydrogen production system can not only perform oxidation treatment on the once pretreated wastewater to mainly reduce the COD content of the once pretreated wastewater, but also produce hydrogen. With the increasing demand for energy saving and emission reduction, the demand for hydrogen is gradually increasing, and the application scenarios of hydrogen are also increasing. Therefore, using the oxidation and hydrogen production system can improve the energy saving and environmental protection benefits. Then, the wastewater after oxidation treatment and electrolytic hydrogen production is subjected to secondary pretreatment to ensure that the total dissolved solid substances 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. This helps to improve the recovery rate of lithium. After that, the wastewater after secondary pretreatment is subjected to lithium precipitation treatment, and the wastewater after lithium precipitation treatment is subjected to wastewater post-treatment to meet the required wastewater discharge and / or recycled material recovery standards. It can be seen that the battery black powder treatment method and the wastewater treatment equipment can effectively purify the battery black powder leaching solution precipitate mother liquor and improve the energy saving and environmental protection benefits.

[0030] In a fifth aspect, there is provided a wastewater treatment device, comprising: an oxidation and hydrogen production system for oxidizing and electrolyzing hydrogen from the wastewater to be treated, the oxidation and hydrogen production system comprising a wastewater pretreatment module, an electrolytic cell, a direct current power supply and a hydrogen storage tank, the anode and the cathode of the electrolytic cell being connected to the positive and negative poles of the direct current power supply respectively, the anode oxidizing the wastewater to be treated through an anode electrochemical reaction, the cathode producing hydrogen through a cathode electrochemical reaction, the exhaust structure of the electrolytic cell being connected to the hydrogen storage tank, and the wastewater pretreatment module being used for adding a chlorine salt to the wastewater to be treated to increase the concentration of chloride ions in the wastewater to be treated before the oxidation and hydrogen production.

[0031] According to an embodiment of the present application, the wastewater pretreatment module comprises a chlorine salt solution preparation unit, a metering control unit and a chlorine salt solution delivery unit, the chlorine salt solution preparation unit being used for preparing a chlorine salt solution with a desired concentration, the chlorine salt solution delivery unit being used for delivering the chlorine salt solution to the wastewater to be treated so as to mix the chlorine salt solution with the wastewater to be treated, and the metering control unit being used for metering and controlling the amount of the chlorine salt added to the wastewater to be treated.

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

[0033] According to the embodiment of the present application, the wastewater treatment device comprises: a main cylinder, which has an electrolysis zone and a gas float zone arranged in sequence from bottom to top, and is provided with 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 gas float zone; the electrolysis zone constitutes the electrolysis tank; an electrolysis device, which comprises a direct current power supply and an anode and a cathode arranged in the electrolysis zone, and the anode and the cathode are connected to the positive and negative poles of the direct current power supply respectively; when working, the anode performs oxidation treatment on the wastewater entering the electrolysis zone through the input port by anode electrochemical reaction and generates oxygen, and the cathode generates hydrogen by cathode electrochemical reaction; a hydrogen recovery device, which comprises 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 cover located at the upper end of the side wall; the lower end of the side wall is provided with an open end and / or the side wall itself adopts a membrane material which can permeate ions and water but cannot permeate bubbles; the end cover is provided with an exhaust port connected to a hydrogen storage tank through an exhaust pipe, and the exhaust pipe serves as the exhaust structure; an oxygen up-floating channel, which is formed by the space between the anode of the electrolysis device and the hydrogen recovery device, and is used for guiding the oxygen generated by the anode upwards into the gas float zone; a floating scum cleaning mechanism, which is installed at the top of the gas float zone and is used for discharging the floating scum generated at the top of the gas float zone from the second output port; the outlet of the chlorine salt solution conveying unit is connected to the input port in a conductive manner or / and extends into the electrolysis zone in a conductive manner; when the outlet of the chlorine salt solution conveying unit extends into the electrolysis zone in a conductive manner, the outlet of the chlorine salt solution conveying unit is located at the upper part of the electrolysis zone and outputs chlorine salt solution downwards or / and is located at the lower part of the electrolysis zone and outputs chlorine salt solution upwards.

[0034] According to the embodiment of the present application, the wastewater treatment device comprises: a main cylinder, which has an electrolysis zone and a gas float zone arranged in sequence from bottom to top inside the main cylinder, and which is provided with 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 gas float zone; the electrolysis zone constitutes the electrolysis tank; an electrolysis device, which comprises a direct current power supply and anode and cathode electrodes arranged in the electrolysis zone at intervals, and which is connected to the positive and negative poles of the direct current power supply respectively; in operation, the anode electrode performs oxidation treatment on the wastewater entering the electrolysis zone through the input port by anode electrochemical reaction, and the cathode electrode generates hydrogen by cathode electrochemical reaction; a hydrogen recovery device, which comprises a gas isolation component corresponding to each cathode electrode, and which is sleeved outside the corresponding cathode electrode and has a side wall arranged around the cathode electrode and an end cover located at the upper end of the side wall; the lower end of the side wall is provided with an open end and / or the side wall itself adopts a membrane material capable of allowing ions and water to pass through but not allowing bubbles to pass through; the end cover is provided with an exhaust port connected to a hydrogen storage tank through an exhaust pipe serving as the exhaust structure; an aeration device, which is arranged between the electrolysis zone and the gas float zone and is used for aeration in the main cylinder; a scum cleaning mechanism, which is installed at the top of the gas float zone and is used for discharging the scum generated at the top of the gas float zone from the second output port; the outlet of the chlorine salt solution conveying unit is connected to the input port in a conductive manner or / and extends into the electrolysis zone in a conductive manner; when the outlet of the chlorine salt solution conveying unit extends into the electrolysis zone in a conductive manner, the outlet of the chlorine salt solution conveying unit is located at the upper part of the electrolysis zone and outputs chlorine salt solution downward or / and is located at the lower part of the electrolysis zone and outputs chlorine salt solution upward.

[0035] According to the embodiment of the present application, the outlet of the chlorine salt solution conveying unit is located above the aeration device.

[0036] According to the embodiment of the present application, the upper part of the gas float zone is provided with a lateral partition plate located inside the main cylinder and spaced apart from the inner wall of the main cylinder by a certain distance, and a bottom partition plate connected between the bottom of the lateral partition plate and the inner wall of the main cylinder; the lateral partition plate and the bottom partition plate constitute a notch located at the upper part of the side of the gas float zone; the second output port is arranged on the side wall of the main cylinder and is in lateral communication with the notch; and the scum cleaning mechanism is installed at the top of the gas float zone and is used for pushing the scum generated at the top of the gas float zone to the notch.

[0037] According to the embodiment of the present application, the electrolysis device comprises a plurality of anode electrodes and a plurality of cathode electrodes, and the anode electrodes and the cathode electrodes are staggered and arranged in the electrolysis zone along the horizontal direction.

[0038] According to the embodiment of the present application, the upper part of the electrolysis zone is provided with a first water distributor, which inputs the wastewater to be treated from the input port into the electrolysis zone in a uniform distribution manner on the cross section of the electrolysis zone.

[0039] According to the embodiment of the present application, the chloride salt solution delivery unit outputs the chloride salt solution through a second water distributor extending into the electrolysis zone, which inputs the chloride salt solution into the main cylinder in a uniform distribution manner on the cross section of the electrolysis zone.

[0040] The wastewater treatment device has the wastewater pretreatment module for adding chloride salt into the wastewater to be treated before the oxidation treatment and electrolysis hydrogen production, so as to increase the concentration of chloride ions in the wastewater to be treated, which can react with oxygen generated at the anode during electrolysis to generate hypochlorite, and the hypochlorite has strong oxidation effect on the organic matter in the wastewater to be treated, so as to enhance the oxidation treatment effect of the oxidation and hydrogen production system on the wastewater to be treated, and more significantly reduce the COD content of the wastewater to be treated.

[0041] The present application is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present application will be apparent from the following description, which is given by way of example only, and with reference to the accompanying drawings in which: BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which constitute a part of this specification, are included to illustrate the present application and to provide a better understanding of the same. The drawings provided in the accompanying drawings and the descriptions thereof provided in the present specification can be used to explain the present application, but do not constitute undue limitations on the present application.

[0043] Figure 1 A process flow chart of a battery black powder treatment method according to an embodiment of the present application.

[0044] Figure 2 A process flow chart of a battery black powder treatment method according to an embodiment of the present application. Figure 1 A process flow chart of a battery black powder leaching solution extraction wastewater production process in the method shown.

[0045] Figure 3 A process flow chart of a battery black powder treatment method according to an embodiment of the present application.

[0046] Figure 4 A process flow chart of a battery black powder treatment method according to an embodiment of the present application. Figure 3 A process flow chart of a battery black powder leaching solution extraction wastewater production process in the method shown.

[0047] Figure 5 A structure schematic diagram of a wastewater treatment device according to an embodiment of the present application. DETAILED DESCRIPTION

[0048] The application will be described in detail below with reference to the drawings. Those skilled in the art can implement the application based on the description. Before the application is described in detail with reference to the drawings, it should be particularly pointed out that:

[0049] The technical solutions and technical features provided in the various parts including the following description can be combined with each other without conflict. In addition, in the case of possibility, these technical solutions, technical features and related combinations can be given a specific technical subject and protected by a related patent.

[0050] The embodiments of the application involved in the following description are generally only a part of the embodiments and not all the embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of patent protection.

[0051] Regarding the terms and units in this specification: The terms "include", "contain", "have" and any variations thereof in the specification and the corresponding claims and related parts are intended to cover non-exclusive inclusion. In addition, other related terms and units can be reasonably interpreted based on the related content provided in the specification.

[0052] Figure 1 A process flow chart of a battery black powder treatment method according to an embodiment of the application. Figure 2 A process flow chart of a battery black powder treatment method according to an embodiment of the application. Figure 1 A process flow chart of the generation process of battery black powder leaching solution raffinate wastewater in the method shown. Figures 1-2 A battery black powder treatment method, comprising the following steps.

[0053] Step one: reacting battery black powder with a leaching agent to obtain a leaching solution containing a plurality of dissolved metal salts, the plurality of dissolved metal salts containing lithium.

[0054] Step two: separating the plurality of dissolved metal salts, the separation using an extraction method, and obtaining the lithium-containing raffinate wastewater.

[0055] Step three: pretreating the raffinate wastewater once to ensure that the solid suspended matter concentration in the once-pretreated wastewater obtained after the pretreatment is ≤5 mg / L, the oil content is ≤5 mg / L, the chemical oxygen demand is ≤500 mg / L, and the pH value is 6-9.

[0056] Step four: inputting the once pretreated wastewater into an oxidation and hydrogen production system to perform oxidation treatment and electrolytic hydrogen production, thereby obtaining the wastewater after oxidation treatment and electrolytic hydrogen production. The oxidation and hydrogen production system comprises an electrolytic tank, a direct current power supply and a hydrogen storage tank, the anode and the cathode of the electrolytic tank are connected to the positive and negative electrodes of the direct current power supply respectively, the anode performs oxidation treatment on the once pretreated wastewater through anode electrochemical reaction, the cathode produces hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic tank is connected to the hydrogen storage tank.

[0057] Step five: performing secondary pretreatment on the wastewater after oxidation treatment and electrolytic hydrogen production to ensure that the wastewater after secondary pretreatment mainly contains lithium salt and other dissolved metal salts which can be separated from the lithium salt through subsequent lithium precipitation treatment.

[0058] Step six: performing lithium precipitation treatment on the wastewater after secondary pretreatment to obtain lithium precipitate converted from the lithium salt and wastewater after lithium precipitation treatment, and the wastewater after lithium precipitation treatment mainly contains the other dissolved metal salts.

[0059] Step seven: performing wastewater post-treatment on the wastewater after lithium precipitation treatment to achieve the required wastewater discharge and / or recycling standard of the to-be-recycled substances.

[0060] Specifically, as Figure 2As shown, in the embodiment, the battery dross mainly comes from ternary lithium cathode material; the leaching agent adopts a sulfuric acid solution, the plurality of soluble metal salts in the leaching solution includes nickel sulfate, cobalt sulfate, manganese sulfate and lithium sulfate; the extraction method specifically includes a plurality of extraction separation processes and a plurality of back-extraction separation processes; wherein, the first extraction separation process is used to obtain the first extraction liquid for obtaining the manganese sulfate and the first raffinate for retaining the nickel salt and the cobalt salt from the leaching solution; the second extraction separation process is used to obtain the second extraction liquid for obtaining the cobalt sulfate and the second raffinate for retaining the nickel sulfate from the first raffinate; the third extraction separation process is used to obtain the third extraction liquid for obtaining the nickel sulfate and the third raffinate from the second raffinate; the first back-extraction separation process is used to obtain the first back-extraction liquid for obtaining the manganese sulfate and the first back-extraction raffinate from the first extraction liquid; the fourth extraction separation process is used to obtain the fourth extraction liquid for obtaining the manganese sulfate and the fourth raffinate from the first back-extraction liquid; the second back-extraction separation process is used to obtain the second back-extraction liquid for obtaining the cobalt sulfate and the second back-extraction raffinate from the second extraction liquid, the second back-extraction liquid is a cobalt sulfate solution; the third back-extraction separation process is used to obtain the third back-extraction liquid for obtaining the nickel sulfate and the third back-extraction raffinate from the third extraction liquid, the third back-extraction liquid is a nickel sulfate solution; the fourth back-extraction separation process is used to obtain the fourth back-extraction liquid for obtaining the manganese sulfate and the fourth back-extraction raffinate from the fourth extraction liquid, the fourth back-extraction liquid is a manganese sulfate solution; the raffinate wastewater containing the separated lithium includes mixing the third raffinate and the fourth raffinate to form the raffinate wastewater.

[0061] Specifically, the first extraction separation process adopts P204 extractant; and the second extraction separation process adopts P507 extractant; and the third extraction separation process adopts P507 extractant; and the fourth extraction separation process adopts C272 extractant. P204 extractant, P507 extractant and C272 extractant are existing extractants, and their name codes are known. These extractants will introduce organic matter, thereby increasing the treatment difficulty of the battery dross leaching solution raffinate wastewater.

[0062] The following will be combined with Figure 1 As shown, the battery dross treatment method of the embodiment is further described in detail.

[0063] In step three, first, the raffinate wastewater (i.e. the raffinate wastewater of the battery black powder leaching solution) is first introduced into the air flotation tank 11 for air flotation impurity removal treatment. The air flotation tank 11 is a kind of existing sewage treatment equipment which mainly uses a large number of micro-bubbles to capture and adsorb fine particulate adhesive substances to make them float, thereby achieving the effect of solid-liquid separation. Here, the main role of the air flotation tank 11 is to remove most of the SS (solid suspended matter), oil and COD in the raffinate wastewater. Subsequently, the raffinate wastewater output from the air flotation tank 11 is introduced into the activated carbon decolorizing device 12. The activated carbon decolorizing device 12 is used to adsorb impurities in the wastewater by using activated carbon, thereby further removing the SS, oil and COD in the raffinate wastewater. Subsequently, the raffinate wastewater output from the activated carbon decolorizing device 12 is sequentially introduced into the filter press 13 and the precision filter 14 (a microfiltration filter is used) to achieve solid-liquid separation, thereby obtaining the once pretreated wastewater with a solid suspended matter 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.

[0064] In step four, the oxidation and hydrogen production system 21 comprises an electrolytic tank, a direct current power supply and a hydrogen storage tank. The anode and the cathode of the electrolytic tank are respectively connected to the positive and negative electrodes of the direct current power supply. The anode is used to oxidize the once pretreated wastewater through anode electrochemical reaction, and the cathode is used to produce hydrogen through cathode electrochemical reaction. The exhaust structure of the electrolytic tank is connected to the hydrogen storage tank. The anode can be the same or similar to the anode of the electro-catalytic oxidation reactor (such as a titanium-based metal oxide coating electrode), and the cathode can be the same or similar to the cathode of the electro-coagulation reactor (so as to facilitate hydrogen evolution).

[0065] In an optional embodiment, the oxidation and hydrogen production system 21 comprises a wastewater pretreatment module. The wastewater pretreatment module is used to add a chloride salt to the once pretreated wastewater before the oxidation treatment and electrolytic hydrogen production, thereby increasing the concentration of chloride ions in the once pretreated wastewater. Chloride ions can react with oxygen generated at the anode during electrolysis to generate hypochlorite, which has a strong oxidizing effect on 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 more significantly reducing the COD content of the wastewater to be treated.

[0066] Generally, the concentration of chloride ions in the once pretreated wastewater is increased by adding and mixing a chloride salt to the once pretreated wastewater, and the mass ratio of the addition amount of sodium chloride to the measured chemical oxygen demand in the once pretreated wastewater is 1-10. In this embodiment, sodium chloride is used as the chloride salt, and the mass ratio of the addition amount of sodium chloride to the measured chemical oxygen demand in the once pretreated wastewater is 3.

[0067] In step five, first, the wastewater after the oxidation treatment and electrolytic hydrogen production enters the pH adjusting tank 31, and the role of the pH adjusting tank 31 is to add alkali to the wastewater after the oxidation treatment and electrolytic hydrogen production so as to increase the pH value of the wastewater after the oxidation treatment and electrolytic hydrogen production. In this embodiment, the pH value of the wastewater after the oxidation treatment and electrolytic hydrogen production in the pH adjusting tank 31 is adjusted to 11. In this way, the metal ions such as nickel, cobalt, manganese and copper in the wastewater after the oxidation treatment and electrolytic hydrogen production are precipitated in the form of hydroxide. Subsequently, the wastewater after the oxidation treatment and electrolytic hydrogen production output by the pH adjusting tank 31 is sequentially subjected to solid-liquid separation by the filter press 32 and the precision filter 33 (a microfiltration filter is used). Subsequently, the wastewater after the oxidation treatment and electrolytic hydrogen production output by the precision filter 33 enters the pH adjusting tank 34, in which the pH value of the wastewater after the oxidation treatment and electrolytic hydrogen production is adjusted to 6-7 (sulfuric acid is added), and the purpose is to recover sodium sulfate in the subsequent step. Subsequently, the wastewater after the oxidation treatment and electrolytic hydrogen production is sequentially subjected to evaporation concentration crystallization by the evaporation concentration crystallizer 35 and thickening by the thickener 36. The evaporation concentration crystallizer 35 specifically uses an MVR evaporation concentration crystallization device, and the concentration multiple is 5, so that the sodium sulfate in the wastewater after the oxidation treatment and electrolytic hydrogen production is crystallized and precipitated, and then solid-liquid separation is realized by the centrifugal separator 37. The wastewater after the secondary pretreatment mainly contains lithium salt and other soluble metal salts which can be separated from the lithium salt by subsequent lithium precipitation treatment.

[0068] In step six, the wastewater after the secondary pretreatment is input into the lithium precipitation reactor 41, and lithium carbonate is generated by the reaction of lithium ions in the wastewater after the secondary pretreatment with sodium carbonate added into the lithium precipitation reactor 41. Then, solid-liquid separation is realized by the centrifugal separator 42.

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

[0070] The material balance table of each step of the battery black powder treatment method in the above embodiment is shown in Tables 1 and 2 (the material balance table is divided into Tables 1 and 2).

[0071] Table 1:

[0072]

[0073]

[0074] Table 2:

[0075]

[0076]

[0077] Figure 3A process flow chart of a battery black powder treatment method according to an embodiment of the present application. Figure 4 A process flow chart of a battery black powder treatment method according to an embodiment of the present application. Figure 3 A process flow chart of a battery black powder treatment method according to an embodiment of the present application. Figures 3-4 A process flow chart of a battery black powder treatment method according to an embodiment of the present application.

[0078] Step one: 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.

[0079] Step two: separating the plurality of soluble metal salts by using a precipitation method to obtain a precipitation mother liquor containing the separated lithium.

[0080] Step three: performing a first pretreatment on the precipitation mother liquor to ensure that the first pretreated wastewater obtained after the first pretreatment has a solid suspended matter 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.

[0081] Step four: inputting the first pretreated wastewater into an oxidation treatment and hydrogen production system to perform oxidation treatment and electrolytic hydrogen production, thereby obtaining oxidation treatment and electrolytic hydrogen production wastewater. The oxidation and hydrogen production system comprises an electrolytic tank, a direct current power supply, and a hydrogen storage tank. The anode and cathode of the electrolytic tank are connected to the positive and negative poles of the direct current power supply, respectively. The anode performs oxidation treatment on the first pretreated wastewater through anode electrochemical reaction, the cathode produces hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic tank is connected to the hydrogen storage tank.

[0082] Step five: performing a second pretreatment on the oxidation treatment and electrolytic hydrogen production wastewater to ensure that the second pretreated wastewater obtained after the second pretreatment mainly contains lithium salts and other soluble metal salts that can be separated from the lithium salts through subsequent lithium precipitation treatment.

[0083] Step six: performing lithium precipitation treatment on the second pretreated wastewater to obtain lithium precipitates converted from the lithium salts and lithium precipitation treatment wastewater mainly containing the other soluble metal salts.

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

[0085] Specifically, as shown in Figure 4As shown, in the present embodiment, the battery black powder mainly comes from lithium iron phosphate positive electrode material; the leaching agent adopts sulfuric acid solution, lithium iron phosphate in the battery black powder is decomposed into lithium ion, iron ion and phosphate ion in the sulfuric acid solution; the precipitation method specifically comprises: reacting the leaching solution with a mixed solution of sodium hydroxide and hydrogen peroxide, so that the iron ion reacts with the phosphate ion to generate iron phosphate precipitate; obtaining the precipitate mother liquor in which the separated lithium is contained comprises: performing solid-liquid separation on the reaction liquid after the leaching solution reacts 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 in which the separated lithium is contained also comprises: washing the iron phosphate precipitate after the solid-liquid separation with water, sequentially performing alkali precipitation method treatment, first solid-liquid separation filtration treatment and reverse osmosis membrane filtration treatment on the washing water after the washing, and then mixing the concentrated liquid generated by the reverse osmosis membrane filtration treatment with the liquid phase as the precipitate mother liquor. The clear liquid generated by the reverse osmosis membrane filtration treatment can be reused.

[0086] The principle that lithium iron phosphate in the battery black powder is decomposed into lithium ion, iron ion and phosphate ion in the sulfuric acid solution can be expressed as:

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

[0088] The principle that the leaching solution reacts with a mixed solution of sodium hydroxide and hydrogen peroxide to make the iron ion react with the phosphate ion to generate iron phosphate precipitate can be expressed as:

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

[0090] The following will be combined Figure 3 to further illustrate the treatment method of the battery black powder in the present embodiment.

[0091] In step three, first, the precipitation mother liquor enters flocculation and precipitation system A61 and flocculation and precipitation system B63 (between flocculation and precipitation system A61 and flocculation and precipitation system B63, a filter press and a precision filter 62 are arranged in sequence, and the filter press is not shown in the figure) in sequence, flocculation and precipitation system A61 precipitates and separates iron, aluminum and other metal ions in the precipitation mother liquor by adding sodium hydroxide, calcium hydroxide, hydrogen peroxide and PAM flocculant, and flocculation and precipitation system B63 precipitates and separates magnesium, copper and other metal ions in the precipitation mother liquor by adding sodium hydroxide and PAM flocculant. Then, the wastewater after the first pretreatment is obtained by passing through the filter press (not shown in the figure), the precision filter 64 and the pH adjusting tank 65 (the pH is adjusted to about 6) in sequence.

[0092] In step four, the oxidation and hydrogen production system 71 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 performs oxidation treatment on the wastewater after the first pretreatment through anode electrochemical reaction, the cathode generates hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected to the hydrogen storage tank. Among them, the anode can use the same or similar anode as the electro-catalytic oxidation reactor (such as a titanium-based metal oxide coating electrode), and the cathode can use the same or similar cathode as the electro-coagulation reactor (to facilitate hydrogen evolution).

[0093] In an optional embodiment, the oxidation and hydrogen production system 71 comprises a wastewater pretreatment module, which is used to add chloride salt to the wastewater after the first pretreatment to increase the concentration of chloride ions in the wastewater after the first pretreatment before the oxidation treatment and electrolytic hydrogen production. Chloride ions can react with oxygen generated at the anode during electrolysis to generate hypochlorite, and hypochlorite has strong oxidation effect on 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 more significantly reducing the COD content of the wastewater to be treated.

[0094] Generally, the concentration of chloride ions in the wastewater after the first pretreatment is increased by adding and mixing chloride salt in an amount of 1-10 times the mass ratio of the measured chemical oxygen demand in the wastewater after the first pretreatment based on the amount of sodium chloride. In this embodiment, sodium chloride is used as the chloride salt, and the mass ratio of the amount of sodium chloride added to the measured chemical oxygen demand in the wastewater after the first pretreatment is 3.

[0095] In step five, the wastewater after the oxidation treatment and electrolytic hydrogen production is first subjected to evaporation concentration and crystallization in evaporative concentrator 81 and freezing crystallization 82 for evaporation concentration treatment for sodium sulfate crystallization and freezing crystallization treatment for sodium sulfate crystallization, and then subjected to solid-liquid separation in centrifugal separator 83. The wastewater after secondary pretreatment mainly contains lithium salt and other dissolved metal salts that can be separated from the lithium salt after subsequent lithium precipitation treatment.

[0096] In step six, the wastewater after secondary pretreatment is input into lithium precipitation reactor 91, and lithium carbonate is generated by the reaction of lithium ions in the wastewater after secondary pretreatment with sodium carbonate in lithium precipitation reactor 91. Then, solid-liquid separation is realized in centrifugal separator 92.

[0097] In step seven, the wastewater after lithium precipitation treatment is acidified in mother liquor acidifier, and then miscellaneous salt is obtained by drum drying.

[0098] The material balance table of each step of the battery black powder treatment method of the above embodiment is shown in Tables 3-5 (the material balance table is divided into Tables 3-5).

[0099] Table 3:

[0100]

[0101]

[0102] Table 4:

[0103]

[0104]

[0105] Table 5:

[0106]

[0107]

[0108] Figure 5 A structure diagram of a wastewater treatment device according to an embodiment of the present application. The wastewater treatment device can be used in the battery black powder treatment method and the oxidation and hydrogen production system in the wastewater treatment equipment.

[0109] The wastewater treatment device comprises a main cylinder 101, an electrolysis device 102, a hydrogen recovery device 103, an aeration device 107 and a scum cleaning mechanism 105. The main cylinder 101 has an electrolysis zone 1011 and a gas float zone 1012 arranged in sequence 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 a second output port 1015 corresponding to the upper part of the gas float zone 1012. The electrolysis device 102 comprises a direct current power supply 1021, an anode 1022 and a cathode 1023 arranged in the electrolysis zone 1011. The anode 1022 and the cathode 1023 are connected to the positive and negative poles of the direct current power supply 1021, respectively. In operation, the anode 1022 performs oxidation treatment on the wastewater entering the electrolysis zone 1011 through the input port 1014 by anode electrochemical reaction, and the cathode 1023 generates hydrogen by cathode electrochemical reaction. The hydrogen recovery device 103 comprises a gas isolation component corresponding to each cathode 1023. The gas isolation component is sleeved outside the corresponding cathode 1023 and has a side wall 1031 surrounding the cathode and an end cover 1032 located at the upper end of the side wall 1031. The lower end of the side wall 1031 is provided with an open end and / or the side wall 1031 itself adopts a membrane material that can permeate ions and water but cannot permeate bubbles (for example, the membrane material adopts a diaphragm used in alkaline water electrolysis hydrogen production). The end cover 1032 is provided with an exhaust port connected to a hydrogen storage tank through an exhaust pipe 1033. The aeration device 107 is arranged between the electrolysis zone 1011 and the gas float zone 1012 for aeration in the main cylinder 101. The scum cleaning mechanism 105 is installed at the top of the gas float zone 1012 for discharging the scum generated at the top of the gas float zone 1012 from the second output port 1015.

[0110] In addition, the wastewater treatment device further comprises a wastewater pretreatment module 108 for adding a chloride salt to the wastewater to be treated to increase the concentration of chloride ions in the wastewater to be treated before oxidation treatment and electrolytic hydrogen production. Specifically, the wastewater pretreatment module 108 comprises 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 (such as a sodium chloride solution) with a desired concentration. The chloride salt solution delivery unit is used to deliver the chloride salt solution to the wastewater to be treated to mix the chloride salt solution with the wastewater to be treated. The metering control unit is used to meter and control the amount of chloride salt added to the wastewater to be treated. Generally, the metering control unit is used to control the amount of chloride salt added to the wastewater to be treated to be 1-10 times the mass ratio of the measured chemical oxygen demand in the wastewater to be treated based on sodium chloride.

[0111] The working principle of the wastewater purification treatment and hydrogen production system is as follows: the wastewater to be treated enters the main cylinder 101 through the input port 1014, at the same time, the wastewater pretreatment module 108 adds a chlorine salt solution to the wastewater to be treated, and the aeration device 107 (usually air aeration) generates a large number of bubbles which converge with the wastewater to be treated entering the main cylinder 101 through the input port 1014 in a reverse flow. These bubbles adhere to the suspended particles in the wastewater to be treated, and use the buoyancy to make these suspended particles float to the surface of the air flotation zone 1012 to form scum. The scum is then discharged from the second output port 1015 by the scum cleaning mechanism 105 and can enter the defoaming device for further treatment. The chlorine salt solution can be mixed with the wastewater to be treated by aeration. Then, the wastewater enters the electrolysis zone 1011 from the air flotation zone 1012. When the electrolysis device 102 is working, the anode 1022 performs oxidation treatment on the wastewater entering the electrolysis zone 1011 through the input port 1014 by anode electrochemical reaction (the anode 1022 generates oxygen bubbles, the oxygen bubbles react with the chlorine ions added by the wastewater pretreatment module 108 to generate hypochlorite, and the hypochlorite has 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 more significantly reducing the COD content of the wastewater to be treated). The cathode 1023 generates hydrogen by cathode electrochemical reaction. At this time, the hydrogen is collected by the gas isolation component and introduced into the hydrogen storage tank through the exhaust pipe 1033. The material (usually a mixture of water and solid residue) at the lower part of the electrolysis zone 1011 is discharged from the first output port 1013.

[0112] In the electrolysis device 102, the anode 1022 can use the same or similar anode as the electro-catalytic oxidation reactor (such as a titanium-based metal oxide coating electrode), and the cathode 1023 can use the same or similar cathode as the electro-flocculation reactor (to facilitate hydrogen evolution). Generally, the electrolysis device 102 includes a plurality of anodes 1022 and a plurality of cathodes 1023, which are staggered and spaced apart in the horizontal direction in the electrolysis zone 1011.

[0113] In an alternative embodiment, the main cylinder 101 has a precipitation zone 1016 at the lower part of the electrolysis zone 1011. Generally, the bottom of the precipitation zone 1016 forms a conical discharge chute, and the discharge port is located at the bottom of the conical discharge chute.

[0114] The floating scum cleaning mechanism 105 can be a scraper. In addition, in order to facilitate the processing of floating scum, the upper part of the air flotation zone 1012 is provided with a lateral partition plate inside the main cylinder 101 and spaced a certain distance from the inner wall of the main cylinder 101, and a bottom partition plate connected between the bottom of the lateral partition plate and the inner wall of the main cylinder 101, the lateral partition plate and the bottom partition plate form a notch 1016 located at the upper side of the air flotation zone, and the second output port 1015 is arranged on the side wall of the main cylinder 101 and is in lateral communication with the notch 1016; the floating scum cleaning mechanism 105 is installed at the top of the air flotation zone and is used to push the floating scum generated at the top of the air flotation zone to the notch 1016.

[0115] Since the floating scum mainly contains suspended particles and bubbles, it has poor fluidity and is easy to block the pipeline. The above design can push the floating scum cleaned by the floating scum cleaning mechanism 105 (scraper) into the notch 1016 for temporary storage, and then use the second output port 1015 on the side of the notch 1016 as an overflow port to make the floating scum flow out of the second output port 1015 naturally, avoiding the blockage of the second output port 1015. In addition, the above design can also make the upper part of the main cylinder 101 outside the second output port 1015 be completely closed, reducing noise, reducing safety hazards, and improving the appearance of the equipment.

[0116] In an optional embodiment, the electrolysis zone 1011 is provided with a water distributor 106, and the water distributor 106 inputs the wastewater to be treated input from the input port 1014 into the electrolysis zone 1011 in a uniform distribution manner on the cross section of the electrolysis zone 1011. Specifically, the water distributor 106 has a main water inlet pipe connected with the input port 1014 and water distribution manifolds spaced apart on the main water inlet pipe, and the main water inlet pipe is arranged in a horizontal direction, and the water distribution manifolds are arranged vertically downward.

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

[0118] The above wastewater treatment device can also cancel the aeration device 107, and use the oxygen bubbles generated by the anode 1022 during the oxidation treatment of the wastewater in the electrolysis zone 1011 to achieve the effect similar to air flotation. The space between the anode of the electrolysis device and the hydrogen recovery device can form an oxygen upward channel, so as to guide the oxygen generated by the anode upward into the air flotation zone.

[0119] In the above wastewater treatment device, the outlet of the chlorine salt solution conveying unit 108 can be connected and communicated with the input port 1014 (such asFigure 5 The outlet of the chlorine salt solution delivery unit 108 can be located at the upper portion of the electrolysis zone and output the chlorine salt solution downward and / or at the lower portion of the electrolysis zone and output the chlorine salt solution upward when the outlet of the chlorine salt solution delivery unit extends into the electrolysis zone and is in communication with the electrolysis zone 1011. Similar to the water distributor 106 described above, the outlet of the chlorine salt solution delivery unit 108 can be configured to deliver the chlorine salt solution into the main cylinder in a manner that is uniformly distributed across the cross-section of the electrolysis zone when the outlet of the chlorine salt solution delivery unit extends into the electrolysis zone and is in communication with the electrolysis zone.

[0120] The above description relates to the present application. A person of ordinary skill in the art will be able to implement the present application based on the above description. All other embodiments obtained by a person of ordinary skill in the art without creative effort based on the above description of the present application shall 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 plurality of soluble metal salts contain lithium; separating the plurality of soluble metal salts by using an extraction method, and obtaining raffinate wastewater containing the separated lithium; performing primary pretreatment on the raffinate wastewater, so that the concentration of solid suspensions in the wastewater after the primary pretreatment 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 wastewater after the primary pretreatment into an oxidation and hydrogen production system to perform oxidation treatment and electrolytic hydrogen production, so as to obtain wastewater after the oxidation treatment and electrolytic hydrogen production; performing secondary pretreatment on the wastewater after the oxidation treatment and electrolytic hydrogen production, so that the wastewater after the secondary pretreatment mainly contains 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 wastewater after the secondary pretreatment to obtain lithium precipitates converted from the lithium salts and wastewater after the lithium precipitation treatment, wherein the wastewater after the lithium precipitation treatment mainly contains the other soluble metal salts; performing wastewater post-treatment on the wastewater after the lithium precipitation treatment to reach required wastewater discharge and / or recycling standards; 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 wastewater after the primary pretreatment 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 ternary lithium positive materials, the leaching agent is a sulfuric acid solution, the plurality of soluble metal salts in the leaching solution contain nickel sulfate, cobalt sulfate, manganese sulfate and lithium sulfate, and the extraction method specifically comprises a plurality of extraction and separation processes and a plurality of back-extraction and separation processes. The first extraction separation process is used to obtain a first extraction solution containing the manganese sulfate and a first extraction residue solution containing nickel and cobalt salts from the leaching solution; the second extraction separation process is used to obtain a second extraction solution containing the cobalt sulfate and a second extraction residue solution containing the nickel sulfate from the first extraction residue solution; the third extraction separation process is used to obtain a third extraction solution containing the nickel sulfate and a third extraction residue solution from the second extraction residue solution; the first back extraction separation process is used to obtain a first back extraction solution containing the manganese sulfate and a first back extraction residue solution from the first extraction solution; the fourth extraction separation process is used to obtain a fourth extraction solution containing the manganese sulfate and a fourth extraction residue solution from the first back extraction solution; the second back extraction separation process is used to obtain a second back extraction solution containing the cobalt sulfate and a second back extraction residue solution from the second extraction solution, wherein the second back extraction solution is a cobalt sulfate solution; the third back extraction separation process is used to obtain a third back extraction solution containing the nickel sulfate and a third back extraction residue solution from the third extraction solution, wherein the third back extraction solution is a nickel sulfate solution; the fourth back extraction separation process is used to obtain a fourth back extraction solution containing the manganese sulfate and a fourth back extraction residue solution from the fourth extraction solution, wherein the fourth back extraction solution is a manganese sulfate solution; and the extraction residue wastewater containing the separated lithium is obtained by mixing the third extraction residue solution and the fourth extraction residue solution to form the extraction residue wastewater. The primary pretreatment comprises sequentially performing a gas float impurity removal treatment, an activated carbon adsorption treatment and a first solid-liquid separation filtration treatment on the extraction residue wastewater. The method further comprises increasing the concentration of chloride ions in the wastewater after the primary pretreatment and electrolysis for hydrogen production; and adding and mixing a chloride salt in the wastewater after the primary pretreatment, wherein the mass ratio of the amount of sodium chloride added to the chemical oxygen demand of the wastewater after the primary pretreatment is 1-10, so as to increase the concentration of chloride ions in the wastewater after the primary pretreatment.

2. The method of claim 1, wherein the battery sludge is treated by: The first extraction separation process uses P204 extractant; the second extraction separation process uses P507 extractant; the third extraction separation process uses P507 extractant; and the fourth extraction separation process uses C272 extractant.

3. The method of claim 1, wherein the battery sludge is treated by the steps of: The secondary pretreatment comprises sequentially performing an alkali precipitation treatment, a second solid-liquid separation filtration treatment, a pH value adjustment treatment, a sodium sulfate crystallization evaporation concentration treatment and a third solid-liquid separation filtration treatment on the wastewater after the oxidation treatment and electrolysis for hydrogen production, wherein the pH value adjustment treatment is used to adjust the pH value of the wastewater to be treated to 6-7. ​ 4. A wastewater treatment apparatus characterized by: The method for treating the battery black powder leaching solution extraction residue wastewater in the battery black powder treatment method of any one of claims 1-3; The battery black powder leaching solution extraction residue wastewater is generated by the following process: battery black powder is reacted with a leaching agent to obtain a leaching solution containing a plurality of soluble metal salts, wherein the plurality of soluble metal salts contain lithium; and the plurality of soluble metal salts are separated by using an extraction method, and the extraction residue wastewater containing the separated lithium is obtained. The method comprises: The once pretreatment system is used for once pretreating the raffinate wastewater, so that the once pretreated wastewater has a solid suspended substance concentration of less than or equal to 5 mg / L, an oil content of less than or equal to 5 mg / L, a chemical oxygen demand of less than or equal to 500 mg / L, and a pH value of 6-9; The oxidation and hydrogen production system is used for oxidizing and electrolyzing the once pretreated wastewater, so as to obtain oxidized and electrolyzed wastewater; The twice pretreatment system is used for twice pretreating the oxidized and electrolyzed wastewater, so that the twice pretreated wastewater mainly contains lithium salt and other dissolved metal salts which can be separated from the lithium salt by subsequent lithium precipitation treatment; The lithium precipitation treatment system is used for precipitating lithium from the twice 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 The wastewater post-treatment system is used for post-treating the lithium precipitation treated wastewater to meet the required wastewater discharge and / or recycling standards; 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, the anode oxidizes the once pretreated wastewater through anode electrochemical reaction, the cathode generates hydrogen through cathode electrochemical reaction, and the exhaust structure of the electrolytic cell is connected to the hydrogen storage tank; The battery black powder mainly comes from the positive electrode material of a ternary lithium battery, the leaching agent is a sulfuric acid solution, the multiple dissolved metal salts in the leaching solution include nickel sulfate, cobalt sulfate, manganese sulfate and lithium sulfate, and the extraction method specifically comprises multiple extraction and separation processes and multiple back-extraction and separation processes. The first extraction separation process is used to obtain a first extraction solution containing the manganese sulfate and a first extraction residue solution containing nickel and cobalt salts from the leaching solution; the second extraction separation process is used to obtain a second extraction solution containing the cobalt sulfate and a second extraction residue solution containing the nickel salt from the first extraction residue solution; the third extraction separation process is used to obtain a third extraction solution containing the nickel sulfate and a third extraction residue solution from the second extraction residue solution; the first back extraction separation process is used to obtain a first back extraction solution containing the manganese sulfate and a first back extraction residue solution from the first extraction solution; the fourth extraction separation process is used to obtain a fourth extraction solution containing the manganese sulfate and a fourth extraction residue solution from the first back extraction solution; the second back extraction separation process is used to obtain a second back extraction solution containing the cobalt sulfate and a second back extraction residue solution from the second extraction solution, wherein the second back extraction solution is a cobalt sulfate solution; the third back extraction separation process is used to obtain a third back extraction solution containing the nickel sulfate and a third back extraction residue solution from the third extraction solution, wherein the third back extraction solution is a nickel sulfate solution; the fourth back extraction separation process is used to obtain a fourth back extraction solution containing the manganese sulfate and a fourth back extraction residue solution from the fourth extraction solution, wherein the fourth back extraction solution is a manganese sulfate solution; and the separated lithium-containing extraction residue wastewater is obtained by mixing the third extraction residue solution and the fourth extraction residue solution to form the extraction residue wastewater.

5. A wastewater treatment apparatus as claimed in claim 4, characterised in that: The oxidation and hydrogen production system comprises a wastewater pretreatment module, which is used to add a chlorine salt to the once-pretreated wastewater to increase the concentration of chloride ions in the once-pretreated wastewater before the oxidation treatment and electrolytic hydrogen production.

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