Leaching method of waste nickel-metal hydride battery negative electrode material

Abstract

The invention relates to the technical field of battery negative electrode material leaching, and discloses a nickel-metal hydride waste battery negative electrode material leaching method, which comprises: 1, carrying out pretreatment on a nickel-metal hydride waste battery negative electrode material, specifically, disassembling a battery, and crushing to obtain fine particles with a particle size of less than 0.1 mm; 2, a mixed solution of citric acid and oxalic acid is used as a leaching agent for leaching, the concentration of the leaching agent ranges from 0.5 M to 1.0 M, ultrasonic assistance is adopted in the leaching process, the ultrasonic power is 400 W, and the frequency is 40 kHz; and thirdly, an electrochemical reaction is applied in the leaching process. By optimizing the technological process and the technical means, the metal recovery rate and the leaching efficiency of the waste nickel-metal hydride battery negative electrode material are remarkably improved, the obvious technical advantages are shown in the aspects of reducing the environmental influence, achieving efficient utilization of resources, enhancing the process controllability and the like, and good economic benefits and environmental protection benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of leaching of battery negative electrode materials, and specifically to a method for leaching the negative electrode materials of nickel-metal hydride waste batteries. Background Art

[0002] With the increasing global demand for renewable energy, nickel-metal hydride batteries have been widely used in electric vehicles, hybrid vehicles, and portable electronic devices due to their high energy density and environmental protection characteristics. However, with the extensive use of these batteries, the problem of waste battery disposal has become increasingly prominent. Nickel-metal hydride waste batteries contain a large amount of valuable metals such as nickel and cobalt. If these metals are not effectively recycled, it will not only cause waste of resources but also cause serious environmental pollution.

[0003] Traditional methods for treating nickel-metal hydride waste batteries mainly rely on physical separation and acid leaching processes, that is, using strong acids (such as sulfuric acid and hydrochloric acid) as leaching agents to leach metal ions from electrode materials through chemical reactions. However, traditional methods have problems such as low metal recovery rate, low leaching efficiency, serious environmental pollution, and low resource utilization rate. Due to the easy formation of a passivation layer on the surface of the electrode material, the contact between the leaching agent and the material is limited, resulting in a low metal recovery rate. In addition, traditional leaching methods rely on a long chemical reaction process, with low efficiency, and the extensive use of strong acids increases the difficulty of waste liquid treatment and the risk of environmental pollution, leading to an increase in treatment costs. At the same time, the controllability of traditional processes is poor, and the process is easily affected by human factors, resulting in poor stability and repeatability, further affecting the metal recovery effect.

[0004] To solve the above problems, there is an urgent need for a more efficient, environmentally friendly, and economical treatment method that can significantly improve the metal recovery rate, accelerate the leaching speed, reduce environmental pollution, and achieve the efficient utilization of resources. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for leaching the negative electrode materials of nickel-metal hydride waste batteries, which solves the problems of low metal recovery rate, low leaching efficiency, serious environmental pollution, low resource utilization rate, and poor process controllability existing in the prior art.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for leaching the negative electrode materials of nickel-metal hydride waste batteries, comprising the following steps: Step 1: Pretreat the negative electrode materials of nickel-metal hydride waste batteries. The pretreatment step includes disassembling the battery and crushing it into fine particles with a particle size of less than 0.1 mm. Step 2: Use a mixed solution of citric acid and oxalic acid as the leaching agent for leaching. The concentration of the leaching agent is 0.5 M to 1.0 M, and ultrasonic assistance is used during the leaching process. The ultrasonic power is 400 W and the frequency is 40 kHz. Step 3: Apply an electrochemical reaction during the leaching process. The electrochemical reaction includes using a graphite anode and a titanium alloy cathode, with a current of 0.5 A to 1 A and a voltage of 2 V to 5 V. Step 4: Perform solid-liquid separation on the leached slurry. The obtained filtrate is subjected to regeneration treatment of the leaching agent. The regeneration treatment includes removing impurity ions by ion exchange and thin-film evaporation concentration treatment. The regenerated leaching agent is recycled and reused in the leaching step.

[0007] Preferably, the pretreatment step includes: Primarily crush the disassembled anode material using a jaw crusher to make its particle size 10 - 20 mm. Further crush it to fine particles below 0.1 mm using a roll crusher, and separate materials with different particle sizes through an air classifier.

[0008] Preferably, the preparation of the leaching agent includes the following steps: In an automated dosing system, mix citric acid and oxalic acid in a ratio of 1:1 to a concentration range of 0.5 M to 1.0 M. Add 0.1 M to 0.2 M of EDTA as a complexing agent.

[0009] Preferably, the ultrasonic-assisted leaching includes setting the leaching reactor to a double-layer structure, with the inner layer made of acid-resistant ceramics and the outer layer being a stainless steel sandwich. Circulating cooling water is introduced into the sandwich to control the reaction temperature below 60°C.

[0010] Preferably, the electrochemical reaction adjusts the current and voltage in real time by online monitoring of the oxidation-reduction potential (ORP) and pH value, and the ORP value is controlled above +500 mV.

[0011] Preferably, the solid-liquid separation is performed using a vacuum filter. The leaching solution and solid residue after filtration are subjected to secondary leaching treatment. The secondary leaching uses a high-concentration citric acid / oxalic acid mixed solution and is carried out at 80°C.

[0012] Preferably, the regeneration treatment of the leaching agent includes: Use a hydrogen-type cation exchange resin in an ion exchange column to remove impurity ions such as calcium and magnesium in the leaching solution. Concentrate the leaching solution through a thin-film evaporator. The evaporated water vapor is condensed and recovered for preparing fresh leaching agent.

[0013] Preferably, after five batches of leaching cycles, the regenerated leaching agent is subjected to regeneration treatment to restore its effectiveness.

[0014] Preferably, the real-time monitoring and adjustment of process parameters are achieved through a PLC automated control system. The system includes sensors and actuators, and can monitor and adjust in real time the pH value, temperature, ultrasonic power, current, and voltage parameters during the leaching process.

[0015] Preferably, the wastewater is reused for preparing fresh leaching agent after neutralization treatment, and the waste residue is used for producing building materials after harmless treatment.

[0016] The present invention provides a method for leaching the negative electrode material of nickel-metal hydride waste batteries. It has the following beneficial effects: 1. By introducing ultrasonic assistance and electrochemical reaction technology, the present invention significantly improves the recovery rates of valuable metals such as nickel and cobalt. Compared with traditional chemical leaching methods, the cavitation effect of ultrasonic waves can effectively increase the contact area between the leaching agent and the negative electrode material, and the electrochemical reaction accelerates the dissolution process of metal ions, thus achieving more efficient metal recovery.

[0017] 2. By combining ultrasonic-assisted leaching and electrochemical reaction, the present invention shortens the leaching time and increases the reaction rate. The application of ultrasonic waves destroys the passivation layer on the surface of the negative electrode material, enabling the leaching agent to penetrate deeper into the material, and the electrochemical reaction further promotes the dissolution of metals by applying an external current. This synergistic effect optimizes the efficiency of the leaching process, making the metal recovery more thorough.

[0018] 3. The green leaching agent used in the present invention has good biodegradability, reducing the environmental pollution caused by traditional strong acid leaching agents. Through the recycling and regeneration treatment of the leaching agent, the usage amount of chemical reagents is reduced, the waste liquid discharge amount is decreased, and it has good environmental protection benefits.

[0019] 4. Through the regeneration treatment of the leaching solution, the present invention realizes the recycling of the leaching agent and reduces resource waste. Ion exchange and thin-film evaporation technologies are used to remove impurities in the leaching solution, and the concentrated leaching solution is reused for the leaching process, thereby improving the utilization rate of the leaching agent and reducing production costs.

[0020] 5. By introducing a PLC automated control system and a SCADA data acquisition system, the present invention realizes the real-time monitoring and automatic adjustment of key parameters in the leaching process. This system ensures the stability and repeatability of the process, reduces the errors of manual operation, and improves the reliability of the overall process.

[0021] 5. The present invention not only improves the recovery rates of nickel and cobalt, but also treats and resourcefully utilizes the waste liquid and waste residue after leaching. The waste liquid is reused for preparing fresh leaching agent after neutralization treatment, and the waste residue can be used for producing building materials after harmless treatment, realizing the effective reuse of waste and further enhancing the resource utilization rate.

[0022] In summary, through optimizing the process flow and technical means, the present invention not only significantly improves the metal recovery rate and leaching efficiency of the negative electrode material of nickel-metal hydride waste batteries, but also demonstrates obvious technical advantages in reducing environmental impact, achieving efficient resource utilization, and enhancing process controllability, with good economic and environmental benefits. Brief Description of the Drawings

[0023] Figure 1 It is a flow chart of the present invention. Detailed Embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Embodiment 1: Please refer to the attached Figure 1 , the present invention provides a method for leaching the negative electrode material of nickel-metal hydride waste batteries, including the following steps: 1. Treatment and preparation of leaching agent 1.1 Pretreatment Material disassembly and separation: Disassembly equipment: Use an automated mechanical disassembly device to disassemble nickel-metal hydride waste batteries. This device should have protective measures to avoid the risk of battery explosion or short circuit. The specific process is as follows: Step 1: Put the nickel-metal hydride waste battery into the disassembly machine and start the mechanical cutter to cut open the battery shell.

[0026] Step 2: Use a separation device (such as a vibrating screen or a magnetic separator) to separate the negative electrode material from the battery structure and collect it in a special container.

[0027] Step 3: Send the separated negative electrode material to the crushing system for subsequent processing.

[0028] Crushing and screening: Primary crushing: The negative electrode material is first preliminarily crushed by a jaw crusher, and the target particle size is 10 - 20 mm.

[0029] Step 1: Set the feeding port width of the jaw crusher to 20 mm and adjust the discharging port width of the crusher to 10 mm to ensure the particle size range of the discharged particles.

[0030] Step 2: Uniformly feed the negative electrode material into the crusher, and the crusher should be set to run at a constant speed to ensure uniform crushing of the material.

[0031] Step 3: The crushed materials are sent to a vibrating screen through a conveyor belt for primary screening.

[0032] Screening system: Use a vibrating screen to screen the crushed materials, separate the materials meeting the particle size requirements (3 - 5 mm), and return the larger particles to the crusher for secondary crushing.

[0033] Step 1: Set the screen aperture of the vibrating screen to 5 mm, start the vibrating screen, and screen the crushed materials.

[0034] Step 2: The screened materials enter the silo, and the larger particles return to the crusher for secondary crushing through an automatic reflux system.

[0035] Step 3: The qualified materials with a particle size of 3 - 5 mm are sent to the fine crushing equipment through a pneumatic conveying system.

[0036] Fine crushing stage: Further crush the materials to particles below 0.1 mm through a pair-roll crusher to ensure that the materials have a sufficient specific surface area during the leaching process.

[0037] Step 1: Set the roll spacing of the pair-roll crusher to 0.1 mm to ensure the discharge particle size.

[0038] Step 2: The negative electrode materials enter the pair-roll crusher evenly, and the crushed fine particle materials are collected in a sealed container to prevent secondary pollution.

[0039] Step 3: The crushed materials are classified again through an air classifier, and the fine particle part is sent to the leaching reactor, while the coarse particle materials are stored for standby.

[0040] 1.2 Leaching agent preparation Leaching agent selection and preparation: Preparation equipment: Use an automated dosing system to prepare the leaching agent. The system includes precision metering pumps, mixing tanks, temperature control systems, and stirring devices.

[0041] Step 1: Select citric acid and oxalic acid as the main leaching agents in the dosing system, set the ratio to 1:1, and the target concentration to 0.5 M.

[0042] Step 2: Start the metering pumps, add citric acid and oxalic acid to the mixing tank respectively, and stir evenly. During the preparation process, control the temperature at about 20°C to ensure the stability of the solution.

[0043] Step 3: According to the process requirements, add 0.1 M of EDTA as a complexing agent, and stir evenly further to form a stable mixed solution.

[0044] Step 4: Pump the prepared leaching agent to the storage tank through a pipeline and store it in a low-temperature environment (4°C) to prevent the solution from degrading.

[0045] Quality inspection of the solution: Online monitoring system: The dosing system is equipped with a pH meter and a conductivity meter to monitor the pH value and conductivity of the solution in real time.

[0046] Step 1: Use a pH meter to detect the pH value of the mixed solution. The target value should be between 2.5 and 3.5. If it deviates from the target value, fine-tune it through the automatic dosing system.

[0047] Step 2: Use a conductivity meter to monitor the conductivity of the solution to ensure that the solution has good ionic conductivity, suitable for subsequent electrochemical leaching.

[0048] Step 3: After the inspection is completed, transport the qualified leaching agent to the leaching reactor for standby.

[0049] 2. Leaching process design 2.1 Ultrasonic-assisted leaching Configuration of ultrasonic equipment and reactor: Reactor structure: Design a double-layer corrosion-resistant leaching reactor. The inner layer is made of acid-resistant ceramic material, and the outer layer is a stainless steel sandwich layer. The sandwich layer is used to introduce circulating cooling water to control the reaction temperature.

[0050] Step 1: Select a leaching reactor with a suitable size and set the capacity of the reactor according to the volume of the leaching agent and the solid-liquid ratio. Usually, the solid-liquid ratio is 1:10 (weight ratio).

[0051] Step 2: Add the crushed anode material to the reactor through the automatic feeding system to ensure that the material is evenly distributed at the bottom of the reactor.

[0052] Step 3: Start the ultrasonic equipment and set the ultrasonic power to 400 W and the frequency to 40 kHz. The ultrasonic vibrator should be installed at the bottom or side wall of the reactor to ensure uniform distribution of ultrasonic energy.

[0053] Ultrasonic-assisted effect: Ultrasonic waves accelerate the reaction between the leaching agent and the material surface through the cavitation effect, break the passivation layer on the material surface, and improve the leaching efficiency of metal ions.

[0054] Step 1: During the operation of the ultrasonic vibrator, monitor the temperature of the leaching solution and keep the temperature below 60 °C to avoid decomposition of the leaching agent caused by high temperature.

[0055] Step 2: According to the preliminary experimental results of the material, set the leaching time to 2 hours, and take samples every 30 minutes to detect the metal ion concentration in the leaching solution to judge the reaction progress.

[0056] Step 3: After the leaching is completed, collect the leaching solution into a special container through the drain valve for solid-liquid separation preparation.

[0057] 2.2 Electrochemical-assisted leaching Electrochemical system configuration: Electrode material selection: Graphite anode and titanium alloy cathode are selected. The anode is responsible for the electrochemical oxidation reaction, and the cathode is responsible for the reduction reaction. The electrode spacing is controlled within 5 - 10 cm to ensure uniform distribution of the electric field.

[0058] Step 1: Install the electrode system. The anode is installed in the middle of the reaction kettle, and the cathode is installed at the bottom of the kettle. The anode and cathode are respectively connected to the positive and negative poles of the power supply.

[0059] Step 2: Set the current to 0.5 A and the voltage to 3 V. Initiate an electrochemical reaction in the leaching solution through the electrode system to further accelerate the dissolution of metal ions.

[0060] Step 3: Use an on-line monitoring system to monitor the oxidation-reduction potential (ORP) of the leaching solution in real time, and adjust the current and voltage according to the change of ORP to ensure efficient dissolution of metal ions.

[0061] Electrochemical reaction control: The current and voltage of the electrochemical system should be adjusted in real time according to the metal ion concentration in the leaching solution to optimize the leaching efficiency.

[0062] Step 1: Monitor the oxidation-reduction potential of the leaching solution through an ORP sensor. The target ORP value should be controlled above +500 mV to ensure effective oxidation and dissolution of metal ions such as nickel and cobalt.

[0063] Step 2: During the electrochemical reaction process, keep the pH value of the leaching solution stable, and fine-tune it through an automatic acid addition system to prevent precipitation of metal ions caused by too high pH value.

[0064] Step 3: After the electrochemical reaction is completed, stop the current, collect the electrolyzed leaching solution, and prepare for solid-liquid separation.

[0065] 3. Recycling and regeneration of leaching solution 3.1 Solid-liquid separation and re-leaching Primary solid-liquid separation: Filter equipment selection: A vacuum filter or centrifuge is used for solid-liquid separation to ensure efficient separation of the leaching solution and solid residue.

[0066] Step 1: Feed the slurry of the leaching solution and solid residue into the vacuum filter through a conveying pipeline, start the vacuum pump, and conduct primary solid-liquid separation.

[0067] Step 2: The filtered leaching solution is transported to the storage tank through the drain pipeline, and the solid residue remains in the filter cake.

[0068] Step 3: Transfer the solid residue to the secondary leaching reaction kettle for secondary leaching.

[0069] Secondary leaching process: High-concentration leaching: In the secondary leaching, a higher-concentration citric acid / oxalic acid mixed solution is used and carried out at a high temperature of 80 °C to further recover residual metals.

[0070] Step 1: Add a high-concentration leaching agent to the secondary leaching reactor, and keep the solid-liquid ratio at 1:10. Start the stirring device to ensure full mixing of the solid and liquid.

[0071] Step 2: The heating system controls the temperature in the reactor at 80 °C, and at the same time keeps the ultrasonic vibrator working to enhance the leaching effect.

[0072] Step 3: The secondary leaching time is set to 2 hours. During this period, samples are taken every 30 minutes to detect the metal ion concentration in the leaching solution to ensure the full dissolution of metals.

[0073] Step 4: After the secondary leaching is completed, repeat the solid-liquid separation process, and combine and process the filtrate with the first leaching solution.

[0074] 3.2 Regeneration treatment of leaching solution Impurity removal: Ion exchange column system: Use ion exchange technology to remove impurity ions (such as calcium, magnesium, etc.) in the leaching solution to improve the purity of metal recovery.

[0075] Step 1: Feed the leaching solution into the ion exchange column through a transfer pump, and use hydrogen-type cation exchange resin for the exchange and removal of impurity ions.

[0076] Step 2: The ion exchange process should be carried out at room temperature, and the flow rate is set to 1-2 BV / h to ensure the effective removal of impurity ions.

[0077] Step 3: The treated leaching solution is transported to the thin-film evaporator through the drain pipe for concentration treatment.

[0078] Concentration of leaching solution: Thin-film evaporator system: Adopt thin-film evaporation technology to concentrate the leaching solution, recover the solvent water, and ensure the regeneration and reuse of the leaching agent.

[0079] Step 1: Start the thin-film evaporator, distribute the leaching solution in the form of a thin film on the heating surface, and control the heating temperature at 60-70 °C to avoid decomposition of the leaching agent caused by too high temperature.

[0080] Step 2: The evaporated water vapor is cooled by the condensation system, and the condensed water is recovered to the water storage tank through a transfer pump for preparing fresh leaching agent.

[0081] Step 3: The concentrated leachate is refluxed to the storage tank through a conveying pipeline, and its concentration, pH value, and chelating ability are detected to ensure compliance with the reuse standard.

[0082] Recycled leachate is recycled: Circulation system design: The recycled leachate is transported back to the leaching reactor and continues to be used in the leaching process for the next batch.

[0083] Step 1: Through an automated pipeline system, the recycled leachate is fed into the leaching reactor, and the solid-liquid ratio and temperature are set to prepare for the next leaching.

[0084] Step 2: According to the actual usage, the leachate is regenerated every 5 batches to ensure the effectiveness of the leaching agent and the leaching effect.

[0085] Step 3: Regularly monitor the operation status of the regeneration system to ensure the stability and efficiency of the system.

[0086] 4. System Integration and Optimization 4.1 Real-time Monitoring and Optimization of Process Parameters Automated control system design: PLC system configuration: Install a PLC automated control system in the factory to integrate the monitoring and control of each process link.

[0087] Step 1: Connect the PLC system to the sensors and actuators of each device to ensure that all parameters (such as pH value, temperature, ORP, ultrasonic power, etc.) are uploaded to the PLC system in real time.

[0088] Step 2: Set the control logic of the PLC system to automatically adjust the operation status of the device according to the monitored process parameters, such as adjusting the current and voltage of the electrochemical system and regulating the addition amount of the leaching agent.

[0089] Step 3: The PLC system should have a fault diagnosis function, be able to automatically detect and alarm, and ensure the safety and reliability of the system operation.

[0090] SCADA system integration: Data collection and analysis: Real-time collection, storage, and analysis of data are achieved through the SCADA system.

[0091] Step 1: Connect the SCADA system to the PLC system to collect data of each process parameter in real time and generate historical trend charts and real-time data charts.

[0092] Step 2: The SCADA system should be able to calculate and analyze key parameters (such as metal recovery rate, energy consumption, reagent consumption, etc.) and provide optimization suggestions.

[0093] Step 3: Regularly generate process operation reports to provide data support for process improvement and optimization.

[0094] 4.2 Integrated Recovery and Waste Liquid Treatment Metal Recovery System: Electrolysis and Chemical Precipitation Process: Select a suitable metal recovery process according to the types of metals in the leaching solution.

[0095] Step 1: For nickel recovery, adopt electrolytic deposition technology, control the pH value of the electrolyte between 5 - 6, and the current density at 2 - 3 A / dm² to deposit high-purity nickel.

[0096] Step 2: For cobalt recovery, add a precipitant (such as sodium sulfide or sodium hydroxide) to precipitate cobalt in the form of cobalt hydroxide or cobalt sulfide. The precipitation process should be carried out under stirring conditions to ensure the uniformity of precipitation.

[0097] Step 3: The precipitated metal compounds are separated by filtration or centrifugation, further purified and then sent to the smelting process to obtain the final metal products.

[0098] Waste Liquid Treatment and Water Resource Recycling: Wastewater Treatment System: After the waste liquid is neutralized to adjust the pH value to neutral, it enters the wastewater treatment system.

[0099] Step 1: Add sodium hydroxide or lime slurry to the neutralization tank to adjust the pH value of the waste liquid to 7 - 8, and mix thoroughly with a stirrer to ensure the complete neutralization reaction.

[0100] Step 2: The neutralized waste liquid undergoes solid-liquid separation in a sedimentation tank. The precipitated solid waste is processed by a filter press, and the filtrate is discharged after passing the discharge standard test.

[0101] Step 3: The treated water resources are recycled to the water storage tank through the circulating water system for use in leaching agent preparation or equipment cooling, realizing the recycling of water resources.

[0102] Waste Residue Treatment and Resource Utilization: Solid Waste Residue Treatment: The solid waste residue is harmlessly treated and then resourcefully utilized, such as for building material production or landfill treatment.

[0103] Step 1: Send the solid waste residue to the heat treatment furnace through the conveying system for roasting treatment. The roasting temperature is controlled at 800 - 1000 °C to destroy harmful substances.

[0104] Step 2: The roasted waste residue is ground by a ball mill, and the powder material can be used to produce building materials such as cement and bricks.

[0105] Step 3: The waste residue that cannot be resourcefully utilized is harmlessly treated and then sent to the landfill for safe landfill.

[0106] Example 2: The present Example 2 provides a method for leaching the negative electrode material of nickel-metal hydride waste batteries, comprising the following steps: 1. Pretreatment and preparation of leaching agent 1.1 Pretreatment Material disassembly and separation: The same as in Example 1, an automated mechanical disassembly device is used to disassemble nickel-metal hydride waste batteries, the negative electrode material is separated, and collected in a special container.

[0107] Crushing and screening: The negative electrode material is processed through a multi-stage crushing system: Primary crushing to a particle size of 10 - 20 mm.

[0108] Further crushing by a pair-roll crusher to fine particles below 0.1 mm.

[0109] After classification by an air classifier, the fine particle material is fed into the leaching reactor.

[0110] 1.2 Preparation of leaching agent Preparation equipment: The same as in Example 1, an automated dosing system is used to prepare the leaching agent with a concentration of 0.5 M to 1.0 M and an EDTA concentration of 0.1 M to 0.2 M.

[0111] Quality detection of the solution: Online monitoring is carried out using a pH meter and a conductivity meter to ensure that the pH value and conductivity of the prepared solution meet the standards.

[0112] 2. Leaching process design 2.1 Ultrasonic-assisted leaching Configuration of ultrasonic equipment and reactor: The same as in Example 1, a double-layer corrosion-resistant leaching reactor is used, with an acid-resistant ceramic inner layer and a stainless steel sandwich outer layer.

[0113] Ultrasonic-assisted effect: The ultrasonic power is set to 500 W, and the frequency remains unchanged at 40 kHz.

[0114] Temperature control: The reaction temperature is controlled below 60 °C, and the temperature is adjusted through a circulating cooling water system.

[0115] Leaching time and efficiency control: The leaching time is set to 2 hours, and the metal ion concentration is sampled and detected every 30 minutes in the middle.

[0116] 2.2 Electrochemical-assisted leaching Configuration of the electrochemical system: The same as in Example 1, the electrode materials are selected as a graphite anode and a titanium alloy cathode, with a current of 0.5 A to 1 A and a voltage of 2 V to 5 V.

[0117] Electrochemical reaction control: Use an on-line monitoring system to monitor ORP and pH values, and adjust the current and voltage according to the monitoring data.

[0118] 3. Recycling and regeneration of leachate 3.1 Solid-liquid separation and re-leaching Primary solid-liquid separation: The same as in Example 1, a vacuum filter is used for solid-liquid separation.

[0119] Secondary leaching process: Use a high-concentration citric acid / oxalic acid mixed solution and carry out secondary leaching at 80 °C.

[0120] 3.2 Regeneration treatment of leachate Impurity removal: The same as in Example 1, use a hydrogen-type cation exchange resin in an ion exchange column to remove impurity ions.

[0121] Leachate concentration: Concentrate the leachate through a thin-film evaporator, and the evaporated water vapor is condensed and recycled for preparing fresh leaching agent.

[0122] Recycling of regenerated leachate: The same as in Example 1, the regenerated leachate is transported back to the leaching reactor for recycling.

[0123] 4. System integration and optimization 4.1 Real-time monitoring and optimization of process parameters Automation control system design: The same as in Example 1, install a PLC automation control system to integrate the monitoring and control of each process link.

[0124] SCADA system integration: Realize real-time data acquisition, storage and analysis through the SCADA system.

[0125] 4.2 Comprehensive recovery and waste liquid treatment Metal recovery system: The same as in Example 1, use electrolytic deposition technology to recover nickel and recover cobalt by chemical precipitation method.

[0126] Wastewater treatment and water resource recycling: After neutralization treatment, it is reused for preparing fresh leaching agent, and the waste residue is used for producing building materials after harmless treatment.

[0127] Compared with Example 1, the only change in Example 2 is that the ultrasonic power is increased from 400 W to 500 W. This adjustment aims to explore the influence of different ultrasonic powers on the leaching efficiency of metal ions. The remaining process steps, equipment configurations and parameter settings are the same as in Example 1 to ensure the reliability and repeatability of the comparative test results.

[0128] Example 3: Example 3 discloses a leaching method for the negative electrode material of nickel-metal hydride waste batteries, which includes the following steps: 1. Pretreatment and preparation of leaching agent 1.1 Pretreatment Material disassembly and separation: The same as in Example 1, use an automated mechanical disassembly device to disassemble nickel-metal hydride waste batteries, separate the negative electrode material, and collect it in a special container.

[0129] Crushing and screening: The negative electrode material is processed through a multi-stage crushing system: Primary crushing to a particle size of 10 - 20 mm.

[0130] Further crush by a pair-roll crusher to fine particles below 0.1 mm.

[0131] After classification by an air classifier, the fine particle material is sent to the leaching reactor.

[0132] 1.2 Preparation of leaching agent Preparation equipment: The same as in Example 1, use an automated dosing system to prepare the leaching agent with a concentration of 0.5 M to 1.0 M and an EDTA concentration of 0.1 M to 0.2 M.

[0133] Quality detection of the solution: Use a pH meter and a conductivity meter for on-line monitoring to ensure that the pH value and conductivity of the prepared solution meet the standards.

[0134] 2. Leaching process design 2.1 Ultrasonic-assisted leaching Configuration of ultrasonic equipment and reactor: The same as in Example 1, use a double-layer corrosion-resistant leaching reactor with an acid-resistant ceramic inner layer and a stainless steel sandwich outer layer.

[0135] Ultrasonic-assisted effect: The ultrasonic power is set to 400 W and the frequency remains unchanged at 40 kHz.

[0136] Temperature control: The reaction temperature is controlled below 60°C and the temperature is adjusted through a circulating cooling water system.

[0137] Leaching time and efficiency control: The leaching time is set to 2 hours, and the metal ion concentration is sampled and detected every 30 minutes in the middle.

[0138] 2.2 Electrochemical-assisted leaching Configuration of the electrochemical system: Different from Example 1, the current of the electrochemical reaction is set to 0.8 A, and the other electrode materials are a graphite anode and a titanium alloy cathode, and the voltage remains in the range of 2 V to 5 V.

[0139] Electrochemical reaction control: Use an on-line monitoring system to monitor the ORP and pH value, and adjust the current and voltage according to the monitoring data.

[0140] 3. Recycling and Regeneration of Leachate 3.1 Solid-Liquid Separation and Re-leaching Primary solid-liquid separation: The same as in Example 1, a vacuum filter is used for solid-liquid separation.

[0141] Secondary leaching process: A high-concentration mixed solution of citric acid / oxalic acid is used, and secondary leaching is carried out at 80 °C.

[0142] 3.2 Regeneration Treatment of Leachate Impurity removal: The same as in Example 1, a hydrogen-type cation exchange resin is used to remove impurity ions in an ion exchange column.

[0143] Leachate concentration: The leachate is concentrated by a thin-film evaporator, and the evaporated water vapor is condensed and recycled for preparing fresh leaching agent.

[0144] Recycling of regenerated leachate: The same as in Example 1, the regenerated leachate is transported back to the leaching reactor for recycling.

[0145] 4. System Integration and Optimization 4.1 Real-time Monitoring and Optimization of Process Parameters Automation control system design: The same as in Example 1, a PLC automation control system is installed to integrate the monitoring and control of each process link.

[0146] SCADA system integration: Real-time data collection, storage, and analysis are achieved through the SCADA system.

[0147] 4.2 Comprehensive Recovery and Waste Liquid Treatment Metal recovery system: The same as in Example 1, electrolytic deposition technology is used to recover nickel, and cobalt is recovered by chemical precipitation method.

[0148] Wastewater treatment and water resource recycling: After neutralization treatment, it is recycled for preparing fresh leaching agent, and the waste residue is used for producing building materials after harmless treatment.

[0149] Compared with Example 1, the only change in Example 3 is that the current in the electrochemical reaction increases from 0.5 A to 0.8 A. This adjustment aims to explore the influence of different currents on the leaching efficiency of metal ions. Other process steps, equipment configurations, and parameter settings are the same as in Example 1 to ensure the reliability and repeatability of the comparative test results.

[0150] Table 1 Experimental Data Table of Examples Example Ultrasonic power (W) Current (A) Leaching time (hours) Nickel recovery rate (%) Cobalt recovery rate (%) ORP (mV) Leaching agent concentration (M) Temperature (°C) Solid-liquid ratio (g / ml) Example 1 400 0.5 2 93.2 90.8 +510 0.5 60 1：10 Example 2 500 0.5 2 94.0 91.3 +515 0.5 60 1：10 Example 3 400 0.8 2 94.5 92.0 +520 0.5 60 1：10 1. Influence of Ultrasonic Power on Leaching Effect Comparison between Example 1 and Example 2: When the ultrasonic power increases from 400 W to 500 W, the nickel recovery rate slightly increases from 93.2% to 94.0%, and the cobalt recovery rate increases from 90.8% to 91.3%.

[0151] The ORP value rises from +510 mV to +515 mV.

[0152] Summary: The increase in ultrasonic power slightly improves the recovery rates of nickel and cobalt, indicating that higher ultrasonic power can more effectively promote the reaction between the leaching agent and the material surface. However, considering the increase in energy consumption and the relatively small increase in recovery rate, further increasing the ultrasonic power may require a trade-off in its economy.

[0153] 2. Influence of Electrochemical Reaction Current on Leaching Effect Comparison between Example 1 and Example 3: When the electrochemical reaction current increases from 0.5 A to 0.8 A, the nickel recovery rate increases from 93.2% to 94.5%, and the cobalt recovery rate increases from 90.8% to 92.0%.

[0154] The ORP value rises from +510 mV to +520 mV.

[0155] Summary: Higher current significantly improves the recovery rates of nickel and cobalt, indicating that stronger electrochemical reactions can more effectively promote the dissolution of metal ions. However, with the increase in current, the power consumption also rises, so a balance needs to be achieved between the recovery rate and energy consumption.

[0156] 3. Comprehensive Analysis Recovery rates of nickel and cobalt: Whether increasing the ultrasonic power or raising the current has a positive impact on the recovery rates of nickel and cobalt. Among them, the increase in current has a more obvious effect on improving the recovery rate.

[0157] ORP value: The ORP value rises with the increase in ultrasonic power and current, indicating that the redox ability of the reaction solution is enhanced and the reaction efficiency is improved.

[0158] Optimal process conditions: Judging from the experimental data, Example 3 (ultrasonic power of 400 W and current of 0.8 A) has the highest metal recovery rate, but its energy consumption and economic benefits need to be further evaluated to determine the optimal process conditions.

[0159] Comparative Example 1: This comparative example presents a traditional leaching method for the negative electrode material of nickel-metal hydride waste batteries, including the following steps: Traditional Comparative Example To further verify the superiority of the leaching method in Example 1, a comparative experiment was carried out using the traditional process. The traditional comparative example adopted the conventional acid leaching process without using ultrasonic assistance and electrochemical reaction, and other process steps were the same as those in Example 1.

[0160] 1. Process flow of the traditional comparative example 1.1 Pretreatment Material disassembly and separation: The same as in Example 1, an automated mechanical disassembly device was used to disassemble nickel-metal hydride waste batteries, and the negative electrode material was separated and collected in a special container.

[0161] Crushing and screening: The negative electrode material was processed through a multi-stage crushing system: Primary crushing to a particle size of 10 - 20 mm.

[0162] The roll crusher further crushed it into fine particles with a size of less than 0.1 mm.

[0163] After being classified by an air classifier, the fine particle material was sent to the leaching reactor.

[0164] 1.2 Preparation of leaching agent Preparation equipment: The same as in Example 1, an automated dosing system was used to prepare the leaching agent with a concentration of 0.5 M to 1.0 M and an EDTA concentration of 0.1 M to 0.2 M.

[0165] Quality detection of the solution: Online monitoring was carried out using a pH meter and a conductivity meter to ensure that the pH value and conductivity of the prepared solution met the standards.

[0166] 2. Leaching process design 2.1 Leaching process Leaching reaction: In the traditional comparative example, only the leaching agent was used for chemical leaching without using ultrasonic assistance and electrochemical reaction.

[0167] Usage of leaching agent: The same mixed solution of citric acid and oxalic acid as in Example 1 was used, and the solid-liquid ratio was 1:10.

[0168] Temperature control: The reaction temperature was controlled at 60 °C, and the leaching time was set to 2 hours.

[0169] Stirring conditions: During the entire leaching process, a mechanical stirring device was used to uniformly mix the reactants to ensure sufficient contact between the leaching agent and the material.

[0170] 3. Treatment of leaching solution 3.1 Solid-liquid separation Solid-liquid separation: The same as in Example 1, a vacuum filter was used for solid-liquid separation, and the obtained leaching solution after separation entered the subsequent treatment steps.

[0171] 3.2 Regeneration of Leaching Solution Impurity removal and concentration: The same as in Example 1, an ion exchange column was used to remove impurity ions, and the leaching solution was concentrated by a thin-film evaporator.

[0172] 3.3 Recycling of Leaching Solution Recycling: The regenerated leaching solution was transported back to the leaching reactor and continued to be used for the leaching of the next batch.

[0173] Table 2 Experimental Data Table of Comparative Examples Example Ultrasonic power (W) Current (A) Nickel recovery rate (%) Cobalt recovery rate (%) ORP (mV) Leaching agent concentration (M) Temperature (°C) Solid-liquid ratio (g / ml) Example 1 400 0.5 93.2 90.8 +510 0.5 60 1：10 Comparative Example 1 None None 82.5 79.3 +450 0.5 60 1：10 In the traditional comparative example, ultrasonic assistance and electrochemical reaction were not used, and the leaching process completely relied on the chemical reaction between the leaching agent and the negative electrode material. The experimental results showed that: Nickel recovery rate: The nickel recovery rate of the traditional comparative example was 82.5%, significantly lower than 93.2% of Example 1. This was because the lack of ultrasonic assistance led to a decrease in the contact efficiency between the leaching agent and the material surface, and at the same time, the lack of the promoting effect of electrochemical reaction on the dissolution of metal ions.

[0174] Cobalt recovery rate: The cobalt recovery rate of the traditional comparative example was 79.3%, also lower than 90.8% of Example 1.

[0175] ORP value: The ORP value of the traditional comparative example was +450 mV, lower than +510 mV of Example 1, indicating that the redox ability of the chemical reaction was weaker.

[0176] The traditional comparative example was significantly inferior to Example 1 in terms of the recovery rates of nickel and cobalt. By introducing ultrasonic assistance and electrochemical reaction technologies, the leaching efficiency and metal recovery rate can be significantly improved, indicating that the improved process of Example 1 has obvious advantages in terms of recovery effect and efficiency.

[0177] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for leaching negative electrode materials of waste nickel-hydrogen batteries, characterized in that: The following steps are involved: Step 1: pre-treating the negative electrode material of the waste nickel-hydrogen battery, wherein the pre-treating step includes disassembling the battery and crushing it into fine particles with a particle size of less than 0.1 mm; Step 2: using a mixed solution of citric acid and oxalic acid as a leaching agent for leaching, the concentration of the leaching agent is 0.5M to 1.0M, and the leaching process is assisted by ultrasound, the ultrasonic power is 400W, and the frequency is 40kHz; Step 3: applying an electrochemical reaction during the leaching process, wherein the electrochemical reaction includes using a graphite anode and a titanium alloy cathode, a current of 0.5 A to 1 A, and a voltage of 2 V to 5 V; Step 4: The leached slurry is subjected to solid-liquid separation, and the obtained filtrate is subjected to a leaching agent regeneration treatment, wherein the regeneration treatment includes ion exchange to remove impurity ions and thin film evaporation concentration treatment, and the regenerated leaching agent is recycled for use in the leaching step.

2. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The pre-processing step comprises: The disassembled negative electrode material is crushed by a jaw crusher to a particle size of 10-20 mm; The particles are further crushed to fine particles below 0.1 mm by a double-roll crusher, and materials of different particle sizes are separated by an air classifier.

3. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The leaching agent preparation comprises the following steps: In an automated dispensing system, citric acid and oxalic acid were mixed in a 1:1 ratio to a concentration range of 0.5 M to 1.0 M; 0.1 M to 0.2 M EDTA was added as a complexing agent.

4. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The ultrasonic assisted leaching includes setting the leaching reactor as a double-layer structure, the inner layer is acid-resistant ceramic, the outer layer is a stainless steel interlayer, and circulating cooling water is passed through the interlayer to control the reaction temperature below 60°C.

5. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The electrochemical reaction is performed by online monitoring of oxidation-reduction potential (ORP) and pH value, and the current and voltage are adjusted in real time. The ORP value is controlled to be above +500mV.

6. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The solid-liquid separation is performed by a vacuum filter, and the filtered leachate and solid residue are subjected to secondary leaching treatment, wherein the secondary leaching uses a high concentration of citric acid / oxalic acid mixed solution and is performed at 80°C.

7. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The regeneration process of the leaching agent comprises: Using hydrogen-type cation exchange resin in an ion exchange column to remove impurity ions such as calcium and magnesium from the leachate; The leaching solution is concentrated by a thin film evaporator, and the evaporated water vapor is condensed and recovered for the preparation of fresh leaching agent.

8. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: The regenerated leaching agent is regenerated after five batches of leaching cycles to restore its effectiveness.

9. The method for leaching the negative electrode material of waste nickel-hydrogen batteries according to claim 1, characterized in that: Real-time monitoring and adjustment of process parameters are achieved through a PLC automatic control system, which includes sensors and actuators and can monitor and adjust pH value, temperature, ultrasonic power, current and voltage parameters in the leaching process in real time.

10. The method for leaching negative electrode materials of waste nickel-hydrogen batteries according to claim 1, characterized in that: The wastewater is reused in the preparation of fresh leaching agent after neutralization treatment, and the waste residue is used in the production of building materials after harmless treatment.

Images