Research On A New Process For Wet Recovery Of Valuable Metals From Waste Nickel-cobalt-manganese Ternary Lithium Battery Cathode Material

Lithium-ion batteries have become an important energy storage device to support the development of modern economy and society.Retired spent lithium-ion battery cath-ode materials are rich in valuable metals,which are important secondary resources and must be recycled.The wet process is one of the main ways to recover valuable metals fr-om spent lithium-ion batteries.All valuable metals in spent lithium-ion batteries are red-uced and leached into the solution,resulting in high loss of nickel and cobalt removal by chemical precipitation,high cost of saponification extraction separation and purification,and a large amount of NH₃-N wastewater produced by saponification.The development of green and efficient wet recovery process has become an urgent need for the industry.In this paper,the cathode material of spent nickel-cobalt-manganese ternary lithium bat-tery is selected as the research object,and a new process of pressure-enhanced selective reduction leaching-oxygen-enriched pressure acid leaching-controlled potential oxidati-on-synergistic extraction purification-extraction combined ion exchange separation’is proposed.It provides a reference for the efficient recovery of valuable metals such as Ni,Co,Li and Mn.The main research results are as follows:The selective reduction leaching of Ni,Co,Li and other valuable metals is realized by pressure-enhanced selective reduction leaching,and Mn is inhibited from separating in the slag,which solves the technical problem of high cost of Mn purification,separation and recovery in the traditional leaching process.Under the conditions of sulfuric acid concentration of 120 g/L,mass ratio of 20%Na₂SO₃,liquid-solid ratio of10:1,stirring speed of 450 r/min,temperature of 140℃and time of 150 min,the leaching rates of Ni,Co and Li reached more than 99%,and the leaching rate of Mn was controlled within 3%.The process of acid leaching+vulcanization precipitation+oxygen rich pressure acid leaching was studied.The dealuminized slag was first dissolved in acid,then cured and precipitated to recover Ni and Co.Under the conditions of sulfuric acid concentration of 95 g/L,liquid-solid ratio of 6:1,stirring 400 r/min,temperature 110℃,time 120 min,90%O₂and pressure 1.2 MPa,the leaching rates of Ni and Co reached more than 98%.To solve the problem of Ni and Co recovery lost in the process of dealuminization of leaching solution,and improve the comprehensive recovery rate of Ni and Co.The process of controlling potential oxidation-synergistic extraction separation of manganese and iron was studied.Mn and Fe were initially oxidized from the leaching solution,and then Mn and Fe were separated by deep purification of synergistic extraction.It solves the problem of large operating load and high cost caused by the direct entry of Mn and Fe into the extraction system in the traditional recovery process.The E-p H diagram of Mn-H₂O system was drawn.Using the difference of redox potential of Na₂S₂O₈,Mn²⁺and Fe²⁺,Mn and Fe in the leaching solution were removed by controlling the potential oxidation,and the removal rates were 93.62%and 96.18%,respectively.The P204-N235 non-saponification synergistic extraction system was constructed to deeply purify and separate trace Mn and Fe in the solution.The removal rate could reach more than 99%.The log D-log[P204]and log D-p H diagrams of the distribution ratio D of Ni,Co,Fe and Mn extracted by P204-N235 with the concentration of P204 and the p H of the aqueous phase were drawn,respectively.The extraction mechanism that two P204 molecules are required for each metal ion and at most one free H⁺is released is revealed.In the extraction process,N235 does not participate in the extraction,but only plays a role in regulating the p H of the system,which realizes the non-saponification extraction and avoids the harm of NH₃-N wastewater produced by traditional saponification extraction to the environment.The process of step-by-step recovery of nickel,cobalt and lithium by extraction combined with ion exchange was studied.Cyanex 272 was used to extract and recover Co from the solution after removing Mn and Fe,and then P507 was used to extract and recover Ni.The purification solution with concentration ratio Co/Ni of 37452/1 and Ni/Li of 426500/1 was obtained respectively.Finally,D751 resin was used to adsorb and recover Li from P507 raffinate.The recovery rate of Li is more than 99%.The liquid after adsorption is recycled,and the amount of high sodium salt wastewater treatment is reduced by 3/4.The purified solution obtained by separation and purification meets the requirements for the production of electric nickel,cobalt sulfate and lithium carbonate products.The above technologies obtained in this study have been tested in industrial production.The industrial test results show that the leaching rate of Ni,Co and Li in the cathode material of spent Ni-Co-Mn ternary lithium battery is more than 99%,more than97%of Mn is inhibited to separate in the slag,and the recovery rate of Li is more than99%.The purification solution obtained by leaching purification separation and purification meets the requirements of production control index.The process technology obtained by pressure-enhanced selective reduction leaching,leaching solution controlled potential oxidation-collaborative extraction deep purificat-ion and separation of manganese and iron can provide technical support and reference for green and efficient recovery of valuable metals in cathode materials of waste batteries.