Study On The Recovery Of Valuable Metals From Spent Lithium Ion Batteries Using Acid Leaching-Extraction-Precipitation Process

The recycling of spent lithium-ion batteries have become a hot topic due to it contains Li,Co,Ni,Mn,and other valuable metals and hydrofluoric acid,organic solvents,and other harmful substances.In this study,base on the problems of inefficient recovery of valuable metals and secondary pollution of HCl and NO₂ harmful gases in traditional processes,a novel acid leaching-extraction-precipitation process for recovering valuable metals is proposed,and the contents of collaborative leaching kinetics,reduction mechanism and process parameter optimization are investigated.In this study,the mechanical crushing and sieving pretreatment were used for the positive electrode mixed fragments.The results show that under the optimal conditions of shaking rate 250 r/min and sieving time of 2.0 h,the sieving efficiency of the cathode mixed powder is 78.5%.The process is simple and environmentally friendly.Sulfuric acid,L-ascorbic acid,and sulfuric acid-L-ascorbic acid were used to leaching valuable metals from the cathode mixed powder.The results show that L-ascorbic acid help to improve the leaching efficiency of Li,Co,Ni,and Mn.Under the optimal conditions of sulfuric acid concentration 1.5 mol/L,L-ascorbic acid concentration 0.25 mol/L,temperature 60?,time 60 min,liquid-solid ratio 15 m L/g,and stirring speed 300 r/min,the leaching efficiency of Li,Co,Ni,and Mn are 99.69%,99.56%,99.60%,and 99.87%,respectively,and the C content in the leaching residue is 90.61%.The collaborative leaching kinetics and reduction mechanism were investigated.The results show that within20 min of the leaching reaction,the leaching kinetics of Li,Co,and Ni are conform to the unreacted nuclear shrinkage model,and the apparent activation energies are 7.00 k J·mol^-1,14.22 k J·mol^-1,and 4.69 k J·mol^-1,respectively.L-ascorbic acid provides reducing functional groups-OH,C=O and C-H,reducing insoluble Co???,Ni???,and Mn???to Co???,Ni???,and Mn???,and promote the dissolution of metal oxides to form sulfates.The yellow iron sodium vanadium method and the ammonium bicarbonate precipita-tion method were used to remove Fe,Al and Cu,respectively.The results show that under the optimal conditions of reaction temperature 95?,reaction time 2 h,and final p H 3.0?3.5,the removal rate of Fe is 96.5%and the loss rates of Li,Co,Ni,and Mn are all less than 0.3%.Under the optimal conditions of reaction temperature 90?,final p H 6.5,and reaction time 2 h,the removal rates of Al and Cu are 99.9%and 94.5%,respectively,and the loss rates of Ni,Co,and Mn are only 4.0%.The results of selective nickel recovery using dimethylglyoxime show that under the optimal conditions of dimethylglyoxime concentration 0.5 mol/L,stirring speed 200 r/min,end point p H 5.0 and reaction time 20min,the recovery efficiency of Ni is 97.5%,and XRD results indicate that the product is C8H14N4Ni O4.In this research,the solvent extraction-precipitation method was used to recover Mn,Co,and Li in the leaching solution.The results show that under the optimal conditions of20%P204+10%TBP+70%sulfonated kerosene,p H 3.3,O/A 1/8,time 5 min,and saponification rate of 10%,the extraction efficiency of Mn is 99.5%,while the loss rate of Li and Co are less than 5%.Under the optimal conditions of 25%P507+10%TBP+65%sulfonated kerosene,p H 4.5,O/A 1.5/1,time 10 min and saponification rate 70%,the extraction efficiency of Co is 99.1%,while the loss rate of Li is less than 5%.The loaded organic phase was washed and stripped with sulfuric acid,and the stripping liquid was separately precipitated to recover Mn,Co,and Li by Na HCO₃,?NH₄?₂C₂O₄ and saturated Na₂CO₃.The results show that the recovery efficiencies of Mn,Co,and Li are 92.0%,99.8%,and 91.0%,respectively,and XRD characterization results show that the product phases are Mn CO₃,Co C₂O₄·H₂O and Li₂CO₃,respectively.In this paper,the acid leaching-extraction-precipitation process is used to achieve efficient recovery of Ni,Co,Mn,and Li from the cathode mixed powder,which provides a new idea for the recycling of spent lithium-ion batteries.