Optimization of Leaching of Lithium and Cobalt from Spent Lithium-Ion Batteries by the Choline Chloride-Citric Acid/Malonic Acid DES Using Response Surface Methodology.

Deep eutectic solvents (DESs) are eco-friendly leaching agents which have emerged as potential candidate for recovery of valuable metals from spent LIBs (lithium-ion batteries). Earlier reports show use of more mount of chemicals, long leaching duration and less efficiency. The present work has been carried out to observe the leaching efficiency of two DES-water blend systems such as ChCl:CA(2:1) +30% HO and ChCl:MA(1:1)+20% HO for the leaching of Li and Co from cathodic material of spent LIBs using design of experiments and optimization through CCD (central composite design) of Response surface methodology(RSM) approach. Polynomial quadratic model for ChCl:CA (2:1)+35% HO and the linear model for ChCl:MA(1:1)+20% HO were selected on the basis statistical parameter values.The physico chemical properties like density, viscosity, conductivity and refractive index of DES-water blend have been determined in the temperature range 298.15 to 328.15K. The influence of temperature, leaching duration and stirring speed on the leaching efficiency has been scrutinized. Cobalt leaching efficiency (99.83%) was higher as compared to that of lithium (96.51%) using citric acid based DES-water blend under the conditions temperature 353 K, leaching time 117 minutes and stirring speed 920 rpm. FTIR and UV-Vis spectra of DES-water blend before and after leaching were recorded. DLS and Zeta potential results confirm higher leaching efficiency of choline chloride-citric acid based DES-water blend.