The reductive leaching of waste lithium ion batteries in presence of iron ions: Process optimization and kinetics modelling

Abstract

Recycling of lithium-ion batteries (LIBs) is essential not only to protect the environment but also to recover valuable metals, such as lithium and cobalt. The effect of ferrous (Fe2+) has been explored on LIBs leaching, as a reducing agent. The influence of four different parameters including agitation rate, pH, ferrous concentration and temperature has been investigated on LIBs leaching to optimize the leaching process and kinetics modelling. While ferrous ions did not have significant effect on lithium recovery, the cobalt recovery was increased from 33.6% to 88.7% when ferrous concentration were increased from 0 g/L to 6 g/L. The results indicated that the highest lithium and cobalt recoveries achieved at agitation rate = 500 rpm, pH = 0.5 (∼0.57 mol/L H2SO4), ferrous concentration = 6 g/L, and temperature = 75 °C. The kinetics modelling indicated that adding ferrous ions to leaching environment decreases the ash layer formation by reducing the metals in particles surface and transfer them in liquid medium. The activation energies for cobalt and lithium dissolution were 58.71 kJ/mol and 37.45 kJ/mol, respectively. After process optimization, the chemical ferrous ions were replaced by iron scraps were obtained from 18650 LIBs shells. The results showed that 92.67% of lithium and 98.91% of cobalt are recovered by adding 6 g/L iron scrap to the leaching environment. Therefore, the iron scrap can be used as an efficient, economic and sustainable reducing agent for LIBs leaching, at low concentrations of sulfuric acid.