The amount of discarded dry batteries are presently found to be increasing globally and waste cathode active materials of the lithium ion battery industry are among them. Hydrometallurgical operations are being applied to recover the valuable metals from these waste batteries. To find an economic and environmentally friendly process, the bioleaching process was applied in the present investigation for recovery of valuable metals. Its principle is the microbial production of sulfuric acid and simultaneous leaching of metals._x000D_
Bioleaching of spent lithium ion secondary batteries, containing LiCoO2, has been studied in this investigation. A new method for recovery of cobalt, potentially the basis of an economic and environmentally friendly process was examined. The present study has been carried out using chemolithotrophic and acidophilic bacteria Acidithiobacillus ferrooxidans, which utilises elemental sulfur and ferrous ion as the energy source to dissolve metals from spent batteries. Bio-dissolution of cobalt was found to be faster than lithium. The effect of initial Fe(II) concentration, initial pH and solid/liquid (w/v) ratio were studied in detail. Higher Fe(II) concentration showed a decrease in dissolution due to co-precipitation of Fe(III) with the metals in the residues. Similarly, at higher initial pH values and higher solid/liquid ratio (w/v) metal dissolution was found to be inhibited. The optimised conditions for bio-dissolution were solid/liquid (w/v) ratio - 10 g/L, initial Fe(II) concentration - 3 g/L, elemental sulfur - one per cent (w/v) and initial pH - 2.5. In the optimised conditions, cobalt dissolution was observed to be about 60 per cent, whereas that of lithium was ten per cent after 20 days. A first order kinetic model was derived to study the rate of dissolution of both the metals._x000D_
FORMAL CITATION:Mishra, D, Kim, D-J, Ralph, D E, Ahn, G-J and Rhee, Y-H, 2006._x000D_
Bioleaching of valuable metals from waste cathode materials of the lithium ion battery industry using acidithiobacillus ferrooxidans, in Proceedings Green Processing 2006, pp 49-54 (The Australasian Institute of Mining and Metallurgy: Melbourne).