Separation of nickel(II), cobalt(II) and lanthanides from spent Ni-MH batteries by hydrochloric acid leaching, solvent extraction and precipitation

The separation of nickel(II), cobalt(II) and lanthanides from chloride leach liquors of spent nickel-metal hydride (Ni-MH) batteries is described. After leaching in 12 mol L− 1 HCl, the traces of iron(III) and zinc(II) were extracted in a single stage with pure TBP (25 °C, A/O ratio = 1 v/v). Cobalt was extracted (93.6%) in two stages with Alamine 336 (10% vol. in kerosene, 25 °C, A/O = 1 v/v, free acidity = 4.3 mol L− 1). More than 98% of the lanthanides present in the raffinate were recovered through one of the following routes: (i) extraction with PC88A (20 vol.% in kerosene, 25 °C, A/O = 1 v/v, one stage, pH 1); (ii) precipitation as oxalates at pH 0.5. Nickel(II) was precipitated (> 99%) as oxalate at pH 2. Metals separation in acidic medium avoids partial or total neutralization of the leachate and reduces the amount (and salinity) of the wastewater generated in the separation processes.