Precipitation of La and dissolution enhancement of Ni by a one pot oxidative leaching process from mixed batteries

Abstract A single oxidative leaching process was developed for simultaneous enhancement of dissolution of nickel and precipitation of lanthanum by using Na2S2O8 in sulfuric acid solution from a heat-treated mixture of batteries containing 50 wt.% alkaline batteries, 25 wt.% Ni-MH batteries, and 25 wt.% Ni-Cd batteries. The effect of leaching parameters was investigated, including the concentrations of sulfuric acid, Na2S2O8, and H2O2, the temperature, and the leaching time. The results show that almost all metals such as zinc, manganese, and cadmium are dissolved by 2 M sulfuric acid, but the leaching efficiency of nickel is 86.8%. However, in a leaching process using Na2S2O8, the leaching efficiency of Ni is enhanced while lanthanum is selectively precipitated in the form of NaLa(SO4)2·H2O at the same time, and this result is supported by XRD, ICP, and SEM analysis. Under the optimum conditions of 2 M H2SO4, 10 vol.% H2O2, 10 vol.% 1 M Na2S2O8, and 95 ℃, 97.8% of the nickel is leached while 98.8% of the lanthanum is selectively precipitated. This study shows that the separation and purification stages can be simplified to recover La and valuable metals.