Recovery of rare earths from acid leach solutions of spent nickel-metal hydride batteries using solvent extraction

The extraction of rare earths from acid leach solutions of spent nickel-metal hydride batteries using a primary amine extractant of N1923 was studied. The effects of feed pH, temperature, agitation rate and time on the extraction of rare earths, as well as stripping agent composition and concentration, phase ratio on the stripping were investigated. In addition, the extraction isotherm was determined. The pilot plant test results showed that the extraction of rare earths reached 99.98% after a five-stage counter current extraction. The mixed rare earths oxalates with the 99.77% purity of rare earth elements and impurity content less than 0.05% were obtained by the addition of oxalic acids in loaded strip liquors. The extractant exhibited good selectivity of rare earths over base metals of iron, nickel, copper and manganese.

Graphical AbstractEffect of feed pH on the extraction of metals. The primary amine extractant of N1923 can be used to highly separate rare earths over Fe, Ni, Cu, Mn and Zn from acid leach solutions. The extraction of rare earths reached 99.98% and rare earth oxalates with RE elements purity of 99.77% was obtained in fully-continuous pilot plant testFigure optionsDownload full-size imageDownload as PowerPoint slide