Application of ion-exchange fibers towards the chromatographic separation of valuable metals of Ni, Co, Ce, La and Nd from spent nickel-metal hydride batteries

Abstract

Recycling valuable metals from spent nickel-metal hydride (NiMH) batteries has significant environmental and economic benefits. This study aimed to separate and recover nickel (Ni), cobalt (Co), cerium (Ce), lanthanum (La), and neodymium (Nd) from waste NiMH batteries using ion-exchange fibers as the adsorbent material in an adsorption chromatography process. Static adsorption experiments showed the metal adsorption processes followed the Langmuir model, indicating mono layer coverage, and quasi-second order kinetics, suggesting chemisorption. In the chromatographic separation study, optimal conditions of pH 2, 1/10 diluted feed solution, fully packed column, 3 mL/min flow rate, and 0.2 mol/L acid elution enabled effective separation of the five metals. According to distribution coefficients, the metals were preferentially adsorbed in the order: Nd3+ > La3+ > Ce3+ > Co2+ > Ni2+. Transition metals Ni2+ and Co2+ were first separated from rare earths Ce3+, La3+ and Nd3+. Subsequently, good separation among the rare earth elements was achieved. After ten adsorption-desorption cycles, the fibers maintained excellent stability with only 9.2 % capacity loss. The results demonstrate the adsorption chromatography method can efficiently recover mixed metals from waste NiMH batteries individually for full value utilization.