Separation of neodymium from rare earth metals via hollow fiber supported liquid membrane

Abstract

This study investigated the separation of neodymium ions from mixed rare earth via hollow fiber supported liquid membrane (HFSLM). The effects of type and concentration of extractant/stripping agent i.e. PC88A/H2SO4 and Cyanex 272:TOPO/HNO3, pH in feed solution, flow patterns of feed and stripping solutions as well as flow rates of feed and stripping solutions were investigated. The optimum condition was identified and reported: PC88A/ H2SO4 hybrid at 4.5 pH of feed solution, 0.5 M PC88A as extractant, 1M H2SO4 in stripping solution and operating temperature of 303 K. For synergistic extractants, 0.5:0.5M/M of Cyanex 272:TOPO, 4 M HNO3 as stripping solution at 4.5 pH of feed solution and temperature of 303 K were reported. Flow rate of feed and stripping solution of 100 mL/min was found to be the most practical setup. In conjunction with the experimental work, a new model on convection, diffusion, reaction and accumulation was developed in order to predict the concentration of neodymium ions via HFSLM. Upon verification, the hypothetical concentration of neodymium ions in feed and stripping solutions aligned closely with the experimental results. Average standard deviations for extraction and stripping predictions were 1.9% and 1.2%, respectively. This robust model with its high accuracy provides a greater understanding of transport mechanism across the feed to the stripping solution; a design scale-up for industrial application could prove useful.