Separation of cobalt, neodymium and dysprosium using amorphous zirconium phosphate

Abstract

The purpose of this study was to investigate the separation of Co, Nd and Dy from a ternary Co-Nd-Dy solution using amorphous zirconium phosphate (am-ZrP). Am-ZrP was synthesized by a precipitation method at room temperature and subsequently characterized by Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, X-ray diffraction, solid-state 31P magic angle spinning nuclear magnetic resonance spectrometry and sodium hydroxide titration (with and without background salt). The ion exchange kinetics of am-ZrP that were determined in ternary 1mM equimolar solutions at equilibrium pH2.5. The effect of pH on the adsorption was studied in ternary 1mM equimolar solutions and the uptakes of the metals increased with increasing pH until approximately pH3.5. The adsorption isotherms of Co, Nd and Dy were tested in a series of ternary equimolar solution, the total uptake amounted to 4.13meq/g at pH ~3.0. The preference of am-ZrP for these metals occurred in decreasing order Dy>Nd≫Co. The separation of Co, Nd and Dy from their 1mM equimolar ternary mixture was investigated on an am-ZrP column. Effects of loading (7.8%, 62% and 100%) on the separation were compared by measuring the corresponding HNO3 elution fractions. It was found that with a lower metal loading of 7.8%, three clear elution bands were obtained. Am-ZrP exhibited selective separation properties towards the ternary Co-Nd-Dy system, which contribute to the future scale-up studies for the recycling of NdFeB magnets.