Extraction of rare earth metal ions with an undiluted hydrophobic pseudoprotic ionic liquid

Abstract

Recovering and concentrating rare earth metals (Nd and Dy) from waste permanent magnets rather than discarding them into the environment without pretreatment is critical for metal recycling and environmental responsibility. In this work, we used an undiluted hydrophobic pseudoprotic ionic liquid composed of trioctylamine and decanoic acid as an extractant to separate rare earth metals from aqueous media with a solvent extraction technique. This ionic liquid proved to be excellent with low viscosity and extractability reaching 100% for Nd and Dy in the presence of salts like sodium chloride and sodium nitrate. In acidic media, extractability decreased with increasing acid concentrations. Under all our experimental conditions, the rare earth metals (Nd and Dy) were found to be preferentially extracted compared to nickel with the distribution ratios of Dy higher than those of Nd.