Separation of fluorine/cerium from fluorine-bearing rare earth sulfate solution by selective adsorption using hydrous zirconium oxide

Abstract

Separation of fluorine/cerium from fluorine-bearing rare earth sulfate solution using selective adsorption was studied using hydrous zirconium oxide as an adsorbent. The relevant parameters studied for fluoride adsorption were the effects of contact time, pH, n_F/n_Ce ratio, initial fluoride concentration and coexisting ions. The material was characterized using XRD, SEM, EDS, Raman, FTIR and XPS. The Raman, FTIR and XPS spectra suggest that an ion-exchange reaction between the hydroxyl ion on hydrous zirconium oxide and fluoride is involved. Most of the fluoride adsorption takes place in the first 3 min. The adsorption capacities of fluoride and cerium both increase with an increase in solution pH, and the optimum pH is suggested to be 0.3–0.6. The loss of cerium is higher at a low n_F/n_Ce ratio. High initial fluoride concentration is unfavorable for the separation. The accompanied rare earth ions have no significant influence on the adsorption of fluoride. The adsorbed fluoride can be desorbed effectively with 0.1 mol l⁻¹ NaOH which shows utility of the adsorbent in a sustainable manner. In addition, the effectiveness of the method was also evaluated using real bastnaesite sulfuric acid leaching solution. This work presents a potential use of hydrous zirconium oxide for adsorption and separation of fluorine from cerium in fluorine-bearing rare earth sulfate solution and it is expected to eliminate the influence of fluorine on the extraction separation of rare earths.