Abstract
Cerium is the largest constituent of the rare earth elements (REE) bearing ores, up to 50%. As such, Ce is overproduced by the industry in order to meet demand for less abundant REE required for advanced applications. Ce removal is the first step in REE purification, because the high fraction of Ce lowers the throughput of subsequent steps and negatively impacts manufacturing costs. Most chemical Ce separation methods are based on the low hydrolysis pH of Ce(IV) compared to the other trivalent lanthanides. The present work focused on cerium removal from a synthetic mixed REE sulphate solution representing a H2SO4 leach solution. Oxidation of Ce(III) was achieved with hydrogen peroxide (H2O2) followed by precipitation as Ce(OH)4 under controlled pH and Redox conditions. Batch tests revealed Ce removal levels between 50 and 90 %, and REE losses < 5 %, depending on the pH and H2O2 dosage. It was determined that Ce(III) oxidation was the rate limiting step, while Ce(IV) precipitation was fast and quantitative. The batch trials informed subsequent continuous tests.