Recovery of rare earth from ion-adsorption rare earth ores with a compound lixiviant

Abstract

The present research investigates the use of ammonium nitrate and ammonium sulfate as a compound lixiviant, and ammonium acetate as an inhibitor for aluminum in the recovery of rare earth elements from ion-adsorption rare earth ores. It is previously shown that rare earth ions, adsorbed physically on ion-adsorption rare earth ores, could be easily recovered via an ion exchange mechanism with inorganic monovalent salt solutions. A standardized desorption procedure was established to systematically investigate the effects of elution conditions such as compound lixiviant concentration, ammonium nitrate/ammonium sulfate molar ratio, particle size, elution flow rate, pH and inhibitor concentration on the leaching of rare earth and aluminum. It was determined that the leaching rate of rare earth exceeded 80% under the optimum elution conditions: particle size <74μm, compound lixiviant concentration 2.0%, ammonium nitrate/ammonium sulfate molar ratio 4:1, pH 5.5, ammonium acetate concentration 0.05%, elution flow-rate 0.5ml/min and room temperature. At these conditions, the inhibition rate of aluminum exceeded 80%.