Selective Removal of Iron from Acid Leachate of Red Mud by Aliquat 336

Extraction of valuable rare-earth elements (REEs) from red mud is important for both resource recovery and waste treatment of red mud. However, the Fe present in red mud makes the extraction of REEs unsatisfactory, because Fe(III) is co-extracted and is difficult to remove. In this study, the feasibility and mechanism of selective removal of Fe from the acid leachate of red mud using Aliquat 336 were investigated. According to the theoretical calculation, Fe(III) mainly existed as FeCl3 species in a wide range of chloride concentrations, and the concentration of FeCl4− species significantly increased with chloride concentration. The extraction studies show that the chloride concentration strongly affects the extraction of Fe. The Fe removal efficiency is > 98% when the chloride concentration is 2.65 mol L−1, while the loss of REEs is < 7%. Dilute HCl acid was selected as the stripping agent; the stripping efficiency of Fe in one stripping stage reached > 90% under the optimal conditions.