Precipitation Trends of Scandium in Synthetic Red Mud Solutions with Different Precipitation Agents

This research presents an alternative method for scandium (Sc) recovery from impure bauxite residue solutions containing Fe(III), Al, Ca, Nd, and Y through the use of hydroxide and phosphate precipitation. Among hydroxide donors, ammonia solution removed the most Fe(III) from solution, while co-precipitation of other elements in the synthetic pregnant leach solution remained negligible. When using dibasic phosphate as the precipitant, in the pH range of 1.5-2.5, both Sc and Fe were removed rapidly, while co-precipitation of other ions remained low. Experimental results were used to propose the preliminary design of a three-stage precipitation process capable of producing a scandium product from highly impure process solutions.