A novel electrochemical method for the removal of aluminum from ionic rare earth leachate

The separation of aluminum (Al) from ionic rare earth (RE) leachate is a complex challenge due to their similar chemical properties. Conventional industrial separation process required the use of chemical precipitant leads to considerable loss of RE. Herein, a novel cleaner approach of anionic membrane electrolysis (AME) combined with cyclone electrolysis for removal Al from ionic rare earth leachate was developed. The diffusion of RE3+ and neutralization of H+ and OH– were inhibited efficiently by the anionic membrane. Cyclone mixing reduced the loss of rare earth and improved Al removal compared with mechanical mixing. Working parameters including electrode speed, temperature, pH and Al concentration of catholyte, magnesium sulfate concentration and initial pH of anolyte were investigated to explore ways for more efficient Al removal and reduction of rare earth loss. Under the optimal conditions, the removal efficiency of Al and the loss ratio of RE were 93.3 % and 1.84 % respectively. The Al removal data was fitted to the pseudo-zero order model under optimal conditions, k was 0.409 mg·L−1·min−1. Loss of RE was attributed to the direct deposition on the electrode surface due to the high local pH of cathode. This work provides a new insight into the clean removal of Al impurity from actual RE leachate in magnesium sulfate system.