Removal of fluorine from red mud (bauxite residue) by electrokinetics

- The electrokinetic technique can remove fluorine from red mud efficiently.
- The removal efficiency of fluorine increased significantly with potential gradient.
- Electroosmosis is the main transport mechanism for the removal of red mud fluorine.

The feasibility of the electrokinetic treatment for the removal of fluorine from the red mud was evaluated. Three electrokinetic experiments were conducted in a self-made electrokinetic apparatus with deionized water as electrolyte, and the potential gradient was set at 0.5, 1.0 and 1.5 V/cm respectively. The effects of the potential gradient on the removal of fluorine and the chemicophysical properties of the red mud were investigated. The results revealed that the fluorine content in the red mud decreased gradually and the red mud properties such as pH and electrical conductivity (EC) were significantly redistributed from the cathode to the anode regions after the electrokinetic treatment. Among the given potential gradients the removal rate of fluorine increased with the potential gradient. 1.5 V/cm had the highest removal rate 63.2% and 1.0 V/cm had very significant and steady electroosmotic flow (EOF). This research shows that the electrokinetic treatment is a novel technique that has high efficiency and promising application for the removal of fluorine from the red mud.