Removal of Fluoride Wastewater by Capacitive Deionization

For water reclamation and for better water quality, development of advanced wastewater treatment technologies has been an important issue. Capacitive deionization (CDI) captures ions in the porous conductive materials in an electric field and thus remove ions from water. The captured ions can be released once the system is discharged. Compare to membrane filtration, CDI does not require large power consumption to overcome osmotic pressure and does not have fouling problems. Therefore, CDI, which was originally developed to deionize seawater and brackish waters, has also been found applications in wastewater treatment. We have studied the removal of fluoride from HF by CDI and found good removal efficiency. As there are always other anions in the fluoride wastewater, we would like to continue our study on the treatment of fluoride by CDI, especially on the effects of other anions on the removal of fluoride. Also, NH4F is also commonly used in the semiconductor industry. The oxidation/reduction and other reactions of NH3+ may introduce adsorption competition with fluoride or affect the removal of fluoride in CDI. Thus, in this work, the speciation of nitrogen in CDI will also be investigated. The reaction kinetics and removal of fluoride from real semiconductor wastewater will also be examined. The results of this work will provide knowledge of the performance of CDI on removal of fluoride and the development of water reclamation technology from fluoride wastewater via CDI.