Fluoride removal from aqueous solution using Ce-modified red mud as adsorbent

Fluorine pollution has become an urgent global public health concern due to its adverse effects on aquatic organisms and human life, which raises the imperative demand for development of economical and efficient fluoride adsorbents. In this study, we demonstrate that solid waste of red mud (RM) originating from the aluminum industry can be converted into fluoride adsorbents by the integration of cerium-based compounds. Besides the adsorption kinetics and isotherm, the effects of adsorbent dosage, contact time, pH of solution, initial concentration, temperature, and competitive ions on the defluoridation performance of the absorbents have been systematically investigated. Benefitting from the strong affinity between cerium species and F- ions as well as the structure advantage, the optimized RM derived fluoride absorbents show the maximal adsorption capacity above 14.74 mg·g-1 at 298 K at pH=7. More importantly, our RM derived fluoride absorbents can be applied for the wastewater with heavy fluorine pollution (up to 60 mg·L-1), multiple interference ions (NO3-, SO42-, and Cl-), and wide pH range (2-8), which outperforms most RM based defluorination materials ever reported. The present work gives a full understanding of fluoride absorption behavior and mechanism, and also offers potential practical applications of the RM-derived functional materials for wastewater treatment.