Preparation and characterization of red mud sintered porous materials for water defluoridation

This research was undertaken to characterize a porous material prepared from red mud and to investigate the capacity of zirconium hydroxide-modified red mud porous materials (Zr-modified RMPMs) for the removal of fluoride from aqueous solutions. An organic foam template was used for the preparation. After sintering, the RMPM had a porosity up to 80 % with the pore size controlled between 50 and 100 μm. Batch experiments were performed to study the defluoridation of water using Zr-modified RMPM under various experimental conditions. Kinetic data revealed that the equilibrium for fluoride removal was achieved within 60 min. The fluoride sorption process was well fitted to the pseudo-second-order rate kinetics and pore diffusion models. The optimum fluoride removal was observed between pH range 3 and 4 and the adsorption capacity for fluoride by Zr-modified RMPM was 0.6 mg/g. Results from this study demonstrated potential use of Zr-modified RMPM in defluoridation of drinking water.

► A porous material (RMPM) was prepared for the removal of fluoride.
► Zirconium hydroxide can be better adhered to three-dimensional space of the RMPM.
► The fluoride adsorption by the Zr-modified RMPM is essentially chemical adsorption.
► The material could be regenerated via NaOH solution, and desorption rate reaches 85%.