Adsorptive removal studies of fluoride in aqueous system by bimetallic oxide incorporated in cellulose

Abstract

Fluoride adulteration in drinking water has been established as one of the solemn problems across the world because it causes severe diseases like fluorosis. This study demonstrates fluoride adsorption using aluminium and lanthanum impregnated cellulose matrix (ALIC) prepared by ultrasound assisted technology (ALIC(U)) and co-precipitation (ALIC(P)) method. The ultrasonication technology is much faster than conventional methods. It enhances the surface area due to the cavitation effect and enhances the trapping of metal ions in the cellulose matrix by increasing the collision rate of metal ions and the biopolymer molecules. The surface areas of ALIC(U) and ALIC(P) were 196.91 and 130.93 m2/g, and the adsorption capacities of ALIC(U) and ALIC(P) were 88.67 and 33.33 mg/g, respectively. The adsorption mechanism is based on the participation of hydroxyl groups of cellulose and cationic metal hydroxide via H-bonding, ion-exchange, and ion-pair complexation. The equilibrium adsorption and kinetics studies have been performed to understand the mechanism and rate of adsorption of both ALIC (U and P). The rate constant of adsorption process for ALIC(U) and ALIC(P) is 0.135 g mg−1 min−1 and 0.04 min−1, respectively. The Gibbs free energy and entropy of ALIC (U and P) ensure the spontaneous and feasible nature of adsorption.