Synthesis of metal ion entrapped silica gel/chitosan biocomposite for defluoridation studies.

This article focused on the development of silica gel/chitosan (SGCS) composite for fluoride removal. To enhance the fluoride selectivity of biocomposite, lanthanum-III (La) was incorporated into SGCS composite namely LaSGCS composite. A comparative evaluation of defluoridation capacity (DC) of LaSGCS composite, SGCS composite, silica gel (SG) and chitosan (CS) was made in batch mode. The results showed that LaSGCS composite possesses an enhanced DC of 4900 mg F-/kg whereas SGCS composite, SG and CS possess the DCs of 1556, 1296 and 52 mg F-/kg, respectively. The various equilibrium parameters, viz., contact time, pH, co-anions, different initial fluoride concentrations and temperature were optimized. The experimental data were analysed using various isotherms and kinetic models. The thermodynamic parameters have been calculated to find the nature of fluoride sorption. The mechanism of fluoride sorption by LaSGCS composite has been proposed. The sorbents were characterized using FTIR, XRD, TGA and SEM with EDAX analysis. A comparison of the DCs of the reported sorbents with that of LaSGCS composite has been made. Suitability of the fabricated biocomposite at field conditions was tested with a field sample taken from a nearby fluoride rife village. The present work provides a budding platform for the development of defluoridation technology.