Selective sorption of fluoride using Fe(III) loaded carboxylated chitosan beads

Chitosan beads (CB) as such have very low defluoridation capacity (DC) of 52 mgF−/kg have been suitably modified by carboxylation followed by chelation with Fe3+ ion (Fe-CCB), in order to effectively utilize both hydroxyl and amine groups for defluoridation. The modified beads showed enhanced DC to a very significant level of 4230 mgF−/kg. The fluoride removal process is governed by both adsorption and complexation mechanism. The sorbent was characterized using Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM) analysis. The experimental data have been analysed using isotherm and kinetic models. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated to predict the nature of sorption. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village.

Graphical abstractFe(III) loaded carboxylated chitosan beads (Fe-CCB) possesses higher defluoridation capacity than the raw chitosan beads. The fluoride selectivity of Fe-CCB is mainly due to the simultaneous process of both adsorption and complexation. This is a new dimension in the field of fluoride removal.Figure optionsDownload full-size imageDownload as PowerPoint slide