A simple one-pot in-situ method for the synthesis of aluminum and lanthanum binary oxyhydroxides in chitosan template towards defluoridation of water

Aluminum and lanthanum binary oxyhydroxides on chitosan template (CS@ALMOH) was synthesized by greener in-situ one-pot method for defluoridation of drinking water. Characterization by FTIR, XPS, TGA/DSC and SEM with EDAX revealed that the material was a composite of chitosan and aluminum-lanthanum with primary particle size of micrometer level. The prepared material shows relatively fast adsorption kinetics to fluoride removal within 15 min, good adsorption capacity with wide pH ranges of 3-9 and selectivity. The mechanism of fluoride removal using the synthesized materials were by both electrostatic interaction as well as ion-exchange. Equilibrium sorption results were well described by Freundlich, Langmuir and D-R isotherms and the sorption capacities were approximately 49.54 mg/g for CS@ALMOH and 33.39 mg/g for ALMOH. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. This bifunctional adsorbent with aluminum and lanthanum oxyhydroxides impregnated onto chitosan polymeric matrix exhibits a pronounced fluoride adsorption capacity over already reported materials in the literature and the resulting CS@ALMOH material can be used in a broad pH range, which suggests its great potential for the decontamination of fluoride polluted water. The suitability of the CS@ALMOH material has been tested with the field samples collected in a nearby fluoride endemic area.