Chitosan-Fe-Al-Mn metal oxyhydroxides composite as highly efficient fluoride scavenger for aqueous medium

Nano-particles are highly efficient fluoride adsorbents, but agglomerate easily due to their high surface activity and are difficult to separate from aqueous medium after use. Mixed-metals oxyhydroxides nano-particles were prepared into a natural polymeric matrix of chitosan to overcome these problems. Hydrous mixed-metal oxyhydroxides, loaded chitosan composite (Fe-Al-Mn@chitosan) was prepared using abundantly available laterite clay and waste from steel industry via co-precipitation method. Fluoride removal using Fe-Al-Mn@chitosan composite followed Freundlich isotherm model which revealed multilayer adsorption on heterogeneous surface sites. Fe-Al-Mn@chitosan exhibited maximum adsorption capacity of 40 +/- 0.5 mg/g, while if only the inorganic mass fraction of composite was considered; the value reached 55 +/- 0.5 mg/g. Fluoride adsorption on Fe-Al-Mn@ chitosan followed the pseudo-second order kinetics with rapid adsorption. No significant effect of other competitive ions was observed on F- adsorption using Fe-Al-Mn@chitosan composite. The composite adsorbent is found to be effective to produce drinking water from fluoride contaminated groundwater.