Removal of fluoride from drinking water by a chitin-based biocomposite in fixed-bed columns

Abstract

A detailed fluoride adsorption study in packed columns with chitin or a chitin-based biocomposite is reported. The biocomposite was preconditioned by an acidification process, which produced a suitable material to be used in a continuous fluoride adsorption process.An empty bed contact time (EBCT) of 20min was determined as adequate. The fluoride concentration of the artificially prepared influent was 5.1mg/L. About 200 and 300 bed volumes of contaminated water were treated before saturation of packed columns with biocomposite or chitin, respectively. Fluoride was desorbed from the fluoride exhausted chitin and biocomposite by using a NaOH solution as eluent: the regeneration efficiencies were 85 and 84% for chitin and biocomposite, respectively. Finally, continuous fluoride adsorption experiments were carried out with natural fluoride contaminated water (3.9mgfluoride/L). The chitin and biocomposite fluoride selectivity was determined as follows: SO42−>HCO3−>F−>Cl−>NO3−.Results of this study confirmed the potential of chitin-based biocomposites as adsorbents materials of fluoride and other anions present in water. However, the preconditioning of the biocomposite should be considered.