Removal of Fluoride from Aqueous Solution Using Aluminum-Impregnated Chitosan Biopolymer

Aluminum impregnated chitosan (AIC) was prepared and applied as an adsorbent for the removal of fluoride from aqueous solutions. The process involved two stages: (i) isolation of chitosan from chitin, (ii) impregnation of aluminum in isolated chitosan at fixed pH. SEM and EDS techniques were used to characterize the composition of adsorbent AIC. Dynamic adsorption experiments on AIC were carried out at various pH, contact times, adsorption dosages, and initial fluoride concentration to determine optimum adsorption properties. The experimental data were analyzed using two adsorption models, Langmuir and Freundlich, with the later system providing the best fit. Thermodynamic parameters showed the adsorption process as spontaneous and endothermic. The adsorption process follows first-order kinetics for which a mechanism has been proposed. Reusability of the AIC was tested up to four consecutive cycles. The desorption experiment showed 92% elution of adsorbed fluoride at a pH of 12. Finally, the performance of the adsorbent material was studied on field water samples collected from a fluorosis endemic-region.