Evaluation of Defluoridation of Water by Adsorption with Sugarcane Bagasse derived Activated Carbon

Sustained consumption of water with fluoride concentrations above the WHO guideline value of 1.5 mg/L is of health concern because of its contribution to dental and skeletal fluorosis, and neurological and thyroid disorders. Accordingly, the development of a cost-effective, locally available and environmentally benign adsorbent for fluoride removal from water is of importance. In the present study, oven dried and ground sugarcane bagasse was calcined at 500°C for 2 hours and then activated with 30% aqueous solution of phosphoric acid. The resulting sugarcane bagasse derived activated carbon (SBAC) was characterized by proximate analysis, ultimate analysis, nitrogen adsorption, scanning electron microscopy, FT-IR spectroscopy, and X-ray diffraction. The potential for fluoride removal from water with SBAC was evaluated for adsorbent dosage, contact time, pH and initial fluoride concentration. Calcination and activation increased fixed carbon concentration from 19.1 to 69.7%. Pore volume and BET surface area measurement showed that micropores accounted for 84% of the total pore volume. The FTIR spectrum revealed the presence of surface functional groups including C=C, P–O-C and P–O–P, which could play a significant role in the SBAC sorption of fluoride. The SBAC applied at 20 g/250 ml of water, 5 h contact time and pH 5 reduced the fluoride concentration in fluoride simulated water by 86% from 7.0 to 0.98 mg/L. A lesser removal of 82.7% was observed for natural groundwater with 6.7 mg/l fluoride concentration and was attributed to competition for active sites by coexisting ions. The Langmuir isotherm did not adequately describe the adsorption data suggesting a lack of uniformity on the adsorption surface.