Mitigation of Fluoride Contamination in Drinking Water Supply Sources by Adsorption Using Bone Char: Effects of Mineral and Organic Matrix

This study focused on fluoride (F-) contamination of water sources in Bahimi village, Cameroon. After the first investigation, results revealed that all water samples collected had elevated concentrations of fluoride ions (2.3 +/- 0.1) mg/L to (4.5 +/- 0.2) mg/L above the WHO guidelines (less than 1.5 mg/L). To mitigate the F- levels, the use of bone char (BC) as an adsorbent material was proposed and its performance was tested. BC was prepared from bovine bones at different calcination temperatures (350 degrees C, 450 degrees C, 550 degrees C and 650 degrees C) and residence times (1 h and 2 h). The prepared materials were characterized in detail by SEM/EDS, BET, FTIR, and XRD. The BET findings indicated that the surface area of BC samples decreased with increasing calcination temperature and residence time. At a lower heating temperature and holding time (350 degrees C, 1 h), the prepared BC exhibited a higher specific surface area (112.3 +/- 0.3) m2/g and adsorption capacity for F- in the sampled water. Also, the batch adsorption experiments showed that the optimized adsorbent dose of 8 g/L facilitates the reduction in the F- level of the sampled water below the acceptable limit level (1.5 mg/L) within 5 min of treatment. The presence of Ca2+ and Mg2+ in natural water has a positive effect on the removal of F- in BC resulting in a high adsorption performance range of (72.5 +/- 1.4)% to (80.3 +/- 0.6)%. It was found that the adsorption of Ca2+ on the BC surface occurs via cation exchange with Na+. However, an increase in dissolved organic carbon (DOC) in the treated water limited the application of BC. Overall, the study presented a cost-effective adsorbent for the removal of this recalcitrant ion in the water source.