Novel carbonized bone meal for defluoridation of groundwater: Batch and column study

Low cost naturally available bone meal was carbonized and its fluoride adsorption capacity was explored. Carbonized bone meal (CBM) produced at 550°C, 4 h carbonization time and a heating rate of 60°C/min, showed fluoride adsorption capacity of 14 mg g^-1. Adsorbent was characterized using scanning electron microscopy, X-ray diffraction, X-ray fluoroscence, thermogravimetric analysis and Fourier transform infrared spectroscopy to highlight its physical and chemical properties. Best fluoride uptake capacity was observed for 0.2 mm particle size, 7 g L^-1 adsorbent concentration and at pH 6.5. Fluoride uptake was endothermic and chemisorption in nature. Effective diffusivity and mass transfer coefficient were obtained as 6 × 10^-11 m² s^-1 and 9 × 10^-5 m s^-1 from shrinking core model. Sulphate and carbonate showed the highest interference effect on adsorption of fluoride by CBM. Maximum desorption was observed at basic pH (pH 12). Fixed bed study was performed and effect of different parameters (bed height, inlet flow rate and initial concentration) was investigated. Efficiency of the adsorbent using real life fluoride contaminated groundwater solution was also observed.