Activated Charcoal and Natural Soil Granules for Removing Fluoride from Aqueous Solution and Groundwater

Abstract Many effective and efficient treatment technologies have been applied for fluoride removal, but are found to be energy-intensive, expensive, requiring high operational and capital inputs, and need advanced technologies and skilled manpower. Adsorption, by contrast, is a flexible, efficient, simple-to design, and cost-effective treatment method. Many adsorbent types along with recently emerged nanoadsorbents represent a very promising treatment technology, but the limitations of this technology are still being studied. This implies that a lot of work is required by the scientific community to effectively apply this technology towards environmental sustainability, particularly in the water sector. In this work, thermally treated granular medium adsorbent prepared using combination of Regur soil, Omnibus soil and activated charcoal are used as adsorbent for defluoridation experiment. The fluoride reduction in aqueous solution after 1 h was 70% with adsorbent dosage of 4.8 g with 5 mg/L as the starting fluoride and 78% for groundwater sample with 3.6 mg/L starting fluoride. Reduction in fluoride was significantly observed for a pH range of 2 to 14, highest fluoride reduction was observed at pH range of 6 to 10. The isotherm model study gave better fit for Langmuir isotherm with regression parameter (R 2 = 0.98) than the Freundlich isotherm (R 2 = 0.84) which signifies monolayer adsorption. The study adhered to pseudo-second order kinetics. Surface morphology of the granular medium is also studied using SEM and EDAX and due to fluoride ions adsorption on the adsorbent surface there was textural change observed. This study indicated that thermally processesed soil and activated charcoal adsorbent was effective for defluoridation of aqueous solution with 70% reduction and groundwater with 78% reduction and hence can be used as cost effective adsorbent as naturally available materials with minimum processing are being used. However future research studies can be carried out with varying ratios of other efficient natural materials in order to increase the efficiency of defluoridation.