Removal of fluoride from aqueous solution using nanoscale rice husk biochar

Fluoride (F^-) is a geogenic contaminant which is reported to be hazardous for human health. Considering the present groundwater F^- contamination scenario particularly in India, development of a technology for efficient F^- removal is an urgent need. The present study assessed the suitability of nanosized rice husk biochar in removal of F^- from aqueous solution. The nanoscale adsorbent prepared by a facile technique showed very high removal efficiency (90% removal) using minimum adsorbent dose (1 g L⁻¹) and less contact time period (60 min). The sorption equilibrium data fitted well to both Freundlich (R² = 0.995) and Langmuir (R² = 0.991) isotherm models. The maximum adsorption capacity observed were 12.6 mg g⁻¹ and 21.7 mg g⁻¹ for Freundlich and Langmuir respectively, Nanosized rice-husk biochar showed better adsorption capacity as compared to other biomass based adsorbents. The sorption data showed better fit to the pseudo second-order kinetics as compared to the pseudo first-order kinetic model. The novel nanomaterial derived from an agricultural waste product could remove F^- from aqueous solution in a promising and cost-effective way indicating that it might be an excellent choice for the removal of F^- from contaminated groundwater.