Green synthesized iron oxide nanoparticles from natural magnetite: an effective adsorbent for fluoride removal in aqueous phase

Abstract

Removing fluoride from contaminated water is critical to safe drinking water as it is one of the harmful elements to health. In this study, iron oxide nanoparticles (IONP) synthesized using an environmentally friendly method were used to defluoridate fluoride-contaminated water. This study used Camellia sinensis (tea) leaf extract as a reducing agent to produce IONP from natural magnetite. Scanning electron microscopy observations showed the formation of spherical and sub-spherical IONP aggregates in the range of 40–100 nm. With a contact time of 30 min at or near neutral pH, over 90% of the fluoride was removed from the aqueous medium when an adsorbate dose of 5 g/L was used. The fluoride removal agreed reasonably well with the pseudo-second-order kinetic model. Since the zero-point charge of the IONPs was 8.15, the fluoride adsorption was higher at acidic pH. The adsorption process was exothermic as the extent of defluoridation was on the order of 293 > 298 > 303 K. Coexisting chloride had an unfavourable effect on fluoride removal, but adsorption occurred quickly. The present study confirmed the successful synthesis of IONP from natural magnetite using tea leaf extract, representing a more environmentally friendly approach than existing methods. Since synthesized IONPs can effectively remove fluoride from water, this method can be used to develop a fluoride removal filter that can be used at the household level.