Removal of Fluoride in Water Using Activated Carbons Prepared From Selected Agricultural Waste Materials

Abstract

Water is essential to life, but many people do not have access to clean and safe drinking water and many die of water borne or water related infections. Fluoride is one of the anionic contaminants which are found in excess in both surface and groundwater due to geochemical reactions and anthropogenic sources like industrial wastewater disposal. Many methods like coagulation, precipitation, membrane processes, electrolytic treatment and ion – exchange are some of the methods used for the defluoridation of water. But the most widely used method is the adsorption process. Though various conventional and non-conventional adsorbents have been assessed for the removal of fluoride from water, this research aims to promote innovative use of local raw materials and relatively low cost techniques in the production of activated carbons for fluoride adsorption. Activated carbons were prepared from coconut shells, cocoa pod husks and palm kernel shells by carbonisation of the residues to obtain chars which were activated at 900 ^o C using steam as the activating agent. Analysis of fluoride was done before and after treating water with the derived activated carbons. The water treatment experiment using fluoride as a model pollutant demonstrated that activated carbons prepared from agricultural waste materials have a good potential for fluoride removal. Adsorption of fluoride was also found to be influenced by the type and concentration of other ions in the treated water.

Keywords: fluoride, adsorption, carbons, waste, pH, ions, fluorosis, Langmuir isotherms.