Removal of fluoride from aqueous solutions by Eichhornia crassipes biomass and its carbonized form

The purpose of this paper is to suggest an efficient defluoridation process that does not require a large investment. The conventional processes of fluoride removal from water are ion exchange, reverse osmosis, and electrodialysis. However, the utility of these processes has been limited because of their expensive operation and subsequent problem of disposing of the waste being generated. Sorption is an effective technology for the treatment of industrial wastewater. Eichhornia crassipes and the activated carbon derived from this plant were examined to assess their capacity for the removal of fluoride from wastewater by batch techniques. Systematic batch studies on fluoride adsorption equilibrium and kinetics by E. crassipes and low-cost activated carbons prepared from E. crassipes were carried out. Studies were conducted to determine the optimum operating system parameters required for the establishment of columns such as contact time, dose, and size of the adsorbent. The adsorption of fluoride on noncarbonized and carbonized E. crassipes increases with increasing temperature (25, 35, 45 degreesC), thereby indicating that the process is endothermic in nature in all of the cases examined. The adsorption data were very well fitted by the Freundlich adsorption isotherm model. The Lagergren first-order rate equation was applied for the determination of the rate constants. Carbonized E. crassipes showed better removal efficiency than the noncarbonized plant. Further, the activation temperatures in the preparation of activated carbon played an important role. Carbon activated at 600 degreesC exhibited better performance than that activated at 300 degreesC. Column studies were also performed with an initial concentration of 15 ppm. The effluent volume at breakthrough was found to be 100 bed volumes, and the column capacity was calculated as 4.4 mg/g.