ADSORPTION OF FLUORIDE IONS FROM 0 WASTE WATER USING FLYASH

Abstract

Fluoride-related health hazards are a serious environmental problem across the globe. They can occur due to both natural as well as anthropogenic activities. Drinking water containing fluoride may be beneficial or detrimental depending upon its concentration and total amount consumed. Fluoride concentrations between 0.5-1 .5 rng/L are beneficial. especially to infants for the prevention of dental caries or tooth decay, but concentrations above 1.5 mg/L cause mottling of teeth in mild cases but fluorosis (dental or skeletal) and several neurological disorders in severe cases. Defluoridation is generally carried out by adsorption, chemical treatment. electrochemical methods. dialysis and the ion-exchange process. Among them. adsorption is found to be effective, environmental friendly and economical. Under the above backdrop. the present study has been undertaken to develop suitable fly ash adsorbent lbr dc-fluoridation from wastewater. In the continuing search to achieve the desired objective. Fly Ash was selected as a suitable adsorbent for dc-fluoridation from aqueous solutions. Batch experiments were performed to study the adsorption of fluoride ions on Fly Ash adsorbent. Characterization of adsorbent was carried out using various techniques such as XRF, BET Surface Area analysis. FTIR. XRD. and FE-SEM. Effects of process parameters like adsorbent concentration. contact time, pH, and temperature on the removal of fluoride ions from wastewater have been investigated using the above adsorbent to determine the optimum process conditions for maximum removal. The fluoride concentration of 20 mg/L is removed up to 94% by Fly Ash. Effects of initial fluoride concentration on the removal have also been investigated. Optimum adsorbent concentration for the removal of fluoride ions at agitation period of 30 miii is found to be I g/50 ml. To facilitate mathematical modelling adsorption kinetic models as well as adsorption isotherms have been developed. Adsorption of Fluoride ions on Fly Ash adsorbent has been found to follow pseudo second order kinetic model among the pseudo first order, pseudo second order, Weber-Morris model and Elovich model fitted to the experimental data. Amongst the conventional isotherms such as Langmuir, Freundlich and Temkin isotherms, the Langmuir isotherm gave better prediction of specific uptakes for Fluoride ions at equilibrium for Fly Ash adsorbent.