REMOVAL OF FLUORIDE FROM INDUSTRIAL WASTE WATER

Abstract

Fluoride (F-) ion pollution in groundwater has become one of the most serious problems worldwide due to natural and anthropogenic activities. The prevalence of fluorosis is mainly due to prolonged intake of high concentration of fluoride (more than 1.5 mg/L) in drinking water.The problem is deteriorated due to the lack of appropriate and eco-friendly defluoridation technology. Many researchers have reported several physico and chemisorptions treatment technologies briefly, i.e. adsorption,ion-exchange,precipitation-coagulation,electrolytic defluoridation, electrodialysis and membrane processes such as reverse osmosis, nanofiltration, donnan dialysis for fluoride removal. In the continuing search to achieve the desired objective, RHA and AH coated RHA were selected as suitable adsorbent for defluoridation from aqueous solutions. Characterization of both adsorbents was carried out using various techniques such as BET Surface Area analysis, FTIR, XRD, FE-SEM and EDAX. 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 adsorbents to determine the optimum process conditions for maximum removal. To facilitate mathematical modelling adsorption kinetic models as well as adsorption isotherms have been developed. Adsorption of Fluoride ions on RHA and Al-I coated RHA adsorbents have been found to follow pseudo first order kinetic model for RICA and peudo second order for AH coated RHA. Amongst the conventional isotherms such as Langmuir and Freundlich, the Langmuir isotherm gave better prediction of specific uptakes for. Fluoride ions at equilibrium for RHA and Freundlich isotherm was better fit for AH coated RHA. The monolayer adsorption capacity (qmax) for RHA and AH coated RHA adsorbent was found to be 3.703 mg/g and 3.814 mg/g respectively.