DEFLUORIDATION BY SORPTION ON AGGRO-WASTE CARBONS

Abstract

Fluoride in water is one of the dissolved chemical impurities which has a peculiar importance. Its presence to an optimum level is desired in the drinking water but excess has adverse effects on the health of human beings and animals. World Health Organization (W.H.O.) has recommended an optimum concentration of fluoride in drinking water between 1.0 - 1.5 mg/1, but the recent reports from various parts of the world are emphasizing on the unsuita-bility of W.H.O. guidelines for fluoride concentration in drinking water. We have also data in India to suggest that even 0.4 mg/1 of fluoride in drinking water is causing mild, moderate and severe forms of dental fluorosis and therefore we are looking for water with less and less fluoride contamination. Thus defluoridation of water is must as a public health measure. For this purpose various techniques have been developed in India as well as other parts of the world. We are looking for more economical methods to tackle this problem. Methods tried for defluoridation of water can be of three basic types viz. adsorption, ion exchange and precipitation. Adsorption on two agro-waste carbons (rice husk and corn cab) have been studied, as it is quite clear that these two materials could give an econo- mic means two tackle this problem. Fluoride adsorption capacity of the two materials and effects of various factors such as sorption time, sorbent size, sorbate and sorbent concentrations have been studied.