Studies on defluoridation of water by coal-based sorbents

Drinking water containing fluoride above a level of 1 mg dm(-3) is consider ed to be unsafe for human consumption. Higher intake of fluoride can cause potential health hazards. The conventional processes of fluoride removal fr om water are ion exchange, reverse osmosis and electro-dialysis. However, t he utility of these processes has been limited due to their expensive opera tion and subsequent disposal problem of the waste brine generated. Defluori dation of water samples by coal-based sorbents was studied at different ads orbent dosages. First-order adsorption rate constants using the Lagergren e quation, the Freundlich adsorption isotherm, the Langmuir adsorption isothe rm, film diffusion and pore diffusion coefficients have been evaluated for each system. The effect of pH on fluoride removal and the mechanism has als o been discussed. Copyright (C) 2001 Society of Chemical Industry.