Studies on defluoridation of water by coal-based sorbents

Drinking water containing fluoride above a level of 1 mg dm(-3) is considered to be unsafe for human consumption. Higher intake of fluoride can cause potential health hazards. The conventional processes of fluoride removal from water are ion exchange, reverse osmosis and electro-dialysis. However, the utility of these processes has been limited due to their expensive operation and subsequent disposal problem of the waste brine generated. Defluoridation of water samples by coal-based sorbents was studied at different adsorbent dosages. First-order adsorption rate constants using the Lagergren equation, the Freundlich adsorption isotherm, the Langmuir adsorption isotherm, film diffusion and pore diffusion coefficients have been evaluated for each system. The effect of pH on fluoride removal and the mechanism has also been discussed. Copyright (C) 2001 Society of Chemical Industry.