“Since all methods [to remove fluoride] produce a sludge with very high concentration of fluoride that has to be disposed of, only water for drinking and cooking purposes should be treated, particularly in the developing countries.”
Reference: Fluorosis (see Interventions), World Health Organization
ABSTRACT: The fluoride removal ability of industrial waste (fly ash) from ground water was studied at different concentrations, contact times, reaction temperatures, adsorbent dosage, coexisting anions and pH of the solution. The rate constants of adsorption, intraparticle transport, mass transfer coefficients and thermodynamic parameters have been calculated at 303 K, 313 K and 323 K. The empirical model has been tested at various concentrations for the present system. The removal of fluoride is favourable at low concentration (5 ppm), high temperature (313 K) and under highly acidic conditions. The batch adsorption process fitted well the Langmuir isotherm and the adsorption kinetics followed the pseudo-second-order rate equation. The physicochemical properties of fly ash were characterized by X-ray diffraction, Fourier Transform infrared spectroscopy and scanning electron microscopy.