Removal of fluoride from acidic wastewater by clay mineral: Effect of solid-liquid ratios

The ability of three Tunisian clays (H, MK and ZB) to remove fluoride from acidic waste solution has been investigated. The studies were carried out as functions of solid-liquid percentage (10, 20 and 30%), contact time, pH and effect of concentrations of other ions. The kinetic study shows that the percentage of fluoride removed increased with the agitation time. The equilibrium was achieved within 48 h minimum and the highest adsorption was reached for MK clay for clay-lixiviat suspension of 10%. Moreover, for all samples, the fluoride adsorption obeyed the Langmuir isotherm model. On the other hand, the influence of other ions on fluoride removal depends of the relative affinity of the ions by the type of clays and the relative concentrations of these ions.