Removal of fluoride from aqueous solution using granular acid-treated bentonite (GHB): batch and column studies.

Removal of fluoride from aqueous solution using granular acid-treated bentonite (GHB) was studied by batch and column adsorption experiments. The results of the batch adsorption experiments demonstrated that the maximum fluoride removal was obtained at pH of 4.95 and it took 40 min to attain equilibrium. Kinetics data fitted pseudo-second-order model. Batch adsorption data was better described by Redlich-Peterson and Freundlich isotherm models than Langmuir isotherm model. The adsorption type of GHB was ion exchange. Column experiments were carried out at different influent fluoride concentrations and different flow rates. The capacities of the breakthrough and exhaustion points increased with the decrease of flow rate and the increase of initial fluoride concentration. The experimental results were well fitted with Thomas model. Exhausted GHB was regenerated by alkali/alum treatment. The total sorption capacity of GHB was increased after regeneration and activation.