Fluoride removal using Regenerated Spent Bleaching Earth (RSBE) from groundwater: Case study on Kuhbonan water

The aim of this study was to recover industrial waste (spent bleaching earth (SBE)) and use it as an adsorbent in fluoride removal from aqueous solution. Waste SBE was obtained from the oil industry, and acid and alkaline were used to recover it. Experiments were carried out in a batch system, and the effects of parameters including pH, adsorbent doses, fluoride initial concentration and contact time on the adsorption of fluoride using regenerated spent bleaching earth (RSBE) were examined. In addition, the optimum conditions obtained in this study were tested on Kuhbonan water. The results revealed that as the adsorbent dose, contact time and pH increased, the fluoride removal efficiency increased as well. The maximum fluoride adsorption was obtained at pH = 7 and an equivalent time of 180 min. Furthermore, when the fluoride initial concentration in water increased, fluoride removal efficiency decreased. The maximum adsorption capacity of RSBE was 0.6 mg/g fluoride (2.5–8 mg F−/L, 10 g RSBE/L and pH = 7). The kinetics analysis showed that the rate of fluoride adsorption on RSBE was 0.64 mg/g·min0.5. In addition, the results showed that when 10 g RSBE/L was added to Kuhbonan water, fluoride residual can reach levels allowable by WHO guidelines.

Research highlights
► Recovery of waste soils.
► Adsorption of fluoride.
► Water treatment.