Comparison of aluminum modified natural materials in the removal of fluoride ions

[Display omitted] •F− removal was determined by natural and Al modified hematite, zeolite and calcite.•Adsorption kinetic data were best fitted to pseudo-second order and Elovich models.•The sorption isotherms data were best fitted to Langmuir–Freundlich model.•The adsorption of fluoride was chemisorption on heterogeneous materials.•Aluminum modified zeolite shows the best characteristics for removal of fluoride. The removal behaviors of fluoride ions from aqueous solutions and drinking water by aluminum modified hematite, zeolitic tuff and calcite were determined. Drinking water containing naturally 8.29mg of fluoride ions per liter was characterized. The hematite, zeolitic tuff and calcite were aluminum modified by an electrochemical method. The effects of contact time and the dose of adsorbent were determined. The PZC (point of zero charge) values for aluminum modified hematite, zeolitic tuff and calcite were 6.2, 5.8 and 8.4, respectively. Adsorption kinetic data were best fitted to pseudo-second-order and Elovich models and equilibrium data to Langmuir–Freundlich isotherm model. The highest fluoride sorption capacities (10.25 and 1.16mg/g for aqueous solutions and drinking water respectively) were obtained for aluminum modified zeolite with an adsorbent dosage of 10g/L and an initial F− concentration of 9 and 8.29mg/L for aqueous solutions and drinking water respectively (the final concentrations were 0.08 and 0.7mg/L respectively). The main mechanism involved in the adsorption of fluoride ions is chemisorption on heterogeneous materials according to the results obtained by fitting the data to kinetic and isotherm models respectively. Aluminum modified zeolitic tuff showed the best characteristics for the removal of fluoride ions from water.