Adsorptive removal of fluoride ions from aqueous solution by using sonochemically synthesized nanomagnesia/alumina adsorbents: An experimental and modeling study

• Wet impregnation followed by sonochemical approach was applied.
• A new, layered berry like MgO/γ-Al2O3 nanocomposite (13–25 nm) was synthesized.
• Higher defluoridation rate and adsorption capacity of the nanosorbent.
• Langmuir type behavior in the batch adsorption equilibrium tests.
• The better fitness of linear pseudo second order kinetic model.

Wet impregnation followed by sonochemical approach was applied to dope γ-Al2O3 with MgO nanocrystals in order to synthesize a new and more efficient fluoride nanosorbent (4–30 nm). The effects of operating conditions such as pH, fluoride concentration, contact time and dosage were studied. The adsorbents were characterized by using the pHZPC measurement and FTIR, HR-SEM, XRD, EDAX, and BET analyses. The optimum fluoride removal (>85%), adsorption capacity of ∼5.6 mg/g, was obtained at 140 min, neutral pH range of 6.3–7.3, and adsorbent dosage of 0.5 g/L. The isomorphic substitution of OH− of brucite in the nanosorbent with fluoride ions could be herein the dominant sorption mechanism. Furthermore, other ions (Cl−, SO42−, HCO3−, PO43−) in the solution had very little interference in the fluoride adsorption. However, PO43− was the greatest competitor for fluoride adsorption. Finally, the experimental adsorption equilibrium and kinetic data were closely followed the Langmuir adsorption isotherm and pseudo second order kinetic model respectively.