[Fluoride Removal Efficiency of Novel Material:Magnetite Core/Zirconia Shell Nanocomposite]

Magnetite core/zirconia shell nanocomposite (abbreviated as Fe₃O₄@ZrO₂ hereafter) was obtained using one-step co-precipitation method and its performance for removal of fluoride ion from water was studied. The results showed that the Langmuir maximum adsorption capacity of fluoride ion by Fe₃O₄@ZrO₂ was 35.46 mg·g^-1, which was far higher than those of magnetite, activated alumina and activated carbon. Studies of adsorption kinetics indicated that the adsorption of fluoride ion by Fe₃O₄@ZrO₂ was fast and could be well described by the pseudo-second-order model. The adsorption process of fluoride ion was an endothermic reaction. The adsorption of fluoride ion by Fe₃O₄@ZrO₂ decreased with increasing pH. Chloride, nitrate and sulfate anions, which commonly coexist in drinking water, had little effect on F^- adsorption, although the coexistence of HCO₃^- and CO₃^2- reduced the adsorption significantly by increasing the pH of the solution system. The fluoride adsorbed by Fe₃O₄@ZrO₂ could be successfully desorbed with 1 mol·L^-1 NaOH solution as desorption agent. The desorption rate reached 99.5%-99.6%. The F^--desorbed Fe₃O₄@ZrO₂ could be reused for the removal of F^- after regeneration via restoring the protonation status of surface hydroxyl groups on hydrous zirconia. The removal efficiency of fluoride by Fe₃O₄@ZrO₂ from actual well water was lower than that from pure water, but concentration limit for fluoride in drinking water could still be attained by increasing the dosage to a sufficiently high level. Fe₃O₄@ZrO₂ is a promising material for fluoride removal due to its good performance, simple preparation method and easy separation from water by providing an external magnetic field.