Fe 3 O 4 superparamagnetic nanoparticles (NPs) modified with zirconia (ZrO 2 ) were synthesized (Fe 3 O 4 @ZrO 2 ) using a chemical co-precipitation method and used as nanoadsorbent in removal excessive fluoride from aqueous solutions. This adsorbent combines the advantages of magnetic nanomaterial and Fsorbent floc, with magnetic separability and high affinity toward fluoride, which provides distinctive merits including easy preparation, high adsorption capacity, and easy isolation from sample solutions by the application of an external magnetic field. The prepared Fe 3 O 4 @ZrO 2 magnetic nanoparticles were characterized by XPS, XRD, SEM, EDXA, BET, FTIR, and VSM techniques. Affecting parameters on removal of fluoride, such as mass ratio of Fe 3 O 4 to ZrO 2 , solution pH, adsorption time, initial fluoride concentration, and co-existing anions were investigated. The high adsorption capacity calculated by Langmuir equation was 158.6 mg g -1 for Fe 3 O 4 @ZrO 2 (2:5) in pH 2.5. The adsorption capacity increased with temperature and the kinetics followed a pseudo-secondorder rate equation. The enthalpy change (∆H 0 ) and entropy change (∆S 0 ) was 25.02 kJ mol −1 and 3.76 J mol −1 K −1 , which substantiates the endothermic and spontaneous nature of the fluoride adsorption process. Furthermore, the residual concentration of fluoride using Fe 3 O 4 @ZrO 2 NPs as adsorbent could reach 0.3 mg L −1 with an initial concentration of 20 mg L −1 . Also application of Fe 3 O 4 @ZrO 2 NPs for removal of fluoride from real samples was tested. All of the results suggested that the Fe 3 O 4 @ZrO 2 NPs with strong and specific affinity toward fluoride could be excellent adsorbent for treatment of fluoride contaminated water.

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