| Summary: | In this study, iron oxide (Fe<sub>3</sub>O<sub>4</sub>) was coated with ZrO<sub>2</sub>, and doped with three rare earth elements((Y/La/Ce), and a multi-staged rare earth doped zirconia adsorbent was prepared by using uniform design U<sub>14</sub>, Response Surface methodology, and orthogonal design, to remove As<sup>3+</sup> and As<sup>5+</sup> from the aqueous solution. Based on the results of TEM, EDS, XRD, FTIR, and N<sub>2</sub>-adsorption desorption test, the best molar ratio of Fe<sub>3</sub>O<sub>4</sub>:TMAOH:Zirconium butoxide:Y:La:Ce was selected as 1:12:11:1:0.02:0.08. The specific surface area and porosity was 263 m<sup>2</sup>/g, and 0.156 cm<sup>3</sup>/g, respectively. The isothermal curves and fitting equation parameters show that Langmuir model, and Redlich Peterson model fitted well. As per calculations of the Langmuir model, the highest adsorption capacities for As<sup>3+</sup> and As<sup>5+</sup> ions were recorded as 68.33 mg/g, 84.23 mg/g, respectively. The fitting curves and equations of the kinetic models favors the quasi second order kinetic model. Material regeneration was very effective, and even in the last cycle the regeneration capacities of both As<sup>3+</sup> and As<sup>5+</sup> were 75.15%, and 77.59%, respectively. Adsorption and regeneration results suggest that adsorbent has easy synthesis method, and reusable, so it can be used as a potential adsorbent for the removal of arsenic from aqueous solution.
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