Highly efficient adsorption of Sb(iii) and Sb(v) from water using a hybrid functional Zr–Fe metallic oxide composite

Abstract

For the removal of highly toxic and non-degradable metalloid antimony (Sb), many metal oxides as low-cost adsorbents have been studied; however, their adsorption capacity is still unsatisfactory for application. In this work, a novel hybrid functional Zr–Fe metallic oxides (HF-ZFOs) composite was successfully prepared by a solvothermal method for the removal of Sb(III) and Sb(V) from water. Adsorption experimental data show that the maximum adsorption capacity for Sb(III) and Sb(V) is 114.05 and 157.13 mg g⁻¹, respectively. The Freundlich and Temkin isotherm model can well describe the adsorption process of Sb(III) and Sb(V), respectively. The kinetic data followed the pseudo-second-order model. The adsorption process was a spontaneous endothermic reaction. Coupled with the IR and XPS results, the mechanisms of the HF-ZFOs composite for Sb(III) and Sb(V) are attributed to the following: (i) the surface functional groups (ZrO(OH) and FeO(OH)) on the HF-ZFOs composite were protonated to form Zr⁴⁺, ZrO(OH)⁺ and FeO(OH)⁺, which can increase the surface positive charges and be effective adsorption sites to capture the anions (SbO₃⁻) from aqueous solution; (ii) electron transfer of Sb(III) to Fe(III) oxyhydroxide occurred in solution, leading to partial oxidation of Sb(III) to Sb(V); (iii) the electrostatic attraction and surface complexation between them eventually resulted in a better adsorption capacity.