Removal of Antimonite (Sb(III)) and Antimonate (Sb(V)) from Aqueous Solution Using Carbon Nanofibers That Are Decorated with Zirconium Oxide (ZrO₂)

Zirconium oxide (ZrO₂)-carbon nanofibers (ZCN) were fabricated and batch experiments were used to determine antimonite (Sb­(III)) and antimonate (Sb­(V)) adsorption isotherms and kinetics. ZCN have a maximum Sb­(III) and Sb­(V) adsorption capacity of 70.83 and 57.17 mg/g, respectively. The adsorption process between ZCN and Sb was identified to be an exothermic and follows an ion-exchange reaction. The application of ZCN was demonstrated using tap water spiked with Sb (200 μg/L). We found that the concentration of Sb was well below the maximum contaminant level for drinking water with ZCN dosages of 2 g/L. X-ray photoelectron spectroscopy (XPS) revealed that an ionic bond of Zr–O was formed with Sb­(III) and Sb­(V). Based on the density functional theory (DFT) calculations, Sb­(III) formed Sb–O and O–Zr bonds on the surface of the tetragonal ZrO₂ (t-ZrO₂) (111) plane and monoclinic ZrO₂ planes (m-ZrO₂) (111) plane when it adsorbs. Only an O–Zr bond was formed on the surface of t-ZrO₂ (111) plane and m-ZrO₂ (111) plane for Sb­(V) adsorption. The adsorption energy (E_ad) of Sb­(III) and Sb­(V) onto t-ZrO₂ (111) plane were 1.13 and 6.07 eV, which were higher than that of m-ZrO₂ (0.76 and 3.35 eV, respectively).