Removal of Sb(V) from complex wastewater of Sb(V) and aniline aerofloat using Fe₃O₄–CeO₂ absorbent enhanced by H₂O₂: efficiency and mechanism

Effective elimination of heavy metals from complex wastewater is of great significance for industrial wastewater treatment. Herein, bimetallic adsorbent Fe₃O₄–CeO₂ was prepared, and H₂O₂ was added to enhance Sb(V) adsorption by Fe₃O₄–CeO₂ in complex wastewater of Sb(V) and aniline aerofloat (AAF) for the first time. Fe₃O₄–CeO₂ showed good adsorption performance and could be rapidly separated by external magnetic field. After five adsorption/desorption cycles, Fe₃O₄–CeO₂ still maintained good stability. The maximum adsorption capacities of Fe₃O₄–CeO₂ in single Sb(V), AAF + Sb(V), and H₂O₂+AAF + Sb(V) systems were 77.33, 70.14, and 80.59 mg/g, respectively. Coexisting AAF inhibited Sb(V) adsorption. Conversely, additional H₂O₂ promoted Sb(V) removal in AAF + Sb(V) binary system, and made the adsorption capacity of Fe₃O₄–CeO₂ increase by 14.90%. H₂O₂ could not only accelerate the reaction rate, but also reduce the optimal amount of adsorbent from 2.0 g/L to 1.2 g/L. Meanwhile, coexisting anions had little effect on Sb(V) removal by Fe₃O₄–CeO2+H₂O₂ process. The adsorption behaviors of Sb(V) in three systems were better depicted by pseudo-second-order kinetics, implying that the chemisorption was dominant. The complexation of AAF with Sb(V) hindered the adsorption of Sb(V) by Fe₃O₄–CeO₂. The complex Sb(V) was oxidized and decomposed into free state by hydroxyl radicals produced in Fe₃O₄–CeO₂+H₂O₂ process. Then the free Sb(V) was adsorbed by Fe₃O₄–CeO₂ mostly through outer-sphere complexation. This work provides a new tactic for the treatment of heavy metal-organics complex wastewater.