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5075411 
Journal Article 
The oxidation and sorption mechanism of Sb on delta-MnO2 
Sun, Q; Liu, Cun; Alves, ME; Ata-Ul-Karim, ST; Zhou, DMei; He, JZ; Cui, PeiXin; Wang, YuJun 
2018 
Yes 
Chemical Engineering Journal
ISSN: 1385-8947 
342 
429-437 
WOS:000440404800043 
Manganese (Mn) oxide is considered as a potential regulator of the fate of many contaminants in soil due to its abundance and reactivity. The present study investigated the oxidation and sorption mechanisms of antimony (Sb) on delta-MnO2, by combining batch equilibrium experiments, kinetic experiments and various spectroscopic techniques. The collective results confirmed the high Sb(III)-oxidizing capacity of Mn(IV) sites on delta-MnO2 and the oxidation reaction was proton-driven. However, the oxidation process was gradually inhibited by the accumulation of manganese antimonate precipitates, the production of less reactive Mn(III), and the site-blocking effects of products Mn(II) and Sb(V) on the surface. Different from the direct sorption of Sb(V) by delta-MnO2, the oxidation of Sb(III) destroyed the surface structure of delta-MnO2 and exposed more reactive sites as evidenced by Xray powder diffraction (XRD) and transmission electron microscopy (TEM). The stronger Sb(V) sorption along with the oxidation of Sb(III), therefore, could be attributed to several binding modes, i.e., Mn(II) cation bridge, precipitation with Mn(II), along with inner-sphere complexations with surface Mn(IV) and Mn(III) sites. Sb(V) was sorbed at the edge sites of delta-MnO2 forming monodentate mononuclear complex with a configuration of MnO(H)-Sb(V) as confirmed by supplementary X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (EXAFS) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy techniques. The findings altogether help to contribute to a better understanding on the geochemical dynamics of Sb with delta-MnO2 in subsurface environment. 
Sb; Oxidation; Sorption; Manganese oxide