Abstract
The environmental mobility of antimony (Sb) is largely unexplored in geochemical environments. Iron oxide minerals are considered major sinks for Sb. Among the different oxidation states of Sb, (+) V is found more commonly in a wide redox range. Despite many adsorption studies of Sb (V) with various iron oxide minerals, detailed research on the adsorption mechanism of Sb (V) on hematite using macroscopic, spectroscopic, and surface complexation modeling is rare. Thus, the main objective of our study is to evaluate the surface complexation mechanism of Sb (V) on hematite under a range of solution properties using macroscopic, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic, and surface complexation modeling. The results indicate that the Sb (V) adsorption on hematite was highest at pH 4–6. After pH 6, the adsorption decreased sharply and became negligible above pH 9. The effect of ionic strength was negligible from pH 4 to 6. The spectroscopic results confirmed the presence of inner- and outer-sphere surface complexes at lower pH values, and only outer-sphere-type surface complex at pH 8. Surface complexation models successfully predicted the Sb (V) adsorption envelope. Our research will improve the understanding of Sb (V) mobility in iron-oxide-rich environments.
Highlights
Published: 21 March 2021Elevated concentrations of antimony (Sb) in soil, sediments, and water bodies occur due to heavy mining operations and the subsequent use of antimony (Sb) in many industrial applications [1,2,3]
Antimony (Sb) is used as a hardening agent in lead bullets, and Sb is released into the environment when the bullets corrode [4,5]
Greatly elevated concentrations of Sb in the soil (17,500 mg kg−1 ) due to anthropogenic activities compared to background concentrations (0.05–0.22 mg kg−1 ) have been reported [9]
Summary
Elevated concentrations of antimony (Sb) in soil, sediments, and water bodies occur due to heavy mining operations and the subsequent use of antimony (Sb) in many industrial applications [1,2,3]. Another well-established contamination source has been linked to military and civilian shooting ranges. Among the two major oxidation states (III and V) of Sb in the geochemical environments, Sb (V) is reported as the most dominant species prevalent in wide redox range (360 to −140 mV) while Sb (III) is considered to be more toxic [1,10,11,12,13,14].
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