Antimony (V) Adsorption at the Hematite–Water Interface: A Macroscopic and In Situ ATR-FTIR Study

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.

Antimony Isotope Fractionation Revealed from EXAFS during Adsorption on Fe (Oxyhydr)oxides

“…Therefore, the amount of Sb adsorbed on each oxide under acidic conditions is greater than under basic conditions. A similar observation was made for Sb on Fh, Goe, and Hem in previous adsorption edge studies. , …”

“…Previous studies using crystal truncation rod X-ray diffraction report similar results for Sb and Hem at pH 5.5 . However, Mierzwa et al demonstrate inner- and outer-sphere complexation at pH 5–7 yet only outer-sphere complexation at pH 8 using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and surface complexation modeling. This differs from our results under alkaline conditions, likely due to the different Sb/Fe molar ratios and characterization methods.…”

“…Crystal truncation rod X-ray diffraction showed Sb is bound by edge and corner-sharing on Hem at pH 5.5 . Recently, Mierzwa et al concluded that Sb adsorbs on Hem as inner and outer-sphere surface complexes at pH 5–7 but only as an outer-sphere complex at pH 8. These studies reveal Sb­(V) complexes with Fh as a strong inner-sphere complex, whereas the inner- and outer-sphere complexes formed with Hem and Goe are pH-dependent.…”

Bio‐Based Hybrid Catalysts for the Synthesis of Pharmacologically Active Xanthenes

“…An extremely sharp band was seen at 572 cm −1 for FT‐IR spectra of both the nano linear dextrin (a) and Fe 3 O 4 @NLD (b), corresponding to stretching vibrations of the Fe−O bond, suggesting a reaction between nano linear dextrin and magnetic Fe 3 O 4 nanoparticles [12a] . An extremely sharp band was seen at 640 cm −1 for FT‐IR spectra corresponding to stretching vibrations of the Sb−O bond, suggesting a reaction between magnetic nano linear dextrin and antimony [30] …”

The Characterization of Ukrainian Volcanic Tuffs from the Khmelnytsky Region with the Theoretical Analysis of Their Application in Construction and Environmental Technologies

“…The use of hematite to remove oxyanions is well documented [76]. This mineral very effectively forms surface complexes with oxyanions of As 5+ and As 3+ [77][78][79], Cr 6+ and Cr 3+ [80][81][82], U 6+ [83], Sb 5+ [84], and Se 4+ [85] which is most often favoured by an acidic environment. Importantly, it has been shown that natural minerals containing hematite have a similar ability to remove arsenic as their synthetic analogues [79].…”