Elevated concentrations of antimony (Sb) in the ecological environment have received considerable attention due to the harmful consequence involved. This study synthesized sulphidated ferrihydrite with different S:Fe molar ratios to efficiently remove Sb(V) from water. As the S:Fe molar ratio ranged from 0.00 to 1.48, the removal efficiency of Sb(V) by sulphidated ferrihydrite first decreased before increasing considerably. Sulphidated ferrihydrite with an S:Fe molar ratio of 0.74 exhibited a strong affinity towards Sb(V) with an optimal removal capacity of 963.74 mg Sb/g, which was 3.2-fold higher than that of ferrihydrite. In the kinetic experiments, the removal behavior of Sb(V) was well described by the pseudo-second-order model, suggesting that the removal process was controlled via chemisorption. Moreover, Sb(V) was efficiently removed over a wide pH range of 3.00-11.00, and coexisting anions (NO3-, Cl-, SO42-, SiO32-, CO32- and PO43-) exhibited marginal impact on the Sb(V) removal by sulphidated ferrihydrite (S:Fe ≥ 0.44). The characterization results of XRD, SEM, TEM mapping and etched XPS revealed goethite to be the dominant phase of sulphidated ferrihydrite with an S:Fe molar ratio of 0.15, while a mixed constitution of mixed-valent iron (hydro)oxides and iron sulphide was formed when the S:Fe molar ratio exceeded 0.44. Moreover, sulphidated ferrihydrite acted as a donor for Fe and S for the effective retention of Sb(V) by two main pathways: precipitation (tripuhyite, FeSbO4) and complexation (≡S-H and ≡Fe-OH). Therefore, sulphidated ferrihydrite is a promising material for eliminating Sb(V) contamination from water.
Keywords: Antimony; Complexation; Iron−based adsorbent; Sulphidation; Tripuhyite.
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