Physicochemical Effects of Sulfur Precursors on Sulfidated Amorphous Zero-Valent Iron and Its Enhanced Mechanisms for Cr(VI) Removal

Amorphouszerovalent iron (AZVI) has gained considerableattentiondue to its remarkable reactivity, but there is limited research onsulfidated amorphous zerovalent iron (SAZVI) and the influence ofdifferent sulfur precursors on its reactivity remains unclear. Inthis study, SAZVI materials with an amorphous structure were synthesizedusing various sulfur precursors, resulting in significantly increasedspecific surface area and hydrophobicity compared to AZVI. The Cr(VI)removal efficiency of SAZVI-Na2S, which exhibited the mostnegative free corrosion potential (-0.82 V) and strongest electrontransfer ability, was up to 8.5 times higher than that of AZVI. Correlationanalysis revealed that the water contact angle (r = 0.87), free corrosion potential (r = -0.92),and surface Fe(II) proportion (r = 0.98) of the SAZVIsamples played crucial roles in Cr(VI) removal. Furthermore, the enhancedelimination ability of SAZVI-Na2S was analyzed, primarilyattributed to the adsorption of Cr(VI) by the FeS x shell, followed by the rapid release of internal electronsto reduce Cr(VI) to Cr(III). This process ultimately led to the precipitationof FeCr2O4 and Cr2S3 onthe surface of SAZVI-Na2S, resulting in their removal fromthe water. This study provides insights into the influence of sulfurprecursors on the reactivity of SAZVI and offers a new strategy fordesigning highly active AZVI for efficient Cr(VI) removal.