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

Lin, Zishen; Xu, Jiang; Zhu, Aibin; He, Chi; Wang, Changzhao; Zheng, Chunli

doi:10.1021/acs.langmuir.3c01037

Cited by 5 publications

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References 73 publications

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“…As a fascinating platform for environmental remediation, zerovalent iron (Fe 0 ) has received remarkable attention. Especially, nanoscale Fe 0 particles , have been actively constructed for harnessing Cr(VI) owing to their high reactivity and large surface area. During the remediation process of Cr(VI) by Fe 0 , Cr(VI) is reduced to Cr(III) both at the solid–liquid interface and in solution.…”

Section: Introductionmentioning

confidence: 99%

Reaction Thermodynamics of Zerovalent Iron and Hexavalent Chromium at the Solid–Liquid Interface and in Solution

Bulin,

Guo

2024

Langmuir

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Zerovalent iron (Fe 0 ) is a promising candidate for remediating hexavalent chromium (Cr(VI)) via adsorption and (or) reduction. Herein, the reaction between Fe 0 and Cr(VI) at the solid−liquid interface and in solution under varying pHs was inspected using the methodology of equilibrium thermodynamics. First, species distribution functions of aqueous Cr(VI), Cr(III), Fe(III), and Fe(II) are deduced to illuminate the quantitative distribution of aqueous metal species. Second, the plausible reaction at pH = 0−14 either at the solid−liquid interface or in solution is determined according to the species distribution function. Third, the spontaneity of each reaction is evaluated via a thermodynamic calculation based on the van't Hoff equation. The results present the following. (1) At the solid−liquid interface, the redox reaction 2Cr(VI) + 3Fe 0 → 2Cr(III) + 3Fe(II) is spontaneous, inducing complete Cr(VI) → Cr(III) reduction at pH = 0−14. Especially, the high spontaneity of the redox reaction is mainly ascribed to Fe 0 oxidation, which serves as a highly spontaneous subreaction. (2) In solution, the redox reaction Cr(VI) + 3Fe(II) → Cr(III) + 3Fe(III) is nonspontaneous at pH = 6 and 7, whereas it is spontaneous at pH = 6−7, 0−5, and 8−14. Accordingly, no Cr(VI) → Cr(III) reduction at pH = 6−7 and complete Cr(VI) → Cr(III) reduction at pH = 0−5 and 8−14 are expected. Particularly, the nonspontaneity of the Cr(VI) reduction at pH = 6−7 is majorly attributed to water ionization, which is involved as a highly nonspontaneous subreaction. On the contrary, the spontaneity of the Cr(VI) reduction at pH = 0−5 and 8−14 is mainly owing to acid−base neutralization, which is involved as a highly spontaneous subreaction. This work may deepen our knowledge about the chemistry involved in hexavalent chromium remediation by the zerovalent iron.

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Section: Introductionmentioning

confidence: 99%