Work

Organic acids promote the generation of reactive oxygen species by Fe(III)-modified montmorillonite: Unraveling the Cr(VI) reduction mechanism

Year: 2024

Type: article

Abstract: Widespread iron-bearing clay minerals exhibit excellent performance in remediating Cr(VI) contamination in aqueous and soil environments. However, the environmental factors and mechanisms underpinning Cr(VI) reduction via Fe(III)-exchanged clay surfaces remain insufficiently explored. In this study, we delve into the synergistic effects of Fe(III)-exchanged montmorillonite (MMT) and organic acids on Cr(VI) reduction. The results showed that Cr(VI) removal efficiency was significantly influenced by the type and concentration of organic acid , as well as the initial pH of the solution. Notably, the presence of ascorbic acid (H 2 A) significantly promoted Cr(VI) reduction by Fe(III)-exchanged MMT at pH 3.0, achieving rates 4–7 times higher than those observed with other organic acids . Spectral analyses identified Cr(OH) 3 , Fe(III)-Cr(III) complexes and Cr 2 O 3 as the primary reduction products of Cr(VI). Further investigations through chemical probe experiments and radical quenching tests demonstrated that exchangeable Fe(III) on the surface of MMT was reduced to Fe(II) by H 2 A. The resulting Fe(II) participates in Fenton reaction, generating superoxide radical (O 2 •– ) and hydroxyl radical (•OH), which act as potent electron donors to facilitate Cr(VI) reduction. Additionally, both H 2 A and Fe(II) directly contribute to the partial reduction of Cr(VI). These findings expand the potential applications of Fe(III)-exchanged MMT in treating Cr(VI)-contaminated wastewater, providing a promising strategy for environmental remediation and pollution control .

Source: Environmental Technology & Innovation

DOI: 10.1016/j.eti.2024.103975