Oxalated zero valent iron enables highly efficient heterogeneous Fenton reaction by self-adapting pH and accelerating proton cycle. (15th May 2023)

• Record Type: Journal Article
• Authors: Zhang, Xu; Sun, Hongwei; Shi, Yanbiao; Ling, Cancan; Li, Meiqi; Liang, Chuan; Jia, Falong; Liu, Xiao; Zhang, Lizhi; Ai, Zhihui
• Is Part Of: Water research. Volume 235(2023)
• Publication Date: 2023-05-15
• Subjects: Zero-valent iron -- Oxalic acid -- Heterogeneous fenton reaction -- Proton transfer -- Thiamphenicol; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119828
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: OA-ZVI bm /H2 O2 removed TAP efficiently at pH 3.5–9.5 for more than 13 cycles. OA-ZVI bm /H2 O2 self-adapted the solution pH to weak acidic conditions. The highly proton-conductive FeC2 O4 ·2H2 O shell enabled H + transfer to Fe 0 core. Effective H + cycle of OA-ZVI bm /H2 O2 drove Fe(II) production and Fenton reaction. Abstract: Heterogeneous Fenton reactions of zero-valent iron (ZVI) requires the sufficient release of Fe(II) to catalyze the H2 O2 decomposition. However, the rate-limiting step of proton transfer through the passivation layer of ZVI restricted the Fe(II) release via Fe 0 core corrosion. Herein we modified the shell of ZVI with highly proton-conductive FeC2 O4 ·2H2 O by ball-milling (OA-ZVI bm ), and demonstrated its high heterogeneous Fenton performance of thiamphenicol (TAP) removal, with 500 times enhancement of the rate constant. More importantly, the OA-ZVI bm /H2 O2 showed little attenuation of the Fenton activity during 13 successive cycles, and was applicable across a wide pH range of 3.5–9.5. Interestingly, the OA-ZVI bm /H2 O2 reaction showed pH self-adapting ability, which initially reduced and then sustained the solution pH in the range of 3.5–5.2. The abundant intrinsic surface Fe(II) of OA-ZVI bm (45.54% vs. 27.52% in ZVI bm, according to Fe 2p XPS profiles) was oxidized by H2 O2 and hydrolyzed to generate protons, and the FeC2 O4 ·2H2 O shell favored the fast transfer of protons to inner Fe 0, therefore, the consumption-regeneration cycle of protons were accelerated to drove the production of Fe(II) for Fenton reactions, demonstrated by the more prominent H2 evolution and nearly 100% H2 O2 decomposition by OA-ZVI bm . Furthermore, the FeC2 O4 ·2H2 O shell was stable and slightly decreased from 1.9% to 1.7% after the Fenton reaction. This study clarified the significance of proton transfer on the reactivity of ZVI, and provided an efficient strategy to achieve the highly efficient and robust heterogeneous Fenton reaction of ZVI for pollution control. Graphical abstract: The proton-conductive FeC2 O4 ·2H2 O shell accelerates the cycle of H + and the heterogeneous Fenton reaction of OA-ZVI bm /H2 O2 . Image, graphical abstract