Interfacial slow-release reduction modulates iron cycling on the ZVI surface: Accelerated electron transfer and generation of Fe(II)

Slow iron cycling is an important factor limiting the reactivity of zero-valent iron (ZVI). Developing novel strategies to facilitate iron cycling is vital for the ZVI practical application. This study reports a novel interfacial slow-release reduction strategy for synthesizing L-ZVI with excellent performance by adding L-ascorbic acid 2-phosphate sesquimagnesium salt hydrate (AAPS). Experiments revealed that AAPS slowly released ascorbic acid via acid-catalyzed hydrolysis, thereby using reduction to promote Fe(III)/Fe(II) cycling, a process that regulates iron cycling while preventing low utilization by direct adding reductants. The enhanced content of Fe(II) and self-corrosion of L-ZVI facilitated the release of Fe(II) into the solution. Electrochemical experimental and comparisons of hydrogen production demonstrated that L-ZVI exhibited exceptional electron transfer and selectivity capacity. The strategy alters the electronic structure of L-ZVI, lowers work function, and shifts the band center upward. Cr (VI) was chosen as the model contaminant to investigate the reactivity of L-ZVI. L-ZVI can remove Cr (VI) within 7 min completely, exhibiting a reaction rate constant ( k obs ) of 0.6809 min⁻¹ , which was 154.75-fold higher than that of ZVI (0.0044 min⁻¹) and significantly surpassing the performance of other reported water treatment materials. This article presents a novel strategy for developing efficient iron-based materials.