Integrated Influence of Bulk Cations on the Degradation Of Florfenicol by Smectite-Intercalated Ultrafine Zero-Valent Iron

Abstract

Smectite intercalated ultrafine iron clusters (SZVI) demonstrate exceptional reactivity against contaminants attributed to the nanoscale interlayer confinement which restricts the iron clusters to dimensions of about 0.5 nm. However, the presence of specific cations significantly affects its reactivity. This study aims to clarify the mechanisms by which bulk K+, Mg2+, and Ca2+ influence the configuration of SZVI and its reactivity toward florfenicol (FF) as a model contaminant. Our findings revealed that each cation distinctly influenced the inter-particle aggregation, and the interlayer spacing, water content, and Brønsted acidity of SZVI, thereby affecting its degradation efficiency to varying degrees. Divalent cations such as Mg2+ and Ca2+ induced a reaction favorable interlayer but also led to pronounced inter-particle aggregation, which generally diminished degradation efficiency. An exception was observed at 2 mM of Mg2+, which uniquely promoted an enhanced dechlorination efficiency. K+ exhibited a contrasting effect on the interlayer region yet protected SZVI from water corrosion, manifesting a 1.7 times higher electron utilization efficiency than SZVI in presence of Mg2+. These insights offer mechanistic understanding into tailoring the reactivity of SZVI for optimizing the efficiency of its practical applications.

Keywords: Ultrafine iron cluster, Smectite Interlayer, Confined water, Dechlorination