A Kirkendall strategy for the efficient degradation of trichloroethylene from groundwater using cellulose nanofiber-supported sulfidated nZVI

Abstract

Nanoscale zero-valent iron (nZVI) is a promising reductant for the degradation of chlorinated hydrocarbons in contaminated groundwater. However, the inherent iron oxide shell limits its dechlorination reactivity. Here, a preparation strategy was proposed to enhance the Kirkendall effect of nZVI, aiming to alleviate the diffusion limitation of Fe atoms. Specifically, sulfidation and cellulose nanofibers (CNF) were employed to alter the shell composition, inducing radial nanocrack formation on S-nZVI@CNF. The type and content of surface groups on CNF are crucial to the nanocrack density, which in turn influences the number of dechlorination sites on S-nZVI@CNF. For the degradation of trichloroethylene (TCE) using carboxylated CNF-modified S-nZVI (S-nZVI@TOCNF), the radial nanocracks enhance its electron-donating capacity, while sulfidation suppresses the side reaction of H₂ evolution. Compared with nZVI, S-nZVI@TOCNF demonstrates higher dechlorination reactivity (k_m = 0.0098 L.g⁻¹.min⁻¹) and selectivity (ε_e = 19.6 %), thereby accelerating TCE degradation through the β-elimination pathway. Additionally, S-nZVI@TOCNF shows resistance to interference, adaptability across a wide pH range (3.0–11.0), recyclability, and stability. Notably, 92.2 % of TCE from real groundwater was removed. This study employed a Kirkendall strategy to achieve the precise customization of nZVI with varied dechlorination capabilities, enhancing its potential for chlorinated hydrocarbon remediation in groundwater.