Microbial-induced Kirkendall effect for aged nanosized zero-valent iron regeneration and enhanced pollutant reductive...

Aged nanosized zero-valent iron (A-nZVI) suffers from severe surface passivation, significantly limiting its reactivity for sustainable environmental remediation. This study pioneers a novel, mild bio-regeneration strategy for A-nZVI by leveraging the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 to induce the Kirkendall effect. The resulting bio-regenerated nZVI (BR-nZVI) demonstrated remarkably enhanced pollutant removal performance, exhibiting approximately 50-fold higher removal rate constant for Cr(VI) compared to A-nZVI, coupled with superior environmental adaptability and cyclic stability. Multiple characterizations reveal that the heterogeneous mass diffusion of biogenic iron oxides/sulfides triggered the Kirkendall effect, thus promoting the preferential outward migration of iron to generate a unique yolk-shell nanostructure. This microbially induced Kirkendall effect remarkably enhanced the nZVI's specific surface area, porosity, hydrophobicity, and electron transfer capability, thereby facilitating enhanced contaminant reductive removal. Furthermore, our bio-regeneration approach is applicable to various sulfur sources and ZVI particle sizes, and demonstrates broad applicability for the efficient removal of different pollutants such as Tetrabromobisphenol A. These findings highlight microbial-induced Kirkendall engineering as an innovative and effective strategy to regenerate aged ZVI, significantly advancing its sustainable application in environmental remediation.