Chemical Bond Bridging across Two Domains: Generation of Fe(II) and In Situ Formation of FeS x on Zerovalent Iron

Effective sulfidationof ZVI lies in the chemical bridgingof FeS x and ZVI, and the key pathwaysare Fe(II) production from ZVI itself and in situ formation of FeS x on the ZVI surface. Sulfidation of zerovalent iron (SZVI)can strengthenthe decontaminationability by promoting the electron transfer from inner Fe-0 to external pollutants by iron sulfide (FeS x ). Although FeS x forms easily,the mechanism for the FeS x bonding onthe ZVI surface through a liquid precipitation method is elusive.In this work, we demonstrate a key pathway for the sulfidation ofZVI, namely, the in situ formation of FeS x on ZVI surface, which leads to chemical bonding across two domains:the pristine ZVI and the newly formed FeS x phase. The two chemically bridged heterophases display superioractivity in electron transportation compared to the physically coatedSZVI, eventually bringing about the better performance in reducingCr(VI) species. It is revealed that the formation of chemically bondedFeS( x ) requires balancing the rates forthe two processes of Fe(II) release and sulfidation, which can beachieved by tuning the pH and S(-II) concentration. This studyelucidates a mechanism for surface generation of FeS x on ZVI, and it provides new perspectives to design high-qualitySZVI for environmental applications.

Automated summary

The effective sulfidation of ZVI relies on the chemical bridging of FeSx and ZVI, which is achieved through the in situ formation of FeSx on the ZVI surface. This leads to the bonding between the pristine ZVI and the newly formed FeSx phase, resulting in superior electron transportation activity compared to physically coated SZVI. The study elucidates the mechanism of surface generation of FeSx on ZVI and provides new perspectives for the design of high-quality SZVI for environmental applications.