Insights into the electron activation mechanisms at the micro level by nano zero-valent iron supported by molybdenum disulfide (nZVI@MD) from preparation to application

Both molybdenum disulfide (MoS2) and nano zero-valent iron (nZVI) exhibit excellent adsorption abilities. However, the constrained conductivity of MoS2 and the lack of selectivity of nZVI for electron transfer still pose challenges. In this study, we designed a series of novel nano zero-valent iron supported by molybdenum disulfide composites (nZVI@MD) with multiple electron-rich active sites, including iron dopant replacement, iron atom intercalation and exposed Mo4+, for effective removal of Cr(VI). Results showed that preparation temperature and the amount of MoS2 added were identified as the two most significant factors affecting the reduction properties of nZVI@MD. Systematic experiments revealed that the nZVI@MD exhibited good anti-interference performance, stability and reusability due to its excellent electron selectivity. Characterization results exhibited that iron atoms replaced the sulfur vacancies in MoS2 and inserted into an intercalation of MoS2 during the preparation process. The mechanisms underlying the uptake of Cr(VI) by nZVI@MD can be proposed as follows: (i) electrostatic interactions, (ii) reduction reaction, and (iii) co-precipitation involving Fe-O-Cr. Furthermore, nZVI@MD exhibited excellent electron activity, hydrophilicity and oxidation resistance, confirmed by density functional theory (DFT) calculations. This work provided new strategies and mechanistic insights for the rational design of adsorbents.