Nano-sized Zero-Valent Iron Coupled with Sulfidation and Ferrous Implantation Enhances the Reduction–Oxidation Removal of Iodinated Contrast Medium

The feasibility and mechanism of nanosized zerovalent iron (nZVI) coupled with sulfidation and ferrous implantation (S-nZVI/Fe2+) especially for the removal of iodinated contrast medium (ICM) are poorly known. This study showed that the efficient removal of ICM diatrizoate (DTA) could be achieved by S-nZVI/Fe2+ under neutral and aerobic conditions. The DTA degradation rate was significantly elevated in the S-nZVI/Fe2+ system, with an increase of 38.2, 29.5, and 13.0 times the removal rate constants compared with those of the nZVI, nZVI/Fe2+ and S-nZVI systems, respectively. Analysis of the products and detection of reactive species suggested that both the reductive and oxidative removal of DTA were enhanced by S-nZVI/Fe2+ under aerobic conditions. The coupled effect of sulfidation and Fe2+ implantation could maintain the solution pH around 5 and retard the consumption of Fe(0) by O2, thereby promoting the corrosion of Fe(0). This effect not only inhibited the recombination of the generated atomic hydrogen but also facilitated the Fenton-like reaction for •OH production, resulting in enhanced DTA removal with two fundamental stages: the efficient deiodination stage and the mild oxidation stage. Generally, these findings provided new insights into improving the removal efficiency of complicated ICM under mild conditions through an enhanced-nZVI strategy