Preparation of formic acid modified industrial zero-valent iron (FA-ZVIbm) for CdII-EDTA removal: CdII capturing and self-enhanced oxidative degradation of EDTA

Cadmium (Cd) contamination is highly toxic to human health, and the complexed Cd in wastewater is tricky to remove owing to its stable chelating structure. In this study, industrial zero-valent iron (ZVI) was modified by ball-milling with tiny formic acid (FA), and the as-prepared sample (FA-ZVI bm ) was attempted in the treatment of Cd II -ethylenediaminetetraacetic acid (Cd II -EDTA). Little FA addition to ball-milling could dramatically improve the performance of FA-ZVI bm towards Cd II -EDTA elimination and raise the elimination rate constant by more than 200 times. Results ascertained that the (HCOO) 2 Fe II shell formed on FA-ZVI bm promoted Cd II -EDTA decomplexation and activation of dissolved O 2 to reactive oxygen species (ROS) for oxidative degradation of EDTA ligands. Cd II -EDTA was instantly decomplexation by Fe 3+ replacement, and the decomplexed Cd 2+ was rapidly captured by FA-ZVI bm . At the same time, the EDTA ligands underwent oxidative degradation, avoiding the re-chelation ecological hazard. Interestingly, we found that replacement decomplexation has a synergistic mechanism for activating dissolved O 2 to ROS , facilitating oxidative destruction of EDTA ligands. Furthermore, the FA-ZVI bm fixed-bed reactor could remediate Cd II -EDTA contaminated environmental water one-stop, and the effluent stably meets the emission standards. This study demonstrated that FA-ZVI bm could be a viable approach for Cd II -EDTA decontamination and clarified the remediation mechanism.