Selective Abatement of Organic Contaminants by Trace Complexed Mn(Ii)-Catalyzed Periodate Via High-Valent Manganese-Oxo Species

Mn(II) is one of the most efficient catalysts for periodate (PI)-based oxidation process, with the in-situ formed colloidal MnO2 simultaneously serving as catalyst and oxidant for the degradation of organic contaminants. Herein, it was interestingly found that the complexation of Mn(II) by ethylene diamine tetraacetic acid (EDTA) could further enhance the performance of PI-based oxidation for the selective organic contaminant degradation. The complexation by EDTA modulates the reaction pathway between Mn(II) and PI, and triggers the generation of high-valent manganese-oxo (MnV-oxo) species as the dominant reactive species, evidenced by methyl phenyl sulfoxide probing, 18O-isotope labeling technique and mass spectroscopic characterization. The formation of Mn(III) by PI-mediated single electron oxidation of Mn(II) and the stabilization of Mn(III) by EDTA complexation are the prerequisites for the further oxidation of Mn(III) by PI via the oxygen atom transfer step to produce MnV-oxo species. Except EDTA, other analogous ligands (e.g., ([S,S]-ethylenediaminedisuccinic acid (EDDS), L-glutamic acid N,N-diacetic acid (GLDA)) were also proved to improve the performance of Mn(II)/PI process and favor the dominance of MnV-oxo species. This study may shed light on the role of functional ligands in tuning the efficiency and reaction pathways of Mn(II)-catalyzed peroxides and peroxyacids processes.