A tale of two metal ions: contrasting behaviors of high oxidation states of Cu and Mn in a bicarbonate–H2O2 system†
Abstract
In this study, the contrasting activities and pathways of Mn2+/Cu2+–HCO3− systems for Congo red (CR) dye degradation are presented. The Mn2+–HCO3− system (with the well-known MnIVO as the reactive species) did not degrade CR, while the Cu2+–HCO3− system (with high-valent Cu proposed as the reactive species) had a good oxidizing ability for CR. Further, HO radicals in the classic Fenton-like system made no contribution to CR degradation with both Cu and Fe ions as catalysts. The results indicate that reactive species in metal–HCO3− AOPs need prudent examination and better understanding of the underlying mechanism would benefit the development of more efficient AOPs.