Catalytic selectivity in activating peroxymonocarbonate with a commercial MnO2 catalyst for water remediation

Abstract

An in-situ formed peroxymonocarbonate (HCO4-) oxidation system from an equilibrium reaction of H2O2 and HCO3– was established for eliminating organic pollutants in water. With H2O2 as a co-existing oxidant in the system, a commercial available MnO2 was able to proceed selective catalytic activation of HCO4- to generate reactive oxygen species (ROS), such as ·OH and CO3·-. The MnO2 catalyst showed excellent catalytic ability, structural stability and recyclability in the HCO4--based oxidation system for removing tetracycline. The degradation rate of tetracycline reached 86 % and the catalyst could be used for at least 5 times with only 0.1 ppm of Mn leached in water. The kinetic study indicated that HCO4- was more related to the degradation of tetracycline and generated ·OH at the yield of 40 % was primarily from HCO4- activation rather than H2O2 activation. The evaluation of ROS and quenching experiments suggested that CO3·- was most responsible for tetracycline degradation. The catalyst characterization and reaction mechanism indicated that low-valent Mn species were the active sites for HCO4- activation. Finally, in-situ formation of HCO4- derived from CO2 in Na2CO3 solution with H2O2 was preliminarily explored, presenting a MnO2-catalzyed CO2-derived HCO4--based oxidation system for pollutant control. This study shows that a cheap and commercial available MnO2 can be an efficient, facile and selective catalyst for in-situ formed HCO4--based advanced oxidation processes.