S modified manganese oxide for high efficiency of peroxydisulfate activation: Critical role of S and mechanism

Abstract

Mn2O3 as a typical Mn based semiconductor has attracted growing attention due to its peculiar 3d electron structure and stability, and the multi-valence Mn on the surface is the key to peroxydisulfate activation. Herein, an octahedral structure of Mn2O3 with (111) exposed facet was synthesized by a hydrothermal method, which was further sulfureted to obtained a variable-valent Mn oxide for the high activation efficiency of peroxydisulfate under the light emitting diode irradiation. The degradation experiments showed that under the irradiation of 420 nm light, S modified manganese oxide showed an excellent removal for tetracycline within 90 min, which is about 40.4% higher than that of pure Mn2O3. In addition, the degradation rate constant k of S modified sample increased 2.17 times. Surface sulfidation not only increased the active sites and oxygen vacancies on the pristine Mn2O3 surface, but also changed the electronic structure of Mn due to the introduce of surface S2−. This modification accelerated the electronic transmission during the degradation process. Meanwhile, the utilization efficiency of photogenerated electrons was greatly improved under light. Besides, the S modified manganese oxide had an excellent reuse performance after four cycles. The scavenging experiments and EPR analyses showed that •OH and 1O2 were the main reactive oxygen species. This study therefore provides a new avenue for further developing manganese-based catalysts towards high activation efficiency for peroxydisulfate.