Activation of peroxymonosulfate by bimetallic CoMn oxides loaded on coal fly ash-derived SBA-15 for efficient degradation of Rhodamine B

Abstract

• Mesoporous SBA-15 is successfully synthesized with coal fly ash as the silicon source. • CoMn/SBA-15 exhibits excellent performance for RhB degradation by activating PMS. • Synergistic effects of Co and Mn species are inferred. • Non-radical ( 1 O 2 ) rather than radicals (SO 4 − and OH) contributes most to the degradation. • Mechanisms of PMS activation and the degradation pathways of RhB are proposed. In this study, we successfully synthesized SBA-15 mesoporous molecular sieve with coal fly ash (CFA) as the silicon source, fabricated bimetallic CoMn catalysts with the obtained SBA-15 as the support, and evaluated their performance for activating peroxymonosulfate (PMS) to degrade the Rhodamine B (RhB) in an aqueous solution. The characterization results signified that MnCo 2 O 4 spinel was formed and uniformly dispersed on SBA-15 for the as-prepared CoMn/SBA-15. The CoMn/SBA-15/PMS system exhibited markedly higher RhB removal efficiency compared with Co/SBA-15/PMS and Mn/SBA-15/PMS under the same reaction conditions. Moreover, bimetallic CoMn/SBA-15 presented much lighter metal leaching than the monometallic catalysts. Chemical quenching tests and electron paramagnetic resonance experiments ascertained the generation of free radicals (SO 4 − and OH) and non-radical (singlet oxygen, 1 O 2 ) reactive oxygen species by PMS activation and the dominant role 1 O 2 in RhB degradation. The formed intermediate products by RhB degradation were identified with LC-MS analyses. We have also performed LC-MS analyses to determine the formed intermediate products during RhB degradation. The present results demonstrate the pronounced potential of CFA as a silicon source of molecular sieve support for preparing various heterogeneous catalysts for the PMS-based oxidation of organic pollutants in wastewater.