Zeolitic Imidazole Framework-67 (ZIF-67) as a heterogeneous catalyst to activate peroxymonosulfate for degradation of Rhodamine B in water

Metal organic frameworks (MOFs) can exhibit chemical, photo and biomimetic catalytic activities. While MOFs have been intensively investigated as photo-catalysts to degrade pollutants in water, studies of wet chemical oxidation catalyzed by MOFs are still quite limited. Particularly, the activation of peroxymonosulfate (PMS) represents a widely-used chemical oxidation reaction for chemical synthesis and environmental remediation. Yet little effort has been made to evaluate MOFs as a catalyst for the PMS activation. In this study, it is proposed to use a cobalt-based MOF, ZIF-67, as a heterogeneous catalyst to activate PMS to degrade Rhodamine B (RB) dye. Through the RB degradation, ZIF-67 as the PMS activation catalyst was evaluated and its underlying mechanism was proposed. Additionally, factors affecting the PMS activation were also examined, including ZIF-67 loading, temperature, pH, UV irradiation and ultrasonication. A ratio of 1/3/1 (RB/PMS/ZIF-67) is the most effective ratio to degrade RB in water. The higher temperature, UV irradiation and ultrasonication also enhanced the RB degradation using PMS activated by ZIF-67. The recyclability test revealed that ZIF-67 can be used continuously with stable and effective catalytic activity. These features reveal that ZIF-67 can be an interesting and promising heterogeneous catalyst to activate PMS for the degradation of organic pollutants in water. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.