Visible light assisted activation of peroxymonosulfate by bimetallic MOF based heterojunction MIL-53(Fe/Co)/CeO2 for atrazine degradation: Pivotal roles of dual redox cycle for reactive species generation

The present study illustrates a synthesis method for preparation of bimetallic metal organic framework (MOF) based heterojunction photocatalyst MIL-53(Fe/Co)/CeO2 (MIL-CO) and its potential towards activation of peroxymonosulfate (PMS) in water, under visible light irradiation. The catalyst/PMS system was employed to degrade and mineralize Atrazine (ATZ) in aqueous medium. 0.01 g/L of binary composite with 10 wt% CeO2 (MIL-CO(10)) and 0.25 g/L of PMS could achieve 99% ATZ degradation, for 10 mg/L ATZ concentration, within 60 min visible light exposure. The binary catalyst was characterized thoroughly using various techniques. Influences of different process parameters, like, catalyst and PMS dose, initial ATZ concentration, initial solution pH, process temperature, coexisting ions and organics, etc., were investigated. Applications of different radical scavengers and in-depth EPR investigation established the existence of degradation mechanisms involving the dominance of radical SO4∙-,OH∙,O2∙-,h+,O21 based process. Moreover, the applicability of MIL-CO/PMS/Vis system was studied in different real-life water matrixes. Various intermediates and byproducts were identified and probable degradation pathways were suggested. Detailed toxicity analysis was carried out to determine the elimination efficiency of harmful contaminants by the catalytic system. The binary composite showed excellent catalytic activity over six consecutive cycles with negligible metal leaching and remarkable structural stability. Surface bound redox interconversions of transition metal ions, coupled with efficient charge separation through heterojunction formation, result activation of PMS and ATZ molecules and generation of reactive species. Overall, the MIL-CO/PMS/Vis system has demonstrated extraordinary potential of binary MOF based heterojunction photocatalysts towards visible light driven mineralization of refractory pollutants.