New insight into the regulation mechanism of visible light in naproxen degradation via activation of peroxymonosulfate by MOF derived BiFeO3

BiFeO3 (BFO) nanocage prepared by metal-organic-framework derivatization (MOF-d) was adopted as activator to first investigate the effect mechanism of visible-light on naproxen-degradation via peroxymonosulfate (PMS) activation. MOF-d BFO expressed more excellent PMS activation ability than hydrothermal-synthetic BFO, due to highly ordered mesopores. A 3.0 times higher pseudo-first-order degradation rate constant was achieved after visible-light introduced. The quenching experiments indicated that the contribution of ROS in naproxen degradation followed the order of SO4 center dot->1O(2) approximate to center dot OH in MOF-d BFO/PMS/dark system, while changed into h(+)>1O(2) > >O-2 center dot-approximate to SO4 center dot-> center dot OH after visible-light introduced. EPR tests first revealed that visible-light promoted 1O(2) yield (non-radical pathway) but suppressed center dot OH and SO4 center dot-generation (free-radical pathways). N-2-purging experiments further proved that 1O(2) primarily originates from the reaction between h(+) and PMS, equivalently to that between O-2 and e(-)-h(+) in MOF-d BFO/PMS/vis system. Under visible-light, PMS activation via Fe (III) might be hindered by e(-) filling on Fe 3d orbital and anion PMS preferred to approach h(+) rather than e(-), resulting in the decrease of center dot OH and SO4 center dot-yields. Moreover, PMS faces competition from adsorbed-O-2 and oxygen vacancies for e- capture. The degradation-pathways for naproxen in dark and under visible light were both proposed in MOF-d BFO/PMS system.