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

BiFeO (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 SO>O ≈ •OH in MOF-d BFO/PMS/dark system, while changed into h>O > >OSO> •OH after visible-light introduced EPR tests first revealed that visible-light promoted O yield (non-radical pathway) but suppressed •OH and SO generation (free-radical pathways). N-purging experiments further proved that O primarily originates from the reaction between h and PMS, equivalently to that between O 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 •OH and SO yields. Moreover, PMS faces competition from adsorbed-O 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.