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•->1O2 ≈ •OH in MOF-d BFO/PMS/dark system, while changed into h+>1O2 > >O2•-≈SO4•-> •OH after visible-light introduced. EPR tests first revealed that visible-light promoted 1O2 yield (non-radical pathway) but suppressed •OH and SO4•- generation (free-radical pathways). N2-purging experiments further proved that 1O2 primarily originates from the reaction between h+ and PMS, equivalently to that between O2 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 SO4•- yields. Moreover, PMS faces competition from adsorbed-O2 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.