Heterogeneous photo-Fenton degradation of bisphenol A over Ag/AgCl/ferrihydrite catalysts under visible light

The conventional heterogeneous Fenton reaction is often confined by the lower regeneration of Fe 2+ , which then inhibits the decomposition of H 2 O 2 and the generation of OH. Here we propose a novel idea to significantly accelerate the redox cycling of Fe 2+ /Fe 3+ in heterogeneous Fenton reaction by introducing photo-generated electrons from plasmonic particles. Towards this aim, novel plasmonic Ag/AgCl nanoparticles coated ferrihydrite (Ag/AgCl/Fh) have been synthesized. Compared with pure Fh, a remarkable enhancement in the photo-Fenton degradation towards bisphenol (BPA) can be observed for all Ag/AgCl/Fh samples under visible light. Noticeably, the rate constant of 6%Ag/AgCl/Fh is 0.0506 min −1 , which is about 5.1 times as high as that of pure Fh (0.0099 min −1 ). Moreover, the catalytic activity of 6%Ag/AgCl/Fh on the degradation of BPA remains quite efficient with a low Fe leaching after 4 recycles. The results of the effect of initial pH indicates that Ag/AgCl/Fh samples exhibit relatively high photo-Fenton catalytic activity even at pH 6. The electron spin resonance (ESR) analysis reveals that OH plays a significant role in the photo-Fenton reaction. The concentration of OH can even reach 267.6 μmol/L after 60 min, which is much higher than that of pure Fh (69.2 μmol/L). The measurement of Fe 2+ concentration and the XPS Fe2p spectra of Ag/AgCl/Fh before and after the degradation of BPA indicate the loading of Ag/AgCl can accelerate the conversion of Fe 3+ /Fe 2+ by the photo generated electrons from Ag nanoparticles due to the surface plasmon resonance (SPR) effect under the visible light irradiation.