Efficient photodegradation of Acid Red B by immobilized ferrocene in the presence of UVA and H2O2.

SiO2-C2H4-ferrocene (SiCFe) was synthesized by covalent grafting of ferrocene on functionalized silica gel with a -C2H4- linkage. On the basis of characterization by diffuse reflectance UV-vis spectra (DRS) and Fourier transform infrared spectra (FT-IR), ferrocene has been successfully anchored on the silica gel. Under UVA (lambdamax=365 nm) irradiation, the catalyst exhibited high photocatalytic activity in the degradation of Acid Red B (ARB), especially in the presence of H2O2. Meanwhile, the catalytic activity of SiCFe was maintained effectively even after reused for 4 times without any significant destruction of ferrocene. The influence of initial solution pH and wavelength of UV light on the catalyst's activity was also investigated. Electron spin resonance (ESR) studies revealed that both OH and HO2/O2- radicals were involved as the active species in the ARB degradation process. Furthermore, results of total organic carbon (TOC) and FT-IR analysis indicated that ARB degradation proceeded by the cleavage of NN, followed by hydroxylation and opening of phenyl rings to form aliphatic acids and further oxidization of the aliphatic acids to produce carbon dioxide and water. A possible reaction mechanism was proposed on the basis of all the information obtained under various experimental conditions.