The catalytic process of poly-silicate-ferric (PSF) and generation mechanism of hydroxyl radical based on photo-Fenton system

Poly-silicate-ferric (PSF) was developed as an heterogeneous UV-Fenton catalyst, which was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), UV-vis diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) and scanning electron microscopy (SEM). The catalytic process of PSF and generation mechanism of hydroxyl radical based on photo-Fenton system were studied in detail. In the heterogeneous UV-Fenton system, the kapp value of Orange II degradation was as high as 0.268 min−1, which was 1.5 times compared to that with α-FeOOH as catalyst. As a result, the Orange II decolouration and mineralization rates were as high as 99.9% and 92.5% after 40 min treatment, respectively. Moreover, the hydroxyl radical concentration would increase to a peak value of 13.4 μmol/L at about 15 min. The fundamental cause of the high hydroxyl radical generation lay in the high release ability of iron ions from PSF. The peak concentrations of total iron ions and ferrous ions could increase to 4.53 mg/L and 1.57 mg/L at 20 min and 10 min, respectively. After treatment, the re-adsorption of iron ions on the surface of PSF could avoid the additional pollution caused by iron ions. The results confirmed that PSF was a high activity catalyst for an heterogeneous UV-Fenton system.