No abstract

A novel bentonite clay-based Fe-nanocomposite (Fe-B) was successfully developed as a heterogeneous catalyst for photo-Fenton discoloration and mineralization of an azo-dye Orange II. X-ray diffraction (XRD) analysis clearly reveals that the Fe-B nanocomposite catalyst mainly consists of Fe2O3 (hematite) and SiO2 (quartz) crystallites, and the Fe concentration of the Fe-B catalyst determined by X-reflective fluorescence (XRF) is 31.8 wt %. The catalytic activity of the Fe-B was evaluated in the discoloration and mineralization of Orange II in the presence of H2O2 and UVC light (254 nm). It was found that the optimal Fe-B catalyst dosage is around 1.0 g/L, and the efficiency of discoloration and mineralization of Orange II increases as initial Orange II concentration decreases or reaction temperature increases. In addition, at optimal conditions (10 mM H2O2, 1.0 g of Fe-B/L, 1 x 8W UVC, and pH = 3.0), complete discoloration and mineralization of 0.2 mM Orange II can be achieved in less than 60 and 120 min, respectively. The result strongly indicates that the Fe-B nanocomposite catalyst exhibits a high catalytic activity not only in the photo-Fenton discoloration of Orange II but also in the mineralization of Orange II. The reaction kinetics analysis illustrates that the photo-Fenton discoloration of Orange II in the first 15 min obeys the pseudo-first-order kinetics. The reaction activation energy calculated was 9.94 kJ/mol, indicating that the photo-Fenton discoloration of Orange II is not very sensitive to reaction temperature.

A novel nanocomposite of iron oxide and silicate, prepared through a reaction between a solution of iron salt and a dispersion of Laponite clay, was used as a catalyst for the photoassisted Fenton degradation of azo-dye Orange II. This catalyst is much cheaper than the Nafion-based catalysts, and our results illustrate that it can significantly accelerate the degradation of Orange II under the irradiation of UV light (λ = 254 nm). An advantage of the catalyst is its long-term stability that was confirmed through using the catalyst for multiple runs in the degradation of Orange II. The effects of the H2O2 molar concentration, solution pH, wavelength and power of the UV light, catalyst loading, and initial Orange II concentration on the degradation of Orange II were studied in detail. In addition, it was also found that discoloration of Orange II undergoes a faster kinetics than mineralization of Orange II and 75% total organic carbons of 0.1 mM Orange II can be eliminated after 90 min in the presence of 1.0 g of Fe-nanocomposite/L, 4.8 mM H2O2, and 1 × 8W UVC.