Photo-Fenton degradation of ethyl xanthate catalyzed by bentonite-supported Fe(II)/phosphotungstic acid under visible light irradiation.

In this study, using bentonite-supported Fe(II)/phosphotungstic acid composite (HPW-Fe-Organicbent) prepared by mechanochemical synthesis as heterogeneous catalyst, the photo-Fenton degradation of ethyl xanthate under visible light irradiation was studied in detail. The results showed that the degradation of ethyl xanthate was mainly impacted by H2O2 dosage, catalyst dosage and reaction time. HPW-Fe-Organicbent catalyst had a wide applicable range of pH and kept a high catalytic activity even at high pH in the photo-Fenton degradation of ethyl xanthate. It was found that the degradation of ethyl xanthate in the photo-Fenton process catalyzed by HPW-Fe-Organicbent mainly resulted from the hydroxyl radicals. HPW-Fe-Organicbent had an excellent stability in use, and retained almost all of its catalytic activity for four recycling times. Moreover, the kinetics study showed the degradation of ethyl xanthate, with the initial concentration below 50 mg/L, was well fitted by the pseudo-first-order rate model.

Preparation of a new Fenton-like catalyst from red mud using molasses wastewater as partial acidifying agent.

Using molasses wastewater as partial acidifying agent, a new Fenton-like catalyst (ACRM sm ) was prepared through a simple process of acidification and calcination using red mud as main material. With molasses wastewater, both the free alkali and the chemically bonded alkali in red mud were effectively removed under the action of H2SO4 and molasses wastewater, and the prepared ACRM sm was a near-neutral catalyst. The ACRM sm preparation conditions were as follows: for 3 g of red mud, 9 mL of 0.7 mol/L H2SO4 plus 2 g of molasses wastewater as the acidifying agent, calcination temperature 573 K, and calcination time 1 h. Iron phase of ACRM sm was mainly α-Fe2O3 and trace amount of carbon existed in ACRM sm . The addition of molasses wastewater not only effectively reduced the consumption of H2SO4 in acidification of red mud but also resulted in the generation of carbon and significantly improved the distribution of macropore in prepared ACRM sm . It was found that near-neutral pH of catalyst, generated carbon, and wide distribution of macropore were the main reasons for the high catalytic activity of ACRM sm . The generated carbon and wide distribution of macropore were entirely due to the molasses wastewater added. In degradation of orange II, ACRM sm retained most of its catalytic stability and activity after five recycling times, indicating ACRM sm had an excellent long-term stability in the Fenton-like process. Furthermore, the performance test of settling showed ACRM sm had an excellent settleability. ACRMsm was a safe and green catalytic material used in Fenton-like oxidation for wastewater treatment.