Increasing attention has been paid to pyrite due to its ability to generate hydroxyl radicals in air-saturated solutions. In this study, the mineral pyrite was studied as a catalyst to activate molecular oxygen to degrade Acid Orange 7 (AO7) in aqueous solution. A complete set of control experiments were conducted to optimize the reaction conditions, including the dosage of pyrite, the AO7 concentration, as well as the initial pH value. The role of reactive oxygen species (ROS) generated by pyrite in the process was elucidated by free radical quenching reactions. Furthermore, the concentrations of Fe(II) and total Fe formed were also measured. The mechanism for the production of ROS in the pyrite/H2O/O2 system was that H2O2 was formed by hydrogen ion and superoxide anion (O2(·-)) which was produced by the reaction of pyrite activating O2 and then reacted with Fe(II) dissolved from pyrite to produce (·)OH through Fenton reaction. The findings suggest that pyrite/H2O/O2 system is potentially practical in pollution treatment. Moreover, the results provide a new insight into the understanding of the mechanism for degradation of organic pollutants by pyrite.
Rutile Ti1xSnxO2(0.2x<1) solid solutions had been prepared using a sol-hydrothermal method, which combined the conventional sol-gel process with hydrothermal method. Hybrid alkoxides of Ti4+and Sn4+were used as precursors in the sol-gel process and Sn4+served as crystal-inducing agent during the formation of rutile crystal lattice in the hydrothermal process at 200°C. The microstructures and morphologies of nanoparticles were detected with XRD and TEM. Rutile Ti1xSnxO2solid solutions nanoparticles with well-distributed crystallite sizes about 10nm were obtained with Sn4+content above 20mol% without any high temperature calcination. The oxygen sensitivity properties of Ti1xSnxO2solid solutions had also been investigated. It is proved Ti1xSnxO2solid solutions exhibited higher oxygen responses than single TiO2or SnO2. A typical sample of Ti0.5Sn0.5O2presented the best sensitivity is approximately 6 under 400°C.
Compared with a great deal of traditional desulphurization crafts, the catalytic reduction of SO2 with CO to elemental sulfur is considered to be the best technology for the removal of CO2 from flue gas. Adding rare earth oxide CeO2 with variable valences to La2O3formes a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers are allγ-Al2O3, are used as the catalyst for the reduction of CO2 by CO. Under the condition of oxygen, all kinds of catalyst will be poisoned to some extent. However, the oxygen resistance of the catalyst can be improved by changing the composition of the catalyst. It is found through experiments that this poisoning effect is partially reversible. The structure of the catalyst is not completely destroyed. There is still a great distance from the actual application.
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