Visible-Light Photocatalytic Activity of Fe and/or Ni Doped Ilmenite Derived-Titanium Dioxide Nanoparticles.

Pure TiO2 nanoparticles and ones doped with Fe and/or Ni were successfully prepared by a co-precipitation method from ilmenite. The samples were structurally characterized by XRD, XPS, FT-IR, UV-vis, SEM, EDX, AAS and BET measurement. The XRD results showed that all samples were anatase TiO2, and no characteristic peaks of dopants were observed. The crystallite sizes of all doped TiO2 nanoparticles were less than 20 nm and doping TiO2 with metal ions can suppress the crystal growth of the particles. The XRD and XPS results indicated that TiO2 was uniformly doped and its crystalline phase was not changed by doping. The specific surface area of Fe-Ni/TiO2 is bigger than that of the un-doped TiO2. The pore size and pore volume of Fe-Ni/TiO2 is smaller than that of the un-doped. UV-vis spectra of the samples showed that the absorption edge red shifted with increasing doped metal content. The photocatalytic activity was evaluated in oxidative degradation of methylene blue (MB) with H2O2 under visible light irradiation. When doped with a single type of transition metal, the photocatalytic performance of Ni-doped samples was lower than that of Fe-doped ones. For the co-doped catalysts, the catalytic efficiency of 0.5%Fe4%Ni/TiO2 was the highest, reaching 93.34% after 250 min. Metal doping enhanced the photocatalytic decomposition of methylene blue compared with that of pure TiO2 by up to 1.5 times. The synergistic effects of the two metal ions improved the photocatalytic performance. The particles exhibited pronounced activity in degradation of MB as well as efficient recyclability. The photocatalytic degradation mechanism of methylene blue was analyzed.

CuO modified vanadium-based SCR catalysts for Hg0 oxidation and NO reduction.

The catalytic performance of Hg0 oxidation over vanadium-based SCR catalysts modified by different addition amounts of CuO was investigated. All catalysts were prepared by impregnation method and characterized. The 7% Cu/VWTi exhibited high Hg0 oxidation as well as a desired NO removal efficiency at 280-360 °C. The characterization revealed the enhancement of redox properties and well-dispersed active species results in the high catalytic performance after modification. The incorporation model showed that CuO in 7% Cu/VWTi was present in the monolayer dispersion, leading to the highest performance. Moreover, the effects of O2, NO, SO2, NH3 and HCl were explored. It showed all flue gas except NH3 could promote Hg0 oxidation. Fortunately, the inhibiting effect of NH3 could be scavenged if the catalyst is installed at the downstream of the SCR reactor. In addition, the mechanism of Hg0 oxidation over Cu/VWTi was discussed.

Simultaneous removal of SO2 and NOx from flue gas by wet scrubbing using a urea solution.

Nitrogen oxides (NOx) and sulfur dioxide (SO2) are major air pollutants, so simultaneously removing them from gases emitted during fossil fuel combustion in stationary systems is important. Wet denitrification using urea is used for a wide range of systems. Additives have strong effects on wet denitrification using urea, and different mechanisms are involved and different effects found using different additives. In this study, the effects of different additives, initial urea concentrations, reaction temperatures, initial pH values, gas flow rates, and reaction times on the simultaneous desulfurization and denitrification efficiencies achieved using wet denitrification using urea were studied in single factor experiment. The optimum reaction conditions for desulfurization and denitrification were found. Desulfurization and denitrification efficiencies of 97.5% and 96.3%, respectively, were achieved at a KMnO4 concentration 5 mmol/L, a reaction temperature of 70°C, initial urea solution pH 8, a urea concentration of 9%, and a gas flow rate of 40 L/h. The concentrations of the desulfurization and denitrification reaction products in the solution were determined. NOx was mainly transformed into N2, and the NO3- and NO2- concentrations in the solution became very low. The reactions involved in SO2 and NOx removal using urea were analyzed from the thermodynamic viewpoint. Increasing the temperature was not conducive to the reactions but increased the rate constant, so an optimum temperature was determined. The simultaneous desulfurization and denitrification kinetics were calculated. The urea consumption and NO2- , NO3- , and SO42- generation reactions were all zero order. The NO3- generation rate was greater than the NO2- generation rate. The simultaneous desulfurization and denitrification process and mechanism were studied. The results provide reference data for performing flue gas desulfurization and denitrification in factories.