Degradation Of Gaseous Pollutants Research Articles

Nanodiamond-decorated ZnO catalysts with enhanced photocorrosion-resistance for photocatalytic degradation of gaseous toluene

Photocatalytic degradation of indoor volatile organic compounds (VOCs) is considered as one of a promising strategy for resolving indoor pollution problems. Zinc oxide has been widely used in photocatalysis. However, the photocorrosion of ZnO restrains its further application. Herein, we decorated ZnO with nanodiamonds to solve the photocorrosion problem of ZnO for photocatalytic degradation of gaseous toluene. The photocorrosion-resistance of nanodiamond-decorated ZnO catalysts was enhanced. It was demonstrated that after the decoration of nanodiamonds, the optical absorption and transient photocurrent were effectively increased, while the photoluminescence intensity and electrochemical impedance were greatly reduced, indicating that nanodiamonds decoration not only improved the light adsorption for ZnO, but also promoted the charge transfer and eventually enhanced the photocatalytic oxidation efficiency of toluene. We hope that this work could propose possible ways to relieve the photocorrosion of ZnO semiconductor in the photocatalytic application and provide new insights into the degradation of gaseous pollutants.

Distribution and regeneration of hydroxyl free radicals in gaseous and particulate phases of pollutants in near-ground ambient air

Hydroxyl free radicals play the main role in atmospheric oxidative capacity. The formation of secondary fine particulate matter and the degradation of gaseous pollutants in the troposphere are dominated by hydroxyl free radical reactions. The harmful effect of particulate matters to human health is closely related to the free radicals distributed in the particulate matter phase. In this paper, the distribution of hydroxyl free radicals in near-ground ambient air was studied. The hydroxyl free radicals exist not only in the gaseous phase but also in the particulate phase, especially during heavy haze pollution. It is noteworthy that the concentration of hydroxyl free radicals in the particulate phase is about two times higher than that in the gaseous phase. The possible regeneration mechanisms are proposed. The excited electrons (e−) and holes (h+) formed e− - h+ pairs in particulate matters are identified to play a key role in promoting the regeneration of hydroxyl free radicals in particulate phase. Environmentally persistent free radicals in particulate phase could also further promote the chain reaction of free radicals and ultimately result in explosive regeneration in an environment that has been excited. The correlation between radical concentrations in gas species, particulate phases and particulate number concentration has been summary based on the actual monitoring site including Thermal power plant, Yumen street and Chemical street sites.

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

Study of 2-Propanol Photocatalytic Degradation on Surface of Phase-Ratio-Controlled TiO2 Nanoparticles

The crystal form of TiO2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO2 on gaseous organic-pollutant photocatalytic degradation, we synthesized a series of TiO2 nanoparticles with controllable phase ratios. We explored the role of the TiO2 phase ratio on the photocatalytic activity and degradation pathway in the photodegradation of 2-propanol (IPA). We estimated the crystallite size and crystal proportions of anatase and rutile by X-ray diffraction. We used the Brunauer–Emmett–Teller method to calculate the specific surface area and Fourier transform infrared spectroscopy to characterize the surface chemistry of the samples. Our results show the photocatalytic activities of pure anatase and the sample with 8.6% rutile to be much better than those of the samples with a phase junction and pure rutile. As such, anatase is the better option for the study of photodegradation design and preparation of gas-phase organic pollutants.

Photolysis of gaseous butyl acetate using built-in microwave discharge electrodeless lamps

This paper examined the photolysis of gaseous butyl acetate by built-in microwave discharge electrodeless lamps. Bromine and iodine lamps were used to investigate the effects of microwave input power, inlet concentration, gas residence time, and different filling materials on butyl acetate decomposition and energy yield. Water vapor and ammonia were utilized as additional chemicals to determine if they can improve removal efficiency. Built-in structure and external structure were also compared. When the gas flow velocity is 0.025m/s, and the inlet concentration is 1.5mg/m3, the removal efficiency of butyl acetate can reach over 78%, which is the highest in this study. Additional water vapor and ammonia can hardly improve the degradation. To some extent, built-in MDELs are better than external MDELs. The results will help promote the study of microwave discharge electrodeless lamps and their effect on the degradation of gaseous pollutants. Maybe, as the research goes on, it could realize the span from laboratory scale to practical application, and will become an advanced technology for the gaseous pollutants control.