A hybrid catalyst (CZ50) of cuprous oxide and zeolite was prepared and used in a catalytic system in which gaseous 1,2-dichloroethane (1,2-DCE) was degraded. The effects of relative humidity (15 and 65%) and wavelength of irradiation (ultraviolet, blue, green and red light) on the degradation of 1,2-DCE were studied. The experimental results reveal that the hybrid catalyst degraded the hazardous material under visible light. A comparison of the results obtained under ultraviolet and red irradiation at a relative humidity of 15% revealed almost equal degradation efficiencies of 83.8 and 82.2%, respectively. In the system with hybrid catalysts, a lower relative humidity favored 1,2-DCE degradation, indicating that relative humidity critically affects the degradation of hazardous materials. The most important result was that the intermediates of the degradation of 1,2-DCE included ethane, carbon dioxide, and formic acid yielded, which are mostly harmless and non-toxic materials. The experimental results indicated that the method could effectively be used to degrade hazardous materials to provide a healthy and safe environment for workers. 相似文献
Iron water treatment residues are a free by-product with high concentration of iron oxides
Iron water treatment residues has a large potential for arsenic sorption
Soils are highly contaminated by arsenic at wood preservation sites
Iron water treatment residues were added to hot spots contaminated with arsenic
The addition led to significant decrease in leaching of arsenic from the contaminated soil
Iron water treatment residues (Fe-WTR) are a free by-product of the treatment of drinking water with high concentration of iron oxides and potential for arsenic sorption. This paper aims at applying Fe-WTR to a contaminated site, measuring the reduction in contaminant leaching, and discussing the design of delivery and mixing strategy for soil stabilization at field scale and present a cost-effective method of soil mixing by common contractor machinery. Soil contaminated by As, Cr, and Cu at an abandoned wood impregnation site was amended with 0.22% (dw) Fe-WTR. To evaluate the full scale amendment a 100 m2 test site and a control site (without amendment) were monitored for 14 months. Also soil analysis of Fe to evaluate the degree of soil and Fe-WTR mixing was done. Stabilization with Fe-WTR had a significant effect on leachable contaminants, reducing pore water As by 93%, Cu by 91% and Cr by 95% in the upper samplers. Dosage and mixing of Fe-WTR in the soil proved to be difficult in the deeper part of the field, and pore water concentrations of arsenic was generally higher. Despite water logged conditions no increase in dissolved iron or arsenic was observed in the amended soil. Our field scale amendment of contaminated soil was overall successful in decreasing leaching of As, Cr and Cu. With minor improvements in the mixing and delivery strategy, this stabilization method is suggested for use in cases, where leaching of Cu, Cr and As constitutes a risk for groundwater and freshwater. 相似文献
Nitrous oxide (N2O), a potent greenhouse gas, is emitted during nitrogen removal in wastewater treatment, significantly contributing to greenhouse effect. Nitrogen removal generally involves nitrification and denitrification catalyzed by specific enzymes. N2O production and consumption vary considerably in response to specific enzyme-catalyzed nitrogen imbalances, but the mechanisms are not yet completely understood. Studying the regulation of related enzymes’ activity is essential to minimize N2O emissions during wastewater treatment. This paper aims to review the poorly understood related enzymes that most commonly involved in producing and consuming N2O in terms of their nature, structure and catalytic mechanisms. The pathways of N2O emission during wastewater treatment are briefly introduced. The key environmental factors influencing N2O emission through regulatory enzymes are summarized and the enzyme-based mechanisms are revealed. Several enzymebased techniques for mitigating N2O emissions directly or indirectly are proposed. Finally, areas for further research on N2O release during wastewater treatment are discussed.
