Yangfan Chen,Hongyan Yan,Wenxin Teng,Jiangling Li,Weizao Liu,Shan Ren,Jian Yang,Qingcai Liu
NH 3 -SCR technology with commercialized V 2 O 5 -WO 3 (MoO 3 )/TiO 2 catalysts has become the most efficient technology for the removal of NO x from coal-fired power plants. However, the weaknesses of V 2 O 5 -WO 3 (MoO 3 )/TiO 2 catalysts such as the biotoxicity of vanadium species and high cost restrict their increased applicability. Fe 2 O 3 -based NH 3 -SCR catalysts show potential in placing traditional catalysts due to their good N 2 selectivity, excellent environmentally friendly performance, high thermal stability, and low cost. In this work, low cost Fe 2 O 3 -containing solid waste was exploited as the base material for NH 3 -SCR catalyst preparing. Moreover, bulk MoO 3 and MoO 3-x nanosheets decorated Fe 2 O 3 composite NH 3 -SCR catalysts were synthesized and both revealed conspicuously improved NO x removal efficiency compared with bare-Fe 2 O 3 catalyst. However, the N 2 selectivity of these two catalysts showed significant differences. Therefore, comprehensive characterizations, NH 3 oxidation experiments, and in-situ diffusion Fourier transform infrared spectroscopy (DRIFTS) experiments were performed to determine the N 2 O formation pathways of the above two catalysts. The redox properties were highly related to the N 2 O generated from NH 3 oxidation. Moreover, the huge difference in NH 3 and NO adsorption ability led to disparate reaction mechanisms over the two catalysts. This new understanding of the N 2 O formation mechanism has the potential to guide the rational design of improved NH 3 -SCR catalysts suffering from low N 2 selectivity.
Iron and organic carbon (OC) biogeochemical cycling is highly correlated, and dissolved organic matter (DOM), a highly reactive component of soil and water environments, is the main OC source. However, the micro-mechanism of the molecular fractionation of DOM, the spatial OC distribution on iron (oxyhydr)oxides, and how these factors further affect their redox properties remain to be fully understood. Therefore, this study investigated the DOM adsorption properties of iron (oxyhydr)oxides with different crystallinities at the molecular level through the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and transmission electron microscopy/electron energy loss spectroscopy (TEM–EELS) analyses of the liquid-solid phases. Owing to the limited number of adsorption sites, OC sequestration on goethite and hematite surfaces generally followed an “onion” model, in the order of preference of aromatic, aliphatic, and carboxylic acid-rich compounds. Combined with dielectric electrochemical tests and charge differential density calculations, the results revealed that the complexation effect produced by iron ions increased the electron-accepting capacity (EAC) of the DOM remaining in the aqueous solution. In contrast, molecular selective adsorption and oxidative polymerization significantly enhanced the EAC of DOM adsorbed on the surface fraction of iron (oxyhydr)oxides. These findings help elucidate the mechanism of OC sequestration by iron (oxyhydr)oxides. The increased EAC may affect various biogeochemical processes, such as methane production and microbial Fe(III) reduction, facilitating the prediction of OC cycling in natural environments.
Lin Chen,Tingting Fan,Min Yang,Dunfeng Si,Haotian Wu,Song Wu,Jian Xu,Dongmei Zhou
Microplastics weathering by various types of oxidants in the oxic environment and their interaction with environmental contaminants have drawn numerous scientific attention. However, the environmental fate of microplastics under a reducing environment has been largely unresolved. Herein, the change of physicochemical and redox properties of microplastics during the weathering under a sulfate-reducing environment and the interaction with arsenite were addressed. The sulfurization of phenol-formaldehyde resin microplastics under a sulfate-reducing environment generated smooth and porous particles with the induction of organic S species. Multiple spectroscopic results demonstrated thioether and thiophene groups formed by the substitute removal of O-containing functional groups. Moreover, the sulfurization process induced the reduction of carbonyl groups and oxidation of phenolic hydroxyl groups and resulted in the formation of semiquinone radicals. The O-containing functional groups contributed to microplastics redox property and As(III) oxidation while S-containing functional groups showed no obvious effect. The sulfurized microplastics had lower efficiency in mediating arsenite oxidation than the unsulfurized counterparts due to the decreased electron donating capacity. Producing hydrogen peroxides by electron-donating phenol groups and semiquinone radicals and the direct semiquinone radicals oxidation could mediate arsenite oxidation. The findings of this study help us understand the fate of microplastics in redox fluctuation interfaces.
危险品化学品经营许可证（带存储）