Environmental problem is one of three major issues of common concern in the world today.Being a developing socialist country,the environmental problems in china are even more prominent,mainly in population expansion,s...Environmental problem is one of three major issues of common concern in the world today.Being a developing socialist country,the environmental problems in china are even more prominent,mainly in population expansion,sharp decrease of global forest areas,soil erosion,acid rain pollution,water pollution and so on.This essay is to introduce the present status,formation causes and hazardous condition of acid rain pollution in china.Some feasible and effective control measures are put forward according to the actual situation in China.展开更多
Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by...Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet （VUV） is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH （4.5） of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time （9 rain）. Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposi- tion pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.展开更多
In this study, series of nanolayered structures of Zn–Al LDHs were prepared by urea hydrolysis. Nanofibers and nanonets of the Al-doped ZnO were formed via the decomposition of the nanolayers under high pressure and ...In this study, series of nanolayered structures of Zn–Al LDHs were prepared by urea hydrolysis. Nanofibers and nanonets of the Al-doped ZnO were formed via the decomposition of the nanolayers under high pressure and temperature. Nanospheres were also prepared for comparison. The different morphologies of the prepared nanomaterials were confirmed by several techniques. An improvement for the optical properties of the doped zinc oxides was observed through narrowing of their band gap energies because of transforming the nanolayers to nanonets and nanofibers. The photocatalytic activities of the prepared nanomaterials were studied through photocatalytic degradation of the pollutants of acid green dyes. Complete decolorization and mineralization of green dyes happened in the presence of the nanolayers and nanospheres within 4–6 h,while the nanonets and the nanofibers achieved the complete decolorization and degradation of the dyes at shorter time 1.3 h. These results could be explained though the kinetic study of the photocatalytic degradation of dyes. It was concluded that the nanonets and the nanofibers were very effective for the photocatalytic degradation of pollutants.展开更多
文摘Environmental problem is one of three major issues of common concern in the world today.Being a developing socialist country,the environmental problems in china are even more prominent,mainly in population expansion,sharp decrease of global forest areas,soil erosion,acid rain pollution,water pollution and so on.This essay is to introduce the present status,formation causes and hazardous condition of acid rain pollution in china.Some feasible and effective control measures are put forward according to the actual situation in China.
基金supported by the National Basic Research Program (973) of China (No. 2013CB632403)the National Natural Science Foundation (Nos. 21267006, 21221004)+1 种基金the Tsinghua University Initiative Scientific Research Program No. 20131089251the Collaborative Innovation Center for Regional Environmental Quality
文摘Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet （VUV） is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH （4.5） of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time （9 rain）. Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposi- tion pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.
基金the Deanship of Scientific Research in King Faisal University (Saudi Arabia) for funding and providing the facilities required for this research as a part of Annual Research Grants Program (No. 170047)
文摘In this study, series of nanolayered structures of Zn–Al LDHs were prepared by urea hydrolysis. Nanofibers and nanonets of the Al-doped ZnO were formed via the decomposition of the nanolayers under high pressure and temperature. Nanospheres were also prepared for comparison. The different morphologies of the prepared nanomaterials were confirmed by several techniques. An improvement for the optical properties of the doped zinc oxides was observed through narrowing of their band gap energies because of transforming the nanolayers to nanonets and nanofibers. The photocatalytic activities of the prepared nanomaterials were studied through photocatalytic degradation of the pollutants of acid green dyes. Complete decolorization and mineralization of green dyes happened in the presence of the nanolayers and nanospheres within 4–6 h,while the nanonets and the nanofibers achieved the complete decolorization and degradation of the dyes at shorter time 1.3 h. These results could be explained though the kinetic study of the photocatalytic degradation of dyes. It was concluded that the nanonets and the nanofibers were very effective for the photocatalytic degradation of pollutants.
