Photocatalytic reduction of carbon dioxide to methanol and formic acid by graphene-TiO2

Graphene-TiO₂ was obtained by reduction of graphite oxide by the hydrothermal method. Using photocatalytic activity to reduce carbon dioxide to methanol and formic acid was investigated in this study. The results show that the graphene loading affects the absorption of light in the visible light region. A larger surface area can also improve the catalytic activity. The largest yield of methanol and formic acid, under light of 365 nm, can reach 160 and 150 μmol g^?1, respectively, with 8.5% graphene loading. An increase in graphene loading can enhance photocatalytic performance, but too much will also decrease the reduction efficiency by shielding the light from reaching the catalytic surface. The effect of pH was also investigated. The mechanism of the reaction was also discussed in this study.

Implications: Graphene-TiO₂ hybrids were prepared by the hydrothermal method. Surface area and visible light adsorption increased with the graphene loading. Increased graphene loading improved the methanol and formic acid production. Too much graphene loading will decrease the reduction efficiency. The effect of pH shows that the HCO₃^? species prefers the formation of formic acid. The mechanism of the reaction was also discussed in this study.     

大气颗粒物暴露与健康效应研究进展

大气颗粒物一直是影响我国大多数城市空气质量的首要污染物,且呈现出与欧美不同的煤烟、机动车尾气以及开放源复合型污染并存的高浓度污染态势,已有研究发现颗粒物的短期或长期暴露均会对人体产生不良的健康效应。本文从环境科学、暴露科学、环境流行病学和环境毒理学研究等方面系统综述了大气颗粒物健康效应研究的方法和进展,可为我国的大气颗粒物健康效应研究与大气颗粒物环境质量标准的修订提供方法学参考和经验借鉴。目前我国PM10污染尚未得到有效控制,细颗粒物(PM2.5)的污染也已引起关注,建议在不同区域开展空气污染健康效应的系统研究。     

油田企业清洁生产关键影响因素初探

文章阐述油田节能减排对策措施,依据吐哈油田分公司开展清洁生产审核工作成效,论述了油田开展清洁生产节能减排的主要措施,分析影响油田清洁生产的关键因素,结合油田生产实际,提出促进油田清洁生产的有效途径,为提高资源利用效率,减少和避免污染物的产生,保护和改善环境,实现油田可持续发展,有效开展清洁生产工作提供科学管理方面的借鉴。     

Effect of cationic and anionic surfactants on the sorption and desorption of perfluorooctane sulfonate (PFOS) on natural sediments

Sorption and desorption of PFOS at water-sediment interfaces were investigated in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS). CTAB remarkably enhanced the sorption of PFOS on the sediment. In contrast, the influence of SDBS to the sorption of PFOS was concentration dependent. Two contrasting factors were responsible for the phenomenon. One was the sorption of the surfactant itself to the sediment, which enhanced the sorption of PFOS. The other was the increase in solubility of PFOS caused by the adding of surfactants, which decreased the sorption of PFOS. SDBS had a much lower sorption capacity, but rather strong ability to increase the solubility of PFOS. High levels of SDBS remarkably reduced the sorption of PFOS on the sediment. These results imply that cationic and anionic surfactants may have contrast impacts on the distribution and transport of PFOS in the environment.     

Reductive transformation of 2,4-dichlorophenoxyacetic acid by nanoscale and microscale Fe3O4 particles

Reductive transformation of 2,4-dichlorophenoxyacetic acid (2,4-D) by nanoscale and microscale Fe₃O₄ was investigated and compared. Disappearance of the parent species and formation of reaction intermediates and products were kinetically analyzed. Results suggest that the transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), chlorophenol (2-CP, 4-CP) and phenol. About 65% of 2,4-D with initial concentration of 50 μ M was transformed within 48 h in the presence of 300 mg L^?1 nanoscale Fe₃O₄, and the reaction rates increased with increasing dosage of nanoscale Fe₃O₄. The decomposition of 2,4-D proceeded rapidly at optimum pH 3.0. Chloride was identified as a reduction product for 2,4-D in the magnetite–water system. Reductive transformation of 2,4-D by microscale Fe₃O₄ was slower than that by nanoscale Fe₃O₄. The reactions apparently followed pseudo-first-order kinetics with respect to the 2,4-D transformation. The degradation rate of 2,4-D decreased with the increase of initial 2,4-D concentration. In addition, anions had a significant adverse impact on the degradation efficiency of 2,4-D.     

阴离子表面活性剂SDS对菲律宾蛤仔(Ruditapes philippinarum)的急性毒性效应及抗氧化酶活性的影响

选择阴离子表面活性剂十二烷基硫酸钠(SDS)作为污染物,以近海底栖双壳贝类菲律宾蛤仔为受试生物,研究了SDS胁迫对菲律宾蛤仔的急性毒性效应以及长期暴露后菲律宾蛤仔抗氧化酶(SOD,POD,CAT)活性的变化。结果表明,(1)随着SDS浓度的增加,对菲律宾蛤仔的毒性越强表现出"剂量-效应"关系,SDS对菲律宾蛤仔96 h的半数致死浓度LC50=1.466 mg/L;(2)SDS胁迫引起菲律宾蛤仔的SOD、POD、CAT活性显著变化,低浓度SDS对三种酶的活性均具有诱导作用,高浓度SDS对三种酶的活性均具有抑制效应,中浓度组的SOD和POD酶活性呈现先升后降的趋势,而CAT活性受到抑制;(3)不同组织的抗氧化酶活性对SDS的敏感性表现出一定的差异性,对于SOD与CAT,三种组织敏感性为内脏团>外套膜>肌肉组织,而POD敏感性为外套膜>内脏团>肌肉组织。     

挥发性有机化合物处理技术的研究进展

简要介绍了挥发性有机化合物（VOCs）的来源、危害以及控制的意义,对VOCs现有处理技术从回收方法和消除方法两个方面进行了详细评述,并指出其优势和不足。同时,着重阐述了光催化氧化法以及变压吸附技术的研究进展,并提出了进一步研究的方向。     

Comparison of carbonyl compounds emissions from diesel engine fueled with biodiesel and diesel

The characteristics of carbonyl compounds emissions were investigated on a direct injection, turbocharged diesel engine fueled with pure biodiesel derived from soybean oil. The gas-phase carbonyls were collected by 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges from diluted exhaust and analyzed by HPLC with UV detector. A commercial standard mixture including 14 carbonyl compounds was used for quantitative analysis. The experimental results indicate that biodiesel-fueled engine almost has triple carbonyls emissions of diesel-fueled engine. The weighted carbonyls emission of 8-mode test cycle of biodiesel is 90.8 mg (kW h)^?1 and that of diesel is 30.7 mg (kW h)^?1. The formaldehyde is the most abundant compound of carbonyls for both biodiesel and diesel, taking part for 46.2% and 62.7% respectively. The next most significant compounds are acetaldehyde, acrolein and acetone for both fuels. The engine fueled with biodiesel emits a comparatively high content of propionaldehyde and methacrolein. Biodiesel, as an alternative fuel, has lower specific reactivity (SR) caused by carbonyls compared with diesel. When fueled with biodiesel, carbonyl compounds make more contribution to total hydrocarbon emission.     

环境中微量硝基苯同系物的分析进展

介绍了环境中硝基苯系物的主要来源及其危害，着重阐述了近年来国内外废水中微量硝基苯同系检测方法及其进展，并对常见分析方法的优缺点进行了比较。     

河湖底泥修复技术的研究进展

本文综述污染底泥的修复技术,探讨其发展状况及存在的问题。指出物理修复见效快,但成本高;化学修复成本较低但易造成二次污染;生物修复投入低,处理量大,但处理效率低,。将这三类技术联合使用,取长补短,具有较广阔的发展前景。