金属改性对SAPO-34低温还原NO性能的影响

采用浸渍法制备金属改性SAPO-34分子筛催化剂,分析比较了不同单金属（Cu或Co）及不同比例双金属（Cu：Co=1：1、3：1、5：1,质量比）改性催化剂对NO的催化还原性能,评价了不同催化剂的N₂选择性,并采用扫描电子显微镜（SEM）、比表面积测试、X射线衍射分析（XRD）、NH₃-程序升温脱附（NH₃-TPD）等表征手段对催化剂的物化性能进行了分析.结果表明,单金属Cu改性催化剂具有较宽的温度区间,在250~450℃范围内NO的转化率始终保持在100%;双金属改性使NO转化率保持为100%的最低温度下降了25~50℃,显著拓宽了低温段窗口,其中,Cu₃Co₁/SAPO-34催化剂的低温催化还原性能最好,200℃即可实现100%的NO转化率,175℃下的转化率也高达80%以上.Cu-Co双金属改性SAPO-34分子筛催化剂具有优异的低温催化还原NO性能,具有在机动车尾气、工业废气的低温脱硝治理领域应用的潜力.     

核壳结构KNbO3@Co(OH)2的制备及其活化过一硫酸盐降解帕珠沙星的研究

制备了以KNbO₃为载体材料的Co（OH）₂复合材料并对其进行了详细的表征,分析了材料的组成成分、组成形态进而确定了其为核壳结构形貌的KNbO₃@Co（OH）₂.利用合成的样品作为催化剂活化过一硫酸盐（peroxymonosulfate,PMS）来降解帕珠沙星（pazufloxacin,PZF）,结果表明制备的催化剂对PZF的去除效率显著增加.讨论了不同初始PMS剂量对降解效率的影响,发现随着PMS增加可活化生成更多的硫酸根自由基（sulfate radicals,SO₄^·-）和羟基自由基（hydroxyl radicals,HO^·）来降解PZF,但继续增大PMS用量降解效率未见明显提升.酸性和中性pH值条件下利于反应活化PMS降解PZF,而碱性体系减缓反应,甚至强碱体系更易形成Co（OH）₂沉淀不利于反应体系中活性组分CoOH⁺的形成,大大抑制了催化性能.此外,在体系中加入淬灭剂叔丁醇（tert-Butanol,TBA）或者乙醇（ethanol,ETOH）进行自由基的淬灭实验,结果表明SO₄^·-自由基为体系降解PZF过程中主要贡献的自由基,而HO^·自由基的贡献较少.催化剂具有较好的稳定性5次循环之后仍能在10 min之内完全去除PZF.本研究提出了新的思路为制备其他载体的Co（OH）₂核壳结构提供参考依据,同时将该催化剂结合高级氧化技术应用到水体新兴有机污染物净化领域具有很好的应用前景.     

Preparation of hydrophobic hierarchical pore carbon–silica composite and its adsorption performance toward volatile organic compounds

Carbon–silica materials with hierarchical pores consisting of micropores and mesopores were prepared by introducing nanocarbon microspheres derived from biomass sugar into silica gel channels in a hydrothermal environment.The physicochemical properties of the materials were characterized by nitrogen physical adsorption(BET),scanning electron microscopy(SEM),and thermogravimetric(TG),and the adsorption properties of various organic waste gases were investigated.The results showed that microporous carbon materials were introduced successfully into the silica gel channels,thus showing the high adsorption capacity of activated carbon in high humidity organic waste gas,and the high stability and mechanical strength of the silica gel.The dynamic adsorption behavior confirmed that the carbon–silica material had excellent adsorption capacity for different volatile organic compounds(VOCs).Furthermore,the carbon–silica material exhibited excellent desorption characteristics:adsorbed toluene was completely desorbed at 150℃,thereby showing superior regeneration characteristics.Both features were attributed to the formation of hierarchical pores.     

Aerosol optical properties under different pollution levels in the Pearl River Delta (PRD) region of China

To clarify the aerosol hygroscopic growth and optical properties of the Pearl River Delta(PRD)region,integrated observations were conducted in Heshan City of Guangdong Province from October 19 to November 17,2014.The concentrations and chemical compositions of PM_(2.5),aerosol optical properties and meteorological parameters were measured.The mean value of PM_(2.5) increased from less than 35(excellent) to 35-75 μg/m~3(good) and then to greater than 75 μg/m~3(pollution),corresponding to mean PM_(2.5) values of 24.9,51.2,and 93.3 μg/m~3,respectively.The aerosol scattering hygroscopic growth factor(f(RH = 80%)) values were 2.0,2.12,and 2.18 for the excellent,good,and pollution levels,respectively.The atmospheric extinction coefficient(σext)and the absorption coefficient of aerosols(σ_(ap)) increased,and the single scattering albedo(SSA)decreased from the excellent to the pollution levels.For different air mass sources,under excellent and good levels,the land air mass from northern Heshan had lower f(RH) and σ_(sp) values.In addition,the mixed aerosol from the sea and coastal cities had lower f(RH) and showed that the local sources of coastal cities have higher scattering characteristics in pollution periods.     

Identification of potential electrotrophic microbial community in paddy soils by enrichment of microbial electrolysis cell biocathodes

Electrotrophs are microbes that can receive electrons directly from cathode in a microbial electrolysis cell (MEC). They not only participate in organic biosynthesis, but also be crucial in cathode-based bioremediation. However, little is known about the electrotrophic community in paddy soils. Here, the putative electrotrophs were enriched by cathodes of MECs constructed from five paddy soils with various properties using bicarbonate as an electron acceptor, and identified by 16S rRNA-gene based Illumina sequencing. The electrons were gradually consumed on the cathodes, and 25%–45% of which were recovered to reduce bicarbonate to acetic acid during MEC operation. Firmicutes was the dominant bacterial phylum on the cathodes, and Bacillus genus within this phylum was greatly enriched and was the most abundant population among the detected putative electrotrophs for almost all soils. Furthermore, several other members of Firmicutes and Proteobacteria may also participate in electrotrophic process in different soils. Soil pH, amorphous iron and electrical conductivity significantly influenced the putative electrotrophic bacterial community, which explained about 33.5% of the community structural variation. This study provides a basis for understanding the microbial diversity of putative electrotrophs in paddy soils, and highlights the importance of soil properties in shaping the community of putative electrotrophs.     

Density functional theory (DFT) studies of vanadium-titanium based selective catalytic reduction (SCR) catalysts

Based on density functional theory (DFT) and basic structure models, the chemical reactions on the surface of vanadium-titanium based selective catalytic reduction (SCR) denitrification catalysts were summarized. Reasonable structural models (non-periodic and periodic structural models) are the basis of density functional calculations. A periodic structure model was more appropriate to represent the catalyst surface, and its theoretical calculation results were more comparable with the experimental results than a non-periodic model. It is generally believed that the SCR mechanism where NH₃ and NO react to produce N₂ and H₂O follows an Eley-Rideal type mechanism. NH₂NO was found to be an important intermediate in the SCR reaction, with multiple production routes. Simultaneously, the effects of H₂O, SO₂ and metal on SCR catalysts were also summarized.     

Coupling mechanism of activated carbon mixed with dust for flue gas desulfurization and denitrification

To clarify the effect of coking dust, sintering dust and fly ash on the activity of activated carbon for various industrial flue gas desulfurization and denitrification, the coupling mechanism of the mixed activated carbon and dust was investigated to provide theoretical reference for the stable operation. The results show that coking dust had 34% desulfurization efficiency and 10% denitrification efficiency; correspondingly, sintering dust and fly ash had no obvious desulfurization and denitrification activities. For the mixture of activated carbon and dust, the coking dust reduced the desulfurization and denitrification efficiencies by blocking the pores of activated carbon, and its inhibiting effect on activated carbon was larger than its own desulfurization and denitrification activity. The sintering dust also reduced the desulfurization efficiency on the activated carbon while enhancing the denitrification efficiency. Fly ash blocked the pores of activated carbon and reduced its reaction activity. The reaction activity of coking dust mainly came from the surface functional groups, similar to that of activated carbon. The reaction activity of sintering dust mainly came from the oxidative property of Fe₂O₃, which oxidized NO to NO₂ and promoted the fast selectively catalytic reduction (SCR) of NO to form N₂. Sintering dust was activated by the joint action of activated carbon, and both had a coupling function. Sintering dust enhanced the adsorption and oxidation of NO, and activated carbon further promoted the reduction of NO_x by NH₃; thus, the denitrification efficiency increased by 5%-7% on the activated carbon.     

大气污染特征研究及臭氧污染个例分析——以深圳市龙华区为例

根据深圳市龙华区观澜子站空气质量监测数据,对龙华区近年来空气质量状况、主要大气污染物浓度时间变化特征、气象条件和污染物浓度相关性,以及典型臭氧(O_3)污染过程进行了分析。结果表明龙华区空气质量以优良为主,空气质量指数(AQI)超标日中,O_3浓度超标天数最多,其次依次是PM_(2.5)、PM_(10)和二氧化氮(NO_2)。PM_(2.5)、PM_(10)和NO_2在秋冬季的浓度最高,春季次之,夏季最低;而O_3浓度则在夏秋季最高,春季次之,冬季最低。除O_3(日间浓度高于夜间浓度)以外,PM_(2.5)、PM10和NO_2晚间浓度高于日间浓度。此外,相关性研究表明,颗粒物污染以细颗粒物为主,O_3(8 h)和NO_2与颗粒物浓度均呈正相关性。由于地域差异的存在,O_3(8 h)和颗粒物浓度的相关性在不同地域表现也不同。同时,大气污染物浓度与气象条件和人为排放源的相关性较高。     

机载产品盐雾试验结果评定判据分析与探讨

针对当前机载产品盐雾试验标准中缺少明确、可量化评估指标,试验结果评定判据粗略笼统且以定性评价为主,已不能满足产品发展和使用环境扩展需求等现状,在总结国内外现行盐雾试验标准的结果评定要求基础上,分析当前机载产品盐雾结果评定判据存在的问题与不足,从管理和技术两个层面提出改进试验结果评定可操作性的建议,指导机载产品盐雾试验实施与评价。     

石英灯辐射加热条件下低密度碳/酚醛复合材料高温响应及分析

目的研究低密度碳/酚醛复合材料在不同地面加热实验测试响应的差异性,指导材料在实际应用环境下的高温响应分析。方法对低密度碳/酚醛复合材料开展了热流为400 kW/m~2的单侧石英灯辐射加热实验,利用热电偶测温系统测量试件在加热过程中不同位置的温度时间历程,并对试件的烧蚀形貌和微观结构进行观测。同时与热流为464k W/m~2的氧乙炔加热陶瓷板辐射加热实验结果进行对比分析,并且采用有限元方法对材料的传热传质多场耦合计算进行分析。结果对于石英灯辐射加热,在测量点升温到接近200℃时,温度响应拐点都依次出现。由于加热的辐射热源不同,在不同的辐射波段下,多孔材料吸收和发射的热量不同,短时间内氧乙炔加热陶瓷板辐射加热使材料内部升温速率比石英灯辐射加热实验的要快,但长时间加热时现象刚好相反。结论进行传热传质多场耦合计算材料高温响应时,合理确定材料宏观性能随温度的变化至关重要。