复合氧化物汽车尾气净化催化剂抗SO2中毒机理研究

复合氧化物催化剂(ASC)具有较高的活性和良好的抗SO_2中毒性能.用IR、XPS、TPD等技术研究了该催化剂抗SO_2中毒机理,结果表明,与易失活催化剂相比,ASC经500h反应(反应气含SO_2约20ppm),其活性组分价态无显著变化,仅表面发生SO_2的化学吸附,经与约500ppm的SO_2作用20h后,发现仅有少量SO_4~(2-)形成.这是由于在ASC催化剂中添加了特殊助剂,而使催化剂活性组分得到保护的缘故.     

Greenhouse impacts of anthropogenic CH4 and N2O emissions in Finland

The Finnish anthropogenic CH₄ emissions in 1990 are estimated to be about 250 Gg, with an uncertainty range extending from 160 to 440 Gg. The most important sources are landfills and animal husbandry. The N₂O emissions, which come mainly from agriculture and the nitric acid industry are about 20 Gg in 1990 (uncertainty range 10–30 Gg). The development of the emissions to the year 2010 is reviewed in two scenarios: the base and the reduction scenarios.According to the base scenario, the Finnish CH₄ emissions will decrease in the near future. Emissions from landfills, energy production, and transportation will decrease because of already decided and partly realized volume and technical changes in these sectors. The average reduction potential of 50%, as assumed in the reduction scenario, is considered achievable.N₂O emissions, on the other hand, are expected to increase as emissions from energy production and transportation will grow due to an increasing use of fluidized bed boilers and catalytic converters in cars. The average reduction potential of 50%, as assumed in the reduction scenario, is optimistic.Anthropogenic CH₄ and N₂O emissions presently cause about 30% of the direct radiative forcing due to Finnish anthropogenic greenhouse gas emissions. This share would be even larger if the indirect impacts of CH₄ were included. The contribution of CH₄ can be controlled due to its relatively short atmospheric lifetime and due to the existing emission reduction potential. Nitrous oxide has a long atmospheric lifetime and its emission control possiblities are limited consequently, the greenhouse impact of N₂O seems to be increasing even if the emissions were limited somehow.     

不同温湿度条件下微米硼的氧化过程研究

目的 探究不同温湿度条件下微米硼的氧化层结构特征。方法 利用高温水浴浸泡处理去除原料微米硼的表面氧化层,然后在恒温恒湿条件下对微米硼进行加速氧化,利用扫描电子显微镜、透射电子显微镜和X射线光电子能谱对加速氧化后硼颗粒的氧化层厚度及组成进行分析,总结表面氧化层结构及成分组成变化规律,揭示温湿度条件下微米硼的氧化机制。结果 微米硼经高温水浴浸泡处理后,表面氧化层去除率达到50%。随着加速氧化时间的延长,硼颗粒氧化层的厚度逐渐增大,由内向外硼颗粒表面可以用B-BxOy-B2O3三层结构来表示,BxOy总是伴随着B2O3同时出现的,且随着氧化反应的进行,颗粒表面BxOy的含量将超过B的含量。结论 不同温湿度条件下微米硼的氧化机制为O2向B颗粒内部单向扩散的反应机制,B先与O2反应,形成低氧化物BxOy,BxOy进而与O2反应生成B2O3。随着氧化层厚度的增加,O2向B颗粒内部扩散的阻力增大,氧化反应速率随之降低。相比湿度的影响,温度的升高可显著加快硼表面氧化层的形成;温度一定时,湿度的增加可促进硼氧化层的形成。     

天津市滨海河流N2O扩散通量及控制因子

河流是大气温室气体重要的排放源.为了探讨天津市典型景观滨海河流N₂O释放空间特征及影响因素,以天津市6条不同土地利用类型的滨海河流为研究对象,通过顶空-气相色谱法测定了N₂O浓度、饱和度和扩散通量.结果表明,天津市不同景观河流N₂O浓度都处于过饱和状态,表现为大气N₂O的源;N₂O浓度、饱和度和扩散通量均值为（23.85±15.20）nmol·L^-1、（309.71±197.38）%和（27.04±16.46）μmol·（m²·d）^-1,范围分别为12.70～115.69 nmol·L^-1、 164%～1 502%和9.17～244.79μmol·（m²·d）^-1.天津市不同土地利用类型河流N₂O浓度和扩散通量具有较大的空间异质性,表现为：排污河>城市河流>郊区河流>农业河流.天津滨海河流N₂     

电化学微传感器检测水中痕量铜离子

为改善微电极在阳极溶出伏安法检测重金属离子过程中低电流响应和低电催化能力的缺点,提出了一种在碳纤维微电极表面合成还原氧化石墨烯/纳米金材料制得还原氧化石墨烯纳米金修饰碳纤维微电极（rGO/AuNPs CFMEs）的方法.通过SEM表征,所制备的rGO/AuNPs CFMEs具有比表面积高、吸附能力强和催化活性好的特点,因此改性微电极适合作为方波阳极溶出伏安法（SWASV）测定水中铜离子（Cu²⁺）的工作电极.在构建微传感器测试水中痕量铜离子系统后,对pH值、电导率、富集时间和富集电位等检测条件进行了优化.在pH值为4,电导率为36.1S/m,富集时间为360s,富集电位为-1.2V的最佳条件下,铜的线性范围和检出限分别0~1.0μmol/L和2.4nmol/L.此外,微传感器的可重复性、长期稳定性以及选择性也得到了验证.     

热活化和酸活化给水处理厂废弃铁铝泥的吸磷效果

探讨了酸活化和热活化方式对给水厂废弃铁铝泥(ferric and alum water treatment residuals,FARs)吸附磷能力的影响.结果表明,酸活化和热活化均能提高FARs的磷吸附能力,其中经2mol·L-1HCl酸活化的FARs(AH2.0-FARs)和300℃热活化的FARs(H300-FARs)取得最好的磷吸附效果.结合SEM和XRD表征技术对活化机制分析得知,两种活化方式均会使FARs变得疏松、多孔,从而提高FARs对磷的吸附能力.Langmuir和Freundlich两种模型均可很好地反映活化前后FARs的等温吸附过程,FARs对磷的理论饱和吸附量由活化前的20.48mg·g-1分别增加到22.86mg·g-1(AH2.0-FARs)和29.66mg·g-1(H300-FARs).低pH值有利于FARs对磷的吸附.此外,解吸附实验结果表明活化后的FARs能够更好地固定磷.因此,活化后的FARs是一种相对更好的磷的吸附材料.     

铁修饰的污泥生物炭对污泥脱水性能的改善效果

为改善城市污水处理厂污泥的脱水性能,采用铁修饰污泥生物炭作为助滤剂,与FeCl₃一起对污泥进行联合调理。以污泥净产率、污泥比阻和泥饼含水率评价污泥脱水性能;通过污泥Zeta电位、扫描电镜、EDS和泥饼可压缩性系数分析该方法的机理;同时,通过对污泥胞外聚合物、重金属以及总氯含量的分析,探究其调理污泥的环境风险,以明确该方法用于改善污泥脱水性能的可行性。结果表明,在500 ℃下制备的铁修饰污泥生物炭(30%)和FeCl₃(12.82%)联合调理时,污泥脱水的效果最佳;与仅用FeCl₃(12.82%)调理的污泥相比,污泥净产率升高了73.38%、污泥比阻降低了68.75%、泥饼含水率降低了9.03%。在较高温度下制备的铁修饰污泥生物炭,其孔隙结构更为发达、表面铁元素含量更高;与FeCl₃联合调理污泥时,更容易发生絮凝,从而使泥饼的渗透性能更好。而且,在联合调理的条件下,污泥中溶解型、松散结合型和紧密结合型胞外聚合物的含量均有所降低;污泥泥饼中重金属(Cd、Cr、Cu、Pb、Zn)更为稳定,泥饼热解固相产物和非固相产物中总氯含量降低,环境生态风险更小。采用铁修饰污泥生物炭作为助滤剂,可改善污泥脱水性能,并具有实际应用的潜力。     

IL/GO/88A的制备及其对四环素的光催化降解性能

使用离子液体(ILs)辅助生长新型光催化材料IL/GO/88A用于降解四环素(TC),使用XRD、FTIR、SEM、N₂吸附-脱附、UV-vis、EIS等方法分别对催化材料进行了表征分析,考察了催化剂投加量、pH、TC浓度对TC降解的影响。该复合材料表现出高效的TC降解效率。在催化剂投加量为0.30 g·L⁻¹、pH为5.7、TC溶度为10 mg·L⁻¹的条件下,光照180 min后,IL/GO/88A对TC的去除率达到95.7%。催化剂在重复利用3次后仍能保持稳定的性能。此外,阐明了吸附-光催化协同机理,并推断·OH、h⁺是主要的活性物种。本研究结果对开发高效MOFs光催化复合材料并用于处理含四环素废水提供了新思路。     

氧化镁基生物质炭高效去除水体中磷的特性

利用花生壳为前驱体,在高温限氧条件下,将氧化镁(MgO)负载于生物质炭(BC)表面制备出氧化镁基生物质炭(MgOBC)复合材料.系统研究了MgO-BC对水体中P的吸附特性,并探讨了溶液pH值、接触时间、竞争离子等因素对P的吸附效果的影响.结果表明,P的最佳吸附初始pH为7~9,过酸过碱的环境均不利于P的吸附;P的吸附过程可在540 min内达到平衡,且动力学曲线较好地符合伪一级和伪二级动力学模型,拟合系数可达97.3%和99.0%;当Cl~-、HCO_3~-、NO_3~-等共存离子的量浓度达到P的10倍时,MgO-BC对P仍具有较强的吸附能力;P的吸附过程较好地符合Langmuir等温模型,拟合系数达99%,理论最大吸附容量为138.07 mg·g~(-1),远高于其它未经改性或改性的生物质炭和几种典型P吸附剂的吸附容量.此外,吸附P后的复合材料可作为肥料施入土壤,可有效实现P的再利用.综上所述,该MgO-BC复合材料在净化实际P污染水体中有着广阔的应用前景.     

Effects of long-term amendment of organic manure and nitrogen fertilizer on nitrous oxide emission in a sandy loam soil

To understand the effects of long-term amendment of organic manure and N fertilizer on N2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure （OM）, half organic manure plus half fertilizer N （HOM）, fertilizer NPK （NPK）, fertilizer NP （NP）, fertilizer NK （NK）, fertilizer PK （NK） and control （CK） since 1989. Cumulative N2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions （25℃ and 60% water-filled pore space, WFPS）, but more than twice under the optimum denitrification conditions （35℃ and 90% WFPS）. N2O produced by denitrification was 2.1-2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results implied that the long-term amendment of organic manure could significantly increase the N2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N2O emission but sequestered atmospheric C and maintained efficiently applied N in soil.