飞行时间二次离子质谱法在一次污染过程中PM2.5表面组分分析中的应用

团簇离子源的发明和使用，使飞行时间二次离子质谱（TOF-SIMS）法成为材料表面化学分析越来越重要的手段，TOF-SIMS法的主要测试功能包括表层质谱、化学成像及深度剖析3种。采用TOF-SIMS法对一次污染过程中的大气细颗粒物（PM_2.5）的表层进行检测，得到了PM_2.5表面成分的质谱及成像信息。结果表明：PM_2.5表层存在多种金属离子，通过扫描电子显微镜能谱仪的形貌与飞行时间二次离子质谱仪的成像亮度分析可知，K⁺、Na⁺、Mg²⁺响应强度相对较强，含量较高；通过原子吸收光谱仪进行金属离子定量可知，2018年11月4日和12月24日的K⁺、Na⁺、Mg²⁺的平均质量分别为1.809 5、0.443 8、1.526 2 mg；从形态分布上看，PM_2.5表面烟尘集合体含量较多，其次为燃煤飞灰、矿物颗粒和超细未知颗粒；PM_2.5表层的有机物离子C_xH_y片段也较多，经过m/z的测试数据进一步确定，表明颗粒物表层含有大量的脂肪烃和芳香烃；除此之外，还存在含N、O、S等的有机物和无机物。     

Reaction hazard and mechanism study of H2O2 oxidation of 2-butanol to methyl ethyl ketone using DSC,Phi-TEC II and GC-MS

Methyl ethyl ketone (MEK) oxidation via H₂O₂ with tungsten-based polyoxometalate catalysts has gained much attention with an ever-growing body of knowledge focusing on the development of environmentally benign processes in chemical industry. In this study, two calorimetry techniques, differential scanning calorimetry (DSC) and Phi-TEC II adiabatic calorimetry, were employed to analyze the thermal hazards associated with the 2-butanol oxidation reaction system. Hydrogen peroxide was the oxidant and a tungsten-based polyoxometalate as the catalyst. Gas chromatography-mass spectrometry was used for identification of the organic products. Important thermal kinetic data were obtained including “onset” temperature, heat of reaction, adiabatic temperature rise and self-heat rate. From DSC results, three exothermic peaks were detected with a total heat generation of approximately 1.26 kJ/g sufficiently to induce a thermal runaway. Possible reaction pathway for three stages were proposed based on both DSC and GC-MS results. One exotherm was detected by Phi-TEC II calorimeter and the pressure versus temperature profile together with the DSC and GC-MS data demonstrate the complexity of 2-butanol reaction system under both thermal screening and adiabatic conditions.     

土壤腐殖酸慢热解表征实验影响因素研究

以土壤提取的腐殖酸为研究对象,进行了差式量热扫描(DSC)和热重分析(TGA)的可重复性实验、样品质量对比实验和预处理对比实验。综合分析了影响慢热解特征温度参数的因素和效应,并根据作用原理将其总结为热滞后效应和反应平衡滞后效应。结果表明,高级热分析技术用于土壤慢热解表征可重复性良好,差式量热扫描与热重分析结果可比性强,然而热分析曲线和热特征参数对实验条件的响应灵敏,其中样品质量和升温速率的影响尤其显著。研究结果表明,慢热解技术用于土壤有机质分析具有良好的准确性和重现性,提出了保障土壤腐殖酸慢热解质量控制的最佳样品量[DSC为(10±0.1)mg]、最佳气体氛围(He)和最佳升温速率(10℃/min)、精确压实程度等实验条件。     

Processing of whey from dairy industry waste

An investigation carried out in 11 dairies in Serbia has shows that 78.75 % of whey, a by-product of cheese industry, is emitted into river systems, thus contributing to the organic pollution of the environment. This pollution can be avoided by processing of whey into food and pharmaceuticals. It is shown that low-temperature regime of whey concentration and fractionation, based on vacuum concentration and diafiltration, preserves whey proteins undenaturated, as proved by differential scanning calorimetry method. Functional native whey proteins based food products, with potentially high immunomodulatory activity, are obtained.     

Investigation of the role of biopolymer clusters in MBR membrane fouling using flash freezing and environmental scanning electron microscopy

The technique that employs flash freezing and environmental scanning electron microscopy (ESEM) was utilised for detailed investigation of the fouling materials in a membrane bioreactor (MBR). The method involves the flash freezing of a wet sample in liquid nitrogen for 10 s to preserve its structure for direct ESEM observation with a high image resolution. ESEM images show that the sludge cake formed by simple filtration of the MBR bulk sludge has a highly porous, sponge-like structure with a fairly low resistance. However, the fouling layer attached to the membrane surface contains a thin gel layer under the main body of the sponge-like sludge cake, which is similar to that formed by filtration of a dispersion of biopolymer clusters (BPCs). It is apparent that BPCs tend to accumulate on the membrane surface, and the gel layer is largely responsible for the high filtration resistance of the cake layer on the fouled membranes.     

悬浮载体生物膜内硝化菌群空间分布规律

利用16S rRNA寡核苷酸探针荧光原位杂交和共聚焦激光扫描显微镜联用技术,对悬浮载体生物膜内硝化菌群的空间分布规律进行了分析.试验采用3组结构完全相同的悬浮载体生物膜反应器,每个反应器的曝气区为6L,沉淀区为2L,水力停留时间为1.0h,3个反应器的进水COD/NH₄⁺-N分别为15、10和5,从反应器中取出载体颗粒表面的生物膜进行分析,研究各反应器中生物膜的微生物群落结构的变化规律.结果表明,SCBR内载体表面生物膜的总体厚度在80～120μm左右,氨氧化菌和亚硝酸盐氧化菌主要分布在生物膜表面的20～30μm左右范围内.随着进水中COD/NH₄⁺-N的增加,氨氧化菌和亚硝酸盐氧化菌在整个生物膜中所占的比例逐步下降.     

Calorimetric studies on the thermal stability of methyl ethyl ketone peroxide (MEKP) formulations

The energetic decomposition of methyl ethyl ketone peroxide (MEKP) and its formulations have long been known to present a significant risk. Indeed, MEKP has the highest number of reported decomposition incidents of all organic peroxides, many of which have led to significant numbers of fatalities, injuries and damage. It is noteworthy that incidents have been reported at all stages of the product lifecycle.This paper is derived from incident-investigation work and provides a summary of serious incidents involving MEKP, followed by details of calorimetric experiments performed to investigate thermal stability of representative MEKP formulations containing varying amounts of MEKP monomer. In particular we report the wide degree of variation that exists between commercial MEKP formulations, even between materials that are of the same nominal formulation. Such variations are detectable using differential scanning calorimetry (DSC).Follow-up studies performed on a representative MEKP formulation containing MEKP monomer indicate that a risk of decomposition exists at temperatures well below the reported self-accelerating decomposition temperature (SADT) of the products. As such, the experimental results reported here suggest that lower storage temperatures (commonly recommended by manufacturers to maximise shelf life) should be considered as being essential throughout the product lifecycle to reduce the risk of accidents in storage and transportation.     

紫外差示分光光光度法直接测定废水中苯胺

苯胺在不同酸度溶液中具有不同的结构和紫外吸收光谱.以苯胺的酸溶液为参比液,以等浓度的苯胺水溶液为测定液,在280nm处测定苯胺含量.结果表明,当苯胺浓度为1～100mg/L时,吸光度与浓度之间存在良好的线性关系,据此建立了紫外差示分光光度法.该法不需分离可直接测定工业废水中苯胺含量,简便快速,回收率高于96.7％.     

Quantification, morphology and source of humic acid, kerogen and black carbon in offshore marine sediments from Xiamen Gulf, China

Three types of macromolecular organic matters (MOMs), i.e. humic acid (HA), kerogen+black carbon (KB), and black carbon (BC) were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) and scanning electron microscope (SEM). The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content (TOC), while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The δ 13 C values of the three fractions suggested that materials from terrestrial C 3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in δ 13 C values of MOMs in the offshore marine sediments.     

Characterization of cake layer structure on the microfiltration membrane permeability by iron pre-coagulation

A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration (MF) process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride (FC) and polymer ferric sulfate (PFS) pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.