Incorporation of clay nano-particles in aqueous foams

During the process of crude oil/gasoline loading and storage, significant amounts of volatile organic compounds (VOCs) can be emitted to the environment. Stable aqueous foams can be spread as a flexible blanket on the top of the oil to control the VOC emission by providing a mass transfer barrier during the loading process. In this work, novel aqueous foams have been formulated by incorporating clay nano-particles in an aqueous solution of surfactants and polymers. The stability and mass transfer resistance of these foams were investigated at temperatures up to 125 F. In the presence of VOC, clay decreases the rate at which the liquid is drained out of the foam lamellae and increases the foam drainage half-life. These foams were found to be very stable in the presence of gasoline and crude oil and can last much longer than one day at the room temperature. The use of clay in the foam formulation reduces vapor diffusion through the lamellae and vapor emission through the foam column significantly for the first 10 h. Increase in temperature increases the rate of foam breakage due to higher water evaporation and lower liquid viscosity. In spite of this increase, the 0.5% polymer and 0.5% clay foam suppresses vapor emission from a gasoline longer than 3600, 1500 and 1100 min at 75 F, 105 F and 125 F, respectively. This foam also suppresses vapor emission from a crude oil longer than 4200, 2000 and 700 min at 75 F, 105 F and 125 F, respectively.     

Non-passive Transport of Volatile Organic Compounds Infiltrated from a Surface Disk Source

An unsaturated flow and non-passive transport model for water-soluble organic compounds has been implemented in cylindrical coordinates, with a top boundary condition that accounts for different zones of the surface that can be under infiltration or volatilization independently. We simulated two-dimensional infiltration of aqueous mixtures of methanol from a disk source, its redistribution and volatilization in both homogeneous and heterogeneous soils. Simulations showed that the incoming composition significantly affects volumetric liquid content and concentration profiles, as well as the fraction of infiltrated mass of methanol that is released to the atmosphere. Concentration-dependent viscosity had the major impact on the liquid flow. The differences in volumetric liquid content and normalized concentration of methanol became more pronounced during transport through a soil composed of a clay lens embedded within a main matrix of sandy clay loam texture. Dispersion in the liquid-phase was the predominant transport mechanism when dispersivity at saturation was set to 7.8 cm. However, for dispersivity of 1.0 cm, changes in composition led to changes in surface tension inducing significantly higher liquid flow. In this case, liquid-phase advection was the most active transport mechanism for homogeneous soils and highly concentrated infiltrating mixtures.     

23种挥发性有机化合物在3种吸附剂上漏出容量的测定评价

采用吸附热解吸－气相色谱－质谱法对23种挥发性有机化合物Chromosorb 106、Tenax TA、Tenax TG等3种吸附剂上漏出容量进行了测定。根据实验结果确定了不同的化合物应选择不同的吸附剂及相应的采样体积。结果表明,Chromosorb 106可较好地吸附低沸点的挥发性有机化合物,Tenax TA、Tenax TG均可用于沸点较高的挥发笥有机化合物吸附,这对测定大气中的有机化合物含量采样有一定的参考价值。     

粘土孔结构及添加铈对于催化剂上苯吸附-脱附-催化氧化性能的影响

采用3种不同孔结构的粘土材料,即Na型-蒙脱土(Na-mmt)、Al柱撑粘土(Al-PILC)和AlCe复合柱撑粘土(AlCe-PILC),以上述材料为载体,负载Mn和MnCe作为易挥发有机物(VOC)苯的氧化催化剂。利用N2吸附、程序升温还原(TPR)和程序升温表面反应(TPSR)等手段对催化剂的织构-结构、氧化-还原和吸附-脱附等性能进行了表征和分析。结果表明对于具有高比表面积和大孔径的改性粘土材料,添加适量的Ce有利于催化剂对低浓度苯的吸附,吸附量显著增加、脱附温度提高,上述条件都有利于对低浓度苯的深度氧化。同时,这一研究结果对改善"吸附-催化"一体化的低温吸附、高温脱附及氧化性能有极其重要的意义。     

Analytical Solutions for Reactive Transport of Multiple Volatile Contaminants in the Vadose Zone

Groundwater contamination usually originates from surface contamination. Contaminants then move downward through the vadose zone and finally reach the groundwater table. To date, however, analytical solutions of multi-species reactive transport are limited to transport only in the saturated zone. The motivation of this work is to utilize analytical solutions, which were previously derived for single-phase transport, to describe the reactive transport of multiple volatile contaminants in the unsaturated zone. A mathematical model is derived for describing transport with phase partitioning of sequentially reactive species in the vadose zone with constant flow velocity. Linear reaction kinetics and linear equilibrium partitioning between vapor, liquid, and solid phases are assumed in this model.     

The potential use of nanosilver-decorated titanium dioxide nanofibers for toxin decomposition with antimicrobial and self-cleaning properties

While chemical and biological attacks pose risk to human health, clean air is of scientific, environmental and physiological concerns. In the present contribution, the potential use of nanosilver-decorated titanium dioxide (TiO₂) nanofibers for toxin decomposition with antimicrobial activity and self-cleaning properties was investigated. Titanium dioxide nanofibers were prepared through sol-gel reaction followed by an electrospinning process. Following the Japan Industrial Standard (JIS) protocol, decompositions of nitrogen oxide (NOx) and volatile organic compound (VOC) by the TiO₂ nanofibers suggested that these materials were capable of air treatment. To further enhance their anti-microbial activity, silver nanoparticles were decorated onto the TiO₂ nanofibers’ surfaces via photoreduction of silver ion in the presence of the nanofibers suspension. Furthermore, tests of photocatalytic activity of the samples were performed by photodegrading methylene blue in water. The nanofibrous membranes prepared from these nanofibers showed superhydrophilicity under UV. Finally, the possibility of using these hybrid nanofibers in environmental and hygienic nanofiltration was proposed, where the self-cleaning characteristics was expected to be valuable in maintenance processes.     

热催化蜂窝降解室内VOCs实验研究

使用热催化材料降解挥发性有机化合物(VOC)是一种新型的空气净化方式。本文采用陶瓷蜂窝(负载含1%Pt的热催化剂)组成催化装置,研究了其在密闭环境舱中降解空气中甲醛和甲苯的特性。结果表明,在25℃条件下,热催化蜂窝装置对甲醛的降解效果显著,对甲苯无明显降解效果;在170℃条件下,装置对甲醛降解效果明显增强,对甲苯也表现一定降解效果。分析表明,提高温度对降解性能的影响主要表现为催化反应速率的增强。     

Mass and energy flow management in the sector of surface treatment

Vehicle refinishing body shops are concerned by the environmental policy against photochemical air pollution caused by VOC emissions. For supporting these small enterprises the mass and energy flow model IMPROVE has been developed. Based on an LCA-approach, the process steps of vehicle refinishing are modelled. The model IMPROVE helps to disseminate the consequences of product substitution in comparison to so far used products and techniques in the body shop. For the dissemination of experiences practical guidelines have been developed. Moreover, a comprehensible tool for the Solvent Balance is being offered. Thus, various means are available for consulting and also for strategic production planning for the SME in the sector.     

氧化硅-石墨烯气凝胶介孔复合材料的合成及其对苯的吸附性能

采用水热法快速合成了一种新型介孔氧化硅-石墨烯气凝胶复合吸附材料(MSGA)。通过X射线衍射、扫描电镜等方法对MSGA进行表征。结果表明,经过水热反应和冻干处理后的MSGA材料的介孔结构保持完好,介孔氧化硅在MSGA中的分散具有高度均一性。当介孔氧化硅的含量达到88.2(wt)%时,MSGA的比表面积可达395.5m~2/g。MSGA材料对苯蒸汽的常温常压吸附量为10.77mL/g,是石墨烯气凝胶的13倍,吸附穿透时间达到石墨烯气凝胶的34.4倍。在0.8%的环境湿度下,由于材料表面羟基的亲和性,进一步提升了对苯的吸附。得益于超低密度和丰富的内部孔隙结构,MSGA能够适应高达500mL/min的气流量。上述结果表明,该复合材料在VOCs消除领域具有广阔的应用前景。     

Microwave-assisted immobilization of β-cyclodextrin on PEGylated Merrifield resins

β-Cyclodextrin was immobilized on PEGylated Merrifield resin through cross-linking with 1,6-hexamethylene diisocyanate (HMDI) reagent, using conventional and microwave-assisted methodologies. FT-IR analysis of the solid intermediates indicated the attachment of the linker arm to the resin due the appearance of characteristic bands centered at 1716 and 2270 cm⁻¹ and the attachment of cyclodextrin to the resin was accompanied with increased absorption at the OH stretching regions (3330-3400 cm⁻¹). β-Cyclodextrin linked PEGylated resins are water insoluble and can be used to trap volatile organic compounds (VOCs) from water and subsequently be analyzed by headspace HS/GC, after simple filtration and drying steps.