pH dependence of adsorption of n-dodecyl-beta-D-maltoside on solids

Adsorption of surfactants on solids plays an important role in industrial operations such as separation, lubrication, flotation, dispersion, chemical mechanical polishing, and enhanced oil recovery. In this work, adsorption of a typical biodegradable nonionic surfactant, n-dodecyl-beta-d-maltoside, on solids was studied to explore its potential applications. Even though it is a nonionic surfactant, significant pH-dependence was revealed for the adsorption on alumina in the range from pH 4 to 7. The adsorption density was found to be proportional to the concentration of surface AlOH group among Al(OH(2))(+) and AlO(-) groups. The equilibriums among the surface species are governed by pH through surface ionization reactions. The surface AlOH group evidently determines the formation of hydrogen bonding between the surfactant molecules and the solid surface and thus the adsorption. Similar correlation was also found in the case of hematite. The results help to understand the mechanism of adsorption of sugar-based surfactant on solids.     

3D Mapping of Gas Physisorption for the Spatial Characterisation of Nanoporous Materials

Nanoporous materials used in industrial applications (e. g., catalysis and separations) draw their functionality from properties at the nanoscale (1–10 Å). When shaped into a technical form these solids reveal spatial variations in the same properties over much larger length scales (1 μm–1 cm). The multiscale characterization of these systems is impaired by the trade-off between sample size and image resolution that is bound to the use of most imaging techniques. We show here the application of X-ray computed tomography for the non-invasive spatial characterization of a zeolite/activated carbon adsorbent bed across three orders of magnitude in scale. Through the unique combination of gas adsorption isotherms measured locally and their interpretation by physisorption analysis, we determine three-dimensional maps of the specific surface area and micropore volume. We further use machine learning to identify and locate the materials within the packed bed. This novel ability to reveal the extent of heterogeneity in technical porous solids will enable a deeper understanding of their function in industrial reactors. Such developments are essential towards bridging the gap between material research and process design.     

Crystal Engineering: An Outlook for the Future

Crystal Engineering has traditionally dealt with molecular crystals. It is the understanding of intermolecular interactions in the context of crystal packing and in the utilization of such understanding in the design of new solids with desired physical and chemical properties. We outline here five areas which come under the umbrella of Crystal Engineering and where we feel that a proper planning of research efforts could lead to higher dividends for science together with greater returns for humankind. We touch on themes and domains where science funding and translation efforts could be directed in the current climate of a society that increasingly expects applications and utility products from science and technology. The five topics are: 1) pharmaceutical solids; 2) industrial solid state reactions; 3) mechanical properties with practical applications; 4) MOFs and COFs framework solids; 5) new materials for solar energy harvesting and advanced polymers.     

Structure of Porous Adsorbents

Porous solids are gaining in importance as adsorbents and catalysts both for scientific investigations and for industrial applications. Adsorbents having predetermined pore structure can be prepared by specific synthesis. This pore structure can be described in detail and comprehensively by specific parameters, which can be determined by gas adsorption measurements and by other means. Information concerning the bonding state and the concentration of the functional groups on the surface is obtainable by the use of chemical and physical methods of investigation. Other functional groups can be attached to the surface by chemical reactions. It is possible in this way to prepare selective adsorbents.     

Characterization of the hydrophobicity of mesoporous silicas and clays with silica pillars by water adsorption and DRIFT

The hydrophobic-hydrophilic properties of a solid are related to the material chemistry and, often, these properties are relevant to the applications of a particular material. Contrarily to what happens with other properties, such as specific surface areas or pore volumes, the methodologies to ascertain on the hydrophilicity of a porous material are not well defined. In this work, we discuss and relate the information on the hydrophobicity degree obtained from water adsorption isotherms and from diffuse reflectance infrared Fourier transform (DRIFT), in a set of porous materials. The studied materials were mainly mesoporous solids, namely of MCM-41 and SBA-15 types, two xerogels and also different porous clays heterostructures. Both techniques were informative on the hydrophobic-hydrophilic properties of the studied samples, but the correlation between the information obtained by each technique was not straightforward. Water adsorption isotherms are much more sensitive to the differences of the studied materials than the DRIFT spectra. For silica-based mesoporous materials with similar surface chemistry, the water adsorption process and hence, the hydrophobic-hydrophilic properties, is mainly dependent on the pore diameters. However, water adsorption is much more sensitive to changes in the nature of the adsorbent surface than to changes in the pore diameter.     

Sensitive detector of exothermic processes (Sedex)

Sedex is a new apparatus to detect the initial temperature of exothermic processes in substances and reaction mixtures under industrial operating conditions. It is based on a slow heating of samples in a special oven, the detection of any difference between the oven and sample temperatures and the evaluation of this difference. The features and advantages of this method are indicated. The properties of this instrument make it especially useful for industrial applications or anywhere where large numbers of samples must be checked for exothermic processes. Additionally, Sedex provides information about the endothermic changes which may occur in the sample.     

Replication of Micro- and Nanostructures on Polymer Surfaces

Summary : Via geometrical micro- and nanostructures new functionalities like controlled wetting properties, biological adhesive / dehesive properties or surface patterns for guided self assembly can be added to polymer surfaces. This is especially interesting for medical or biotechnological applications, because there is no new approval process necessary. The whole process from producing the structures via EUV-interference lithography to the injection moulding will be shown. How far the limits for the smallness of these structures on polymers are already pushed forward show the results from our latest injection moulded samples. Grooves of 18 nm width - this means world record! - could be reproduced in an industrial process and in an economical very interesting high-volume production.     

Surface characterization of synthetic and mineral carbonate fluoroapatites

As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the physical and surface properties of the synthetic carbonate fluoroapatite and mineral francolite retained for this work have been carefully examined. The average particle size of the powdered samples, determined by laser granulometry, is around 30 microm. Their specific surface areas, measured according to the N(2) BET method, are 8.8+/-0.1 and 13.9+/-0.1 m(2).g(-1), respectively, for the synthetic and the mineral compound. The solubility of both solids has been studied under undersaturation initial conditions. The synthetic compound has a solubility product of 10(-103+/-2), but the mineral francolite, which is highly substituted and poorly crystalline, is more soluble and dissolves incongruently. The amphoteric properties of the hydrous carbonate fluoroapatites surfaces have also been investigated through zeta-potential measurements and potentiometric titrations in KNO(3) medium at 25 degrees C. The experimental data have been interpreted using the computer program FITEQL 3.2, applying either the nonelectrostatic or the constant capacitance model. For both solids, the values of the surface acidity constants determined with the two models are very close, suggesting a weak contribution of the electrostatic interactions. Moreover, the more acidic surface of the synthetic compound compared to that of the mineral one is assigned to the differences in crystallinity and chemical composition between the two solids.     

Magnetic solids in analytical chemistry: A review

Magnetic solids are widely used in detection and analytical systems because of the performance advantages they offer compared to similar solids that lack magnetic properties. These solids can be used to pre-concentrate analytes and for the magnetic separation and molecular identification of biomolecules, and organic and inorganic species. Magnetic solid separation techniques also offer benefits over centrifugation, filtration, and solid-phase extraction. In this review, we describe the synthesis, characterization and applications of a series of solids including silica supports, carbon nanotubes, alumina, organic polymers and other materials, mostly containing magnetite or paramagnetic metals. Also addressed are the future perspectives of magnetic solid applications.     

金属-有机骨架材料在烯烃氧化中的应用

本文分别从以骨架中的金属(金属簇)为催化中心的MOF材料、利用具有催化活性的刚性有机配合物构筑的MOF材料和MOF负载催化材料三个方面详细介绍了MOF作为催化剂在烯烃氧化反应中的应用情况,分析了其各自的优缺点。具有催化活性的刚性有机配合物构筑的MOF材料稳定性较好,能够引入具有光学活性的催化剂,可以作为不对称催化氧化催化剂使用,是未来的一个研究发展方向。     

Untersuchungen an oxidischen Katalysatoren. XXXVII. Zum Einfluß der Herstellungsbedingungen auf die Eigenschaften röntgenamorpher Al2O3?SiO2-Festkörper

Studies on Oxide Catalysts. XXXVII. On the Influence of Preparation Conditions on the Properties of Silica-Alumina Silica-alumina samples of different composition were prepared by coprecipitation from aqueous solutions at pH = 6 and pH = 9, respectively. Structures and properties of the solids were characterized (i.r., DTA, X-ray, molybdato method, surface acidity, catalytic activity in the cracking reaction of cumene). Solid composition and pH value of the precipitation medium equally exhibit influence on the structure of the silica-alumina (kind of incorporation of the aluminium) and thereby on the acidic and catalytic properties of the solids. Silica-alumina of equal composition but precipitated at different pH values may widely differ in their properties including activity-composition dependency.     

Hydrophobins: Proteins that self assemble at interfaces

Hydrophobins are surface active proteins that are produced by filamentous fungi. They are interesting from a Surf Sci point of view because some of their properties as surface active proteins are quite spectacular. In this review, recent advances in understanding these properties will be surveyed. We will attempt to define what the properties are that make them unique. As an understanding of both structure and function of hydrophobins is emerging we see that this is paving the way for industrial applications as well as an understanding of their biological functions.

Major recent advances

Recently there has been a clear increase in attempts to use hydrophobins in applications. We are starting to understand their unique properties as surfactants and especially applications related to the stability and development of foams and various surface treatments are emerging. There are several new reports on molecular structures as well on mechanisms of self-assembly. Hydrophobins have functions in biology that are far from understood, but also here techniques are developing and a broader understanding is emerging.     

餐厨废油制备的生物基两性表面活性剂的油水界面性能

以餐厨废油制备了生物基两性表面活性剂,应用界面张力和动态光散射方法,研究了该生物基两性表面活性剂体系的油水界面性能及在溶液中的聚集行为。 在无外加碱条件下,由餐厨废油制备的表面活性剂表现出良好的界面性能,在50~70 ℃以及pH值为7~12的条件下,均可以将油水界面张力降至超低值(<10^-3 mN/m),在不同的油藏模拟地层水中均保持较好的界面活性;分别在50、-20和4 ℃下保存,其界面活性均未受到明显影响。 在水溶液中形成的聚集体的平均流体力学半径为10~30 nm,无机盐离子的加入可使聚集体的粒径上升。 基于其优良的界面性质和可再生来源,由餐厨废油制备的生物基两性表面活性剂在三次采油方面具有重要的应用价值。     

多孔材料化学:从无机微孔化合物到金属有机多孔骨架

本文主要从无机微孔化合物和金属有机多孔骨架的合成化学和结构化学这两方面来介绍多孔材料化学的研究进展。多孔材料是一类具有规则孔结构的固态化合物,它们在催化、分离、离子交换等工业领域有着广泛的应用。硅铝酸盐是最为人们所熟知的微孔分子筛,经过半个多世纪的发展,人们又相继开发出磷酸盐、砷酸盐、锗酸盐、亚磷酸盐、硫酸盐、亚硒酸盐以及金属硫化物等类沸石无机微孔化合物。近十多年来,配位聚合物与金属有机多孔骨架开始大量兴起,为微孔化合物的多样化与组成的复杂性增添了新的领域。     

Microemulsion method: A novel route to synthesize organic and inorganic nanomaterials: 1st Nano Update

Synthesis of nanoparticles by microemulsion method is an area of considerable current interest. Since the discovery of microemulsions, they have attained increasing significance both in basic research and in different industrial fields. Due to their unique properties, namely, ultralow interfacial tension, large interfacial area, thermodynamic stability and the ability to solubilize otherwise immiscible liquids. The uses and applications of microemulsions are numerous in chemical and biological fields. The nanoparticles not only are of basic scientific interest, but also have resulted in important technological applications, such as catalysts, high-performance ceramic materials, microelectronic devices, high-density magnetic recording and drug delivery. The microemulsion technique promises to be one of the versatile preparation method which enables to control the particle properties such as mechanisms of particle size control, geometry, morphology, homogeneity and surface area. This review aims to give a vivid look on the use of microemulsions for synthesizing and controlling the grain size and morphology of the nanoparticles and at the same time will summarize some recent works carried out in the synthesis of organic and inorganic nanoparticles by this method.     

Biosurfactants: Formulations,properties, and applications

In this review, we attempt to give an overview on the recent progress made on biosurfactants, surface-active biomolecules produced by microorganisms, which are a sustainable alternative to synthetic surfactants. Different biosurfactants, their production techniques, and their physical and chemical properties are discussed. There is a focus on recent studies related to surface properties and rheology of biosurfactants, both being properties which affect their ability to take part in a stable formulation. Biosurfactants can have applications in multiple different industrial sectors, such as agriculture, medicine, personal care, food, petroleum, etc. The specific properties important for applications in these sectors are discussed in detail.     

Microscopic Perspective on the Adsorption Isotherm of a Heterogeneous Surface

Adsorption of dissolved molecules onto solid surfaces can be extremely sensitive to the atomic-scale properties of the solute and surface, causing difficulties for the design of fluidic systems in industrial, medical and technological applications. In this communication, we show that the Langmuir isotherm for adsorption of a small molecule to a realistic, heterogeneous surface can be predicted from atomic structures of the molecule and surface through molecular dynamics (MD) simulations. We highlight the method by studying the adsorption of dimethyl-methylphosphonate (DMMP) to amorphous silica substrates and show that subtle differences in the atomic-scale surface properties can have drastic effects on the Langmuir isotherm. The sensitivity of the method presented is sufficient to permit the optimization of fluidic devices and to determine fundamental design rules for controlling adsorption at the nanoscale.     

反气相色谱法研究煤直接液化残渣经分级提取前后的表面性质变化

采用反气相色谱法（IGC）分别对煤直接液化残渣（DCLR）脱灰处理后不溶物、正己烷不溶物、甲苯不溶物、四氢呋喃不溶物的表面性质进行表征。基于非极性探针净保留体积V_n分别采用Dorris-Gray方法和Schultz方法得到表面色散自由能,基于极性探针V_n得到吸附焓△H^sp,并通过△H^sp作图计算得到酸常数K_a和碱常数K_b。结果表明,经溶剂分级提取后表面色散自由能、K_a和K_b均发生明显变化。而DCLR呈现两性偏碱性这一特征并未随分级提取发生改变。IGC作为一种动力学吸附技术,可快速准确表征DCLR在经分级提取过程中表面性质的变化,相同温度下应用Dorris-Gray方法得到DCLR表面色散自由能略高于Schultz方法。     

Fractal analysis of hydroxyapatite from nitrogen isotherms

Samples of calcium hydroxyapatite, CaHap, were prepared via a wet method and subjected to thermal treatment in air in the temperature range 100-900 degrees C. Nitrogen adsorption-desorption isotherms were obtained on different samples, and their data points were used to analyze the fractal properties of the obtained solids. Both FHH and Neimark's equations were used for such purpose, and the agreement or disagreements between obtained results on using both equations are discussed. Considering the appropriate values of the obtained surface fractal dimensions D, it was concluded that an appreciable defractalization of the prepared hydroxyapatite is only noted upon calcinations at 900 degrees C. Below this temperature the loss in surface area and pore volume result from simultaneous bulk and surface mass transport, which conserve the initial surface roughness and average pore radius. Calcination at 900 degrees C caused sintering to proceed via bulk mass transport, with a consequent pore widening and a decrease in surface roughness.     

Application of programmed thermodesorption of the liquid under quasi-isothermal conditions to investigate physicochemical properties of liquid layers and solid surfaces

This paper presents the results of measurements of the programmed thermodesorption of polar and nonpolar liquids from the surface of different types of solids. The course of thermodesoption was found to depend on the properties of the solid and the wetting liquid. Thermodesorption occurred not exponentially but in steps, which reflects the noncontinuous changes in the properties of the surface layer with the distance from the solid surface. This effect intensified with the increase in polarity of the wetting liquid and the heterogeneity of the solid surface. The earlier investigations showed that application of the method of differential thermal analysis allowed determination of the distribution of the adsorption potential of the liquid on the solid surface.The author is indebted to Prof. M. Jaroniec for very fruitful discussions and to Prof. J. Choma for the activated carbon samples.