Water-organic interface, chemically

Chemically Benign Synthesis at Organic-Water Interface... 

Asterisks indicate that there were insufficient data to correlate results. Sets 1, 5, 9, 13 impeller midway in denser phase, H/4. Sets 2,6, 10,14 impeller midway in lighter phase, 3/7/4. Sets 3,7,11,15 impeller at organic-water interface, ///2. Sets 4, 8, 12, 16 two impellers, one midway in each phase, ///4, 3///4. (Reprinted with permission from Skelland, A.H.P., and Seksaria, R., Ind. Eng. Chem. Proc. Des. Dev. 17 (1), Copyright 1978, American Chemical Society.)... 

LIM ZHONG Chemically Benign Synthesis at Organic—Water Interface 173... 

Soap is one example of a broader class of materials known as surface-active agents, or surfactants (qv). Surfactant molecules contain both a hydrophilic or water-liking portion and a separate hydrophobic or water-repelling portion. The hydrophilic portion of a soap molecule is the carboxylate head group and the hydrophobic portion is the aUphatic chain. This class of materials is simultaneously soluble in both aqueous and organic phases or preferential aggregate at air—water interfaces. It is this special chemical stmcture that leads to the abiUty of surfactants to clean dirt and oil from surfaces and produce lather. 

Many organic electrode processes require the adsorption of the electroactive species at the electrode surface before the electron transfer can occur. This adsorption may take the form of physical or reversible chemical adsorption, as has been commonly observed at a mercury/water interface, or it may take the form of irreversible, dissociative chemical adsorption where bond fracture occurs during the adsorption process and often leads to the complete destruction of the molecule. This latter t q)e of adsorption is particularly prevalent at metals in the platinum group and accounts for their activity as heterogeneous catalysts and as... 

Estuaries exhibit physical and chemical characteristics that are distinct from oceans or lakes. In estuaries, water renewal times are rapid (10 to 10 years compared to 1 to 10 years for lakes and 10 years for oceans), redox and salinity gradients are often transient, and diurnal variations in nutrient concentrations can be significant. The biological productivity of estuaries is high and this, coupled with accumulation of organic debris within estuary boundaries, often produces anoxic conditions at the sediment-water interface. Thus, in contrast to the relatively constant chemical composition of the... 

Clearly, then, the chemical and physical properties of liquid interfaces represent a significant interdisciplinary research area for a broad range of investigators, such as those who have contributed to this book. The chapters are organized into three parts. The first deals with the chemical and physical structure of oil-water interfaces and membrane surfaces. Eighteen chapters present discussion of interfacial potentials, ion solvation, electrostatic instabilities in double layers, theory of adsorption, nonlinear optics, interfacial kinetics, microstructure effects, ultramicroelectrode techniques, catalysis, and extraction. 

Valsaraj, K.T. (1988) On the physico-chemical aspects of partitioning of non-polar hydrophobic organics at the air-water interface. Chemosphere 17, 875-887. 

Injection of steam or heated air into the subsurface provides large amounts of thermal energy, which speeds the mobilization of adsorbed organic contaminants and results in their removal as either a vapor or liquid phase. Elevated temperature increases the vapor pressure of the chemicals involved and promotes transfer of constituents across the air-water interface, which results in the increased removal of contaminants in high-humidity or nearly saturated soil systems. Additionally, the presence of high-temperature water sometimes results in oxidation or hydration of organic contaminants. 

This book deals only with the chemistry of the mineral-water interface, and so at first glance, the book might appear to have a relatively narrow focus. However, the range of chemical and physical processes considered is actually quite broad, and the general and comprehensive nature of the topics makes this volume unique. The technical papers are organized into physical properties of the mineral-water interface adsorption ion exchange surface spectroscopy dissolution, precipitation, and solid solution formation and transformation reactions at the mineral-water interface. The introductory chapter presents an overview of recent research advances in each of these six areas and discusses important features of each technical paper. Several papers address the complex ways in which some processes are interrelated, for example, the effect of adsorption reactions on the catalysis of electron transfer reactions by mineral surfaces. 

Spectroscopic techniques may provide the least ambiguous methods for verification of actual sorption mechanisms. Zeltner et al. (Chapter 8) have applied FTIR (Fourier Transform Infrared) spectroscopy and microcalorimetric titrations in a study of the adsorption of salicylic acid by goethite these techniques provide new information on the structure of organic acid complexes formed at the goethite-water interface. Ambe et al. (Chapter 19) present the results of an emission Mossbauer spectroscopic study of sorbed Co(II) and Sb(V). Although Mossbauer spectroscopy can only be used for a few chemical elements, the technique provides detailed information about the molecular bonding of sorbed species and may be used to differentiate between adsorption and surface precipitation. 

Chemical relaxation methods can be used to determine mechanisms of reactions of ions at the mineral/water interface. In this paper, a review of chemical relaxation studies of adsorption/desorption kinetics of inorganic ions at the metal oxide/aqueous interface is presented. Plausible mechanisms based on the triple layer surface complexation model are discussed. Relaxation kinetic studies of the intercalation/ deintercalation of organic and inorganic ions in layered, cage-structured, and channel-structured minerals are also reviewed. In the intercalation studies, plausible mechanisms based on ion-exchange and adsorption/desorption reactions are presented steric and chemical properties of the solute and interlayered compounds are shown to influence the reaction rates. We also discuss the elementary reaction steps which are important in the stereoselective and reactive properties of interlayered compounds. 

Hoff, J.T., Mackay, D., Gihham, R., and Shiu, W.-Y. Partitioning of organic chemicals at the air-water interface in environmental systems, Environ. Sci. Technol., 27(10) 2174-2180, 1993. 

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