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Possible ways of producing bilayer vesicles are reviewed from the theoretical point of view. The emphasis is on vesiculation driven by a negative bending energy of spherical vesicles, called spontaneous vesiculation. A new model is presented to explain the existence of onions, i.e. concentric spheres of equidistant membranes.
Synthesis of zeolites is characterized by a long lag crystallization period. However, this period is not dead; many precrystallization processes are active, leading to nucleation, followed by rapid crystallization. The most lag-active species are complexes of aluminum and, to a lesser extent, silicium and sodium. If these complexes are exposed to non-equilibrium conditions or outside stress, modified...
Chemicals in the environment continue to cause concern. One method of decreasing the environmental impact of surfactants is to design new molecules that are more efficient and effective in their interfacial activity. New types of surfactants with two hydrophilic and two or three hydrophobic groups in the molecule, called gemini surfactants, exhibit these characteristics. When properly designed, they...
Environmental contaminants in water, soil, and air, as well as changes in their concentration with respect to space and time may be quite effectively detected by the analysis of appropriate indicators (biomatrices from different levels of the food chain, sediments, sludges, dusts) which accumulate these chemicals by several orders of magnitude. However, regular monitoring of the environment...
The use of bentonites as adsorbents results from the reactivity of montmorillonite which is the main mineral in this clay-like material. Montmorillonite, a 2:1 clay mineral, impresses by a diversity of reactions in the interlayer space and at the external surfaces, which are the cause of strong adsorption of heavy metal ions and organic compounds. Bentonite adsorbents are used as crude bentonite,...
The adsorption of ionic surfactants on different soil components such as silica, clay minerals, and humic acids was studied. The adsorption processes were controlled by flow microcalorimetry to determine the molar adsorption enthalpies of surfactant accumulation on clay and silicate surfaces. The evaluation of adsorption results for cationic surfactants has shown different mechanisms for solids having...
The adsorption of dodecylpyridinium chloride and dodecyltrimethylammonium bromide on Na-kaolinite is investigated by studying the effect of electrolyte and temperature on the adsorption, by means of electrophoresis and microcalorimetry. A sharp distinction between adsorption in the first and second layer is observed. The point where these two regions meet is retrieved in all experiments. Second layer...
Data are presented to show that the surfaces of a common clay mineral, montmorillonite, modify the properties of the nearby water to a depth of at least 3.5 nm and that the value of every water property depends exponentially on t, the thickness of the films of adsorbed water, but is independent of the character of the surfaces. The viscosity and yield point are among the properties of the water that...
Enthalpy of charging of hematite surface was determined by calorimetry and also by measuring the dependence of the point of zero charge (p.z.c.) on temperature. The calorimetric experiment was designed in such a way that the point of zero charge was in the middle between the initial and final pH. In that case, the reaction heat corresponds to the difference in standard reaction enthalpies of surface...
In this work the ion exchange kinetics of Cd2+ at Mg2+-montmorillonite have been investigated. These kinetics are fast, i.e., the exchange in diluted suspension is complete after 30 s, therefore, the stopped flow method is applied. The data were analyzed by the kinetic spectrum method, because the reaction cannot be described by classical kinetic models. Two processes were observed: i) A fast one...
In connection with the mathematical modeling of the transport of pollutants in soil the selection of data from literature plays an important role. In the case of sorption of pollutants mainly partition coefficients and rate constants from batch-experiments are available. For the transformation of these sorption parameters to the transport of pollutants in soil, however, the dependence of these parameters...
The paper reports on labscale column studies for in situ surfactant washing of oil-contaminated soils. The displacment efficiency of nonionic surfactants and their blends was tested on small columns. The kinetics of oil displacement and surfactant sorption-desorption were studied. Further, the viscosity behavior of emulsions of varying compositions was investigated. No single optimum HLB value was...
The adsorption on clay minerals and sesquioxides of some polar degradation products of naphthalene and alkylated benzenes was investigated by 14C-tracer experiments. Surface charge density of the solids was measured by titration with sodium polyethene sulfonate and polydiallyldimethyl-ammonium chloride at pH-range 4–7. Adsorption of organic anions reduced the positive charge on oxidic surfaces and...
X-ray microscopy is capable of imaging objects with a higher resolution than light microscopy. The reason is the shorter wavelength of x-rays compared to visible light. Up to now, the smallest structures that can be visualized are about 30 nm in size. It is possible to image objects directly in their aqueous environment without preparational procedures like drying, staining, etc. In the wavelength...
The applicability of x-ray microscopy for the direct investigation of clay aggregates in water is demonstrated. As coagulating agents Ca2+, an anionic and a cationic detergent were used. The internal structures of the aggregates formed by the addition of the surfactant could be clearly visualized.
Micro-surface-enhanced Raman scattering (micro-SERS) has been used to study, in situ, the competitive and displacement adsorption of cetylpyridinium chloride (CPC) and p-nitrophenol (PNP) on charged silver micro particle surfaces. The investigations have shown that this surface spectroscopy is an extremely powerful technique for monitoring the interfacial behavior of CPC and PNP, for assessing adsorbate...
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