摘要:

The stability of water-in-crude oil (or model crude oil) emulsions was determined by means of separation/sedimentation tests and high voltage destabilization tests. First the impact of the state of solvation of asphaltencs on their ability to stabilize emulsions were studied. Secondly, we analyzed the role of naturally occurring waxes in the stabilization of emulsions. Finally, the emulsion stability when both asphaltenes and waxes are involved was investigated.

ISSN:0193-2691    

DOI:10.1080/01932699808913179

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The enthalpy, entropy and heat capacity change of the dissolution of calcium and barium laurates, myristates and palmitates were determined by reaction calorimetry and by solubility at different temperatures. Heat capacity change, due to water restructuring or "iceberg" formation, was found to increase with the chain length. Linearity was observed up to 12 C-atoms in the chain, while the dissolution of chains with 16 C-atoms was accompanied by a significantly higher increase in the heat capacity than it would be expected. This phenomenon was explained on the basis of synergistic effect, i.e. by mutual promotion in the water restructuring.

ISSN:0193-2691    

DOI:10.1080/01932699808913180

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The adsorption of the cationic surfactant dodecyl trimethyl ammonium bromide (DTAB) and of the nonionic surfactant dodecyl octaethylene glycol ether (C12E8) on four different layer silicates and their influence on the sorption processes of the fungizide biphenyl were studied. Unexpectedly, no great differences were found in comparing the adsorption of the two surfactants on the basis of physicochemical investigations, although the adsorption mechanism up to monolayer formation is fundamentally different (ion exchange and physisorption). Thus, the plateau values of the adsorption isotherms and the molar enthalpies of displacement Δ21h are of the same order of magnitude for both surfactants and the same basal spacing by intercalation is observed in the case of swelling clays. The isotherms of the hydrophobic contaminant biphenyl are of the linear Cl-type at all layer silicates and very low adsorption takes place approximately proportionally to the BET (N2) surface area. If the surface is weakly hydrophobized by surfactants (csurfactant<< critical;micelle concentration (CMC)), biphenyl adsorption is clearly increased. These processes can be adequately described using the distribution coefficients K and KOC(Henry coefficient related to the organic carbon content). KOCis hardly influenced by the type of layer silicate for DTA+-layer silicates, whereas the C12E8layer silicate complexes generally show higher, but also different KOCvalues. If the surfactant concentrations are above the CMC, solubilization and adsorption compete for the pollutant molecules, which leads to a significant decrease in biphenyl adsorption.

ISSN:0193-2691    

DOI:10.1080/01932699808913181

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of α-hydroxy group on the phase behavior in a skin lotion model system was studied by determining the phase diagrams for the two systems acetic acid / Laureth 4 / white oil / water and glycolic acid / Laureth 4 / white oil / water using visual observation by optical microscopy. The two acids when combined with surfactant and water gave an isotropic liquid solution, and a lamellar liquid crystal with different amounts of solubilization showing both acids to act as hydrotropes. The result provided essential information about the differences in the phase behavior which can attribute to the presence of a-hydroxy group in the glycolic acid. Small angle x-ray diffraction was used to determine the boundaries of the lamellar liquid crystal phases in the two systems, both acids were found to be located in the water region in the liquid crystal.

ISSN:0193-2691    

DOI:10.1080/01932699808913182

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor