Search results for "Electrokinetic phenomena"
showing 8 items of 38 documents
Treatment of Gaseous Effluents Produced During Electrochemically Assisted Soil Remediation Processes
2021
In many cases, electrochemically assisted soil remediation processes, like electrokinetic or electroheating ones, produce gaseous effluents that need to be collected and treated. Adsorption, absorption, and catalytic and thermal oxidation are often used for the treatment of these gaseous effluents. The chapter describes these technologies reporting their main advantages and disadvantages. Eventually, a comparison of the performances of these technologies was carried out.
An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer
2008
The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer solutions were studied. The rheological behaviour of lecithin-chitosan vesicles was determined by shear stress against shear rate measurements, as well as by the variation on the hysteresis loop area. The results were compared with the rheopectic behaviour of soy lecithin dispersions without chitosan. An important change on the rheological properties of the complex dispersion was observed, depicting in a thixotropic behaviour with a plastic character in the presence of chit…
Synthesis of spherical porous silicas in the micron and submicron size range: challenges and opportunities for miniaturized high-resolution chromatog…
2000
Classical silica technology has reached its limit with respect to an ultimate minimum particle size of about 2 microm in diameter. Here, a novel process is presented which allows one to synthesize porous silica beads and control their particle diameter in situ, within the range of 0.2-2.0 microm. As a result, no sizing is required and losses of silica are avoided. Furthermore, the process enables one to control in situ the pore structural parameters and the surface chemistry of the silica beads. Even though surface funtionalized silicas made according to this process can principally be applied in fast HPLC the column pressure drop will be high even for short columns. In addition, the column…
Viscoelastic properties of concentrated dispersions in water of soy lecithin
2003
Abstract Viscoelastic properties of soy lecithin dispersions at 60, 120, 180 and 240 g l−1 in water have been studied as a function of ionic strength (NaCl concentrations in the range 10−5–10−2 mol l−1) and of preparation method (sonication, freezing–unfreezing). Viscosity measurements of sonicated dispersions in a rotatory viscometer show Newtonian and plastic (Bingham) behavior, whereas the frozen–unfrozen dispersions show a spectacular change in their viscoelastic properties, that is, a non-Newtonian behavior with pseudoplastic characteristics and rheopexy. These properties have been related to electrokinetic characteristics of the segregated vesicles in each case. A decrease in ζ-potent…
Observable Streaming Potential in Membranes
2003
Theories describing the electrokinetic processes in membranes usually involve nonobservable variables. One of these phenomena is the streaming potential, i.e., the electric potential generated by a pressure difference imposed across the membrane system. In this work the streaming potential is successfully described by using observable variables in the framework of thermodynamics of irreversible processes. The observable electric potential is the central quantity of the transport equations. The relaxation with time of this electric potential difference is well explained by the solute flux in these transport equations. The fluxes and forces defined in the formulation permit one to analyze the…
Discontinuous electrokinetic chromatography of parabens using different substituted resonances as pseudostationary phases
1999
Resorcarene derivatives, negatively charged even at moderate pH, were synthesized and employed as pseudostationary phases to achieve mobilities exceeding that of the electroosmotic flow. Under these conditions, a discontinuous electrolyte system was developed which allows the separation of four uncharged homologous 4-hydroxybenzoic esters (parabens) within a zone of resorcarene electrolyte, and the detection of these UV active compounds in a resorcarene-free zone, free from the high UV background absorbance of the resorcarenes. Resorcarenes, with differently charged functionalities (carboxylate and phosphate groups) to provide the electrophoretic mobility and with alkyl residues of differen…
Structural selectivity provided by starburst dendrimers as pseudostationary phase in electrokinetic chromatography
1995
Abstract Starburst dendrimers (SBDs) were used as a pseudostationary phase in electrokinetic chromatography (EKC) of hydrophobic compounds. The selectivity of SBD-mediated EKC (SBD-EKC) was different from those in micellar EKC (MEKC) systems, in spite of the apparent structural resemblance between micelles and SBDs. The SBDs provided similar selectivity as polymer gel packing materials in reversed-phase liquid chromatography (RPLC), showing little selectivity for alkyl groups and clear preference for aromatic compounds, especially for rigid, planar polynuclear aromatic hydrocarbons. The alkylation of SBDs resulted in the increased retention and hydrophobic selectivity while maintaining the …
Optical tweezing electrophoresis of isolated, highly charged colloidal spheres
2001
Abstract We report on a novel optical tweezing experiment measuring the electrophoretic mobility μ of highly charged spherical particles suspended in water at volume fractions Φ≤2×10 −7 . At deionised conditions μ =2.5×10 −8 m 2 V −1 s −1 , it decreases further upon increasing the salt concentration c . We compare our data to measurements at larger Φ, where generally much larger μ and a qualitatively different dependence on the salt concentration are observed. To characterise the dependence on Φ we performed measurements at no added salt. There the mobility increases in the unordered state but stays constant at μ =6.8×10 −8 m 2 V −1 s −1 as the system develops fluid order. In the ordered re…