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Важное петрофизикам в Journal of Colloid and Interface Science (БЕН получает)
bne: Journal of Colloid and Interface Science На сайте Elsiever есть графические резюме статей Молодцы Буду отмечать о самом интересном (что планирую смотреть)
Ответов - 3
bne: Theoretical model for the wetting of a rough surface Pages 472-477 K.M. Hay, M.I. Dragila, J. Liburdy By what mechanism is water propelled along rough surfaces? A theoretical relationship describing the wetting of a rough surface is derived based on capillary and frictional forces Рисунок не импортируется, жаль, красиво. ;-) [img]http://www.sciencedirect.com/cache/MiamiImageURL/B6WHR-4SP3SPV-2-1/0?wchp=dGLzVlz-zSkWb[/img] Electrokinetics in nanochannels: Part I. Electric double layer overlap and channel-to-well equilibrium Pages 526-538 Fabio Baldessari In this paper a new model is described for calculating the electric potential field in a long, thin nanochannel with overlapped electric double layers. Electrolyte concentration in the nanochannel is predicted self-consistently via equilibrium between ionic solution in the wells and within the nanochannel. Differently than published models that require detailed iterative numerical solutions of coupled differential equations, the framework presented here is self-consistent and predictions are obtained solving a simple one-dimensional integral. The derivation clearly shows that the electric potential field depends on three new parameters: the ratio of ion density in the channel to ion density in the wells; the ratio of free-charge density to bulk ion density within the channel; and a modified DebyeЁCHЁ№ckel thickness, which is the relevant scale for shielding of surface net charge. For completeness, three wallЁCsurface boundary conditions are analyzed: specified zeta-potential; specified surface net charge density; and charge regulation. Predictions of experimentally observable quantities based on the model proposed here, such as depth-averaged electroosmotic flow and net ionic current, are significantly different than results from previous overlapped electric double layer models. In this first paper of a series of two, predictions are presented where channel depth is varied at constant well concentration. Results show that under conditions of electric double layer overlap, electroosmosis contributes only a small fraction of the net ionic current, and that most of the measurable current is due to ionic conduction in conditions of increased counterion density in the nanochannel. In the second of this two-paper series, predictions are presented where well-concentration is varied and the channel depth is held constant, and the model described here is employed to study the dependence of ion mobility on ionic strength, and compare predictions to measurements of ionic current as a function of channel depth and ion density. Article Outline 1. Introduction 2. Theoretical formulation 2.1. Distribution of ions (ni(r)) and free-charge (¦СE(r)) 2.2. The potential distribution in a wide, shallow channel (¦Ч(y)) 2.2.1. Boundary condition I (BC I): specified wall-potential (¦Ч(0)=¦Ж) 2.2.2. Boundary condition II (BC II): specified wall-charge density 2.2.3. Boundary condition III (BC III): charge regulation 2.3. Ionic mobility dependence on ionic strength and pH 2.4. Electroosmotic flow 2.5. Net ionic current 3. Parameter estimates in thin EDL regime: zeta potential, surface charge density, and fraction of chargeable sites 4. Theoretical results for constant BGE well concentration, and varying channel depth 5. Conclusions and recommendations Appendix A. Appendix Appendix B. Appendix Appendix C. Appendix References ================= Electrokinetics in nanochannels: Part II. Mobility dependence on ion density and ionic current measurements Pages 539-546 Fabio Baldessari Abstract In the first of this two-paper series, a new model was developed for calculating the electric potential field in a long, thin nanochannel with overlapped electric double layers. The model takes into account the dependence of ion mobility on local ion densities and pH. This model is used here to study and demonstrate the effect of ion density and pH on ionic current measurements. A comparison is shown of predictions based on each of three boundary conditions, as studied in Part I. The model developed in Part I is validated by comparing simulations with measurements of ionic current as a function of sodium borate concentration. Results show that predictions based on extended Debye–Hückel theory for ion mobility significantly improve the accuracy of simulations, but that these do not predict exact scaling behavior. A simple bulk conductivity measurement used as input parameter for the simulations, in place of the predicted bulk conductivity (K0), guarantees agreement with data in the thin EDL region. Results also indicate that the charge regulation boundary condition, complemented with an adequate bulk electrolyte model, provides better agreement with experimental trends than the specified zeta potential or specified surface net charge boundary conditions. Further, it is shown that currents due to advection (by electroosmotic flow) are in all cases studied less than 25% of the total current in the system. Article Outline 1. Introduction 2. Overview of channel-to-well equilibrium model for ionic current 3. Materials and experimental methods 3.1. Nanochannel fabrication 3.2. Electrolyte solutions 3.3. Current and conductivity measurements 4. Bulk electrolyte model for pH and experimental validation 5. Results for varying BGE well concentration and constant channel depth 6. Conclusions and recommendations References =================================================================
bne: Permselectivity and microstructure of anion exchange membranes Pages 215-222 Xuan Tuan Le Abstract The water content, the ion exchange capacity, the transport number of counter-ion of the AMV and AMX anion exchange membranes were determined. The two-phase model (gel phase and interstitial phase) of structure microheterogeneity was validated by means of conductivity measurements. The chronopotentiometric results allowed us to affirm the overall surface homogeneity of the membranes. According to the two-phase model, the influence of the gel phase and the interstitial phase on the membrane permselectivity was discussed in detail. Majorities of co-ions exist in the interstitial phase, thus they have no influence on the transport of counter-ions in the gel phase. The determination of the KCl amount sorbed in the interstitial phase confirmed the existence of partition equilibrium between the interstitial phase and the external solution. Such partition equilibrium can be considered within the microheterogeneous model in order to represent the internal structure of the electromembranes. Article Outline 1. Introduction 2. Experimental methods 2.1. Anion exchange membranes 2.2. Ion exchange capacity 2.3. Water content 2.4. Membrane density 2.5. Membrane resistance 2.6. Solution conductivity 2.7. Amount of sorbed electrolyte 2.8. Transport number of counter-ion in the membrane 2.9. Chronopotentiometry 3. Results and discussion 3.1. Water content and sorption electrolyte in the membranes 3.2. Membrane microstructure 3.2.1. Two-phase model of structure microheterogeneity 3.2.2. Refinement of the two-phase model 3.3. Membrane surface homogeneity 4. Conclusion Acknowledgements Appendix A. Nomenclature References ---------------- Abstract The surface energy of some clays belonging to the smectite group has been calculated starting from crystal structures and combining a partial charge model with the computation of the lattice energy. The dioctahedral smectites studied here include montmorillonite; beidellites; and nontronite. One of the differences between these clays is the location of the substitution in the octahedral sheet or in the tetrahedral one. Another is the possibility of vacancies in cis- or trans-octahedral positions. These locations and vacancies have an effect on the distortion of the crystal framework and therefore on the surface energy. Calculated surface energies of the solid samples increase in the order beidellites > montmorillonite > nontronite. The bond energy between the interlayer cation and the layer appears to follow the same order and to depend both on the nature of the most electropositive elements of the layer and on their location. The trends obtained provide elements for an analysis of data related to interlayer enlargement. Article Outline 1. Introduction 2. Presentation of studied clays 2.1. Montmorillonites 2.2. Beidellites 2.3. Nontronite 3. Computational background 3.1. Lattice energy 3.2. Atomic charges 3.3. Calculations for crystals and layers 4. Results and discussion 4.1. Atomic charges 4.2. Lattice energy 4.3. Surface energy 5. Conclusions References
bne: Coagulation of bitumen with kaolinite in aqueous solutions containing Ca2+, Mg2+ and Fe3+: Effect of citric acid Pages 85-91 Weibing Gan, Qi Liu Abstract Heterocoagulation experiments of kaolinite with solvent-diluted-bitumen were carried out to investigate the effect of hydrolyzable metal cations and citric acid on the liberation of bitumen from kaolinite. The adsorption of Ca2+ and Mg2+ on kaolinite, and zeta potentials of kaolinite and bitumen droplets in solutions containing of Ca2+, Mg2+ and Fe3+ with or without citric acid were also measured. It was found that the heterocoagulation of bitumen with kaolinite was enhanced in the presence of the metal cations from pH 7 to pH 10.5, accompanied by a decrease in the magnitude of the zeta potentials and an increase in the adsorption of the metal cations on kaolinite and possibly on bitumen droplets. The addition of citric acid reduced the degree of coagulation from 90% to less than 40% in the presence of Ca2+ and Mg2+ cations at pH10, and at pH8 for Fe3+. It was found that hydrolyzable metal cations enhanced bitumen–kaolinite interactions through electrical double layer compression and specific adsorption of the metal hydrolysis species on the surface of kaolinite. The effect of metal cations was removed by citric acid through formation of metal–citrate complexes and/or the adsorption of citrate anions, which restored the zeta potentials of both kaolinite and bitumen. Therefore, electrostatic attraction or repulsion was responsible for the coagulation or dispersion of kaolinite particles from bitumen droplets in the tested system. Article Outline 1. Introduction 2. Materials and methods 2.1. Minerals and chemicals 2.2. Experimental methods 2.2.1. Preparation of stock suspensions for zeta potential measurement 2.2.2. Bitumen–kaolinite coagulation 2.2.3. Zeta potential measurement 2.2.4. Adsorption of multivalent metal ions on kaolinite 3. Results and discussion 3.1. Coagulation of bitumen with kaolinite 3.1.1. In the presence of Ca2+, Mg2+ and Fe3+ 3.1.2. In the co-presence of the metal cations and citric acid 3.2. Zeta potentials of kaolinite and bitumen 3.2.1. Effect of multivalent metal cations 3.2.2. Effect of citric acid 3.3. Adsorption of Ca2+ and Mg2+ on kaolinite 3.4. Total potential energy of interaction between bitumen and kaolinite 4. Conclusions Acknowledgements References ========================
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