Dynamic adsorption experiments

Also, other dependent variables associated with CO2-foam mobility measurements, such as surfactant concentrations and C02 foam fractions have been investigated as well. The surfactants incorporated in this experiment were carefully chosen from the information obtained during the surfactant screening test which was developed in the laboratory. In addition to the mobility measurements, the dynamic adsorption experiment was performed with Baker dolomite. The amount of surfactant adsorbed per gram of rock and the chromatographic time delay factor were studied as a function of surfactant concentration at different flow rates. 

Results and Discussion on Dynamic Adsorption Measurements. Baker dolomite was used to study the dynamic adsorption experiment. The computed porosity of the rock was 24%. One concentration below the CMC of AEGS, one at CMC, and two concentrations above CMC were chosen to measure the adsorption of this surfactant with Baker dolomite. The mass of surfactant adsorbed per gram of rock is plotted as a function of flow rate in a semi-log plot in Figure 9. 

The slopes of the peaks in the dynamic adsorption experiment is influenced by dispersion. The 1% acidified brine and the surfactant (dissolved in that brine) are miscible. Use of a core sample that is much longer than its diameter is intended to minimize the relative length of the transition zone produced by dispersion because excessive dispersion would make it more difficult to measure peak parameters accurately. Also, the underlying assumption of a simple theory is that adsorption occurs instantly on contact with the rock. The fraction that is classified as "permanent" in the above calculation depends on the flow rate of the experiment. It is the fraction that is not desorbed in the time available. The rest of the adsorption occurs reversibly and equilibrium is effectively maintained with the surfactant in the solution which is in contact with the pore walls. The inlet flow rate is the same as the outlet rate, since the brine and the surfactant are incompressible. Therefore, it can be clearly seen that the dynamic adsorption depends on the concentration, the flow rate, and the rock. The two parameters... 

Results obtained previously by the authors [8] have shown that the static adsorption capacities of several commercially available ACs, conformed as monolith composites, towards o-DCB were directly related to their micro and narrow mesopore volumes. Of the original twelve ACs studied in these static adsorption measurements the four most promising materials were selected for further study in dynamic adsorption experiments. These samples... 

This equivalent area was then compared with the measured external area and Sbet- The full results of the dynamic adsorption experiments are given in Table 3. 

Dynamic adsorption experiments with -decane in the empty 0.45-m glass chamber and in the chamber with a carpet sample have been used to test the performance of the two-sink model and compare it with the one sink model. The two-sink model provided a much better regression of data points than the previous one sink model. Figures... 

Finally, the microemulsion specific refraction can be correlated with the fraction of sulfonate adsorbed because it is a sensitive function of the relative oil and brine content of the microemulsion. Its utility should also extend to dynamic adsorption experiments. The specific refraction is therefore an extremely useful microemulsion property in adsorption studies as well as in terms of its correlation with microemulsion interfacial tensions versus equilibrated excess phases. 

Sorbie et al. (1987c, 1989d) have applied the above equations to the modelling of dynamic adsorption experiments using HPAM solutions in outcrop sandstone cores. In this work, a series of consecutive floods, first at 50 ppm HPAM concentration, were performed until the core had reached its maximum adsorptive capacity at that concentration (Cq = 50 ppm). A similar series of floods was performed for Cq = 100 ppm and so on. For each flood, both the polymer effluent profile and the tracer ( Cl) profile were measured. Experimental results for the first two 50 ppm floods and the first 100 ppm flood are shown in Figures 7.13 and 7.14, where they are compared with theoretical calculations based on the non-equilibrium adsorption model discussed above. Good semi-quantitative agreement is obtained in this work... 

Flow rate The system must be capable of processing a moderate volume of air per unit time to be of practical use. However, the empirical formulations for the dynamic adsorption coefficient described in this paper are valid only for a certain range of conditions. Experiments will be performed to identify the flow rate/flow channel diameter combination beyond which the formulations are no longer valid. 

Fig. 7 presents partial results of dynamic regime experiments for chromate adsorption and desorption by ODA-clinoptilolite. As shown by breakthrough curves, ODA-clinoptilolite column quantitatively removes chromate species from simulated waste water , apparently more efficiently by lower flow rate. Consequently to similar configuration of chromate and sulfate molecules, such loaded column was more efficient to regenerate with Na2S04 than NaCl solution, as elution curves at the Fig. 7 illustrate. 

Very recently, experiments using new techniques have been performed by Lodewyckx et al. [4], X-ray microtomography coupled with image analysis allows visualising dynamic adsorption of organic vapour and water vapour on activated carbon. Figure 17.3 in [4] shows profiles inside the bed at different times. It is remarkable that the fronts seem to be of constant pattern shape. 

The activated dissociation of H2 (D2) on Cu(l 11) and other single crystal Cu surfaces has played a special role in the development of reactive gas-surface dynamics. Early experiments and theory by Cardillo and collaborators [217-219] first demonstrated the power of molecular beam techniques to probe activated adsorption and the theoretical methodology developed by them (6D quasi-classical dynamics on a model PES) only differs from modem treatments in the use of DFT based PES. 

The complex pore structure of MCM-22 is also reflected in the unique three step uptake profile of bulky 2,2-dimethylbutane (DMB) observed in the dynamic sorption experiment [12], shown in Figure 4. Each step is attributed to adsorption into different sections of MCM-22, but specific assignment is ambiguous. 

Since this book is dedicated to the dynamic properties of surfactant adsorption layers it would be useful to give a overview of their typical properties. Subsequent chapters will give a more detailed description of the structure of a surfactant adsorption layer and its formation, models and experiments of adsorption kinetics, the composition of the electrical double layer, and the effect of dynamic adsorption layers on different flow processes. We will show that the kinetics of adsorption/desorption is not only determined by the diffusion law, but in selected cases also by other mechanisms, electrostatic repulsion for example. This mechanism has been studied intensively by Dukhin (1980). Moreover, electrostatic retardation can effect hydrodynamic retardation of systems with moving bubbles and droplets carrying adsorption layers (Dukhin 1993). Before starting with the theoretical foundation of the complicated relationships of nonequilibrium adsorption layers, this introduction presents only the basic principles of the chemistry of surfactants and their actions on the properties of adsorption layers. 

Many adsorption experiments on long chain fatty acids and other amphiphiles at the liquid/air interface and the close agreement with the von Szyszkowski equation is logically one proof of the validity of Langmuir s adsorption isotherm for the interpretation of y - log c -plots of typical surfactants in aqueous solutions (cf. Appendix 5D). This evidence is also justification for use of the kinetic adsorption/desorption mechanism based on the Langmuir model for interpreting the kinetics and dynamics of surface active molecules. 

More or less systematic studies have been carried out on nonionic surfactants below the CMC but there is lack of systematic studies on micellar and mixed surfactant solutions. Moreover, there is an almost complete lack of studies on ionic surfactants, as discussed in Chapter 7. It seems that comprehensive experiments on adsorption dynamics can be performed on the basis of the recent theories and considerably improved experimental technique in order to understand the formation and action of dynamic adsorption layers better. This of course applies unrestrictedly to proteins, and mixed surfactant/protein systems where the level of imderstanding is even lower than for surfactants solutions (de Feijter Benjamins 1987, Serrienetal. 1992). 

The state of experiments in general seems to be underdeveloped as compared with the level of broad theoretical studies of dynamic adsorption layers on moving bubbles and drops. Most of all the lack of systematic studies, which are obviously necessary for a further development of... 

Desorption experiments are crucial for the validation of adsorption models and in particular for confirming the estimates of the adsoihed masses. Two desorption experiments have been carried out in order to test the reliability of the two-sink model for estimating the masses in the sinks. One of the desorption tests followed dynamic adsorption of n-dodecane, the other the static adsorption of n-decane. The results showed that (1) the masses deposited into the sinks are released very slowly (2) the two-sink model estimates the masses in the sinks reasonably well therefore, this model may be considered a satisfactory tool for estimating chamber (or test material) sinks. It coherently confirmed the existence of two sinks with different saturation rates, also giving reasonable estimates of the relative parameters. 

Later in Chapter 6 a large variety of technologies based on adsorption effects will be described. It will also be shown that in general, these technologies work under dynamic conditions and an improvement of the surfactant s efficiency, made in the by past trial and error or thanks personal experience, is now more and more based on a systematic analysis of the entire technology and the particular impact of the surfactants used. The optimisation of surfactants and their mixtures requires specific knowledge of their dynamic adsorption behaviour [1]. The most frequently used parameter to characterise the dynamic properties of liquid adsorption layers is the dynamic interfacial tension. Many techniques exist to measure dynamic tensions of liquid interfaces having different time windows from milliseconds to hours and days. As direct measurements of the time process of adsorption of surfactants at liquid interfaces are rare... 

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