Adsorption mixed solutes

PVA Particles. Dispersions were prepared in order to examine stabilization for a core polymer having a glass transition temperature below the dispersion polymerization temperature. PVA particles prepared with a block copolymer having M PS) x 10000 showed a tendency to flocculate at ambient temperature during redispersion cycles to remove excess block copolymer, particularly if the dispersion polymerization had not proceeded to 100 conversion of monomer. It is well documented that on mixing solutions of polystyrene and poly(vinyl acetate) homopolymers phase separation tends to occur (10,11), and solubility studies (12) of PS in n-heptane suggest that PS blocks with Mn(PS) 10000 will be close to dissolution when dispersion polymerizations are performed at 3 +3 K. Consequently, we may postulate that for soft polymer particles the block copolymer is rejected from the particle because of an incompatibility effect and is adsorbed at the particle surface. If the block copolymer desorbs from the particle surface, then particle agglomeration will occur unless rapid adsorption of other copolymer molecules occurs from a reservoir of excess block copolymer. 

In the following example, a solid consisting of a soluble constituent A and an insoluble constituent B is considered. Leaching is carried out with a pure solvent S and a solution is produced containing a mass a of A, per unit mass of S and the total mass of A in solution is P. It will be assumed that the quantity of solvent removed in the underflow from each of the thickeners is the same, and that this is independent of the concentration of the solution in that thickener. It will be assumed that unit mass of the insoluble material B removes a mass s of solvent S in association with it. Perfect mixing in each thickener will be assumed and any adsorption of solute on the surface of the insoluble solid will be neglected. In a given thickener, therefore, the ratio of solute to solvent will be the same in the underflow as in the overflow. 

In a scheme complementary to the one just presented where thiols are removed by reductive desorption of thiols, molecules can also be removed during stripping of a UPD layer. This was demonstrated by Shimazu et al. [221] where an alkane thiol SAM was deposited onto a Au(l 11) that had been modified with Pb. Oxidative stripping of the lead also caused thiols to be removed. The empty sites were then subsequently filled with mercaptopropionic acid (MPA). A remarkable result is that the binary SAMs exhibit only one desorption peak. From this it was concluded that a well-mixed layer forms that is very different from the mixed SAM obtained by adsorption from solution containing both types of thiols. In this case the layer exhibits singlecomponent domains that are refiected by two desorption peaks. 

It is also noteworthy that the surface tension of mixed solutions of anionic and cationic surfactants is controlled by the activity of the salt (38). These results indicate that, in adsorption of an ionic surfactant at the solution surface, the accompanying adsorption of the counter ion also plays an important role. 

It is obvious from the data that the total surface adsorption of 1 1 mixed solution (I ) is less than the sum of the surface adsorptions of pure surfactant and RDH solutions. Similarly, rc,F (or TcioS ) is less than rc p-(or r ps") and Troh less than Froh (e.g., for 1 1 CyFNa-... 

Surface Adsorption and Micellization of the Mixed Solution of Fluorocarbon and Hydrocarbon Surfactants... 

For the surface adsorption of binary mixed solution at a constant ionic strength, the Gibbs equation is (6)... 

From Fig.7 the calculated 3 -values of 1i1 CgSOC-CjFNa solution at different surface tension are shown in Table B together with the X g- obtained from the adsorption data by the Gibbs theorem. For the 1i1 mixed solution, assuming ideal (as the solution is dilute), then ... 

Adsorption of Two Surfactants. We now denote a quantity valid at the onset of micellization in the equilibrium mixed surfactant solution by the superscript c. Thus, the chemical potential of surfactant i in the mixed solution or in the mixed surface phase at the onset of micellization is given by... 

The possibi Lity of mixed solution and adsorption phenomena contributing to chromatographic retention must be considered. Several factors are responsible for retention in GC, including bulk liquid partition, liquid interfacial adsorption, and solid support adsorption. One or all of these factors may play a major role depending upon the experimental parameters chosen (e.g., temperature, percent liquid phase, nature of "inert" support, solute. 

Figure 15.7. Adsorption of liquid mixtures on charcoal. Chloroform + acetone and benzene + ethanol. The ordinate gives the amount of each individual substance that is adsorbed, the abscissa the mol fraction of chloroform (mixed with acetone) or the mol fraction of benzene (mixed with ethanol). (Data gathered by Kipling. Adsorption from Solutions of Non-Electrolytes, 1965).

Pyrene-labeled SA mixed monolayers were prepared by adsorption from solutions of the desired concentration of a particular fatty acid, along with a small fraction (1-5%) of the probe Py-C16. All solutions used were of total acid concentration of 5xl0 3M. 

As trial system to test the application of the proposed model the ability of encapsulated XAD-7 was evaluated for the selective separation of berberine from dilute aqueous mixtures of berberine and dopamine, the target secondary metabolite, and an undesirable intermediate metabolite of Thalictrum rugosum plant cell culture [18]. Competitive adsorption experiments were performed in dilute aqueous mixtures of berberine and dopamine, both at initial concentrations of 60 mg l-1, which is representative of actual plant cell culture. Experimental and theoretical results for normalized bulk concentration profiles of berberine and dopamine are shown in Fig. 10. The bulk berberine concentration was reduced to approximately 4.6% of the initial concentration, which indicates that 95.4% of the berberine in the initial mixed solution was adsorbed. Encapsulated XAD-7, therefore, selectively concentrated the berberine from dilute aqueous mixtures of berberine and dopamine. 

Following the investigations of Schiith, Stucky and Unger and their co-workers, various procedures have been proposed for the preparation of M41S and other related materials. For example, Edler and White (1995) have described a method for the low-temperature synthesis of a pure silica form of MCM-41. An essential stage in their preparative route was the controlled ageing of the mixed solution of sodium silicate and cetyltrimethylammonium bromide (CTAB) before the intermediate product was filtered, washed, dried and finally calcined in air at 350°C. Comparison with standard hydrother-mally produced material revealed no significant difference in the adsorption properties. 

Definitions of energies or enthalpies of adsorption from solution 148 Definition of displacement enthalpies (and energies) 149 Definition of the enthalpies (and energies) of mixing 149... 

Bonded stationary phases for NPC are becoming increasingly popular in recent years owing to their virtues of faster column equilibration and being less prone to contamination by water. The use of iso-hydric (same water concentration) solvents is not needed to obtain reproducible results. However, predicting solute retention on bonded stationary phases is more difficult than when silica is used. This is largely because of the complexity of associations possible between solvent molecules and the chemically and physically heterogeneous bonded phase surface. Several models of retention on bonded phases have been advocated, but their validity, particularly when mixed solvent systems are used as mobile phase, can be questioned. The most commonly accepted retention mechanism is Snyder s model, which assumes the competitive adsorption between solutes and solvent molecules on active sites... 

A natural clay has been pillared with mixed solutions containing both A1 and Fe, Ti or Cr. The intercalation-generated solids distribution of acid strengths measured by calorimetric adsorption of ammonia is comparable to that of zeoUtes. The surfaces appear as heterogeneous and show initial adsorption heats close to 150-160 kJ moT if one excludes the first point of the differential heat versus coverage curves, which is much higher (=190kJ mol" ) [109]. 

For the in-situ FTIR analyses, mixed solutions were spread by the same hion onto a house-made minitrough that fitted into the sample chamber of the FTIR instrument. For every in-situ experiment, the close-packed monolayer was initially formed on DI water that was then replaced with ImM CdCl2 solution by careful circulation of the subphase using a peristaltic pump. The background spectrum was taken for a bare water surface when the sample was Ae monolayer on pure water, and was taken for a close-packed monolayer on pure water when the sample was the one on the cadmium-containing subphase. The latter technique enhanced the carboxylate peak relating to ion adsorption. All the experiments were done at room temperature. 

The same steps as discussed above for the case of isotope exchange (diffusion in liquid film, surface reaction, intraparticle diffusion) were considered in a kinetic model [771] of metal ion adsorption from solution. This model was presented in a book with diskettes (FORTRAN program, rate controlled by reaction, by transport or mixed control). 

Fig. 2 The construction of a polymer-cushioned lipid bilayer membrane. (A) Architecture constructed in a sequential way first, onto the functionalized substrate a polymer layer (cushion) is deposited by adsorption from solution and covalent binding, followed by the (partial) covalent attachment of a lipid monolayer containing some anchor lipids as reactive elements (B) able to couple the whole monolayer to the polymer cushion. (C) Alternatively, a lipopolymer monolayer, organized, e.g., at the water-air interface can be co-spread with regular low-mass amphiphiles and then transferred as a mixed monolayer onto a solid support, prefunctionalized with reactive groups, able to bind covalently to the polymer chains of the lipopolymer molecules, (B). (D) By a fusion step (or a Langmuir Schaefer transfer) the distal lipid monolayer completes the polymer-tethered membrane architecture...

Adsorption measurements with different supports or catalysts were carried out by using a mixed solution of cinchonidine and substrate 1 (4 mmol/1 for each) in solvent B. After stirring at 298 K for 1 h, the amount of each compound adsorbed was determined from the decrease in the concentration of the solution, The concentrations were monitored by HPLC. The mean crystallite sizes of Pd in the reduced catalysts were obtained from XRD line broadening. The total surface areas (Sbet) and the areas of Pd metal surface (Spa) were determined using the nitrogen adsorption at 77 K and by the CO chemisorption at 323 K, respectively. 

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