Adsorption concentration effect

E. Bouchaud and M. Daoud, Polymer adsorption concentration effects, J. Phys. (Paris) 48, 1991 (1987). 

Effects of Surfactants on Solutions. A surfactant changes the properties of a solvent ia which it is dissolved to a much greater extent than is expected from its concentration effects. This marked effect is the result of adsorption at the solution s iaterfaces, orientation of the adsorbed surfactant ions or molecules, micelle formation ia the bulk of the solution, and orientation of the surfactant ions or molecules ia the micelles, which are caused by the amphipathic stmcture of a surfactant molecule. The magnitude of these effects depends to a large extent on the solubiUty balance of the molecule. An efficient surfactant is usually relatively iasoluble as iadividual ions or molecules ia the bulk of a solution, eg, 10 to mol/L. 

At equilibrium surfactant concentrations of less than 0.0003 M SDS where the hematite surface is still positively charged, adsorption of surfactant follows its normal pattern due to the electrostatic forces which provide the driving force for adsorption. Sufficient effective surface area must be available for this level of SDS adsorption density. As surfactant adsorption... 

McKinley, J.P. Jenne, E.A. (1991) Experimental investigation and review of the solids concentration" effect in adsorption studies. Environ. Sci. Technol. 25 2082-2087 McKinnon, W. Choung, J.W. Xu, Z. Einch, J.A. (2000) Magnetic seed in ambient temperature ferrite process applied to acid mine drainage treatment. Environ. Sci. Techn. 34 2575-2581... 

Thus for each zone, during a given cycle, the adsorption-desorption process is separated into two distinct events with F or G describing the kinetics of each event. Such an approach is of course valid only for first order rate reactions. In the limit of low concentration, (such as that resulting from slow leaching from a repository) the reaction sites on the rock will not approach saturation and the number of reaction sites can be considered to remain constant during adsorption. Therefore, for a single species in solution at tracer concentrations the reaction should approximate a first order reaction (i.e., where no complications such as concentration effects, step-wise dehydration, dissociation, etc., are present). 

This publication arranges the published papers on adsorption of polymers with special regard to experiment and theory. A summary of all investigated systems is given. The experimental methods are outlined and the amounts adsorbed are discussed as a function of the system and experimental parameters (polymer, adsorbent, solvent, molecular, concentration, time, weight and temperature). Calculated and experimental amounts of saturation, the number of contact points per molecule adsorbed, the thickness of the adsorbed layer, the adsorption isotherms, the heats of adsorption, the effects of desorption are compared. Assumptions on the structur of the adsorbed layer and the mechanism of polymer adsorption are made and discussed. 

Competition between the inhibitor and the growth units will affect the concentration of growth units on the terraces. If the adsorption step is rate-limiting, then this competition can be expected to affect the growth rate in various ways. The area available for adsorption is effectively decreased... 

Other effects may also contribute to band broadening causing reduced achievable plate counts. Besides the already-mentioned wall adsorption, temperature effects (Joule heating) may reduce plate numbers. Sample application can have a strong influence on plate count, especially when large volumes and/or high sample concentrations are injected. Mobility differences between buffer constituents and analyte ions lead to asymmetric (triangular) peaks caused by electrodispersion, which is extremely noticeable with smaller molecules. Differ-... 

On the other hand, for highly retained analyte (phenanthrene) the hnal peak width will not be significantly greater than theoretically estimated. This is because this component shows strong interaction with the stationary phase and while it is being loaded on the column, it will tend to adsorb on the surface immediately after it comes into contact with the stationary phase as a result, even though it takes up to 6 sec to transfer all 100 pL to the column, phenanthrene will be concentrated on the top portion of the column, the so-called adsorption compression effect (Figure 3-27). 

This value indicates that AAH has not only many active sites for ion-exchange process, but also a very well-developed specific surface area. Exchange adsorption is effective at very low equilibrium concentrations. 

The laboratory and field results show that the aquifer basalt has limited capacity for adsorption of As(V), presumably by naturally occurring HFO. However, addition of HFO can significantly increase As(V) adsorption. The effectiveness of HFO addition to this aquifer depends on the HFO concentration and the pH because the concentration of adsorption sites on HFO increases with decreasing pH. Initially, pH adjustment will only be... 

As comprehensively reviewed by Lipson and Guillet (1), inverse gas chromatography (IGC) has been used as a convenient tool to study the thermodynamic properties of polymeric systems. Despite its wide usage, all experimental and theoretical factors in this technique are not fully understood. Loading determination, usually done by means of extraction or calcination, has been considered to be the most significant source of experimental error (2.). Other factors, such as concentration effects associated with large injection sizes, slow diffusion of solute probe molecules in the stationary phase, and adsorption of probes onto the liquid-support interface, may also af-... 

FIGURE 5.44 Biopolymer concentration effect on adsorption. Source Data from Lotsch (1988). 

Figure 5.49 shows the polymer concentration effect on the permeability reduction factor, F, predicted from Eq. 5.36. This figure shows that F is a weak function of polymer concentration, and it increases shghtly within a low concentration range. Concentration quickly reaches a plateau. This effect is consistent with the polymer adsorption shown in Figure 5.43. 

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