Competitive adsorption/displacement

Gu, B., T. L. Mehlhorn, L. Liang, and J. F. McCarthy. 1996. Competitive adsorption, displacement, and transport of organic matter on iron oxide. II. Displacement and transport. Geochimica et Cosmochimica Acta 60 2977-2992. 

Surface dilatational rheology is a very sensitive technique to analyze the competitive adsorption/displacement of protein and LMWE emulsifier at the air-water interface (Patino et al., 2003). A common trend is that the surface dilatational modulus increases as the monolayer is compressed and is a maximum at the highest surface pressures, at the collapse point of the mixed film, and as the content of LMWE in the mixture increases. At higher TT, the collapsed protein residues displaced from the interface by LMWE molecules have important influence on the dilatational characteristics of the mixed films. The mechanical properties of the mixed films also demonstrate that, even at the highest tt, the LMWE is unable to displace completely protein molecules from the air-water interface. 

Competitive adsorption of molecules at interfaces, or the displacement of one stabilizing molecule by another, is an important process in food manufacture. Molecular rearrangement at interfaces not only affects the... 

Wijmans, C.M., Dickinson, E. (1999). Brownian dynamics simulation of the displacement of a protein monolayer by competitive adsorption. Langmuir, 15, 8344-8348. 

Displacement-Purge Cycle This cycle, which is somewhat similar to the previous one, differs from it in that a gas or vapor which adsorbs about as strongly as the adsorbate is used to remove the adsorbate (see Figure 1) Removal is thus facilitated both by adsorbate partial-pressure reduction in the fluid around the particles and by competitive adsorption of the displacement medium. As with the inert-purge cycle, the maximum delta loading is the equilibrium loading ... 

No attempt was made to reduce the ash content of the humic acid samples, since drastic purification methods can cause abnormal changes in humate characteristics, and it was believed that most organic acids in their natural environment would be in salt form and associated with other colloidal matter. Though competition from displaced cations may have contributed to the smaller uptake by humic acid (HA II) in the adsorption stage (as shown in Table 2.1), any residual counterions should have had little effect on the metal-ion extraction step. 

From a process-engineering point of view, there is now a better understanding of the development of concentration profiles in chromatographic columns under overloaded conditions available. This includes in particular the quantitative description of displacement and tag-along effects caused by competitive adsorption. Since it is now possible (as mentioned before) to simulate concentration profiles on a personal computer, the choice of the appropriate mode... 

Figure 8. Fibrinogen-albumin competition adsorption onto Silastic, poly(NVP)/ Silastic, and poly(H EM A)/Silastic. Untreated Silastic and films grafted with poly(NVP) (2.7 mg/cm ) or poly(HEMA) (5.8 mg/cm/) were equilibrated in solutions containing 0.01 mg fibrinogen/ml plus the concentration of albumin corresponding to the albumin/fibrinogen ratio depicted. The solvent was O.OIM HEPES, 0.147M NaCl, 0.02% azide, pH 7.4. Equilibration was carried out at 37°C for 20 hrs and was ended by dilution displacement rinse with buffer. The films were further rinsed by soaking for at least 20 hrs prior to counting to determine the fibrinogen on the film.

The two breakthrough curves of both components are described by convex isotherms with competitive adsorption and show a typical displacement effect for the weaker retained R-enantiomer. 

Figure 6.28 compares measured and simulated profiles for the batch separation of EMD53986. Very good agreement between theory (solid lines) and experiment (symbols) is achieved using the multi-component modified-Langmuir isotherm (Fig. 6.21). Also shown are the simulation results neglecting component interaction by using only the single-component isotherms (dashed line), which deviate strongly from the observed mixture behavior. Typical for competitive adsorption is the displacement of the weaker retained R-enantiomer and the peak expansion of the stronger adsorbed S-enantiomer.

---