Adsorption of the surfactant

The adsorption of the surfactant Aerosol OT onto Vulcan Rubber obeys the Langmuir equation [237] the plot of C/x versus C is linear. For C = 0.5 mmol/1, C/x is 100 mol/g, and the line goes essentially through the origin. Calculate the saturation adsorption in micromoles per gram. 

The third generation are latices made with independentiy prepared surfactant to mimic the in situ prepared functional monomer surfactant. These emulsifiers are often A—B block polymers where A is compatible with the polymer and B with the aqueous phase. In this way surface adsorption of the surfactant is more likely. These emulsions are known to exhibit excellent properties. 

The presence of calcium and magnesium ions increases the adsorption of the surfactants at the water-air interface and leads to a corresponding lowering of the surface tension at the CMC as shown by the data in Table 4. A C16 branched AOS gives a lower surface tension than a linear C16 AOS this too is in agreement with other model studies and theoretical predictions [42, and Sec. 2 on interfacial tension). 

Within the low-capacity region between the adsorption/desorption peaks around the electrocapillary maximum (ecm see Fig. 3.18), the depression of the base current is greatest because of maximum adsorption of the surfactant in that area. 

One of the main problems to be solved in the analysis of cationic surfactants is the strong adsorption of the surfactant to glassware, tubing and apparatus. To avoid losses, the solvent system used should contain a substantial percentage of organic solvent. Additionally, mobile phases containing more than 20-25% methanol will help to inhibit micelle formation [46]. 

These types of surfactants have the largest share of world-wide total production [14] and the highest application rates in household, trade and industrial processes. As these compounds were handled mainly in aqueous systems, they were consequently discharged with the waste-water. After a more or less efficient wastewater treatment (WWT) process, which results in an elimination, i.e. degradation by wastewater biocoenosis and/or adsorption of the surfactants to the sludge, these polar compounds and their metabolites either reach the environment by wastewater discharges or are adsorbed to wastewater sludge,... 

The model for the adsorption of the surfactant mixtures includes six parameters Tioo, F onoo Py l i> 2 and fCnon. which can be obtained by regression analysis. 

It is noted that the molecular interaction parameter described by Eq. 52 of the improved model is a function of the surfactant concentration. Surprisingly, the dependence is rather significant (Eig. 9) and has been neglected in the conventional theories that use as a fitting parameter independent of the surfactant concentration. Obviously, the resultant force acting in the inner Helmholtz plane of the double layer is attractive and strongly influences the adsorption of the surfactants and binding of the counterions. Note that surface potential f s is the contribution due to the adsorption only, while the experimentally measured surface potential also includes the surface potential of the solvent (water). The effect of the electrical potential of the solvent on adsorption is included in the adsorption constants Ki and K2. 

In the detergency process, fatty materials (i.e. dirt, often from human skin) are removed from surfaces, such as cloth fibres, and dispersed in water. It is the surfactants in a detergent which produce this effect. Adsorption of the surfactant both on the fibre (or surface) and on the grease itself increases the contact angle of the latter as illustrated in Figure 4.7. The grease or oil droplet is then easily detached by mechanical action and the surfactant adsorbed around the surface of the droplet stabilises it in solution. 

This process results in hydration of the bulders with simultaneous adsorption of the surfactant. 

The first three mechanisms of surfactant adsorption have been criticized mainly because crack propagation velocities in comminution devices are often much more than the rate of adsorption of the surfactants normally used as grinding aids (20). There is considerable evidence and concurrence of opinion on the prevention of agglomeration as the mechanism of grinding aid action (21). 

Once the negative charges on the particle surface have been neutralised further adsorption of the surfactant occurs via the tail on to the hydrophobic patches of the surface and also by association of the hydrocarbon chains. Detailed adsorption studies have been reported on polystyrene latices (36). The additional adsorption provides a positive charge to the particles and restabilization occurs.. The sterpnasa of this phenomenon is... 

Fourier-transformed infrared spectroscopy (FT1R), either in the transmission mode(70), the grazing incidence reflection (GI) mode(7,5) or the attenuated total reflection (ATR) mode(7,2), has been the most widely used experimental tool for the characterization and structure determination of SA monolayers. GI-IR is especially useful in determining the molecular orientation in the film structures because it senses only the vibrational component perpendicular to the substrate surface(7,5). Polarized ATR-IR can also be used to study molecular orientation(7,77). McKeigue and Gula-ri(72) have used ATR-IR to quantitatively study the adsorption of the surfactant Aerosol-OT. 

System 1. Under ideal conditions the adsorption of a surfactant into the EDL proceeds as described in Chap. 3. The border of efficiency of anionic and cationic surfactants is IP or PZC, as follows from the correlation of e.g. adsorption density, potential and notability are dependent on pH [e.g. 44,129,167,174-176]. The course of such an adsorption is shown in Fig. 15. If H+ or OH" react with the surface of one mineral the released ions or their hydrolytic products can adsorb on unequally charged surface of the other mineral and cause an activated adsorption of the surfactant, or they can inhibit the adsorption, as shown on the schemes ... 

Surfactants also aid the comminution of the particles by bead milling, whereby adsorption of the surfactant at the solid/liquid interface and in cracks facilitates their disruption into smaller units. 

By adsorption of the surfactant from phase A, jA is increased and thus A j becomes larger. In addition to this a fraction of the interfacial tension ym acts on the horizontal plane having a value of i/, [> cos 0 with 0 being the contact angle in B, i.e. the oily phase. The resulting force R is called contact tension and is defined as ... 

While kinetics are mostly responsible for the stability of macroemulsions, thermodynamics plays a role because adsorption of the surfactant or polymer on the interface of the globules affects the stability in a major way. In what follows it will be shown that thermodynamics can explain some of the overall features observed experimentally regarding the stability of emulsions. 

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