Wetting immersional

The depth of immersion of the solid in the wetting liquid is determined by the contact angle 0 the smaller the value of 0, the greater the depth of immersion. When 0 = 0°, immersion is complete. Here again, the relation of ySA — ySL to 7U, as given in equation 6.4, determines the value of 0. 

The surface free energy change per unit area or driving force for the three different types of wetting can be expressed as 

From these expressions we can see that in all wetting processes, reduction of the interfacial tension between substrate and the wetting liquid jSL is beneficial, but that reduction of the surface tension of the liquid yM per se is not always of benefit. 

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A. Heats of Adsorption from Heat of Immersional Wetting Data.288... 

Zettlemoyer, A.C., 1965. Immersional wetting of solid surfaces. Industrial and Engng. Chemistry, 57 27-36. 

In immersional wetting, the solid, which is not originally in contact with the liquid, is immersed completely in the liquid. The area of liquid-gas interface, therefore, remains unchanged. The free energy change for immersion of a solid in a liquid is given by... 

Suppose that the solid is originally not in contact with water but is immersed completely (i.e., immersional wetting). In this case, the water penetrates the capillaries in the solid. The energy change for immersional wetting, called the adhesion tension, is given by ... 

According to this approach wettability is equated to the work exchanged by the immersion system with its surroundings when the process of immersional wetting of... 

The wettability, which we propose to denote A immy, is directly measured by the difference between two surface tensions. This difference was called the adhesion tension by Adamson (1967) and the work of immersional wetting per unit area by Everett (1972). It has also been referred to as the wetting tension . 

Of the four types of wetting phenomena examined in the previous section, only immersional wetting lends itself to direct microcalorimetric measurement spreading and adhesion experiments would involve too small interfacial areas (say, no more than c. 100 cm2), whereas condensational wetting would require measurements up to p/p° = 1. As we saw in Chapter 3, these are the conditions where accurate measurements of the amounts of gas adsorbed are difficult to achieve. For this reason we confine the following recommendations to immersion microcalorimetry.. ... 

Thermodynamically, three types of wetting can be distinguished spreading, adhesional and immersional wetting. Figure 5.8 shows the underlying physical phenomena, illustrated for the case of a solid, a liquid and a gas. 

Immersional wetting (fig. 5.8c) takes place if the solid is completely wet, that is, it is the result of spreading for S > 0 during the entire process, as in case (a). It is a less general phenomenon than adhesional wetting. It is noted that forced immersion of only partially wettable objects in a liquid leads in practice to the entrainment of air bubbles on the surface. 

Dekany, I. and Nagy, L. G. Immersional wetting and adsorption displacement on hydrophilic/hydrophobic surfaces.. Colloid Interface Sci. 147(1) 119—28, 1991. 

Adsorption and immersional wetting on hydrophilic and hydrophobic silicates... 

Adsorption capacities, specific surface areas and immersional wetting data of different kaolinite-and illite organocomplexes... 

Figure 5. The molar immersional wetting enthalpy on illite organocomplexes with different hydrophobicity (O) in methanol, and ( ) in benzene.

Figure 8. The molar immersional wetting enthalpy on organo-montmorillonite with different hydrophobicity in methanol (----nonswelling illite,--swelling montmorillonite).

Immersional wetting enthalpy on Na-Y and dealuminated Y zeolites (after heating at 623 K) in different organic liquid... 

Immersional wetting corresponds to a process where a solid—vacuum or solid-vapor interface is replaced by a soHd—liquid one. When starting from a solid-vacuum interface, the free energy variation during the process is (per unit area)... 

Three types of wetting have been distinguished (Osterhuf, 1930) (1) spreading wetting, (2) adhesional wetting, and (3) immersional wetting. The equilibria involved in these phenomena are well known. 

A third type of wetting is immersional wetting, where a substrate not previously in contact with a liquid is immersed completely by the liquid (Figure 6-5). In this case, the surface free energy change per unit area is... 

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