Preferential wettability

If two materials with preferential wettability of two liquids are considered, the liquids have a tendency to flow along the surface of the material to which they have the greatest affinity. The behavior of drop on the zone-selectively modified with hydrophilic and hydrophobic material is shown in Figure 7.19b. The liquid drop was placed on the boundary of hydrophilic and hydrophobic zones on a plate immersed in another immiscible liquid. In the case of octane drop for the plate immersed in water, it was moved toward the hydrophobic zone and settled and when the two-zone plate was dipped in octane and a water drop was placed on the boundary, and the drop settled in the hydrophilic zone... 

Equilibrium displacement experiments Equilibrium displacement experiments were carried out to determine pore-size distribution from air-brine curves, capillary pressure versus saturation, and preferential wettabilities of reactive and non-reactive oil/ water systems (10). The well-defined synthetic system, described in the previous section and used in the dynamic displacement experiments, was used in the equilibrium displacement studies. The equilibrium displacement characteristics were determined by a constant speed centrifugal technique (11). 

Flotation separation utilizes differences in surface wettability of materials. This process is being widely used by mining industry and has been proposed for the separation of plastics waste [15], [16]. A schematic of flotation column is shown in Fig 4. In the process the materials to be separated are treated with various chemicals which make some fractions preferentially wettable. The separation occurs in a column where the mixture to be separated is contacted with water in which air bubbles are dispersed. Air bubbles attach themselves to the hydrophobic particles floating them to the surface while hydrophilic particles sink to the bottom. In another version of this process, when both of the materials to be separated are either hydrophilic or hydrophobic but exhibit different critical surface tensions of wetting (defined as a surface tension of a liquid in which the solid exhibits transition from hydrophilic to hydrophobic behaviour), a liquid medium can be selected such that... 

Wettability refers to the preferential spreading of one fluid over solid surfaces in a two-fluid system and is dependent upon the interfacial tension. The wetting... 

Fig. 12.11 Examples of pesticide concentration vs. depth, indicating preferential flow of each pesticide in individual field plots. Symbols C continuous I intermittent P ponding S spiinkhng TG technical grade EC emulsifiable concentrate WP wettable powder U undisturbed D disturbed (Ghodrati and Jury 1990)...

In conU ast to the internal surface reversed-phases described above, Kima-ta s internal surface reversed-phases are synthesized without use of enzymes. These Ci, Cg, Cig, and phenylethyl-modified porous silica supports are treated with HCI at 100 C for 5 h to cleave preferentially the ester bonds at the external surface (127). Hydrolysis inside the pores is extfemely slow because of hydrolysis products that are enriched in the pores, low wettability, and the presence of air bubbles. The generated silanol groups are reacted with 3-glycidoxypropyl-trimethoxysilane, which is then hydrolyzed to hydrophilic diol groups. Several variations of Kimata s supports with different hydrophobicity exist, so these phases can be used for analyzing a broad spectrum of analytes. 

Wettability. The wettability of the porous medium refers to its preference for one or the other fluid in becoming wet. It is defined as the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids (7). In a rock-oil-brine system, it is a measure of the preference that the rock has for either the oil or the water. A water-wet rock is preferentially wetted by the water phase, and similarly for an oil-wet system, the rock primarily makes contact with the oil phase. 

When separate phase hydrocarbons and grovmdwater are both present in a porous rock, one of the two immiscible phases will preferentially adhere to the rock matrix. The wettability of the rock is a measure of which fluid preferentially adheres to the rock. The boundary between two immiscible fluids... 

Is the formulation wettable with fast drop penetration time Is there possible preferential wetting of active vs. excipients Is little growth required, applying only a nucleation stage of granulation ... 

Mobility control is one of the most important concepts in any enhanced oil recovery process. It can be achieved throngh injection of chemicals to change displacing fluid viscosity or to preferentially rednce specific flnid relative permeability through injection of foams, or even through injection of chemicals, to modify wettability. This chapter does not address a specific mobility control process. Instead, it discusses the general concept of the mobility control requirement in enhanced oil recovery (EOR). 

Hirasaki et al. (1983) assumed that if an excess water phase wets preferentially to a microemulsion phase and a microemulsion phase preferentially to an oleic phase, then (1) in the absence of an excess water phase, the microemulsion is the wetting phase (2) in the absence of an excess oil phase, the microemulsion is the nonwetting phase and (3) when all the three phases are present, the microemulsion is a spreading phase between the excess oil and excess water. Hirasaki et al. (2008) further pointed out that the current understanding of microemulsion phase behavior and wettability is that the system wettability is likely to be preferentially water-wet when the salinity is below the optimal salinity (Winsor I) and is likely to be preferentially oil-wet when the salinity is above the optimal salinity (Winsor II), even in the absence of alkali. Their view is supported by Nelson et al. (1984), Israelachvili and Drummond (1998), and Yang (2000). 

Seal properties Rock seal properties are usually described in terms of their capillary pressure characteristics, primarily wettability, entry and displacement pressures, and irreducible wetting phase saturation. Wettability defines which fluids will preferentially occupy the smallest rock pores. Entry pressure is the capillary pressure at which the non-wetting phase first displaces the wetting phase, while displacement pressure is the capillary pressure at which the non-wetting phase first forms a continuous network within the pore structure. The irreducible wetting phase saturation describes the initial connate fluid saturation at the top of the capillary column. 

Association of Textile Chemists and Colorists recently [3] described the incorporation of small amoimts of fluorocarbon derivative in a polymeric material normally used to treat textiles for water repellency. They observed that the fluorocarbon preferentially adsorbed at the interfaces and decreased the values to 16 to 18 dynes per cm. Their films clearly showed the ability to self-heal, for when the initially adsorbed layer was deliberately scraped off, additional molecules quickly adsorbed at the interface when the polymer matrix was recured at an elevated temperature. The usefulness of adsorbed films of surface active molecules is thus apparent, and one may expect wide application of this technique to specific problems. The present study, in combination with previous investigations of wettability and surface activity in organic liquids, forms an excellent guide for the design and synthesis of further surface active agents for polymeric systems. 

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