Fractional wettability

Brown, R.J.S. and Fatt, I. 1956. Measurements of fractional wettability of oil-field rocks by the nuclear magnetic relaxation method. Pet. Trans. AIMS 207 262-270. 

The fractional wettability of the porous medium, defined as a measure of the fraction of the internal surface of the porous medium in contact with one fluid (13) was determined by the USBM method (14). In the USBM method for determining wettability, the logarithm to the base 10 of the ratio of areas under a secondary drainage (A3) and an imbibition capillary pressure (A2) versus water saturation curves is used to define the wettability scale. 

Albertsson (Paiiition of Cell Paiiicle.s and Macromolecules, 3d ed., Wiley, New York, 1986) has extensively used particle distribution to fractionate mixtures of biological products. In order to demonstrate the versatility of particle distribution, he has cited the example shown in Table 22-14. The feed mixture consisted of polystyrene particles, red blood cells, starch, and cellulose. Liquid-liquid particle distribution has also been studied by using mineral-matter particles (average diameter = 5.5 Im) extracted from a coal liquid as the solid in a xylene-water system [Prudich and Heniy, Am. Inst. Chem. Eng. J., 24(5), 788 (1978)]. By using surface-active agents in order to enhance the water wettability of the solid particles, recoveries of better than 95 percent of the particles to the water phase were obsei ved. All particles remained in the xylene when no surfactant was added. 

Pome and Stone Fruits. Following the application of DDT and of parathion as wettable powders in control schedules, neither compound has been recovered from the pulp portions of apples, pears, and peaches. A maximum of six spray applications of DDT wettable powder and four spray applications of parathion wettable powder were involved in these studies. As high as 0.4 p.p.m. of DDT and 1.7 p.p.m. of DDT were found in the pulp of apple and pear fruits, respectively, following seasonal treatments with five to six applications of DDT formulated in a petroleum oil fraction. 

Contact angle measurements for a water droplet on an asphaltene modified borosilicate surface confirmed that low concentrations of TFSA molecules change the wettability of the surface from fractionally-wet to water-wet. Table II shows the results of the contact angle measurements all reported results are the average of 10 separate measurements, none of which varied from the mean by more than 5° As the concentration of the TFSA... 

Changing the wettability of reservoir rock surfaces from oil-wet to water-wet, increases the permeability of the formation to oil, decreases the permeability to water, decreases mobility ratio, increases sweep efficiency, increases the flowing fraction of oil at every saturation, and increases oil recovery at the economic limit of the waterflood. 

Particle properties (density, size, porosity, shape, wettability, size distribution) Biofilm properties (density, thickness, active fraction)... 

Saturation (v) is the volume fraction of the total void volume occupied by a specific fluid at a point. Saturation values can vary from zero to 1 with the saturation of all fluids equal to 1. Residual saturation (Sr) is the saturation at which the NAPL becomes discontinuous and immobile due to capillary forces. Residual saturation is dependent upon many factors, including pore size distribution, wettability, fluid viscosity and density ratios, interfacial surface tension, gravity and buoyancy forces, and hydraulic gradients. 

In equation 5, C is amorphous carbon and CF2 changes to many perfluorocarbons, such as CF4, C2F6, etc., by secondary reactions. The surface coverage of graphite fluoride on the anode depends on the relative reaction rates of equations 4 and 5. Equation 6 has been introduced to analyze the wettability of the carbon surface with graphite fluoride formed on it.2 It shows the relationship between the fraction of effective surface for equation 3 per unit surface area of carbon (a) and the contact angle (0) of a fluorine gas bubble on the surface of the carbon electrode.2... 

In conclusion, the design of stable Z-type multilayers requires a deep understanding of the wettability properties of the surfaces on a molecular level, which obviously depends not only on the structured fraction of the films but also on their defect sites and porosity. In the absence of such knowledge, the empirical approach described here for the preparation of stable Z-type films should be valid in the foreseable future. 

Reaction product less wettable than the substrate. The above discussion concerns systems in which the new compound formed at the interface is more wettable than the initial substrate. We will now consider the opposite case and take as an example the Ag/SiC couple (Figure 2.28). In this system, molten Ag reacts slightly with SiC forming Si dissolved in Ag and graphite (at 1100°C the molar fraction of Si in Ag in equilibrium with oc-SiC is about 4 x 10-3). Ag wets SiC before reaction (0 90°) but not graphite (0 90°) (see Table 7.2 and Section 8.1). 

In Section 6.1, we discussed a correlation between wettability and reactivity in metal /oxide systems for a molar fraction of dissolved oxygen greater than 10-5, the contact angle decreases from about 130° to 0° (Figure 6.2). To check if a similar correlation holds for metal/metallic carbide systems, the reactivity between Cu and different carbides at 1100°C can be calculated for the dissolution of carbide MenCm in Cu ... 

Attempts to improve wetting by non-reactive pure metals such as Cu by the addition of ferrous metals such as Ni or Fe have been unsuccessful (Naidich 1981). In contrast, improvements in wetting have been achieved by adding carbide-forming elements such as Cr or Ti. Additions of Cr to Cu above a critical value of the molar fraction of Cr, XCr, produce a sharp wetting transition (Figure 8.10) owing to the formation of a continuous layer of wettable Cr carbides in accord with the reaction ... 

Figure 5. Effect of pH on the wettability of an acid-precipitated protein fraction...

Their data indicate that the flow transition from gas-continuous to pulsed flow occurs at higher- gas and liquid flow rates for nonwettable solids compared to wettable solids. The change in transition condition due to solids wettability occurs because a major fraction of the liquid tends to flow as rivulets over the nonwettable surface and, thus, delays the formation of a liquid film capable of blocking the interstices between the particles. Furthermore, an increase in bed porosity will also move the transition to occur at higher gas and liquid flow rates. 

Van den Mooter et al. prepared solid dispersions of tamazepam in PEG 6000 and polyvinylpyrrolidone K30 (PVP K30) by the fusion (melting) and cooling process. In contrast to the very slow dissolution rate of pure temazepam, the dispersion of the drug in the polymers enhanced the dissolution rate considerably. This can be attributed to improved wettability and dispersibility and a decrease of the crystalline fraction of the drug. 

---