Wettability of particles

Actually, it characterizes the effective wettability of. particles, i.e., the wettability under the actual operating conditions. 

Figure 64. Method op Measuring Wettability of Particles (Kartell and Osterhof, 1927).

The second part of the chapter describes some of our recent work on (1) possible effects of line tension on the wettability of particles at fluid interfaces and (2) lateral interactions between (charged) polystyrene particles in monolayers at a/w and o/w interfaces and the consequences for monolayer... 

One of the problems in predicting efficiency and required pressure drop of a venturi is the chemical nature or wettability of the particulate, which on 0.5-pm-size particles can make up to a threefold difference in required pressure drop for its efficient coUection. Calvert... 

Flotation is a physical process involving relative interaction of three phases solid, water, and air. An understanding of the wettability of the solid surface, physical surface, and chemical phenomena by which the flotation reagents act and the mechanical factors that determine particle-bubble attachment and removal of particle-laden bubbles, is helpful in designing and operating flotation systems successfully. 

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. 

The contact angles of water and adhesive resin on wood are higher in the case of freshly harvested wood compared to stored chips. This means that the surface of particles from this fresh wood is more hydrophobic. This influences the wetting and the penetration negatively and with this the gluability. Reason for this lower wettability of freshly harvested wood is a higher content of some wood chemical components, or wood extractives, as has been determined by water extraction. This result, however, must not be confused with the better wettability of a freshly cut surface, independently if it is freshly harvested or stored wood. 

The collection efficiency of wet scrubbers is dependent on parameters such as the size and quantity of liquid droplets, the liquid/gas ratio, high wa-ter-to-particle relative velocity, wettability of dust, particle density, gas viscosity, etc. For any specific application, the design procedure is to review operating data available from the technical literature or from manufacturers for similar applications. If data are not available, it may be necessary to per form pilot scale tests, which can be used for scale-up purposes. 

Surface modification reactions are used to improve the wettability of glass surfaces by polar stationary phases and to Improve the extent of deactivation by sllylation" [138-146,166]. Miaaiuua procedures have been investigated but only a few are in use. Of these, the most important reactions are etching by hydrogen chloride, leaching with aqueous hydrochloric acid, formation of whiskers and solution deposition of a layer of solid particles. Because of the high purity and thinness of the... 

In practice, evaluating the wettability of a soil is far more uncertain, because soil is a mixture of gravel, sand, silt, and clay particles, as well as other chemical precipitates. The mineral components of soil particles include quartz, feldspar, carbonates, and clay. These components have different wettability by water and oil. Therefore, the retention of oil or water in a soil matrix is heterogeneous and variable. The general wettability of soil or liquid retention in a soil is reported on a statistical basis. 

These include electrostatic interaction between the particles and interaction of particles with the fluid governed by their wettability, morphology and density (17-19) the extent of adsorption of the polymer and its influence on the interaction of particles, the orientation or configuration of the adsorbed polymers (and surfactant when it is present) and resultant interaction of adsorbed layers the hydrodynamic state of the system and its influence on the interaction of floes themselves. 

B.P. Binks and S.O. Lumsdon Influence of Particle Wettability on the Type and Stability of Surfactant-Free Emulsions. Langmuir 16, 8622 (2000). 

The terms used to distinguish colloidal particles on the basis of their affinity to the fluid in which they are dispersed are lyophilic and lyophobic. These terms mean, literally, solvent loving and solvent fearing, respectively. When water is the medium or solvent, the terms hydrophilic or hydrophobic are often used. This terminology is very useful when considering surface activity such as wettability of a surface however, when used to classify colloids, the distinction is not always clear-cut. We consider these two types of colloids separately in the following subsections. 

Another important property is the structure (see Section 4.1) which characterizes the coalescence of primary particles into aggregates resembling chains or bunches of grapes. The dibutyl phthalate (DBP) absorption is commonly accepted as a measure for the carbon black structure. Due to absorption phenomena the DBP number increases with increasing specific surface area. Oil absorption (or, in general, the vehicle demand) is as well an indicator for the structure, but it also depends on the wettability of the black surface. Since linseed oil is a polar system, oil absorption declines as the concentration of surface oxides rises. 

The starting felodipine, as well as micronized felodipine, practically do not dissolve in water, owing to the poor wettability of the felodipine particles. The amount of dissolved felodipine after 1 h was only 0.26 mg and 0.29 mg, for the starting felodipine and the micronized sample, respectively. 

Successful assembly requires matching features of the template, meaning that wavelength and height have to be of the same dimensions. Additionally, adhesion of particles and surface must be avoided by weak repulsive forces. In this context, polyelectrolyte multilayer-wrinkles are particularly useful, as the wettability of the multilayer is determined by the part of the layer adjacent to the film/solution or film/air interface respectively, while the elastic properties are determined by the total film [84], Thus, elastic constants can be adjusted largely independent from wettability properties. 

An example of the importance of the wettability of fine particles is provided by what are called Pickering emulsions, that is, emulsions stabilized by a fdm of fine particles. The particles can be quite close-packed and the stabilizing fdm between droplets can be quite rigid, providing a strong mechanical barrier to coalescence. See Section 5.4.1. 

The presence of solids further complicates the performance requirements for a demulsifier. Emulsions stabilized by fine particles can usually be broken if the wettability of the particles is reversed. Inorganic particles, such as iron sulfides or clay minerals, can be made water-wet, causing them to leave the interface and diffuse into the water phase, or they can be made oil-wet so that they leave the interface and diffuse into the oil phase [68]. Organic particles, such as paraffins and asphaltenes, can be removed from interfaces by dissolution [461,463,466]. 

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