Imbibition kinetics

At first we tried to explain the phenomenon on the base of the existence of the difference between the saturated vapor pressures above two menisci in dead-end capillary [12]. It results in the evaporation of a liquid from the meniscus of smaller curvature ( classical capillary imbibition) and the condensation of its vapor upon the meniscus of larger curvature originally existed due to capillary condensation. We worked out the mathematical description of both gas-vapor diffusion and evaporation-condensation processes in cone s channel. Solving the system of differential equations for evaporation-condensation processes, we ve derived the formula for the dependence of top s (or inner) liquid column growth on time. But the calculated curves for the kinetics of inner column s length are 1-2 orders of magnitude smaller than the experimental ones [12]. 

However, adsorption of surfactant molecules occurs also on the meniscus surface that decreases the interface tension y and therefore the eapillary pressure 2y cos dp,jr, which is the driving force of imbibition. Considering the kinetics of impregnation, one needs to take into account the influence of surfactants on both contact angles and surface tension. 

Since the rate of imbibition of surfactant solutions into a hydrophobed capillary is rather slow, the kinetics of adsorption may be ignored and it is possible to include into Eq. (19) an equilibrium adsorption isotherm a = f C). As a first approximation, the linear form of the isotherm will be used here ... 

Specifically two aspects are addressed (i) the kinetics and mass transfer effects under pseudo stationary conditions, and (ii) the utilization of a unique feature of precipitation onto large carrier particles, viz. transient concentration gradients occurring directly after liquid imbibition. 

In this chapter, we consider the kinetics of spreading over porous substrates. This phenomenon is widely used in the industry printing, painting, imbibition into soils, health care, and home care products, and so on. However, it is only recently that this process started to develop on a theoretical and not just on a purely empirical basis. 

The kinetics of the capillary imbibition of aqueous surfactant solutions into hydrophobic capillaries has been investigated earlier in Section 5.2. It has been shown that the rate of imbibition is controlled by the adsorption of the surfactant molecules in front of the moving meniscus on the bare hydrophobic surface of the capillary. This process results in a partial hydrophilization of the surface of the capillary in front of the moving meniscus and provides the possibility for the aqueous surfactant solution to penetrate into the initially hydrophobic capillary. Therefore, no surfactant molecules on the meniscus, no imbibition. In the following text, the imbibition of surfactant solutions into the porous substrates, which are partially wetted by water, is considered. It is shown that the situation in this case is considerably different from the case of hydrophobic porous media. 

In Chapter 4 we have provided resnlts abont the kinetics of spreading and imbibition when liquids are in contact with porous solid materials. An important conclusion is that the behavior of liqnids in contact with porous materials is... 

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