The competitive adsorption of gelatin and sodium dodecylbenzenesulfonate (SDBS) at hydrophobic surfaces was investigated with surface and interfacial tension measurements, ellipsometry, surface plasmon resonance spectroscopy (SPR), and total internal reflectance fluorescence spectroscopy (TIRF). From both ellipsometry and SPR, initial additions of SDBS after gelatin preadsorption were found to result in a total adsorbed amount increase, as well as in a swelling of the adsorbed layer. At higher SDBS concentrations, both the total adsorbed amount and the amount of gelatin adsorbed decrease, which was observed from ellipsometry, SPR, and TIRF. From surface and interfacial tension measurements, it was found that the critical aggregation concentration (cac) for the SDBS-gelatin system decreases with decreasing pH. Analogous to this, ellipsometry, SPR, and TIRF indicate that the SDBS concentration required to cause a significant decrease in the gelatin adsorbed amount decreases with decreasing pH. The desorption therefore seems to be correlated to the SDBS binding to the adsorbed gelatin molecules rather than to purely competitive adsorption.

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Whentwo immiscible liquids are agitated, a dispersion is formed in which continuous breakup and coalescence of drops occur, and a dynamicequilibrium is attained betweenbreakup and coalescence after a certain time. Effects of the volume fraction of dispersed phase, viscosity of liquid, impeller speed and impeller-to-vessel diameter ratio on the average drop size of a dispersion in a mixing vessel are discussed and correlative equations are proposed. It is also found that the dominant process in deciding average drop sizes in a mixing vessel changes from breakup to coalescence whenthe average energy dissipation rate or the volumetric fraction of dispersed phase is increased.The mixing of immiscible liquid is among the most important chemical or biological engineering operations. In nuclear fuel reprocessing, the performance of mixer-settlers should be analyzed from drop size distribution for optimizing uranium and plutonium extraction.A number of investigators have presented correlative equations that related drop sizes in the mixing vessel to mixing parameters and physical properties of the system. Whentwo immiscible liquids are agitated, a dispersion is formed in which breakup and coalescence of drops occur. After a certain time, a dynamic equilibrium is attained between breakup and coalescence in the mixing vessel. Drops are believed to be broken up by turbulent fluctuations of the ambient liquid in the neighbourhood of the drops. In a dilute dispersion, coalescence may be negligible and the equilibrium spectrum of drop size distribution will depend on the breakup process. The coalescence process may be dominant in a dense dispersion because the probability of collision of drops increases.Effects of the volume fraction of dispersed phase, viscosity of liquid, impeller speed and impeller diameter on the drop sizes in a mixing vessel are discussed in this report and it is found that the coalescence process becomes dominating at higher energy dissipation rate or at larger volume fraction of dispersed phase. Drop sizes estimated by use of the correlative equations obtained in this study are compared with reported values by various authors.

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The scale-up effect of mixing vessels on the drop size of a liquid-liquid dispersion is discussed and correlative equations to estimate drop sizes in breakup and coalescence regions are proposed. It is shown that (n3d2D)(4Npln) is applicable as a scale-up standard and that the average energy dissipation rate, the Webernumberin the mixing vessel or the agitational Reynolds numberis not a satisfying scale-up standard. It is also shownthat the effect of volumefraction of dispersed phase on drop size is affected by the scale-up ratio; that is, the scale-up ratio is expected to have a smaller effect on drop size as the fraction of dispersed phase increases.

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