Abstract

Experiments were carried out to transfer acetic acid from toluene to water under static conditions (inside a 50 cm³ buret) for a fixed initial concentration of 1 mol dm⁻³ of acid in toluene. The phase volumes (i.e., 5 and 10 cm³) were equal for the separate sets of runs at different extraction times. The extraction experiments were carried out for up to 60 min. Complete concentration profiles of the solute in both phases were developed, leading to variable solute concentrations on both sides of the interface at different extraction times. In the ternary system, intermittent ejection phenomena were only visible from the organic to the aqueous phase, over a fraction of the total interfacial area. Two theories of energy instability were verified experimentally through numerical calculations of the instability criteria at different extraction times. The molecular energy of acetic acid in toluene was estimated to be 3000 J mol⁻¹. In both the phases, the Rayleigh number ranged from 10⁸ to 10⁹ due to the unstable density gradients. The interfacial mass transfer coefficient, calculated under static conditions, was one-fifth of that under stirred conditions, where the Marangoni instability was superimposed on the energy instability. The interfacial mass transfer coefficient was higher than the bulk phase transfer coefficient in the raffinate phase, even in the presence of density convection. The dynamic interfacial energy barrier was found to be higher than the static energy barrier, i.e., the free energy of the interface.

摘要

进行实验以在静态条件下（在50cm ³滴定管内）将乙酸从甲苯转移至水中，以得到甲苯中酸的固定初始浓度1mol dm ^{-3 。}相体积（即 5 和 10 cm ³）对于不同提取时间的单独运行组是相等的。提取实验进行长达 60 分钟。开发了两相中溶质的完整浓度曲线，导致在不同的萃取时间下界面两侧的溶质浓度不同。在三元系统中，间歇性喷射现象仅在从有机相到水相的总界面面积的一小部分上可见。通过不同提取时间下不稳定准则的数值计算，实验验证了两种能量不稳定理论。乙酸在甲苯中的分子能估计为3000 J mol ^-1。在这两个阶段中，瑞利数的范围为 10 ⁸到 10 ⁹由于密度梯度不稳定。在静态条件下计算的界面传质系数是搅拌条件下的五分之一，其中马兰戈尼不稳定性叠加在能量不稳定性上。即使存在密度对流，界面传质系数也高于萃余相中的体相传递系数。发现动态界面能垒高于静态能垒，即界面的自由能。