Abstract

The occurrence of unidirectional ejection phenomena (both continuous & intermittent), during mass transfer in binary and ternary systems respectively; reported earlier, have been explained on the basis of the theory of spontaneous surface convection (SSC). Also, intermittent jerking of the interface followed by emulsification coupled with profuse streaming action in the extract phase of two ternary systems has been explained by the same theory. In addition, intermittent circulatory motion in the extract phase only, in a ternary system has been explained on the basis of vertical and/or angular ejections’ restrained motion due to high viscosity of the extract phase. The theory of reversible adsorption and desorption phenomena for the transfer of surface-active solutes in ternary systems have been taken to help in justifying the occurrence of SSC during initial contacting of two phase. In most of the ternary systems reported earlier, vigorous density convection in the form of mushroom type density eddies observed are due to larger unstable density gradient. This is caused by high rates of mass transfer during SSC. SSC in the form of continuous circulatory motion in the extract phase only has been observed during the transfer of a surface inactive solute. Such phenomena occurred in aqueous to organic direction of transfer. The circulatory motion is due to ejections being against gravity. Surface inactive solute’s transfer also caused oscillatory motion of the interface as a whole in a particular system. The nature of most of the phenomena observed in binary and ternary systems appears to be due to molecular motions. The theory of SSC states that if specific energy of driving force of mass transfer is greater than free energy of the interface, interfacial instability occurs. It is probably a simplified version of a concept suggested here that can be explained by the kinetic theory as follows. It states that chemical potential difference of a solute between the two phases, if greater than the interfacial barrier plus molecular energy of the solute (in raffinate phase) then interfacial instability occurs. Thus, cluster of solute molecules in the form of ejections of bulk mass have been found to occur from raffinate to extract phase indicating high rates of mass transfer.

摘要

分别在二元和三元系统的传质过程中发生单向喷射现象（连续和间歇）；早先报道的，已经在自发表面对流（SSC）理论的基础上进行了解释。此外，在两个三元体系的提取阶段，界面的间歇性抖动以及随后的乳化以及大量流动作用已被相同的理论解释。此外，仅在提取相中的间歇性循环运动，在三元系统中已根据提取相的高粘度导致的垂直和/或角喷射的受限运动进行了解释。三元体系中表面活性溶质转移的可逆吸附和解吸现象理论已被用来帮助证明在两相初始接触期间发生 SSC 的合理性。在之前报道的大多数三元系统中，观察到的蘑菇型密度涡流形式的强烈密度对流是由于较大的不稳定密度梯度造成的。这是由 SSC 期间的高传质率引起的。仅在表面非活性溶质的转移过程中观察到在提取相中以连续循环运动形式出现的 SSC。这种现象发生在水向有机方向的转移。循环运动是由于喷射抵抗重力。表面非活性溶质的转移也引起了特定系统中整个界面的振荡运动。在二元和三元系统中观察到的大多数现象的性质似乎是由于分子运动。SSC理论指出，如果传质驱动力的比能大于界面的自由能，就会发生界面不稳定。它可能是这里提出的概念的简化版本，可以通过如下的动力学理论来解释。它指出溶质在两相之间的化学势差，如果大于界面势垒加上溶质的分子能（在萃余相中），则发生界面不稳定。因此，已发现从萃余液到萃取相的大量物质喷射形式的溶质分子簇，表明质量转移率很高。