Mass transfer accompanied by chemical reaction at the surface of a single droplet

Abstract

Mass transfer accompanied by chemical reaction at the surface of a droplet in the free-rise period has been studied. Theoretical analysis was carried out on the basis of two typical models; one is the stagnant spherical drop model proposed by Newman, and the other is the model which accounts for the turbulent circulation in a droplet proposed by Handlos and Baron. Diffusion equations for these models were numerically solved under the boundary conditions which accounts for the chemical reaction at the drop surface. Two cases were discussed. One is the case in which mass transfer resistance in the continuous phase can be ignored, and the other is the case in which it should be accounted for. In the former case, it was found that the mass transfer rate increased with an increase of the initial concentration of reaction component in a droplet when the reaction order is greater than unity. The reverse case occurs when the reaction order is smaller than unity. In the latter case, it was revealed that the mass transfer rate increased with an increase of the initial concentration of the dispersed phase component when it is small but decreased when it is large. On the basis of these results of the theoretical analysis, the extraction rate of acetic acid by Amberlite LA-2, secondary long-chain alkylamine, was examined. As a result of the examination, the experimental results were fairly well explained by the model which takes account of the interfacial reaction of first order with respect to either acetic acid or amine.