Fine Purification of Substances by Countercurrent Sublimation

Abstract

A countercurrent sublimation method is proposed in order to increase the efficiency of the separation and purification of substances such as iodine, the iodides of elements, the chlorides and fluorides of transition metals, and a number of organic compounds by sublimation methods. Ultrasound is used to break the crystal layer formed on a desublimator and shake off the finely dispersed crystal phase into the working zone of a column. The mathematical models of the purification of substances by countercurrent sublimation are proposed that take into account the longitudinal diffusion of an impurity and the change in the size of a crystal along the height of the column. The mathematical models of countercurrent sublimation are verified using the borneol–camphor system. It is shown that the enlargement of crystals substantially affects the degree of the purification of substances in a countercurrent sublimation column.