Sorption problems in the course “Introduction to Macrokinetics” at the Faculty of Chemistry, Moscow State University

Abstract

The purpose of the paper is to draw attention to the need to teach macrokinetics at chemical faculties at universities. Macrokinetics studies the chemical reactions and processes of interphase transfer under the real conditions of macroscopic processes with due consideration given to the diffusion and convective transfer of substances and the transfer of heat in space. Such processes include the overwhelming majority of real technological and natural processes: combustion and explosion processes, operation of catalytic reactors, substance transfer through membranes, biochemical processes in a biological cell, separation of substances in counter-current columns (for example, rectification); chromatographic, ion-exchange, and sorption processes in columns, chemical processes in the atmosphere, water bodies, soils, etc. However, the programmes of various basic chemical courses (for example, physical chemistry) only include some fragments of macrokinetics, which do not allow forming a sufficient understanding of the principles of macrokinetic modelling and its significance in chemistry. The goal of the course in macrokinetics is to shape an understanding of how the knowledge of chemical thermodynamics and phenomenological kinetics from the course of physical chemistry can be used to describe real chemical processes. It should focus on the basic principles of modelling chemical processes.

This course includes three main sections: 1) balance equations in nonequilibrium systems, 2) processes in stationary media, 3) processes in moving media. The first section contributes the most to the formation of “macrokinetic thinking". It demonstrates the principles of constructing macrokinetic models of any chemical processes that complement and bring together the main sections of physical chemistry, i.e. chemical thermodynamics and chemical kinetics. The second and third sections focus on specific macrokinetic problems, which are used to illustrate the key concepts of macrokinetic modelling and continue the course of physical chemistry. These sections are aimed at practising the knowledge acquired in the first section. They should consider the processes that most chemists have to deal with in the course of their work. These tasks include substance transfer through membranes, catalytic homogeneous and heterogeneous reactions, sorption and chromatographic processes, and rectification separation of a mixture of substances. At the same time, it appeared to be more convenient to focus more on sorption processes in order to illustrate and prove the basic aspects of chemical macrokinetics. This is due to the fact that sorption processes are understandable to all chemists. They allow obtaining fairly simple analytical solutions and carrying out numerical calculations within the framework of the course.