Questions of mathematical modelling in the study of acid retardation on ion–exchange resins

Abstract

In this paper, the chemical equilibrium of a multicomponent solution is considered in detail as part of a dynamic model of the acid retardation method. A detailed study of the chemical equilibrium, represented as a system of nonlinear equations, is a key step for building an effective dynamic model in the case of a multicomponent solution. This paper presents an algorithm for efficient calculation of chemical equilibrium using extractive phosphoric acid as an example. This algorithm can be used in a dynamic model to calculate chemical equilibrium at each point of the spatial grid and at each integration step. Moreover, for the concentrations of substances in the experiment on the purification of extractive phosphoric acid, it is shown that the nonlinear system of equations of chemical equilibrium allows one to obtain simple algebraic relations for the connection of the concentration of molecules of the substance with the total concentration of substances of all elements in solution with good accuracy. In addition, it was shown that for each metal, only one type of salt sorption can be considered due to the low concentration of other types, which makes it possible to reduce the number of differential equations in the dynamic model of the acid retardation method.