ION EXCHANGE IN CONTINUOUS PULSED COLUMN

The authors suggest a mathematical description of the process of ion-exchange purification of solutions from heavy metal ions using the continuous pulsed column with KRIZM perforated trays. While developing mathematical description, the following assumptions are used: the ionite is monodisperse and has a spherical shape, the ion exchange equilibrium is described by Nikolsky equation, the velocity of the process is limited by both internal and external diffusion, the ionite and the solution in the device move in opposite directions, the solution moves with the effects of longitudinal and radial mixing. The two-parameter diffusion model is used to describe the solution movement in the device. To solve the task, the authors applied the interval-iterative approach based on a reasonable combination of analytical and numerical methods of the theory of mass-exchanging processes. The kinetic and hydrodynamic parameters of the process are constants on each tray; the equilibrium equation of Nikolsky is replaced with the equation of the tangent to the nonlinear equilibrium dependence. The obtained equations allow calculating the distribution of the solution concentration throughout the height and the radius of the ionite bed on the tray. The sorbate concentrations in the solution and ionite found on one tray become the input data for the calculation of the overlying tray. The general picture of the ion exchange process for the whole device is determined by the successive finding of solutions for all trays. The authors determined the validity of the mathematical model on the example of the waste water purification from nickel ions on the KU-2-8 cationite in the continuous pulsed column. The deviation of the calculated results from the experimental data does not exceed 10 %. The elaborated mathematical model is recommended for practical application.