Abstract
Sorption is often carried out in stirred batch reactors without any consideration of how much mixing is sufficient to avoid the effect of diffusion without compromising yield and cost due to overmixing. Therefore, the focus of this work was to study how the maximum sorption capacity, removal efficiency, kinetics and power consumption (P) of the studied process are affected by different mixing speeds, i.e., impeller speed/minimum impeller speed for complete suspension (N/NJS) ratio values and zeolite suspension mass concentrations. Experiments were conducted in a baffled reactor with the propeller at a standard off-bottom clearance. In addition to the experimental studies, numerical modelling approaches were carried out to investigate the sorption process using a transient multiphase computational fluid dynamics model and fitting selected kinetic models. The results show that an increase in zeolite mass leads to a slight increase in the NJS and consequently PJS. The impeller speed affects the velocities, power consumption, kinetics, final amount and removal efficiency of copper sorbed. The experimentally determined kinetic data fit Ritchie’s kinetic model well. However, for two experiments, performed at N/NJS ratios of 0.8 and 0.6, Mixed kinetic model fits better, suggesting that the second-order reaction is suppressed by diffusion. Due to the influence of diffusion, the experimentally determined sorption efficiency decreased from 59.377% to 54.486% and 46.372% for N/NJS ratios of 0.8 and 0.6, respectively.