Effect of NaX Zeolite Mass and Baffle Presence on Copper Sorption

Sorption is often conducted in stirred batch reactors without assessing the impact of mixing on yield and costs. Operating the mixing in the batch reactor at a state of complete suspension, i.e., at just suspended impeller speed, NJS, is a compromise between these conflicting goals. Therefore, copper sorption on NaX zeolite using a pitched blade turbine was conducted in both baffled and unbaffled batch reactors at NJS. Maintaining constant impeller to reactor diameter ratio (D/dT = 0.32), and impeller off-bottom clearance (C/H = 0.33), kinetic sorption experiments were performed. Besides kinetic sorption experiments and the kinetic analysis of data obtained, to gain insight into the hydrodynamic behaviour of the system, transient multiphase computational fluid dynamics simulations (CFD) were performed. The NJS speed is related to the particle settling speed, wherein a higher zeolite suspension mass concentration requires a greater NJS speed, resulting in increased energy consumption. The differences in NJS speeds for the investigated zeolite suspension mass concentrations were found to be insubstantial, and therefore, the increase in mixing intensity for the tested systems was not deemed significant. Regardless of the zeolite mass used, the values of NJS and PJS (mixing power consumption) were consistently higher in the unbaffled reactor. The hydrodynamic conditions employed were found to have no significant effect on the maximum amount of copper sorbed or process efficiency, but was significantly affected by zeolite mass. The kinetics were affected by both, and, generally, sorption occurred faster in the unbaffled reactor.