Continuous Flow Stirred Cell Microfiltration of Ion Exchange Media to Determine Mass Transfer Kinetics and Equilibrium Data

Abstract

Sorption of copper ions from aqueous feed streams on to polystyrene divinylbenzene Dowex 50W-X8 resins was studied. The experimental work was performed in a continuous flow stirred cell that had a slotted (8 μm × 400 μm) metal microfiltration membrane fitted to the bottom of the cell. The equilibrium parameters for a Langmuir isotherm (qm = 0.116 g g−1, b = 0.003 m3 g−1) were determined from both the batch and the continuous flow experiments, and good agreement between the two different approaches was obtained. Experiments were performed at constant pH (4.5) and ionic strength (0.2 M), using a background sodium nitrate matrix, at feed concentrations of copper up to 636 g m−3. The filtration flux was 582 L m−2 h−1. Increase of the NaNO3 decreased the amount of sorbed copper significantly. The effective diffusion coefficient of copper inside the resin was found to be 7 × 10−11 m2 s−1. The continuous flow stirred cell is shown to be an effective technique for both mass transfer kinetics as well as equilibrium data acquisition, combining both into a single step, and simplifying ion exchange analysis. Once determined, the design parameters can readily be used to model ion exchange contacting in well mixed and column operations.