(527e) Thermodynamic Modeling of Ion Removal Processes

Removal of ionic contaminants from industrial wastewater is a widely practiced water purification process. From thermodynamic modeling perspective, the ion removal process can be considered as either liquid phase adsorption [1, 2] or ion exchange equilibrium problem [3-5]. In this study, we investigate the ion removal process with three different approaches. First, treating the ion removal process as an adsorption process, we explore the applicability of a recently developed adsorption non-random two-liquid (aNRTL) model [6, 7] to describe the ion adsorption behavior on selected adsorbents. Taking into consideration both the adsorbate-adsorbent interactions and the lateral adsorbate-adsorbate interactions, the model successfully correlates the highly complex competitive ion adsorption systems with only three binary interaction parameters. Treating the ion removal process as an ion exchange equilibrium problem, the second approach requires information for the equilibrium constant K and the activity coefficients of ionic species in both the bulk phase and the resin phase. The electrolyte NRTL model [8] and the aNRTL model are used to calculate the activity coefficients of ionic species in the bulk phase and the resin phase respectively. Both approaches correlate the experimental data successfully.

The third approach considers the ion removal process as a phase equilibrium problem for the ions between the bulk phase and the resin phase. Again the electrolyte NRTL model is used to describe the ionic activity coefficients in the bulk phase while the resin phase is considered as a polyelectrolyte system modeled with the polyelectrolyte NRTL model [9]. By establishing equality of chemical potentials of electrolytes in both the bulk phase and the resin phase, this novel approach provides a complete account on the physical nature of both the resin phase and the bulk phase. It uniquely allows computation of concentrations and activity coefficients of both counter-ions and co-ions in the resin phase.

Keywords: ion removal, adsorption NRTL model, electrolyte NRTL model, polyelectrolyte NRTL model

References

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