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Galizia, Michele

Publications and source records attributed to Galizia, Michele.

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Influence of fixed charge concentration and water uptake on ion sorption in AMPS/PEGDA membranes

Water content and charge density strongly influence ion sorption in charged membranes. However, isolating the individual effect of each parameter on ion sorption can be difficult due to experimental challenges associated with independently controlling these two variables during membrane synthesis. This frustrates development and validation of fundamental models and structure/property relationships. In this study, three series of uncharged and negatively charged hydrogel membranes were prepared using poly(ethylene glycol) diacrylate (PEGDA) as a cross-linker and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as an ionic monomer. Here, water content and charge density were controlled by varying AMPS content and PEGDA chain length. Ion sorption in these materials was measured using aqueous NaCl solutions at concentrations ranging from 0.01 to 1.0 M. At constant charge density, salt sorption increased as water content increased. At fixed water content, salt sorption decreased as charge density increased. Salt sorption in membranes with the highest water content and charge density was predicted using the Donnan/Manning model, which accounts for solution and membrane phase thermodynamic non-idealities. However, this approach could not predict sorption in weakly charged and uncharged membranes, presumably due to additional membrane phase thermodynamic non-idealities associated with ion solvation and uncharged polymer segments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Co-ion specific effect on sodium halides sorption and transport in a cross-linked poly(p-styrene sulfonate-co-divinylbenzene) for membrane applications

Here, sodium halide sorption and transport in a cation exchange membrane based on cross-linked poly(p-styrene sulfonate-co-divinylbenzene) (CR61) were investigated experimentally and theoretically. At fixed co-ion valence, sodium halide partitioning between aqueous electrolyte solutions and ion exchange polymers is only minimally sensitive to co-ion chemical identity. NaCl, NaF and NaI exhibit similar solubility coefficients in CR61, which agrees reasonably well with predictions of the Donnan-Manning model, especially at high external salt concentrations. Ion activity coefficients in the membrane were evaluated and ion sorption thermodynamics were investigated. Ion diffusion coefficients in CR61 were predicted using a recently developed framework based on the Manning diffusion model, which accounts for electrostatic effects on ion diffusion, and the Mackie-Meares model, which accounts for tortuosity/area effects on ion diffusion in swollen polymers. Model predictions agree reasonably well with the experimental data, especially at high external salt concentrations. The observed decrease in salt diffusion coefficients in CR61 relative to values in aqueous solutions is due primarily to tortuosity/area effects. Salt diffusion coefficients correlate with co-ion hydrated radius and membrane water content. Finally, salt permeability coefficients predicted using the solution-diffusion model exhibit good agreement with experimental data, especially at external salt concentration greater than 0.1 mol/L.

42 ENGINEERING↗