Ion exchange processes often have great potential to remove ions of interest from contaminated water. However, the feasibility of such processes requires information on the affinity of all ions to the specific exchanger. In this effort, a nanoscale ion exchanger was synthesized by cross-linking a cationic surfactant, quaternary ammonium hydroxypropyl conjugated linoleic acid ester (QACLE). Before testing the cross-linked nanoparticles, the displacement of Cl- from QACLE micelles by added common anions in natural water (F-, HCO3-, NO2-, Br-, NO3-, H2PO4-, HPO42-, SO42-, and CrO42-) was determined in dialysis experiments. The selectivity coefficients for all anions were determined and indicate that NO2-, Br-, NO3-, HPO42-, SO42- and CrO42- have greater affinity to the QACLE micelles than Cl-. For anions with the same valence (1 or 2), the relative affinity to the micelles was proportional to the hydrated radii of the ions, indicated that no inner-sphere complexation occurred. From the associated component mass balance and mass action equations, an overall speciation model was developed to predict the distribution of all anions between the aqueous and micellar phase for complex ionic mixtures. Experimental results of both artificial and real surface waters for non-cross-linked and cross-linked micelles were in good agreement with model predictions.

Modeling ion exchange equilibria in cross-linked cationic surfactant nanoparticle solutions

253rd National Meeting (2017)

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