Recovery of propylene glycol (1,2-PD) from aqueous solution was studied in batch experiments using extractants consisting of ion pairs of Aliquat 336 and phenylboronate in 2-ethylhexanol, toluene, o-xylene, or diisobutyl ketone. The heterogeneous complexation constant beta(11) calculated from the results at 25 degrees C was highest in 2-ethylhexanol (49-100 (mol/L)(-1)). The equilibrium water concentration in the extractants was 8-12 wt % and decreased with increasing uptake of 1,2-PD. Nearly all extractant/diluent systems exhibited stoichiometric overloading. Evidence for aggregation of the ion-pair extractant in the organic phase was found from water solubilization studies and H-1 NMR spectroscopy studies. The complexation constant decreased with increasing temperature. Up to 80% of the extracted 1,2-PD was backextracted into water after acidification with CO2. The extractant could then be regenerated by stripping CO2 from solution at temperatures exceeding 110 degrees C. However, at these temperatures the color of the extractant changes, and the extraction capacity is reduced to about 60% of its original value. Regeneration by contacting with aqueous solutions of Na2CO3 did not cause extractant degradation; regeneration effectiveness increased with increasing pH.