Sorption of neutral components in ion exchange resins. 2. Sorption of D-xylose in sulfonated PS-DVB resins from water-ethanol mixtures

Partition of D-xylose between ion-exchange resins and different water-ethan ol mixtures at 298 K was studied. Gel-type sulfonated poly(styrene-co-divin ylbenzene) resins cross-linked with 4 or 8 wt % divinylbenzene and carrying Na+, Ca2+, or La3+ as the counterion were used as the absorbent phases. So rption of D-xylose increases with decreasing water mole fraction in the sol vent mixture, irrespective of the resin. The increasing sorption is explain ed by the selective water uptake of the resin and the far better solubility of D-xylose in water than in ethanol. At high water contents, sorption of D-xylose increases with decreasing cross-link density, while the enhanced w ater selectivity of the densely cross-linked resin improves sorption at low water contents. The experimental data were compared with the literature da ta for D-glucose. Complexation of both sugars with the metal ions studied i s shown to be negligible, and the sugars are absorbed more effectively by t he resin loaded with the less solvated univalent counterion. The sorption m odel based on the UNIQUAC equation and the affine network theory of elastic ity explains satisfactorily sorption of individual components from the tern ary water-ethanol-sugar solutions.