Selection of resins, equilibrium and sorption kinetics of lactobionic acid, fructose, lactose and sorbitol

The separation of quaternary mixtures of lactobionic acid, lactose, sorbitol and fructose using a gel-type ion-exchange resin loaded with H+, K+ and Ca2+ ions has been investigated. This separation is relevant in order to improve the productivity of lactobionic acid obtained from the enzymatic reaction catalyzed by Glucose–fructose oxidoreductase and glucono-δ-lactonase enzymes. Measurement of the single-component equilibrium isotherms for all four species was carried out in a preparative column packed with the selected resin at temperatures of 293, 313 and 333 K using the frontal analysis and column adsorption–desorption method. Mass transfer coefficients for all species at different temperatures have been estimated by solving the dynamic model of the chromatographic column. From pulse tests of single-component and mixture solutions, the K+ loaded resin was found to be suitable for this quaternary separation. The unfavourable adsorption isotherm for the lactobionic acid is described by the anti-Langmuir model. Other compounds have shown linear equilibrium in the concentration range up to 130 g L−1. Binary and quaternary fixed-bed experiments were well described by the dynamic model using the parameters obtained from the single-component adsorption data.