Acetylaniline modified hypercrosslinked polystyrene resins and their equilibria and kinetics towards glabridin from Glycyrrhiza glabra L. extracts

摘要

As reported in our previous work, crosslinked polymeric adsorbents with high microporous surface areas are proper for glabridin adsorption. In addition, adsorption capacity of the microporous and mesoporous self-crosslinked polystyrene resin XT2-10 was superior to that of the optimal commercial adsorbent BMKB-1 under the same conditions. However, there is still room for further improvement. Based on this, in the following study, a series of novel hypercrosslinked polymeric adsorbents modified with acetylaniline as the cross-linked bridge (labeled as XT8-0, XT8-4, XT8-6, XT8-8 and XT8-10) were synthesized from macroporous crosslinked chloromethylated polystyrene by adding different quantity of acetylaniline in the Friedel-Crafts reaction. The microporous surface areas of hypercrosslinked polymeric resins XT8 occupied more than 55% of the total BET surface areas and these resins were evaluated for adsorption of glabridin. Among the synthesized five resins, XT8-8 possessed the largest adsorption capacity toward glabridin, and it was superior to the previous synthesized self-crosslinked polystyrene resin XT2-10 and much better than the optimal commercial resin BMKB-1. The isotherms could be fitted by Freundlich model and the adsorption was shown to be an exothermic process. The kinetic curves could be characterized by pseudo-second-order rate equation and the adsorption rate of glabridin on XT8-8 was controlled by both intraparticle diffusion and external diffusion. The enthalpy Delta H, Gibb's free energy Delta G and entropy Delta S were calculated to be negative. The reusability of the modified resins was also assessed and the modified resins exhibited considerable reusability. The remarkable adsorption behaviors of XT8-8 were due to its suitable structural design and modification. The hypercrosslinked resins being developed were promising alternatives to commercial adsorbents for adsorbing glabridin and other flavones from herbal plants. (C) 2016 Elsevier B.V. All rights reserved.