Green Synthetic Amide-Modified Hyper-Cross-Linked Adsorption Resin for Efficiently Separating Chlorogenic Acid From Eucommia ulmoides Extracts.

Eucommia ulmoides Oliver leaf is rich in chlorogenic acid, which has antioxidant, antiviral, and anti-inflammatory activities. In this work, a new and green strategy for functional hyper-crosslinked adsorption resin based on Friedel-Crafts reaction of pendant vinyl groups in divinylbenzene with anhydrous ethanol and acrylamide grafting polymerization was developed, and the obtained HCREt-AM resin had excellent performance on chlorogenic acid separation from Eucommia ulmoides Oliver leaf extract. Adsorption isotherm and kinetics study showed the adsorption process fitted by Langmuir adsorption isotherm and pseudo-second-order kinetic equation. The dynamic saturated adsorption capacity of 88.0 mg·g-1 was obtained, and chlorogenic acid content was raised from 7.91% to 48.27%. The pH-controlled ionization of chlorogenic acid determined the adsorption process, and π-π stacking, hydrophobic interactions, hydrogen bonding, and electrostatic interactions are the main adsorption mechanisms.