Selective adsorption of tea polyphenols from aqueous solution of the mixture with caffeine on macroporous crosslinked poly( N-vinyl-2-pyrrolidinone)

Abstract

A macroporous polymeric adsorbent with moderate hydrophobic matrix and hydrogen-bonding moieties was prepared by free radical suspension copolymerization of N-vinyl-2-pyrrolidinone, ethylene glycol dimethacrylate and triallyl isocyanurate. SEM image and N 2 adsorption–desorption isotherm measurements of the resulting resin, defined as PVP–DEGMA–TAIC, show that the average pore diameter and specific surface area are ∼400 nm and 114 m 2/g, respectively. The adsorption behavior of tea polyphenols and caffeine on PVP–DEGMA–TAIC resin indicates that the adsorption of tea polyphenols is driven by combined action of hydrophobic interaction and hydrogen bonding, while the adsorption of caffeine is driven by only hydrophobic interaction. The adsorption from an aqueous solution of a mixture of tea polyphenols and caffeine (initial weight concentration ratio was ∼5/1) on PVP–DEGMA–TAIC shows that the adsorption capacities for tea polyphenols and caffeine were 98 mg/g and 1–2 mg/g with removal percentages of 93% and 8%, respectively. The product eluted with ethanol contains ∼98% tea polyphenols and ∼2% caffeine. These results indicate that selective adsorption of polyphenols from the mixture with caffeine on PVP–DEGMA–TAIC resin was excellent.