Phenol adsorption and desorption with physically and chemically tailored porous polymers: Mechanistic variability associated with hyper-cross-linking and amination

Electrostatic Interactions of Ion-Exchange Materials with Anthocyanins in the Processes of Their Sorption and Electrodialysis Extraction from Liquid Media

“…In accordance with current perceptions, ionexchange materials, like nonpolar resins, enter π-π (stacking) and van der Waals interactions with polyphenols [16,26]. Because of this, the sorption of the latter is intensified upon the transition from an aliphatic (e.g., polyacrylamide) polymer matrix to an aromatic (polystyrene) matrix [27] of resins and membranes.…”

“…This is why the sorption of anthocyanins from alkaline solutions turns out to be higher in comparison with that observed in acidic solutions in the case of anion-exchange materials [14,16,26,31,33]. In the case of cation-exchange materials, an inverse effect is recorded, thus, the sorption of anthocyanins from acidic solutions exceeds that observed in alkaline solutions [26,34].…”

“…In recent years, sorption technologies with ionexchange resins [12][13][14] or electrodialysis modules including ion-exchange and ultrafiltration membranes have been increasingly actively applied for these purposes [10,11,15]. It has been found [16][17][18] that the use of ion-exchange materials promotes growth in the yield with respect to the target product in comparison with nonpolar sorbents, makes it possible to separate polyphenols from sugars and other components of the liquid media under processing [19,20], and promotes an increase in the antioxidant activity of anthocyanins [21]. On the other hand, it is known that phenol compounds and, first of all, anthocyanins and their compounds with amino acids, proteins, and sugars, are the main reason for the deterioration of the transport characteristics of ion-exchange membranes in the electrodialysis processes of wine stabilization and adjustment of pH of fruit juices [22][23][24][25].…”

“…Hydrogen bonds are formed between the fixed groups of these materials (e.g., tertiary amines) and hydroxyl groups of polyphenols [28,29]. In addition, the fixed groups enter electrostatic interactions with polyphenols, in particular, anthocyanins, provided that the latter are in ionic form [16,26,30,31]. It is known [32] that the structure and electrical charge of all anthocyanins depend on pH of the medium (Fig.…”

“…For example, the use of cation-exchange resins for the extraction of biogenic amines and sulfates from wine [35] or protons from fruit juices [36], does not lead to the losses of anthocyanins [35], or these losses are no more than 10-13% [36]. The authors of [16] note that phenol is equally well sorbed by anion-exchange materials from solutions with a pH of 6 and 11. Here, in accordance with the deprotonation reaction constant (pK a = 9.9 [16]), phenol has no electrical charge in a solution at pH of 6 and, hence, should not enter electrostatic interactions with positively charged fixed groups of an anion-exchange resin.…”