Structural and thermodynamic factors on the adsorption process of phenolic compounds onto polyvinylpolypyrrolidone

Abstract

In this studywefindthe possible structural factors that can determine the adsorption process ofsomepure phenolic compounds (PC) onto polyvinylpolypyrrolidone (PVPP), analyzing their adsorption isotherms by using the Langmuir and the Freundlich theories. In this perspective, the adsorption capacity of short size PC would depend on the number and availability of its hydroxyl groups. To intermediate molecular size PC, the improvement in the adsorption capacity presumably depends on its resemblance with the resveratrol molecule. To large size PC, the adsorption capacity was considerably high due to hydroxyl groups disposed in different spatial orientations with respect to the plane. Thermodynamic analyses showed that adsorption onto PVPP of some pure PC correspond to a physisorption process that was spontaneous and enthalpically-driven for PC like catechin (C) and entropically-driven for PC like epigallocatechin gallate (EGCG) and gallic acid (GA). These results implicate potential selective adsorption uses of PVPP.