Interaction Mechanisms and Predictive Model for the Sorption of Aromatic Compounds onto Nonionic Resins

Abstract

Understanding interaction mechanisms between porous sorbents and organic compounds is important in selecting or custom-synthesizing an appropriate sorbent. In this study, sorption isotherms of a set of 14 (XAD-4&7) or 11 (MN200) aromatic compounds were measured for three nonionic resins, and a phase conversion approach (from <i>aqueous</i> phase to <i>n</i>-<i>hexadecane</i> or <i>gas</i> phase) was applied to separate sorbate-sorbent interactions from the overall involved interactions. Subsequently, contributions of individual interactions to the overall Δ<i>G</i> were quantified by poly parameter linear free energy relationships (pp-LFERs). Cavity energy (<i><b>V</b></i>), energy costs for creating cavities in bulk water, is the dominant driving force for the sorption from aqueous phase. Meanwhile, sorption was substantially abated by H-bonding accepting capacities of the solutes (<i><b>B</b></i>) due to the high electron accepting capacity of water molecules. Solute’s H-bonding donating capacity (<i><b>A</b></i>) and polarity/polarizability (<i><b>S</b></i>) are predominantly responsible for the <i>n-hexadecane</i> or gas-phase converted sorptions; <i><b>V</b></i> is also important in the gas-phase converted sorption. XAD-7 has larger <i><b>A</b></i> and <i><b>S</b></i> coefficients than XAD-4 and MN200 for both the original and converted analyses, while the opposite is true for <i><b>V</b></i> coefficients. More promisingly, a predictive model, developed based on the sorption of 7 simple aromatic compounds by the resins, can accurately estimate the sorption behaviors of 7 other relatively complex aromatic compounds within a wide range of concentrations