Polanyi-based models for the competitive sorption of low-polarity organic contaminants on a natural sorbent

The development of appropriate equilibrium sorption relationships for anthr opogenic organic contaminants with soils and sediments is essential to pred icting the extents and rates of solid-water interactions in the environment . In this context, we previously reported results that showed how nonlinear sorption isotherms with nine low-polarity organic chemicals on a silty aqu itard material could be modeled as a combined adsorption-partitioning proce ss. The adsorption component was ascribed to presumed traces of a carbonace ous adsorbent, for which adsorption was well described by a Polanyi-based i sotherm, in this work, we report competitive sorption behavior on. the same material, as observed from batch experiments:in binary solute systems that contain combinations of the previously studied sorbates (chorinated benzen es and polyaromatic hydrocarbons) over wide ranges of concentration. The re sults confirmed our expectation that partitioning is an increasingly domina ting contribution to overall sorption when cosorbates are present. Moreover , the competitive effects could be very well predicted on the basis of Pola nyi-Manes adsorption theory and the prior single solute results. Overall, t he results further validate the applicability of a Polanyi-based modeling a pproach and lend additional support to the hypothesis that this sorbent con tains trace quantities of high surface area carbonaceous material.