Sorption of Organic Contaminants

Abstract

Sorption of organic contaminants plays a dominant role in their rate of transport through porous media such as soils, sediments and aquifers. The rate of abiotic and biotic transformations may also be significantly altered by sorption. This paper presents a brief overview of the current knowledge base on sorption of organic contaminants by natural sorbents, and examines several emerging issues that need further study. Partitioning into sorbent organic matter is viewed as the predominant process for sorption of nonpolar organics from aqueous solutions, and various methods have been proposed for estimating sorption/partition coefficients. Recent experimental and theoretical work has established a basis for predicting organic contaminants sorption from polar mixed solvents (mixtures of water and miscible cosolvents). Data on sorption of ionic and ionogenic organic compounds (e.g., phenols, amines) are limited, and initial efforts are underway to develop models for such sorbates. There also has been a recent resurgence of interest in studying vapor-phase sorption and transport of volatile organic compounds. Much of the early work on sorption dealt with equilibrium sorption, but considerable advances have been made in characterizing and predicting sorption nonequilibrium as well. Molecular-scale measurements are needed in order to provide direct, unequivocal evidence for selection among several contending phenomenological models proposed for describing sorption equilibrium and kinetics.