Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties

Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized as terrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM.