Oxygen sensitivity of natural and synthetic organic macromolecule sorption by activated carbon

The influence of dissolved oxygen (DO) on the sorption of natural and synthetic dissolved organic matter (DOM) by granular activated carbon (GAC) was investigated. The sorption behavior of six of the nine DOMs tested were significantly affected by the presence of DO; these six DOMs included polymaleic acid (PMA), peat humic acid, (PMA), Leonardite humic acid, Suwannee river fulvic acid, and Laurentian fulvic and humic acids. The sorption of Aldrich and Soil humic acids and polystyrene sulfonate (PSS) was not sensitive to the presence or absence of DO. Sensitivity of sorption to DO generally increased with decreasing molecular size, polydispersity, aromaticity and increasing acidity for the five natural DOMs. Sorption of the low molecular weight fractions of PHA, an oxygen-sensitive DOM, was almost twice as great as that of the whole material. Sorption of the low molecular weight fractions of Aldrich HA, an oxygen-insensitive DOM, did not show any sensitivity to oxygen.; Investigation of the influence of aqueous chemistry on the oxygen sensitivity of DOM sorption revealed that PMA, PHA, and Laurentian fulvic acid sensitivities decreased with decreasing pH and with increasing ionic strength. This suggests that linear, flexible and open DOM molecular configurations are more sensitive to the presence of oxygen.; Measurements of the oxygen sensitivity of PMA and Laurentian fulvic acid, and o-cresol sorption on different GAC surfaces indicated that oxygen sensitivity decreases markedly with increasing number of GAC surface functional (acid/base) groups, suggesting that polymerization occurs on surface sites other than those containing acidic or basic surface functional groups. The two raw materials from which the experimental carbons were produced, wood and coal, were found to influence oxygen sensitivity of DOM and o-cresol sorption differently. The similar trends observed for the two DOMs and the o-cresol used for this study indirectly indicate that the polymerization of DOMs and o-cresol occur on the similar surfaces.; The effects of preloading of carbons with DOMs on the subsequent sorption of trichloroethylene (oxygen-insensitive) were observed to be greater when the preloading occurred under oxic conditions than under anoxic conditions, for the same degree of preloading. N{dollar}sb2{dollar}-surface area measurements indicated that this difference is a result of the blockage of GAC pores by polymerized DOM molecules. Preloading was similarly found to decrease uptake of o-cresol (oxygen-sensitive) by 20% and 45% under anoxic and oxic conditions, respectively.