Adsorption and Fractionation of Suwannee River Organic Matter on Metal (Fe, Al) Oxide-Coated Quartz: A Liquid Chromatographic Investigation

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Environmental Engineering Science






The hydrophobic organic acid (HPOA) fraction of the dissolved organic matter (DOM) collected in 2012 at the headwaters of the Suwannee River (SR) was interacted with a metal (Fe, Al) oxide-coated quartz sand, which was sourced from Oyster, VA (referred to as Oyster Sand, “OS”). The adsorption, adsorptive fractionation, and competitive displacement interactions of SR-HPOA on OS were investigated. The novelty of this work is based on the experimental technique employed. Most prior studies of DOM-adsorbent reactions have been performed with either batch or continuous-flow column techniques. However, in this work, the DOM adsorbate and geosorbent were reacted using a rapid and data-rich liquid chromatographic method in which discrete (i.e., noncontinuous) additions of adsorbates are made onto manually adsorbent-packed columns, and eluting fractions are monitored in multiple optical detector channels. All experiments were performed under the same conditions [mobile phase pH 4 and ionic strength 0.005 M (NaCl)]. Fractions of HPOA preferentially adsorbed on OS included relatively aromatic, strongly UV absorbing but weakly fluorescing high-molecular-weight (MW) mixture constituents. These adsorptive fractionation trends were inferred by comparing signals from the different optical detection channels and were also confirmed by size exclusion chromatography analyses of column effluent fractions. Adsorption experiment results were confirmed by desorption studies; SR-HPOA materials released from organically-saturated OS surfaces by injections of KOH or KH2PO4 were relatively high in MW and aromaticity as well as relatively nonfluorescent.