Allen Burton (Committee Member), David Costello (Committee Member), Chad Hammerschmidt (Advisor)
Master of Science (MS)
Goethite is an ideal sorbent for investigations of metal partitioning with iron oxyhydroxides because it is the most abundant iron oxyhydroxide in sediments (Langmuir, 1997; van der Zee et al., 2003), and cations have a strong affinity for goethite (Coughlin and Stone, 1995). Steady-state partitioning of nickel (Ni) and copper (Cu) to nanoscale goethite (a-FeOOH) was investigated experimentally under conditions intended to be representative of those in natural waters. Manipulated conditions included i) sorbent mass, ii) solute metal concentration, iii) reaction time, iv) pH, v) ionic strength (I), and vi) humate concentration (competitive ligand) to examine how these factors influenced the partitioning of Cu and Ni between water and goethite. This work suggests that solute adsorption in natural systems is determined by ambient pH and available competitive ligands. Distribution coefficients widely increased as solution pH was raised above the point of zero net proton charge (PZNPC) of goethite. As humate concentration was increased, a significant decrease in distribution coefficients was observed. Ionic strength had no observed effect on solute adsorption. Increasing reaction time did not increase solute adsorption, which suggests that all possible adsorption occurs within 24 hours of solute introduction. The distribution coefficients for Ni and Cu obtained in this study fall within and above reported ranges for soil/water, suspended matter/water, and sediment/water interfaces. Because KD values from this study are within and above the reported range, goethite may significantly contribute to the adsorption of both Ni and Cu. This study warrants further investigation of metal partitioning to nanoscale goethite within natural surface and pore water to determine its potential significance.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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