The mineral-organic-water interface is ubiquitous in atmospheric and geochemical environments. Surface interactions of organic molecules with minerals occur via a number of mechanisms that modify surface charge, interfacial water structure, and surface functional groups. These properties can directly affect rates of interfacial chemical and photochemical reactions such as dissolution rates of metal oxides. In general, molecular-level understanding of surface processes at solid/liquid interfaces demands using simple model systems and integrating spectroscopic, calorimetric, and mathematical modeling tools. In this talk, results on the surface chemistry of three types of low molecular weight organics on hematite nanoparticles will be shown. The structure of surface complexes was elucidated from adsorption isotherm and pH envelope spectral data, and also modeled using the triple layer surface complexation model. Flow calorimetric measurements were also completed to gain insight into surface charge and heats of adsorption. The role of electrolytes in the adsorption of organics was also investigated. The significance of these results will be discussed in relation to ligand exchange processes using arsenate and dimethylarsinic acid as examples.

Insights onto the complex iron oxide-organic-water interface from <i>in situ</i> studies using ATR-FTIR, flow microcalorimetry, and surface complexation modeling

2019 Fall National Meeting

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Insights onto the complex iron oxide-organic-water interface from in situ studies using ATR-FTIR, flow microcalorimetry, and surface complexation modeling