Aqueous ion interactions with natural mineral surfaces control numerous interfacial processes, such as mineral dissolution, oxidation-reduction, and contaminant transport, all of which have far-reaching implications for important biogeochemical processes. The mechanisms underlying these interactions have been extensively studied over the last few decades, particularly for silicon and aluminum oxides which are two of the most prevalent crustal mineral constituents. This work looks to the explore the role of hydration and hydrolysis on the adsorption of metal cations, Al3+, Cr3+, and Mn2+, at the surfaces of quartz and corundum at pH 3.8 using flow microcalorimetry, quartz crystal microbalance with dissipation (QCMD) measurements, and density functional theory calculations. QCM-D and microcalorimetry results show that Al3+ and Cr3+ adsorb to both surfaces, while Mn2+ adsorbs only to the corundum surface. Furthermore, calorimetry showed the adsorption of Al3+ to both surfaces to be endothermic and reversible, while Cr3+ was exothermic and partially irreversible on both surfaces. Mn2+ adsorption on corundum was endothermic and reversibility was undetermined due to small amount of heats measured. DFT calculations confirmed favorable bonding between the mineral surfaces and Al3+ and Cr3+. It further demonstrated that Mn2+ adsorption on quartz was unfavorable. This work suggests that cation adsorption on these mineral surfaces is a function of hydrolysis, whereas a hydrolyzed species can strongly bind with the surface while an unhydrolyzed species can only interact electrostatically.

Adsorption study of Al3+, Cr3+, and Mn2+ onto quartz and corundum using flow microcalorimetry, quartz crystal microbalance and density functional theory

256th National Meeting (2018)

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