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In aquifers and other natural systems, single mineral systems are rare. Solids are commonly heterogeneous, containing multiple minerals, and mineral interactions are expected. Mineral interactions such as formation of coatings and physical blocking of adsorption sites have the potential to significantly change the adsorption of ions onto solids. To investigate such interactions, batch experiments using Co(II) or Cr(VI) were conducted to compare adsorption edges of these sorbates on pure and mixed mineral systems. Specifically, sorption of 10-5 or 10-6 M Co(II) and Cr(VI) was measured as a function of pH, with a background electrolyte concentration of 0.01 M NaNO3 on 2 to 4 g/L of nanoparticulate (<50 nm) maghemite, quartz, maghemite-quartz physical mixtures, or maghemite-coated quartz. Changes in pH greatly influence adsorption behavior, but changes in sorbent concentration have little effect under the conditions of this study. A significant quantity of Co (up to 100%) sorbed onto maghemite and quartz in the pure mineral systems. In contrast, Cr(VI) only sorbed significantly onto maghemite and was insignificant on pure quartz. In mixed and coated mineral systems, the adsorption of Co and Cr(VI) was closer to that observed for the pure maghemite than the pure quartz systems. This study shows that maghemite is likely the dominant sorbent for Co and Cr(VI) in systems containing both quartz and maghemite.
Troy, Amy, "Co and Cr Adsorption on Maghemite, Quartz, and Maghemite-Quartz Mixtures" (2013). Honors Theses. 2312.
Honors Thesis-Open Access