The nucleation mechanisms and kinetics of manganese oxide nanoparticles at mineral-water interfaces play a crucial role in the fate and transport of heavy metals and the cycling of nutrients in environmental systems. These processes affect the morphology and early distribution of Mn oxide, which can be a template for subsequent new layers of Mn oxide. While the film growth of Mn oxide on mineral surfaces at later stages of nucleation has been studied, the early nucleation and growth of Mn oxide nanoparticles on mineral surfaces is less well known.<br/>Using atomic force microscopy and water chemistry analyses, we investigated the heterogeneous nucleation and growth of Mn oxide nanoparticle at varied ionic strength (IS). Interestingly, for 100 mM IS, we found that heterogeneously nucleated Mn oxide showed a more uniform distribution and larger individual particle sizes on quartz surfaces than those in 1 mM and 10 mM IS systems. Confirming analyses based on classical nucleation theory, 100 mM IS resulted in a slower nucleation rate and better structural matching between nucleating Mn oxides and quartz than was found at 1 mM and 10 mM IS. These findings suggest an important and previously unappreciated role of ionic strength in controlling the nucleation activity of Mn oxide by affecting both Mn(OH)<sub>2</sub> (aq) formation and the system’s saturation.

How does the ionic strength control the nucleation of manganese oxide nanoparticles at quartz-water interfaces?

249th National Meeting (2015)

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