Physical, chemical, and biological transformation of nanoparticles in natural environments can affect their surface properties, and thus their reactivity/toxicity and geochemical cycling. One such transformation is the sulfidation of nanoparticles, both engineered (e.g., Ag) and natural (e.g., Fe(III)-(oxyhydr)oxides). We will discuss our studies of the sulfidation of synthetic Ag, CuO, ZnO, and Fe(III)-(oxyhydr)oxide (ferrihydrite, goethite, and hematite) nanoparticles. Nanoparticles were reacted with Na-sulfide aqueous solution at various sulfide/metal ratios and were characterized before and after sulfidation by X-ray absorption spectroscopy, X-ray diffraction, and transmission electron microscopy, resulting in identification of metal-S species and intermediate sulfur species and an improved understanding of the mechanism(s) of sulfidation. For sulfidated Fe(III)-(oxyhydr)oxide nanoparticles, we investigated the impact of organic matter on Fe-S species at different pH values. An environmental consequence of the sulfidation of these nanoparticles is the release of sorbed contaminants and a reduction in toxicity of the transformed nanoparticles to organisms.

Transformation of metal and metal oxide nanoparticles via sulfidation

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ACS Fall 2022

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