The trisulfur radical ion S3•- controls platinum transport by hydrothermal fluids

Platinum group elements (PGE) are considered to be very poorly soluble in aqueous fluids in most natural hydrothermal-magmatic contexts and industrial processes. Here, we combined in situ X-ray absorption spectroscopy and solubility experiments with atomistic and thermodynamic simulations to demonstrate that the trisulfur radical ion S3 center dot- forms very stable and soluble complexes with both PtII and PtIV in sulfur-bearing aqueous solution at elevated temperatures (similar to 300 degrees C). These Pt-bearing species enable (re)mobilization, transfer, and focused precipitation of platinum up to 10,000 times more efficiently than any other common inorganic ligand, such as hydroxide, chloride, sulfate, or sulfide. Our results imply a far more important contribution of sulfur-bearing hydrothermal fluids to PGE transfer and accumulation in the Earth's crust than believed previously. This discovery challenges traditional models of PGE economic concentration from silicate and sulfide melts and provides new possibilities for resource prospecting in hydrothermal shallow crust settings. The exceptionally high capacity of the S3 center dot- ion to bind platinum may also offer new routes for PGE selective extraction from ore and hydrothermal synthesis of noble metal nanomaterials.

Automated summary

Through a combination of experiments and simulations, it was found that the S3 center dot- ion can form stable and soluble complexes with platinum, being 10,000 times more efficient than other common ligands. Sulfur-bearing hydrothermal fluids play a more important role in the transfer and accumulation of PGE in the Earth's crust, challenging traditional models.