Unique Interface and Unexpected Behavior Help Explain How Heavy Metals Act

Three different kinds of water molecules wrap around platinum-based ion and offer insights for waste material processing and refining of metal.

Refining platinum (Pt), plutonium (Pu) or some other particular metals mostly depends on its behavior at liquid boundaries. Scientists have restricted ways to evaluate the particulars of liquid interfaces. Researchers have described in detail how water molecules envelope a platinum ion.

In order to refine Platinum or any other rare metal, we have to move it from one liquid to another. However, we don’t have knowledge on how to make these movements at molecular level.

Solvent extraction, a method for reprocessing of nuclear waste and refining rare earth elements or precious metals, includes the favored transfer of particular chemical species between 2 immiscible phases. Relatively, very less molecular-scale knowledge is known regarding the mechanisms of this movement across interface.

In order to describe molecular-scale, heavy and anionic-complexes, for example PtCl62-, with positively charged molecules at air/water boundary, scientists combined the synchrotron X-ray experiments with “surface-sensitive sum-frequency generation (SFG)” spectroscopy, and the molecular dynamics simulations. X-rays provided by the Advanced Photon Source surveyed the structural features of some surface-located metal ions. A mixture of dispersing and fluorescence measurements revealed a 2-step adsorption process that relies on the concentration of metal in solution. SFG spectroscopy discovered a unique H2O structure related to it. A fresh sub-ensemble investigation of molecular dynamics simulations was done. The research proves that post adsorption; the PtCl62 partially retains its 1st and 2nd hydration spheres. 3 water molecules can be identified around the ions differentiated by their hydrogen bonding motifs and orientation.

This work is backed by the Department of Energy (DOE); Office of Basic Energy and Sciences; Office of Science; Division of Biosciences, Geosciences, and Chemical sciences.  A science user facility office DOE, Advance Photon Source provides X-rays. National Science Foundation supports ChemMatCARS. Molecular dynamics simulations have been performed at computing resources given on Blues, i.e high-performance computing group run by the ‘Laboratory Computing Resource Center’ present at Argonne National Laboratory.

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