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Review date: July 24, 2003
PNNL-SA-27883

An X-ray Absorption Fine Structure Study of Copper(I) Chloride Coordination Structure in Water up to 325°C

J. L. Fulton, M. M. Hoffmann, and J. G. Darab, Chemical Physics Letters, (2000) In press.

Abstract: X-ray absorption fine structure (XAFS) spectroscopy was used to measure the Cl^- and H2O coordination structure about Cu¹⁺ in water at temperatures up to 325°C. The complete coordination structure about Cu¹⁺ is reported including the coordination numbers, symmetry, distances for the ion-ion and water-ion associations and amount of disorder (Debye-Waller factor and the anharmonicity). For a solution having [Cl^-]/[Cu¹⁺] > 2, the linear dichloro Cu¹⁺ species, [CuCl2]^-, is especially stable and it is predominant from 100°C to 325°C. For a very high salt concentration of 2.0 m NaCl, only the dichloro Cu¹⁺ species is observed with no evidence of higher Cl^- coordination. There is no evidence of hydration waters in the first solvation shell of this dichloro-species. When the overall chloride concentration is equal to the copper concentration, i.e., [Cl^-]/[Cu¹⁺] = 1, a dimer species with a tentative structure [CuCl2]-[Cu(H2O)]⁺ is observed.