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Iodide Retention by Metal Sulfide Surfaces: Cinnabar and Chalcocite

Steven D. BalsleyGeochemistry Research Department, Sandia National Laboratories, P.O. Box 5800, Mailstop 0750, Albuquerque, New Mexico 87185Patrick V. BradyGeochemistry Research Department, Sandia National Laboratories, P.O. Box 5800, Mailstop 0750, Albuquerque, New Mexico 87185James L. KrumhanslGeochemistry Research Department, Sandia National Laboratories, P.O. Box 5800, Mailstop 0750, Albuquerque, New Mexico 87185Howard L. AndersonGeochemistry Research Department, Sandia National Laboratories, P.O. Box 5800, Mailstop 0750, Albuquerque, New Mexico 87185

1996en

ABI

Annotatsiya

Ion exchange between aqueous protons and surface Hg and Cu sites on cinnabar (HgS) and chalcocite (Cu2S) are examined by potentiometric titrations at 25 °C in 1, 0.1, 0.01, and 0.001 M NaCl solutions. Cinnabar and chalcocite surfaces are negatively charged at pH > 3, presumably due to deprotonation of exposed thiol groups. Despite the anionic nature of the two metal sulfide surfaces, iodide sorbs strongly to both. Measured distribution ratios (Kd) far exceed those reported for all other minerals; maximal Kd's of 1375 mL/g (Cu2S) and 3080 mL/g (HgS) were observed between pH 4 and pH 5 and were substantial at all pH's measured (4 < pH < 10). Iodide sorption apparently occurs by exchange of hydroxyls attached to Hg and Cu sites.

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Identifikatorlar

DOI: 10.1021/es960083c

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