Metal-organic-mineral interactions may be important for molybdenum cycling between aqueous and solid phases in the marine environment. Adsorption of molybdate and tetrathiomolybdate onto pyrite (FeS2) was highest at pH 4.8 and decreased as pH increased. All adsorptions were consistent with a one-site adsorption surface as modeled with a Langmuir isotherm. The effect of 2-hydroxypropionic acid (LA) and 2-mercaptopropionic acid (2-MPA) were used to understand the effects of aqueous organic molecules and the presence of oxygen or sulfide functionality. Molybdate adsorption was negligible in the presence of 2-MPA, likely due to 2-MPA outcompeting molybdate for the pyrite surface. Tetrathiomolybdate adsorbed to pyrite when it was added prior to 2-MPA but not when it was added after 2-MPA, likely reflecting similar equilibria between the two species and pyrite. Aqueous iron, which was present during both molybdate and tetrathiomolybdate adsorptions, may also be influencing adsorption to pyrite. Molybdate-LA experiments are currently in progress.

Adsorption of molybdate and tetrathiomolybdate to pyrite in the presence of select organics

245th National Meeting (2013)

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