Reduction and accumulation of gold(III) by Medicago sativa alfalfa biomass: X-ray absorption spectroscopy, pH, and temperature dependence

J. L. Gardea-Torresdey, K. J. Tiemann, G. Gamez, K. Dokken, Irene Cano-Aguilera, Lars R. Furenlid, Mark W. Renner

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We report herein the use of Modicago sativa alfalfa shoot biomass for the removal of gold from aqueous solutions. The accumulation process involves the reduction of Au(III) to colloidal Au(0) and is shown to increase at elevated temperatures and at lower pH. X-ray absorption spectroscopy (XAS) was used to determine that gold(III) was reduced to form gold(0) colloids, which varied in size depending on the PH of the initial solution. The gold cluster radius was 6.2 ± 1 Å at pH 5 and 9.0 ± 1 Å at pH 2. Our findings indicate that essentially another layer of gold atoms was deposited onto the colloid surface at pH 2. Possible mechanisms of bioreduction and accumulation are discussed.

Original languageEnglish
Pages (from-to)4392-4396
Number of pages5
JournalEnvironmental Science and Technology
Issue number20
StatePublished - Oct 15 2000


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