Dissertations and Theses

Date of Award


Document Type



Earth and Atmospheric Sciences

First Advisor

Karin Block


bioleaching, Alcaligenes, faecalis, gold, recovery, mining


Samples from the tailings of the Picacho mine in California were leached using NaCN and native bacteria, Alcaligenes faecalis, in column experiments to compare the gold recovery yields in the effluents. Four columns were treated with a different liquid: water, bacteria, NaCN and a mixture of cyanide and bacteria. After they were leached the effluents were analyzed to determine gold yields. During experiment I the total Au recovered in the effluent in the column treated with bacteria was only 10.09% less than those treated with cyanide (C2) and 81.7% more than the control. In experiment II, Au values measured were below detection limits. In experiment III Au recovered in the effluents for the Bacteria Column was 18.51% less than the Cyanide (C2) column and 34.27% more than the control.. Mass balance calculations for experiment I show that the column treated with bacteria has a higher percentage recovery yield of the Au recovered in both the effluent (18%) and in the two columns treated with cyanide (13% and 15%, respectively). In experiment III, mass balance calculations show that the percentage of Au recovered in the effluents of the columns treated with the bacteria was 15% and the other two columns trreated with cyanide had 25% of Au from the effluents. These findings indicates that the use of A.faecalis as an encouraging option for Au leaching of mine tailings which requires little supervision that translates in lower costs. The leaching treatment with bacteria produced favorable results that challenge cyanidation.



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