Bacterial Cyanide Generation in the Presence of Metal Ions (Na+, Mg2+, Fe2+, Pb2+) and Gold Bioleaching from Waste PCBs
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As an alternative using cyanide chemicals for gold extraction, the application of a cyanogenic bacterium <i>viz.</i> <i>Chromobacterium violaceum</i> (<i>C. violaceum</i>) in YP medium has been investigated. The catalytic roles of metal ions such as Na<sup>+</sup>, Mg<sup>2+</sup>, Fe<sup>2+</sup>, and Pb<sup>2+</sup>, as well as the effect of Na<sub>2</sub>HPO<sub>4</sub> nutrient addition on the cyanide generation efficiency of the bacterium in this medium have been elucidated. While MgSO<sub>4</sub> and FeSO<sub>4</sub> added to the medium were equally effective for cyanide generation, improved efficiency was obtained in the presence of Na<sub>2</sub>HPO<sub>4</sub> and Pb(NO<sub>3</sub>)<sub>2</sub>. In order to examine the effectiveness of <i>C. violaceum</i> cultured in YP medium for the generation of cyanide ions, the dissolution of gold and copper from waste mobile phone printed circuit boards (PCBs), a good source of gold and copper in alkaline conditions, was tested at 30°C, for various pH values and metal ion contents. Gold leaching was found to be 11% in 8 d at pH 11.0 in presence of 4.0 × 10<sup>−3</sup> mol/L MgSO<sub>4</sub>, whereas; copper recovery was high (11.4%) at pH 10.0. Addition of 1.0 × 10<sup>−2</sup> mol/L Na<sub>2</sub>HPO<sub>4</sub> and 3.0 × 10<sup>−6</sup> mol/L Pb(NO<sub>3</sub>)<sub>2</sub> to the YP medium increased copper leaching to 30.3% and 38.1%, respectively, at pH 10.0 in 8 d. However, this effect was not observed for gold leaching.
- JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 44(10), 692-700, 2011
The Society of Chemical Engineers, Japan