Abstract

Iodide-oxidizing bacteria (IOB) oxidize iodide into iodine and triiodide which can be utilized for gold dissolution. IOB can be therefore useful for gold leaching. This study examined the impact of incubation conditions such as concentration of the nutrient and iodide, initial bacterial cell number, incubation temperature, and shaking condition on the performance of the gold dissolution through the experiments incubating IOB in the culture medium containing the marine broth, potassium iodide and gold ore. The minimum necessary concentration of marine broth and potassium iodide for the complete gold dissolution were determined to be 18.7 g/L and 10.9 g/L respectively. The initial bacterial cell number had no effect on gold dissolution when it was 1 × 104 cells/mL or higher. Gold leaching with IOB should be operated under a temperature range of 30–35 °C, which was the optimal temperature range for IOB. The bacterial growth rate under shaking conditions was three times faster than that under static conditions. Shaking incubation effectively shortened the contact time compared to the static incubation. According to the pH and redox potential of the culture solution, the stable gold complex in the culture solution of this study could be designated as gold (I) diiodide.

Highlights

  • Recovery of gold from ores and concentrates traditionally relies on cyanide leaching

  • Impact of the Concentration of the Marine Broth and Potassium Iodide on the Bacterial Growth and the Figure 1 shows the bacterial cell number (Figure 1a) and the leaching yield (Figure 1b) which were obtained in the incubation experiments under different concentration of the marine broth and potassium iodide

  • This study focused on the bioleaching of gold from a gold ore by using Iodide-oxidizing bacteria (IOB)

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Summary

Introduction

Recovery of gold from ores and concentrates traditionally relies on cyanide leaching. Gold recovery with cyanidation process generally involves crushing, grinding, leaching, activated carbon adsorption, desorption, and electrowinning. Cyanide leaching creates serious environmental risks due to its severe toxicity. Several cyanide substitutes have been suggested by some workers [1,2,3,4]. The iodine–iodide gold leaching is well known as an effective and environmental-friendly method for gold leaching without toxic chemicals such as cyanide, aqua regia and mercury [3,5]. According to Gos and Rubo (2001) [6], acute toxicity and ecotoxicity of cyanide are much higher than iodine. Cyanide is classified as a strong water contaminant iodine is designated as slight water contaminant

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