Biological Oxidation of Refractory Sulfidic Ores at Circumneutral pH
Loading...
Authors
Hein Alvial, Guillermo A.
Date
2024-01-31
Type
thesis
Language
eng
Keyword
Sulfide oxidation , Biomining , Neutral bio-oxidation , Gold-bearing ores , Microorganisms
Alternative Title
Abstract
The industrial process for gold recovery, comprising acidic biological oxidation (bio-oxidation) and cyanidation, has demonstrated competitive effectiveness in dealing with the refractoriness of sulfidic gold ores. Nevertheless, many aspects could still be improved to strengthen the process, most prevalently the complexity associated with pH control and neutralization of acidic slurries preceding cyanidation, which results in high cost and generation of new waste streams. Consequently, performing bio-oxidation at circumneutral pH with an in-situ neutralization supported only by culture medium conditions offers a novel biotechnological opportunity to facilitate the standard process and enhance environmental protection. This research reports the capacity of unexplored microorganisms in conventional mining applications to oxidize sulfidic gold ores at circumneutral pH. First, the application of two neutrophilic bacteria, Thiobacillus thioparus, and Starkeya novella, was investigated, and optimal bacterial growth conditions and their capacity to oxidize different matrices were determined. A culture medium containing 4.5 g/L and 0.9 g/L thiosulfate as the initial energy source favored the oxidation of a sulfidic ore, with a maximum of 27.2% and 14% using 1% w/v after 10-day treatment assisted by Thiobacillus thioparus and Starkeya novella, respectively. Subsequently, the fungus Phanerochaete chrysosporium was selected as another biological engine to improve sulfide oxidation. The optimal conditions of the fungal treatment revealed that an initial pH of 5.8 resulted in 23.1% sulfide oxidation using 5% w/v following 14-day treatment. D-optimal response surface methodology suggested a modified culture medium consisting of 12.86 g/L glucose, 2.20 g/L malt extract, 1.67 g/L yeast extract, and 0.49 g/L MgSO4·7H2O to enhance microbial activity and reach 28.7% sulfide oxidation. pH-controlled batch cultures in the pH range of 5.8 to 7.0 showed that a rise in pH was detrimental to microbial activity and, thus, sulfide oxidation. Higher sulfide oxidation was accomplished by replenishing the microbial culture in a 42-day multi-stage bio-oxidation, attaining 51.1% sulfide oxidation in the modified culture medium. Furthermore, corn steep was studied to replace standard ingredients, resulting in 40.6% sulfide oxidation when substituting 1.67 g/L yeast extract. Conventional cyanidation was also performed in oxidized samples. Ultimately, implications and limitations of this research are summarized.
Description
Citation
Publisher
License
Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International