Gold Leaching from an Oxide Ore Using Thiocyanate as a Lixiviant: Process Optimization and Kinetics

Azizitorghabeh, Atefeh; Mahandra, Harshit; Ramsay, J. O.; Ghahreman, Ahmad

doi:10.1021/acsomega.1c00525

Cited by 30 publications

(25 citation statements)

References 39 publications

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“…Fe 3+ is normally used as the oxidant (Equation (4)). However, the reaction occurs in an acidic environment, which would be corrosive to equipment [ 8 , 16 , 17 , 18 ]. Chlorine is also used as an alternative lixiviant for gold due to its high dissolution rate (Equation (5)), but chlorine is strongly corrosive, highly volatile, and hazardous [ 9 , 19 , 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

Investigation on Gold–Ligand Interaction for Complexes from Gold Leaching: A DFT Study

2023

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Gold leaching is an important process to extract gold from ore. Conventional alkaline cyanide process and alternative nontoxic lixiviants including thiosulfate, thiourea, thiocyanate, and halogen have been widely investigated. However, density functional theory (DFT) study on the gold complexes Au(CN)2−, Au(S2O3)23−, Au[SC(NH2)2]2+, Au(SCN)2−, and AuCl2− required for discovering and designing new highly efficient and environmentally friendly gold leaching reagents is lacking, which is expected to support constructive information for the discovery and designation of new high-efficiency and environmentally friendly gold leaching reagents. In this study, the structure information, electron-transferring properties, orbital interaction, and chemical bond composition for complexes Au(CN)2−, Au(S2O3)23−, Au[SC(NH2)2]2+, Au(SCN)2−, and AuCl2− depending on charge decomposition analysis (CDA), natural bond orbital (NBO), natural resonance theory (NRT), electron localization function (ELF), and energy decomposition analysis (EDA) were performed based on DFT calculation. The results indicate that there is not only σ-donation from ligand to Au+, but also electron backdonation from Au+ to ligands, which strengthens the coordinate bond between them. Compared with Cl−, ligands CN−, S2O32−, SC(NH2)2, and SCN− have very large covalent contribution to the coordinate bond with Au+, which explains the special stability of Au-CN and Au-S bonds. The degree of covalency and bond energy in Au–ligand bonding decreases from Au(CN)2−, Au(S2O3)23−, Au[SC(NH2)2]2+, Au(SCN)2−, to AuCl2−, which interprets the stability of the five complexes: Au(CN)2− > Au(S2O3)23− > Au[SC(NH2)2]2+ > Au(SCN)2− > AuCl2−.

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Section: Introductionmentioning

confidence: 99%

Investigation on Gold–Ligand Interaction for Complexes from Gold Leaching: A DFT Study

2023

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“…The proportional-integral-derivative (PID) control algorithm is a typical kind of model-free control method . However, the PID control algorithm needs to use decoupling technology to realize the control of multi-input multi-output (MIMO) system . Another typical model-free adaptive control method is based on neural network adaptive control technology.…”

Section: Introductionmentioning

confidence: 99%

Model-Free Adaptive Control of Hydrometallurgy Cascade Gold Leaching Process with Input Constraints

et al. 2023

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Hydrometallurgy technology can directly deal with low grade and complex materials, improve the comprehensive utilization rate of resources, and effectively adapt to the demand of low carbon and cleaner production. A series of cascade continuous stirred tank reactors are usually applied in the gold leaching industrial process. The equations of leaching process mechanism model are mainly composed of gold conservation, cyanide ion conservation, and kinetic reaction rate equations. The derivation of the theoretical model involves many unknown parameters and some ideal assumptions, which leads to difficulty and imprecision in establishing the accurate mechanism model of the leaching process. Imprecise mechanism models limit the application of model-based control algorithms in the leaching process. Due to the constraints and limitations of the input variables in the cascade leaching process, a novel model-free adaptive control algorithm based on compact form dynamic linearization with integration (ICFDL-MFAC) control factor is first constructed. The constraints between input variables is realized by setting the initial value of the input to the pseudo-gradient and the weight of the integral coefficient. The proposed pure data-driven ICFDL-MFAC algorithm has anti-integral saturation ability and can achieve faster control rate and higher control precision. This control strategy can effectively improve the utilization efficiency of sodium cyanide and reduce environmental pollution. The consistent stability of the proposed control algorithm is also analyzed and proved. Compared with the existing model-free control algorithms, the merit and practicability of the control algorithm are verified by the practical leaching industrial process test. The proposed model-free control strategy has advantages of strong adaptive ability, robustness, and practicability. The MFAC algorithm can also be easily applied to control the multi-input multi-output of other industrial processes.

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“…The principal pre-treatment methods to oxidize refractory gold ores include roasting, pressure oxidation, and bio-oxidation. Roasting and pressure oxidation are effective technologies but have high capital and operating cost associated with increased energy input and emission of greenhouse gases and can be unprofitable for refractory ores with extremely low grades (Azizitorghabeh et al, 2022;Darvanjooghi et al, 2022), Bio-oxidation has several advantages over traditional methods owing to its less energy requirements and environmental impact by decreasing gas emissions and can be suitable for low-grade matrices (Aswegen et al, 2007;Kaksonen et al, 2014b). Bio-oxidation is a biological oxidation technique involving acidophilic bacteria to enhance the extraction of valuable metals by accelerating the oxidation of the sulfide matrix in refractory ores, which in turn improves gold recovery during cyanide leaching.…”

Section: Introductionmentioning

confidence: 99%

“…Until now, most research has comprised bio-oxidation with acidophilic bacteria at low pH, which is based on the oxidation of reduced sulfur species as well as ferric iron through contact and non-contact biological mechanisms (Azizitorghabeh et al, 2022). The overall bio-oxidation reaction of pyrite using acidophilic bacteria is displayed in Equation 1, where Fe 3+ is regenerated throughout the reaction by iron-oxidizing bacteria, which is unlikely to take place at circumneutral pH due to Fe insolubility at pH > 4 (Percak-Dennett et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

A developing novel alternative bio-oxidation approach to treat low-grade refractory sulfide ores at circumneutral pH

Hein

Mahandra

Ghahreman

2023

Front. Sustain. Resour. Manag.

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The extensive neutralization required in acidic bio-oxidation, a conventional pretreatment for low-grade refractory matrices in the gold industry, constitutes one of the principal drawbacks due to the large volume of waste streams. Performing an oxidative pretreatment at circumneutral pH with an in-situ neutralization would avoid the production of undesirable waste, causing potential economic and environmental advantages. For the first time, this investigation evaluates a novel process involving a biological oxidative pretreatment for low-grade refractory ore using two biosafety level 1 neutrophilic microorganisms encompassing Thiobacillus thioparus and Starkeya novella at near-neutral pH. Optimal bacterial growth conditions were determined regarding the culture medium and initial energy source using UV-visible and manual cell counting (cells/mL). Thereafter, biological oxidation of different matrices, including first elemental sulfur and subsequently a refractory sulfidic ore, was evaluated in batch flask cultures and then scaled up into a bioreactor using optimal experimental conditions. Results revealed that culture media containing ca. 4.5 and ca. 0.9 g/L thiosulfate favored biological oxidation of the refractory sulfidic ore using T. Thioparus and S. Novella, respectively, which led to corresponding sulfide oxidation of 27 and 14% within 10 days, comparable to reported studies. The biological action was confirmed by C/S detector and SEM technique of pre- and post-pretreatment residues. Overall, this research is a step forward to advance the understanding of a biological pretreatment out of the highly acidic pH range, promoting the view of a net-zero target by potentially reducing the production of more significant waste streams compared to conventional operations.

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Gold Leaching from an Oxide Ore Using Thiocyanate as a Lixiviant: Process Optimization and Kinetics

Cited by 30 publications

References 39 publications

Investigation on Gold–Ligand Interaction for Complexes from Gold Leaching: A DFT Study

Investigation on Gold–Ligand Interaction for Complexes from Gold Leaching: A DFT Study

Model-Free Adaptive Control of Hydrometallurgy Cascade Gold Leaching Process with Input Constraints

A developing novel alternative bio-oxidation approach to treat low-grade refractory sulfide ores at circumneutral pH

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