Lime use in gold processing – A review

Plessis, Chris A. du; Lambert, H.; Gärtner, Robert S.; Ingram, Kevin D.; Slabbert, Wickus; Eksteen, Jacques

doi:10.1016/j.mineng.2021.107231

Cited by 9 publications

(4 citation statements)

References 100 publications

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“…This was to assess the flotation response of REE and gangue species at pH 9, which has been widely reported in the literature to be suitable for REE recovery using fatty acids as collectors [22][23][24]. Pulp pH 10.5 was selected to assess the feasibility of recovering REE minerals as a byproduct of gold leaching, which is typically carried out at pH range of 10-11 [25][26][27].…”

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confidence: 99%

Recovery of Rare Earth Elements Minerals in Complex Low-Grade Saprolite Ore by Froth Flotation

Abaka-Wood

Johnson²,

Addai‐Mensah

et al. 2022

Minerals

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This study presented the first in a series of investigations currently underway to develop efficacious, cost-effective, and benign processing opportunities to produce rare earth elements (REE)–rich concentrate from an Australian complex low–grade saprolite ore [1.14% total rare earth oxides (TREO) grade], which is primarily exploited for its gold and copper values. This work specifically presented a preliminary flotation investigation carried out on the ore using sodium oleate as a collector. The relative effects of pulp pH, desliming, and depressants were investigated to ascertain any chance of recovering and upgrading REE minerals in saprolite ore using three different processing configurations. Based on the experimental results, flotation processes carried out on raw feed allowed the recovery of the majority of REE minerals (>50%), but the process was unselective, where clay and silicate gangue minerals reported into the flotation concentrate along with the REE minerals. However, desliming before flotation in the presence of depressants (starch and sodium silicate) improved REE minerals flotation selectivity, which produced concentrates assaying 5.87% and 4.22% TREO grades, with corresponding recoveries of 45% and 50% at pulp pH 9 and 10.5, respectively. Mineralogical analysis conducted on selected flotation concentrate indicated that silicate and clay gauge minerals were recovered via the synergistic act of surface activation and entrainment due to their fine to ultrafine nature. A comparison of all the test results revealed a haphazard grade–recovery relationship suggesting that there is an opportunity to further maximize both REE recovery and grade through further flotation studies where other process parameters may be investigated and optimized. The prospect of using magnetic separation has also been suggested.

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confidence: 99%

Recovery of Rare Earth Elements Minerals in Complex Low-Grade Saprolite Ore by Froth Flotation

Abaka-Wood

Johnson²,

Addai‐Mensah

et al. 2022

Minerals

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“…The rest of the minerals such as quartz and calcite are stable under alkaline conditions, so they would act as filler materials and become "aggregates" in geopolymer composites. The substantial amounts of calcite (~26% Ca) measured in the ASGM tailings could be attributed to the (i) use of lime-a well-known compound that transforms to calcite in the environment-for pH control during the CIP process, and (ii) the innate characteristics of the gold ore [58]. The presence of Ca-bearing minerals is an advantage for repurposing the tailings into construction materials because they are essential in the formation of pozzolanic minerals, which could enhance the strength and thermal stability of synthesized geopolymer composites.…”

Section: Discussionmentioning

confidence: 99%

Utilization of Palm Oil Fuel Ash (POFA) as an Admixture for the Synthesis of a Gold Mine Tailings-Based Geopolymer Composite

et al. 2023

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The repurposing of gold (Au) mine tailings from artisanal and small-scale mining (ASGM) operations via alkali activation technology is a promising strategy for waste reduction in developing countries. Direct activation of mine tailings, however, is challenging because these materials contain relatively low aluminum (Al)-bearing minerals. In this study, palm oil fuel ash (POFA) was elucidated as a high Al-bearing waste derived-admixture for the synthesis of an ASGM tailings-based geopolymer composite. Semi-quantitative XRD analysis showed that the tailings contained quartz (SiO2) (~58%), pyrite (FeS2) (~20%) and calcite (CaCO3) (~15%) with minor to trace amounts of aluminosilicates (~7%). Substantial amounts of environmentally regulated pollutants such as mercury (Hg) (40 mg/kg), lead (Pb) (8430 mg/kg) and arsenic (As) (300 mg/kg) were also found in the tailings. SEM-EDS, XRD and ATR-FTIR results showed the successful formation of a hybrid geopolymer-CASH matrix, which improved the unconfined compressive strength (UCS) of geopolymer composites from ~5 MPa to ~7 MPa. Furthermore, POFA did not significantly affect the thermal resistivity of geopolymer composites based on thermal analysis. Finally, the TCLP results showed that the Pb leaching concentrations from ASGM tailings exceeded environmental standards (~15,000 µg/L), which was suppressed after alkali activation to 300–500 µg/L. This means that POFA addition to ASGM tailings-based geopolymer composite improved not only its applicability as backfill, pavements and bricks but also its ability to immobilize toxic elements.

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“…Mercury has historically been used to recover gold, but the cyanidation process is increasingly being used with the highly toxic but less recalcitrant cyanide anion . Currently, cyanide is used in approximately 80% of gold extraction activities with approximately 15% of total cyanide usage coming from the mining industry. , Approximately 1.3–2.7 kg of free cyanide is used per ton of ore to achieve optimal leaching of gold, , and the concentration of cyanide in typical gold processing effluents reportedly ranges anywhere from 100 to 500 mg/L . As large amounts of cyanide are present in gold mining and refining operation effluent, treatment of these wastewaters is a major concern.…”

Section: Introductionmentioning

confidence: 99%

Membrane Contactors as a Cost-Effective Cyanide Recovery Technology for Sustainable Gold Mining

et al. 2023

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Cyanide is the ligand of choice for large-scale gold extraction plants and is increasingly replacing amalgamation for small-scale gold extraction processes. Although cyanide is less recalcitrant than mercury, it is still acutely toxic. Current absorption column-based recovery and oxidation processes have high capital and chemical costs, respectively, and are therefore rarely implemented and only at large-scale operations. Membrane contactors with a pH gradient can be used for selective separation of cyanide into a distillate solution. This study evaluated cyanide recovery using polypropylene (PP) and polytetrafluoroethylene (PTFE) membranes and the impact of operating conditions with synthetic and real mining wastewater. The results show the successful recovery of cyanide with the PTFE and PP membranes, as well as a significant impact of distillate pH, temperature, and feed cyanide concentration on process efficiency. Conversely, distillate cyanide concentrations had a very limited impact on process performance, suggesting limited freshwater resources are required for cyanide recovery. The results of a techno-economic analysis indicate that membrane contactors are cost-effective on large and small scales. While the PTFE membrane system is slightly less expensive at a small scale and the PP membrane system is more advantageous at a large scale, both membrane systems can be considered cost-competitive with current cyanide recovery methods.

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Lime use in gold processing – A review

Cited by 9 publications

References 100 publications

Recovery of Rare Earth Elements Minerals in Complex Low-Grade Saprolite Ore by Froth Flotation

Recovery of Rare Earth Elements Minerals in Complex Low-Grade Saprolite Ore by Froth Flotation

Utilization of Palm Oil Fuel Ash (POFA) as an Admixture for the Synthesis of a Gold Mine Tailings-Based Geopolymer Composite

Membrane Contactors as a Cost-Effective Cyanide Recovery Technology for Sustainable Gold Mining

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