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Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings
Thesis (MEng)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613775450865664 |
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| access_status_str | Open Access |
| author | Ponto, Lobiane |
| author2 | Tadie, Margreth |
| author_browse | Ponto, Lobiane Tadie, Margreth |
| author_facet | Tadie, Margreth Ponto, Lobiane |
| author_sort | Ponto, Lobiane |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description |
Thesis (MEng)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131887 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:41:30.564Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131887 Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings Ponto, Lobiane Tadie, Margreth Mwewa, Brian Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Flotation Desulfurization Gold ores -- Geology Mineral industries -- Waste disposal Thesis (MEng)--Stellenbosch University, 2024. ENGLISH ABSTRACT: The centuries of gold mining in South Africa have produced large quantities of mine waste (waste rocks, tailings, sludges, and wastewater) due to gold demand. Due to the large quantities of this waste, its proper management is challenging and poses environmental hazards of air, water, and land pollution. Tailings, containing sulfur, that are left exposed to atmospheric conditions with access to water (from rain) and oxygen result in acid-generating potential. When formed, acid gets drained to soil and water, thus polluting the environment. The term for the water formed is referred to as acid mine drainage (AMD). AMD affects aquatic life negatively by changing water pH and depositing metal(loids) dissolved in the acid. The treatment of AMD, using methods such as neutralization with lime, is expensive and hence the prevention of its formation is always preferable. In the literature, preventative methods such as covering the tailings with water to prohibit oxygen access have been investigated. However, the challenges of evaporation with time make these processes not as effective. Another preventative method is the use of the flotation process to remove the acid generating material (desulfurize), which was the focus of this study. Flotation does not only recover sulfur-bearing minerals but in the case of gold mining it also recovers valuable minerals such as gold which are often associated with the sulfide minerals. The presence of gold in tailings is attributed to previously inefficient processing methods and to ore refractoriness. Therefore, the aim of this study was to remediate the environment by desulfurizing calcine gold tailings specifically, using a froth flotation process while simultaneously recovering valuable minerals. Froth flotation of calcine mine tailings was investigated experimentally through a diagnostic flotation. Preliminary flotation tests with added activator (CuSO4) and another with DTP at alkaline conditions were discontinued. This is because copper and sulfur concentrations (from CuSO4) may added biasness to those elements’ results. Again, an alkaline flotation using a DTP failed to produce significant froth hence a mixed experimental design using a collector mixture at pH 4 was investigated. Factors considered for this investigation include a collector mixture (xanthate and DTP collectors), solids concentration and collector composition for their effects on sulfur recovery which was a proxy for sulfide minerals. Thereafter, acid generation and neutralization potential tests were conducted on the treated tailings. Value recovery in the form of gold recovery was also investigated. The effect of cyanide concentration was investigated by leaching the feed material and the treated tailings. The results from flotation investigations indicated that flotation has the potential to desulfurize the sulfide mineral tailings. It was established that collector composition positively affected sulfur recovery while solids concentration negatively affected it. Furthermore, the effect of collector mixture concentration was inconclusive. The maximum sulfur recovery was 24.2% at PD75, 90 g/t concentration and 28 wt% solids test conditions. A maximum sulfur feed grade reduction from 4000 to 2000 ppm was achieved in these conditions. This low recovery is attributed to the heavy oxidation and sulfide minerals enclosure in larger particles, thus leading to flotation inefficiency. A feed with the highest gold grade of 3.91 g/t achieved the maximum solids recovery of 10.4% from operating at PD75, 90 g/t collector mixture concentration and 38 wt% solids. It further led to the highest gold grade of 3.31 g/t remaining in the tailings. However, the maximum gold grade of 14.4 g/t in the concentrate was attained at PD25, 150 g/t collector concentration and 38 wt% solids. Recovery of gold from the feed and flotation tailings by cyanidation was determined to investigate the impact of flotation on gold recovery. Preliminary tests were conducted with only cyanide concentration being varied. The results indicated that an increase in cyanide concentration negatively impacted gold recovery on feed material leaching while positively affected gold recovery of the sulfur-lean flotation tailings. This resulted in a maximum gold recovery of 27.4% and 18.6% for feed leaching (at 1 kg/t of cyanide) and flotation tailings (at 3 kg/t of cyanide) respectively. The positive impact on the recovery of the tailings is due to the elimination of the cyanicides (both metal ions and sulfur) which consume cyanide. The low Au recovery is attributed to unliberated sulfides in nonporous-course materials and their oxides and possible Au association with silicates (like quartz). An analysis of the AMD potential showed that the removal of sulfur by sulfur recovery resulted in both the acid-generating (AP) and neutralizing (NP) potential of the flotation tailings being reduced by 6.95 and 19 kgCaCO3/t, respectively. The initial feed was found to be non-acid forming, which would have been partly due to calcining. The effect of froth flotation on the tailings whilst reducing the acid-forming potential also reduced the capacity to buffer acid generation. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-04-07T09:52:20Z 2025-04-07T09:52:20Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131887 Stellenbosch University xvi, 150 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Flotation Desulfurization Gold ores -- Geology Mineral industries -- Waste disposal Ponto, Lobiane Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| title | Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| title_full | Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| title_fullStr | Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| title_full_unstemmed | Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| title_short | Investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| title_sort | investigation of the effect of froth flotation on desulfurization and value recovery of gold tailings |
| topic | Flotation Desulfurization Gold ores -- Geology Mineral industries -- Waste disposal |
| url | https://scholar.sun.ac.za/handle/10019.1/131887 |
| work_keys_str_mv | AT pontolobiane investigationoftheeffectoffrothflotationondesulfurizationandvaluerecoveryofgoldtailings |