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Evaluating processing options for lithium recovery from smectite clays
Thesis (PhD)--Stellenbosch University, 2026.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613941871411200 |
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| access_status_str | Open Access |
| author | Haller, Cara Philipa |
| author2 | Dorfling, Christie |
| author_browse | Dorfling, Christie Haller, Cara Philipa |
| author_facet | Dorfling, Christie Haller, Cara Philipa |
| author_sort | Haller, Cara Philipa |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/136166 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:44:08.546Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/136166 Evaluating processing options for lithium recovery from smectite clays Haller, Cara Philipa Dorfling, Christie Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Lithium -- Metallurgy Clay minerals Leaching Sulfuric acid Ore-dressing Thesis (PhD)--Stellenbosch University, 2026. Haller, C. P. 2026. Evaluating processing options for lithium recovery from smectite clays. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/84654c5b-875c-41f9-9d7a-4c97fbcea569 ENGLISH ABSTRACT: Growing lithium demand has led to increasing interest in low-grade clay deposits. Although direct sulphuric acid leaching is typically the most widely considered processing route for lithium recovery from clays, drawbacks of this approach include high acid consumption, poor selectivity and environmental management challenges. This project evaluated alternative processing options for lithium extraction from smectite clays through bench-scale experiments, including direct leaching with alternative reagents and salt roasting followed by water leaching. Solution purification of the resulting leachate, followed by recovery of lithium in a saleable form, was also investigated experimentally. Subsequently, a techno-economic analysis was performed for the processing route deemed most viable based on the experimental outcomes. A range of organic acids and inorganic salts were screened as alternatives to sulphuric acid, with oxalic acid providing the highest leaching efficiency. In subsequent optimisation tests, sulphuric acid achieved more than 90% lithium dissolution after 2 hours at 1.5 M, 25–60°C and 8% solids. In comparison, oxalic acid reached a maximum of 82% dissolution after 6 hours at 2 M, 40°C and 8% solids. Downstream processing of acid leachates via evaporation and pH adjustment proved challenging due to poor selectivity during leaching. Screening of salts for roasting showed that a binary system of sodium sulphate and calcium sulphate produced the highest lithium dissolution during subsequent water leaching. This combination was used for optimisation tests. Using a clay : total salt ratio of 2:1, Na2SO4 : CaSO4 ratio of 2:1, the material was roasted at 850°C for 1.5 hours. Subsequent leaching at 60°C and 30% solids resulted in 86.3% lithium dissolution after 2 hours. Roasting removed the clay’s swelling properties, allowing leaching at high solids content and therefore increasing lithium concentrations in solution. The roast-leach route was also more selective towards lithium, reducing losses during solution purification. Based on experimental results, a process flowsheet was developed to treat 12 000 tons of clay per day at an average grade of 650 ppm lithium over a 25-year project life. The selected flowsheet comprised sulphate salt roasting, water leaching, initial calcium removal by carbonate precipitation, and solvent extraction with Cyanex 936P for selective lithium recovery. The loaded organic was stripped with sulphuric acid, and the strip liquor was evaporated to increase lithium concentration prior to a second carbonate precipitation step to remove residual calcium. Lithium was finally recovered as lithium carbonate, with modelling predicting a product purity of 99.9%. The base case net present value was negative due to the combination of low feed grade and an overall lithium recovery of 63.4%. Sensitivity analyses indicated that simultaneous reductions in operating costs and increases in revenue are required to achieve profitability. The roasting section accounted for the largest share of operating costs, primarily due to the consumption of sulphate salts and natural gas for heating. This project provides new insights into how key operating variables influence different processing routes for lithium production from smectite clays. In addition, a novel process model was developed to identify major cost drivers and assess sensitivity to costs and revenue for this application. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2026-04-24T07:42:25Z 2026-04-24T07:42:25Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/136166 en Stellenbosch University xxiv, 205 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lithium -- Metallurgy Clay minerals Leaching Sulfuric acid Ore-dressing Haller, Cara Philipa Evaluating processing options for lithium recovery from smectite clays |
| title | Evaluating processing options for lithium recovery from smectite clays |
| title_full | Evaluating processing options for lithium recovery from smectite clays |
| title_fullStr | Evaluating processing options for lithium recovery from smectite clays |
| title_full_unstemmed | Evaluating processing options for lithium recovery from smectite clays |
| title_short | Evaluating processing options for lithium recovery from smectite clays |
| title_sort | evaluating processing options for lithium recovery from smectite clays |
| topic | Lithium -- Metallurgy Clay minerals Leaching Sulfuric acid Ore-dressing |
| url | https://scholar.sun.ac.za/handle/10019.1/136166 |
| work_keys_str_mv | AT hallercaraphilipa evaluatingprocessingoptionsforlithiumrecoveryfromsmectiteclays |