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Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid
Thesis (MEng)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2024
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| _version_ | 1867614061960626176 |
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| access_status_str | Open Access |
| author | Knight, Marcus Alexander |
| author2 | Bradshaw, Steven Martin |
| author_browse | Bradshaw, Steven Martin Knight, Marcus Alexander |
| author_facet | Bradshaw, Steven Martin Knight, Marcus Alexander |
| author_sort | Knight, Marcus Alexander |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/130539 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:46:01.452Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/130539 Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid Knight, Marcus Alexander Bradshaw, Steven Martin Akdogan, Guven Van Wyk, Andries Pieter Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering. Automobiles -- Catalytic converters Hydrometallurgy Hydrochloric acid Leaching Platinum group Thesis (MEng)--Stellenbosch University, 2024. ENGLISH ABSTRACT:Catalytic converters are present in all modern vehicles and contain the PGMs Pt, Pd, and Rh. These PGMs act as catalysts for the oxidation of C, H, and O to CO2 and H2O; and the reduction of NOx to N2, H2O, CO2, and NO. Mining is the primary source of these metals, but much research and development has been conducted into recovery from secondary sources such as e-waste and scrap. Pyrometallurgical methods are most popular for large scale recycling but produce toxic fumes such as sulphur oxides and have a significant electrical requirement. Hydrometallurgical methods show good extraction efficiencies, especially on a smaller scale, but trade the high energy requirements and toxic emissions of pyrometallurgical processes for increased reagent requirements. A need is present for continued investigation into optimizing processes for recovering these PGMs from spent auto-catalysts using more environmentally benign hydrometallurgical methods. The use of ozone as an oxidant in chloride leaching is one option. The gas has a high oxidising potential and is safer and less aggressive when compared to other popular oxidants such as chlorine gas. Therefore, the aim of this investigation was to develop a process for leaching Pt, Pd, and Rh from simulated spent autocatalyst material using ozone and hydrochloric acid. Development of the chosen process was carried out through kinetic and statistical analyses. Experimentation was divided into two stages: Leach 1 and Leach 2. Both leaches were carried out using a Box-Behnken experimental design. The O3 mass flow, initial HCl concentration, and temperature were varied at factor levels of 3.34, 5.01, and 6.68 g/h; 1.0, 3.0, and 5.0 M; and 30, 60, and 90oC respectively. Fifteen runs were conducted with a centrepoint triplicate for each leach. From the results and a statistical analysis, it was concluded that when maximizing the overall PGM extraction the leach was optimized at 5.01 g/h O3, 5.0 M HCl, and 90oC with Pt, Pd, and Rh extractions of approximately 80%, 85%, and 42%. However, at these conditions a significant degree of impurity extraction was observed at 67% and 68% for Al and Mg. Due to the high dependency of Rh and these two impurities on temperature, a desirability analysis determined that adjusting the factor setpoints could potentially facilitate the selective extraction of Pt and Pd (at values >80%) while minimizing the extraction of Rh and impurities. This was the basis for Leach 2. The second leach was conducted at the same O3 mass flows, HCl initial concentrations of 4.0, 5.0, and 6.0 M, and temperatures of 25, 30, and 35oC. The analysis from this leach indicated optimum conditions of 3.34 g/h, 5.0 M, and 25oC. The extractions at these conditions were 64% for Pt and Pd, and Rh, Si, Al, and Mg extractions were 1.3%, 2.6%, 2.8%, and 4.1%. Therefore, the minimization of the Rh and impurity extraction was successful. However, throughout experimentation a decrease in the extractability of the PGMs was observed over time. This is highlighted by the difference in the optimum results for Pt and Pd between Leach 1 and 2, and the similar conditions used to facilitate these extractions. A possible cause of this decrease is the gradual hydroxylation of the PGM oxides as a result of their exposure to humid air. However, further investigation is required to establish exactly what decreased the PGM extractability over time. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2024-03-05T08:10:50Z 2024-04-26T21:17:36Z 2024-03-05T08:10:50Z 2024-04-26T21:17:36Z 2024-03 Thesis https://scholar.sun.ac.za/handle/10019.1/130539 en_ZA en_ZA Stellenbosch University 205 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Automobiles -- Catalytic converters Hydrometallurgy Hydrochloric acid Leaching Platinum group Knight, Marcus Alexander Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid |
| title | Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid |
| title_full | Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid |
| title_fullStr | Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid |
| title_full_unstemmed | Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid |
| title_short | Optimizing a method for leaching PGMs from simulated spent autocatalyst material using ozone & hydrochloric acid |
| title_sort | optimizing a method for leaching pgms from simulated spent autocatalyst material using ozone hydrochloric acid |
| topic | Automobiles -- Catalytic converters Hydrometallurgy Hydrochloric acid Leaching Platinum group |
| url | https://scholar.sun.ac.za/handle/10019.1/130539 |
| work_keys_str_mv | AT knightmarcusalexander optimizingamethodforleachingpgmsfromsimulatedspentautocatalystmaterialusingozonehydrochloricacid |