Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Improving the settleability of a metal sulphide suspension by the application of a magnetic field
Gravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. More especially in sulphide precipitation, where high levels of supersaturation dominate and nucleation is favoured. This results in a large number of colloidal particles with a highly n...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Department of Chemical Engineering
2016
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613210910130176 |
|---|---|
| access_status_str | Open Access |
| author | Gqebe, Sibongiseni Yamkela |
| author2 | Lewis, Alison |
| author_browse | Gqebe, Sibongiseni Yamkela Lewis, Alison |
| author_facet | Lewis, Alison Gqebe, Sibongiseni Yamkela |
| author_sort | Gqebe, Sibongiseni Yamkela |
| collection | Thesis |
| description | Gravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. More especially in sulphide precipitation, where high levels of supersaturation dominate and nucleation is favoured. This results in a large number of colloidal particles with a highly negative surface charge, which remain suspended in solution. The high surface charge of the suspension results in strong attraction/interaction between the ions on the particle surface and counter-ions in solution. Moreover, this strong interaction between ions on the particle surface and counter-ions in solution results in a charge build-up that renders the suspension stable. In order to induce gravitational sedimentation of these particles, a redistribution of ions close to the particle surface is required. This study therefore seeks to redistribute ions close to the particle surface by applying a magnetic field. This results in the reduction of inter-particle electrostatic repulsive forces and subsequent increase in the zeta potential of a suspension. For the purposes of this study, a copper sulphide suspension was used. A T-mixer was used as the reaction zone for the precipitation of each suspension. Subsequent to this, the suspended copper sulphide particles were exposed to a range of field strengths for set exposure times and their zeta potential was measured before and after exposure to the magnetic field. The effect of magnetic field strength, exposure time and particle speed on the zeta potential were tested. All particles had an initial zeta potential value equal to or less than - 40 mV prior to magnetic field exposure. A significant increase in zeta potential was observed with values reaching a maximum of - 16.5 mV when exposed to a 2 T field strength for 40 minutes. An increase in the zeta potential corresponds to a reduction in repulsive electrostatic forces between suspended particles due to the Lorentz force exerted by a magnetic field on the particle surface. DLVO plots were used to quantify this reduction in repulsive electrostatic forces. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/20053 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:31.718Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Chemical Engineering |
| publisherStr | Department of Chemical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/20053 Improving the settleability of a metal sulphide suspension by the application of a magnetic field Gqebe, Sibongiseni Yamkela Lewis, Alison Rodriguez-Pascual, Marcos Chemical Engineering Gravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. More especially in sulphide precipitation, where high levels of supersaturation dominate and nucleation is favoured. This results in a large number of colloidal particles with a highly negative surface charge, which remain suspended in solution. The high surface charge of the suspension results in strong attraction/interaction between the ions on the particle surface and counter-ions in solution. Moreover, this strong interaction between ions on the particle surface and counter-ions in solution results in a charge build-up that renders the suspension stable. In order to induce gravitational sedimentation of these particles, a redistribution of ions close to the particle surface is required. This study therefore seeks to redistribute ions close to the particle surface by applying a magnetic field. This results in the reduction of inter-particle electrostatic repulsive forces and subsequent increase in the zeta potential of a suspension. For the purposes of this study, a copper sulphide suspension was used. A T-mixer was used as the reaction zone for the precipitation of each suspension. Subsequent to this, the suspended copper sulphide particles were exposed to a range of field strengths for set exposure times and their zeta potential was measured before and after exposure to the magnetic field. The effect of magnetic field strength, exposure time and particle speed on the zeta potential were tested. All particles had an initial zeta potential value equal to or less than - 40 mV prior to magnetic field exposure. A significant increase in zeta potential was observed with values reaching a maximum of - 16.5 mV when exposed to a 2 T field strength for 40 minutes. An increase in the zeta potential corresponds to a reduction in repulsive electrostatic forces between suspended particles due to the Lorentz force exerted by a magnetic field on the particle surface. DLVO plots were used to quantify this reduction in repulsive electrostatic forces. 2016-06-21T09:22:55Z 2016-06-21T09:22:55Z 2015 Master Thesis Masters MSc (Eng) http://hdl.handle.net/11427/20053 eng application/pdf Department of Chemical Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Chemical Engineering Gqebe, Sibongiseni Yamkela Improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| thesis_degree_str | Master's |
| title | Improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| title_full | Improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| title_fullStr | Improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| title_full_unstemmed | Improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| title_short | Improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| title_sort | improving the settleability of a metal sulphide suspension by the application of a magnetic field |
| topic | Chemical Engineering |
| url | http://hdl.handle.net/11427/20053 |
| work_keys_str_mv | AT gqebesibongiseniyamkela improvingthesettleabilityofametalsulphidesuspensionbytheapplicationofamagneticfield |