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Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium
Thesis (MSc)--Stellenbosch University, 2016
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2016
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| _version_ | 1869484238978416640 |
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| access_status_str | Open Access |
| author | Barnard, Elaine |
| author2 | Luckay, Robert C. |
| author_browse | Barnard, Elaine Luckay, Robert C. |
| author_facet | Luckay, Robert C. Barnard, Elaine |
| author_sort | Barnard, Elaine |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2016 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/98787 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-07-01T04:11:43.639Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/98787 Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium Barnard, Elaine Luckay, Robert C. Stellenbosch University. Faculty of Science. Department of Chemistry and Polymer Science Solvent extraction Chloride medium Precious metals -- Extraction Amido-ammonium ligands Extractive metallurgy UCTD Thesis (MSc)--Stellenbosch University, 2016 ENGLISH ABSTRACT : This work presents research into the extraction of precious chloridometallate anions by organic receptors in a solvent extraction process. Four novel monocationic amido-functionalized ammonium extractants were designed, synthesized and fully characterized by FT-IR, 1H NMR and 13C NMR spectroscopy, mass spectrometry and elemental analysis. The design features incorporated into the organic receptors include a tertiary amine protonation site, hydrogen-bond donor groups and organic solubilising moieties. These four extractants, L1 –L4 were used to examine the extraction trends for these precious metallates; [AuCl4]-, [PtCl6]2-, [PdCl4]2- and [IrCl6]3-. The findings from this research show that the receptors L1, L2 and L4 show especially high extraction efficiency for [PtCl6]2- with loadings greater than 80% at a three-fold excess of ligand. These values imply that these extractants show high selectivity towards [PtCl6]2- over Cl- because the latter is present in 600-fold excess in the aqueous feed. The extraction efficiency of L2 and L4 outperformed L1 and L3 and these observations have been attributed to the improved organic solubility of the extractants with the octyl rather than butyl substituents. The selectivity of the extractants (L1, L2 and L4) for [PtCl6]2- over [PdCl4]2- was also assessed with L2 showing the highest degree of selectivity towards [PtCl6]2- compared to L1 and L4. At a [L2]:[PtCl6]2-:[PdCl4]2- ratio of 2:1:1 only 21% of [PdCl4]2- was extracted compared to the 62% of [PtCl6]2- extracted. All though L2 did not show 100% selectivity towards [PtCl6]2 the differences in Pt and Pd extraction at low [L2]:[PtCl6]2-:[PdCl4]2- ratios may provide a route for partial separation of these chloridometalates. Backextraction experiments showed that the ligand-Pd(II) complexes can be readily stripped with HNO3 or thiourea in HCl to liberate the free-metal chlorides. Mixing time studies indicated that the equilibrium of extraction of Pd(II) and Pt(IV) can be reached within 10 minutes of shaking the aqueous and organic phases. Doubly-charged amido-functionalized ammonium extractants were designed, synthesized and characterized by FT-IR, 1H NMR and 13C NMR spectroscopy, mass spectrometry and elemental analysis. Theoretically, a doubly-charged ligand can balance the chloridometallate charge by forming a 1:1 neutral complex. Solubility issues were observed with one of the doubly-charged receptors and the formation of a third phase was observed in the other receptors. Attempts were made to prevent, or at least limit the formation of a third phase. The concentration of the free ligand, nature of the diluent, temperature, aqueous acidities and addition of a phase modifier were all experimental parameters that were investigated to eliminate the formation of a third phase, but this proved to be unsuccessful. AFRIKAANSE OPSOMMING : Hierdie werkstuk bied navorsing oor die ontgunning van edele chloridometallaat anione deur organiese reseptore in 'n oplosmiddel ekstrahering proses. Vier nuwe mono kationese amied gefunksioneerde ammonium ligande is ontwerp, gesintetiseer en ten volle gekarakteriseer deur FT-IR, 1H-KMR en 13C-KMR spektroskopie, massaspektrometrie en elementele analise. Die eienskappe wat geinkorpireer is in die ontwerp van die organise reseptore sluit in 'n tersiêre amien protonerings reaksieplek, waterstofbinding donor groepe en groepe wat die oplosbaarheid in organiese oplosmiddels bevorder. Hierdie vier ekstraheermiddels, L1 -L4, word gebruik om die ekstraheer tendense vir hierdie edele metallate ondersoek; [AuCl4]-, [PtCl6]2-, [PdCl4]2- en [IrCl6]3-. Die bevindinge van hierdie navorsing toon dat die reseptore L1, L2 en L4 wys veral hoë ekstraksie doeltreffendheid vir [PtCl6]2- met ladings groter as 80% op 'n drie-vou oormaat ligand. Hierdie waardes impliseer dat hierdie ekstraheermiddels hoë selektiwiteit vir [PtCl6]2- wys teenoor Cl-, omdat laasgenoemde teenwoordig is in 600-vou oormaat in die waterige fase. Die ekstraksie doeltreffendheid van L2 en L4 oortref die doeltreffenheid van L1 en L3 en hierdie waarnemings is toegeskryf aan die verbeterde organiese oplosbaarheid van die ekstraheermiddels met die oktiel eerder as die butiel groepe. Die selektiwiteit van die ekstraheermiddels (L1, L2 en L4) vir [PtCl6]2- teenoor [PdCl4]2- is ook ondersoek. L2 het die hoogste graad van selektiwiteit vir [PtCl6]2- getoon in vergelyking met L1 en L4. By 'n [L2]: [PtCl6]2-: [PdCl4]2- verhouding van 2: 1: 1 was slegs 21% van die [PdCl4]2-ontgin in vergelyking met die 62% van die [PtCl6]2- wat ontgin is. Alhoewel L2 nie 100% selektiwiteit teenoor [PtCl6]2- toon nie, kan die verskille in Pt en Pd ontginning by lae [L2]: [PtCl6]2- : [PdCl4]2- verhoudings wel 'n roete vir gedeeltelike skeiding van hierdie chloridometallates verskaf. Stropings eksperimente het getoon dat die ligand-Pd (II) komplekse maklik gestroop kan word met HNO3 en tioüreum in HCl. Tyd studies het aangedui dat die ekstraheer reaksie se ewewig vir Pd(II) en Pt(IV) ekstraksie binne 10 min bereik kan word.Dubbel-gelaaide amied gefunksioneerde ammonium ligande is ontwerp, gesintetiseer en ten volle gekarakteriseer deur FT-IR, 1H-KMR en 13C KMR spektroskopie, massaspektrometrie en elementele analise. Teoreties kan 'n dubbel-gelaaide ligand die chloridometallate lading balanseer deur die vorming van 'n 1:1 neutrale kompleks. L5 het oplosbaarheids probleme getoon in organiese oplosmiddels en die vorming van ‘n derde fase is waargeneem tydens die ekstrahering deur L6 en L7. Pogings is aangewend om die vorming van ‘n derde fase te voorkom of ten minste te beperk. Die konsentrasie van die vrye ligand, aard van die oplosmiddel, temperatuur, suurheid van die water fase en byvoeging van 'n fase wysiger was almal eksperimentele parameters wat ondersoek is om die vorming van 'n derde fase uit te skakel. Die optimalisering van die bogenoemde parameters was onsuksesvol tot die beperking van ‘n derde fase. 2016-03-09T15:01:40Z 2023-01-04T03:00:11Z 2016-12 Thesis http://hdl.handle.net/10019.1/98787 en_ZA Stellenbosch University xvii, 101 pages : illustrations (some colour) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Solvent extraction Chloride medium Precious metals -- Extraction Amido-ammonium ligands Extractive metallurgy UCTD Barnard, Elaine Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium |
| title | Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium |
| title_full | Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium |
| title_fullStr | Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium |
| title_full_unstemmed | Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium |
| title_short | Competitive extraction using novel amido-ammonium ligands for precious chloridometallates from acidic chloride medium |
| title_sort | competitive extraction using novel amido ammonium ligands for precious chloridometallates from acidic chloride medium |
| topic | Solvent extraction Chloride medium Precious metals -- Extraction Amido-ammonium ligands Extractive metallurgy UCTD |
| url | http://hdl.handle.net/10019.1/98787 |
| work_keys_str_mv | AT barnardelaine competitiveextractionusingnovelamidoammoniumligandsforpreciouschloridometallatesfromacidicchloridemedium |