Dissertations / Theses on the topic 'Platinum – Metallurgy'

There is a great interest in the treatment of spent autocatalyst because, due to large amounts of PGM used by catalytic converters, the autocatalyst scrap is the largest and constantly growing source of PGM available for recycling. A hydrometallurgical method of PGM extraction from honeycomb type catalyst containing platinum (800-1200 ppm) and rhodium (50-60 ppm) using HCl-AlCl$ sb3$-HNO$ sb3$ or HCl-HNO$ sb3$ mixtures was studied. Experimental results of the leaches performed in a bench scale tubular reaction with recycled continuous flow of the leaching solution as well as 1000 cc stirred reactor are presented. The results suggest that Cl$ sp-$ single ion activity plays a decisive role in controlling the PGM dissolution. The extent of PGM recovery increased not by increasing HCl concentration to very high levels, but by keeping a relatively low total Cl$ sp-$ level (2.5 M) with a significant proportion present as AlCl$ sb3$. Rhodium extraction was always 5-10% lower than platinum, and it appears that increasing the AlCl$ sb3$/HCl ratio tends to increase rhodium recovery. High temperature (85-95$ sp circ$C) and an HNO$ sb3$ concentration around 3-3.5 M play very important roles in effectiveness of PGM extraction. The presented method of HCl-AlCl$ sb3$-HNO$ sb3$ tubular reactor leaching supplemented by solvent extraction (Kelex 100) of PGM from pregnant solution appears to be very attractive for small size (5-20 tonnes of catalyst/day) installations.

Using supramolecular principles, we have been designing luminescent lanthanide complexes with a defined hairpin bis-interlacator in order to obtain luminescent probes able to recognise DNA. The complexes are comprised of Platinum(II) terpyridine, which acts as a DNA recognition site and is brought together with a "remote" luminescent lanthanide unit. All the synthetic approaches were based on the accessibility of the lanthanide-platinum complexes by the self-assembly of different components in a one pot reaction. Thus, we have been able to isolate a water soluble heterometallic complex based on thiophenal linkage named [LnPt\(_2\)]Cl\(_2\). The complex has a relatively weak lanthanide luminescence, which increases upon addition of DNA. Photophysical and DNA binding properties of the lanthanide-platinum complex were investigated by UV-vis absorption, luminescent studies and circular and linear dichroism. Oligonucleotides of twelve bases were also used to investigate the intercalation [LnPt\(_2\)]Cl\(_2\) and the mono-intercalator AATP used as control compound. Using bidimensional NMR techniques, we investigated the binding site for [LnPt\(_2\)]Cl\(_2\) and AATP upon interaction with Dickerson-Drew sequence. The sulphur lanthanide-platinum linkage in [LnPt\(_2\)]Cl\(_2\) was replaced with an acetylide one in order to introduce new photophysical features. Thus the self-assembly procedures based on DTPA-bis(amido-acetylide) and a platinum(II) terpyridine led us to isolate a new lanthanide-platinum complex named [LnC\(\equiv\)CPt\(_2\)] (CH\(_3\)SO\(_3\))\(_2\). The photophysical properties and the DNA binding properties toward interaction with CT-DNA were investigated. The complex named LnC\(\equiv\)CPt\(_2\)](CH\(_3\)S)\(_3\))\(_2\) exhibited a relatively strong lanthanide luminescence that increased upon addition of DNA. The bi-functional metal complex [EuLPt](PF\(_6\)) (where Pt=platinum-2,2':6'2"-terpyridine and L=assymmetric DTPA bisamide ligand with a thiopheno pendant arm and a quinoline moiety) was synthesised and the interaction of [EuLPt](PF\(_6\)) with CT-DNA was examined by luminescence spectroscopy, linear and circular dichroism studies and thermal denaturation studies. The [EuLPt](PF\(_6\)) retained the ability to increase its luminescence upon the addition of CT-DNA. The binding properties of the complexes were tested toward interaction with plasmid DNA by gel electrophoresis and properties such as the unwinding angle were measured. The bis-intercalators [LnPt\(_2\)]Cl\(_2\) and [LnC\(\equiv\)CPt\(_2\)](CH\(_3\)SO\(_3\))\(_2\) showed the ability to uncoil DNA almost as well as cisplatin and at low concentrations, while almost double the amount of mono-intercalators, such as [EuLPt](PF\(_6\)) is required to observe the same uncoiling effect.

In order to understand and control the deportment of common impurity elements in the Pt(IV)-Pd(II)-HCl-8-hydroxyquinoline (TN 1911)$ sp{ rm a}$ system, their solvent extraction chemistry in chloride solution has been studied. The investigated elements were Fe(III), Cu(II), Ni(II), Zn(II), Pb(II), Sn(IV), Ag(I), As(V), Sb(V), Bi(III), Se(IV) and Te(IV). Extraction experiments carried out using multi-element and single element feed solutions helped to elucidate the extraction behaviour of the elements with the extractant TN 1911. From the collected data it was deduced that the majority formed anionic chlorocomplexes and extracted via the ion-pair mechanism involving the protonated extractant. Consequently, scrubbing procedures were developed to control the deportment of these elements. These scrubbing steps were then incorporated into a tentative flowsheet which was simulated in a batch-wise fashion in the laboratory. The most contaminating elements were found to be Zn(II), Pb(II), Ag(I), Te(IV), Se(IV) and Bi(III). The first five were effectively scrubbed with 2.0M HCl whereas Bi(III) could only be scrubbed with 2.0M H$ sb2$SO$ sb4$ at A/O ratios of $>$3:1. The element Sn(IV) which was found to build-up in the organic, could only be scrubbed with a 1.0M NaOH solution for long contract times (60 minutes). ftn$ sp{ rm a}$A proprietary alkylated derivative of 8-hydroxyquinoline (Schering Berlin AG).

Thesis (PhD) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: The process route for the production of base and platinum-group metals from natural sulfide ores commonly requires the conversion of high-iron furnace matte into an iron-lean converter matte. This is followed by pre-treatment through cooling of the iron-lean molten matte, physical processing of the solidified matte and hydrometallurgical metal extraction. Lonmin is the third largest producer of platinum-group metals in the world and utilizes Peirce-Smith converters for blowing high-iron furnace matte with air to a final iron concentration or endpoint. The molten matte is water granulated and solidification occurs via fast-cooling. The solidified matte is ground in a closed circuit ball mill with hydrocyclone classification and subjected to first stage atmospheric leaching. The specification of an ideal or desirable converter iron endpoint requires careful consideration. Most importantly, it must ensure the crystallization of converter matte with mineralogical qualities that are within the setpoints of the downstream unit processes and techniques. An additional consideration is for the final blown converter matte to achieve an optimum bulk concentration of the base metals Ni and Cu and platinum-group metals Pt, Pd, Rh, Ru and Ir. Mattes characteristic of variable iron endpoints were regularly produced at the Lonmin converter plant section. Uncertainty by plant metallurgists in knowing the desirable iron endpoint, particularly within the context of the Lonmin base metal refinery, and poor control has had detrimental effects on the mineralogical quality of the final matte and hence on the processing characteristics of the solidified matte particles downstream. A desirable iron endpoint required investigation, selection and implementation at Lonmin. The primary focus of this study was therefore to quantify the effect of a specific iron endpoint on the mineralogy and mineral chemistry of solidified converter matte. A fundamental examination of the solidification process upon cooling was regarded as critical to an in-depth understanding of the attained mineralogy and mineral chemistry as a function of a specific iron endpoint. It became equally important to quantify the effect of the resultant mineralogy, and hence iron endpoint, on the physical property of mineral structures in relation to downstream grinding, liberation and leaching characteristics. Despite considerable industry context, limited in-depth and coherent studies on the effect of a specific iron endpoint on fast-cooled converter matte systems were found in both industrial and scholarly literature. Previous findings in literature offered a limited quantitative understanding of the effect on mineralogy and mineral chemistry. Phase and cooling equilibria of multi-component, iron endpoint specific Ni-Cu-S matte systems were also not fully available. These would have been particularly useful in understanding the complexities of converter matte solidification as a function of iron endpoint. Physical property knowledge of converter matte mineral structures was hardly available and even less so in relation to grinding, liberation and leaching processes. A comprehensive investigation was therefore required to address these extensive knowledge gaps with respect to fastcooled converter matte systems in an industrial framework. Three Peirce-Smith converter production samples, representative of the extent in variability of iron endpoints attained at the converter plant, were used in a systematic investigation coupled to a novel combination of modern analytical techniques, computational thermochemistry and metallurgical testwork. The modern analytical techniques included the application of high resolution transmission electron microscopy and focused ion beam scanning electron microscopy tomography. Computational thermochemistry was applied through the use of MTDATA phase diagram software. Metallurgical testwork involved laboratory batch grinding at various specific energies. Closely associated leach experiments were also considered relevant to this wide-ranging investigation. The Peirce-Smith converter samples investigated were indicative of mattes that attained specific endpoints of 5.17%, 0.99% and 0.15 weight% Fe. The highest combined bulk concentration of the important base and platinum-group metals was achieved in the matte which attained a specific iron endpoint of 0.99%. The mineralogy of all three converter mattes was dominated by nickel sulfide mineral structures matched to the natural mineral of heazlewoodite. Mineral structures of copper sulfide, NiCu-alloy, spinel and OsRu-alloy were also constituents of the different converter mattes. The attainment of a specific iron endpoint was found to result in measurable mineralogical differences with respect to relative mineral abundances, external morphological characteristics and mineral chemistry. The mineralogical differences were particularly distinct between mineral structures of the high (5.17%) and low (0.99% and 0.15%) iron mattes. Subtle mineralogical differences were evident between mineral structures of the low iron mattes. The 0.99% Fe matte was characteristic of a significantly higher NiCu-alloy relative abundance, compared to the 5.17% Fe matte. The NiCu-alloy structures were found to act as the primary collectors of the economically significant platinum-group metals. Mineralogical observations were used to develop an understanding of the underlying mineralization mechanism of NiCu-alloy structures. High-fidelity color and grayscale 3D reconstructions were produced of the resultant mineralized structures. It was shown theoretically that variations in iron endpoint specific starting compositions of oxygen-free liquid matte systems alter the solidification pathway towards the eutectic. Moreover, a quantitative understanding of liquid phase solidification of the high and low iron matte systems, including oxygen, was developed to within ±2.5 oC. Most of the specific energy available for grinding was expended breaking the nickel sulfide matrix, particularly of the high iron matte. The breakage rates of copper sulfide mineral structures in the 5.17% Fe matte were calculated to be higher than in the 0.15% Fe matte at 25kWh/t specific energy. The degree of copper sulfide liberation was shown to be higher for the 5.17% Fe matte than for the 0.15% Fe matte at the same specific energy of grinding. A higher degree of Ni extraction and Cu cementation could be achieved when leaching low iron matte particles. The production of converter matte attaining a specific iron endpoint of 0.99% was found to be the most suitable with respect to endpoint selection criteria. A practical iron endpoint range of 1.6% to 1.0% was recommended for the production of converter matte with a resultant mineralogical quality within the constraints of the Lonmin base metal refinery. This study offers an integrated understanding of base and platinum-group metals production as a function of a desirable iron endpoint at Lonmin. This was not previously available in metal production literature. New technology for the monitoring and consistent control of such a practical iron endpoint range can subsequently be implemented.
AFRIKAANSE OPSOMMING: Die prosesroete vir die produksie van onedel en platinumgroepmetale uit natuurlike swawelertse vereis gewoonlik die omsetting van ’n ysterryke hoogoondmat in ’n ysterarm omsettermat. Hierna volg voorbehandeling deur die afkoeling van die ysterarm gesmelte mat, fisiese verwerking van die soliede mat, en hidrometallurgiese metaalekstraksie. Lonmin is die derde grootste produsent van platinumgroepmetale ter wêreld en gebruik Peirce-Smith-omsetters om ysterryke hoogoondmat met lug te blaas totdat dit ’n finale ysterkonsentrasie- of ystereindpunt bereik. Die gesmelte mat word met water granuleer, en solidifikasie vind deur middel van snelafkoeling plaas. Die soliede mat word in ’n geslotekringbalmeul met hidrosikloonklassifikasie gemaal en aan eerstestadium- atmosferiese loging onderwerp. Die spesifikasie van ’n ideale of gewenste ystereindpunt verg deeglike oorweging. Bowenal moet dit verseker dat die omsettermat kristalliseer met mineralogiese eienskappe wat binne die setpunte van die eenheidsprosesse en - tegnieke verder af in die prosesstroom val. ’n Bykomende oorweging is dat die uiteindelike geblaasde omsettermat ’n optimale massakonsentrasie van die onedel metale Ni en Cu en die platinumgroepmetale Pt, Pd, Rh, Ru en Ir moet bevat. Matte met die kenmerke van wisselende ystereindpunte is gereeld by die Lonminomsetteraanleg geproduseer. Die onsekerheid van metallurge by die aanleg oor die gewenste ystereindpunt – veral binne die konteks van die Lonmin-raffinadery vir onedel metale – sowel as swak beheer het ’n nadelige uitwerking gehad op die mineralogiese gehalte van die uiteindelike mat, en dus ook op die verwerkingskenmerke van die soliede matdeeltjies verder af in die prosesstroom. Die bepaling van die gewenste ystereindpunt het sorgvuldige ondersoek, seleksie en toepassing deur Lonmin vereis. Hierdie studie is dus hoofsaaklik uitgevoer om die uitwerking van ’n spesifieke ystereindpunt op die mineralogie en minerale chemie van soliede omsettermat te kwantifiseer. ’n Grondliggende ondersoek na die solidifikasieproses by afkoeling is as noodsaaklik beskou vir ’n diepgaande begrip van die verworwe mineralogie en minerale chemie as ’n funksie van ’n spesifieke ystereindpunt. Mettertyd het dit egter ewe belangrik geword om die uitwerking van die gevolglike mineralogie, en dus die ystereindpunt, op die fisiese eienskappe van minerale strukture met betrekking tot maling-, vrystellings- en loogprosesse verder af in die prosesstroom te kwantifiseer. Ondanks heelwat bedryfskonteks, het nóg bedryfs- nóg vakkundige literatuur veel diepte- en samehangende studies oor die uitwerking van ’n spesifieke ystereindpunt op snelafgekoelde omsettermatstelsels opgelewer. Vorige bevindinge in die literatuur het boonop ’n beperkte kwantitatiewe begrip van die uitwerking op mineralogie en minerale chemie getoon. Die fase- en afkoelingsekwilibriums van ystereindpuntspesifieke Ni-Cu-S-matstelsels met veelvuldige komponente was ook nie ten volle beskikbaar nie. Dít sou veral goed te pas gekom het om die kompleksiteite van omsettermatsolidifikasie as ’n funksie van ystereindpunt te verstaan. Kennis van die fisiese eienskappe van die minerale strukture van omsettermat was kwalik beskikbaar, terwyl selfs minder inligting oor maling-, vrystellings- en loogprosesse opgespoor kon word. Daarom was ’n omvattende ondersoek nodig om hierdie beduidende kennisleemtes met betrekking tot snelafgekoelde omsettermatstelsels in ’n nywerheidsraamwerk aan te vul. Drie Peirce-Smith-omsetterproduksiemonsters wat die wisselende bestek van ystereindpunte by die omsetteraanleg verteenwoordig, is in ’n stelselmatige ondersoek gebruik, tesame met ’n vernuwende kombinasie van moderne ontledingstegnieke, gerekenariseerde termochemiese bewerkings en metallurgiese toetswerk. Die moderne ontledingstegnieke sluit onder andere in hoëresolusie-transmissie-elektronmikroskopie (HRTEM) en gefokusdeioonstraalskandering-elektron-mikroskopie (FIB SEM) tomografie. Die gerekenariseerde termochemiese bewerkings is met behulp van MTDATAfasediagramsagteware uitgevoer. Metallurgiese toetswerk het die maling van laboratoriumlotte teen verskillende spesifieke energieë behels. Nou verwante loogproefnemings is ook as relevant vir hierdie omvattende studie beskou. Die bestudeerde Peirce-Smith-omsettermonsters het op matte met spesifieke eindpunte van 5.17%, 0.99% en 0.15 gewig% Fe gedui. Die hoogste gekombineerde massakonsentrasie van die belangrike onedel en platinumgroepmetale is in die mat met ’n spesifieke ystereindpunt van 0.99% gevind. Die mineralogie van ál drie omsettermatte is oorheers deur die minerale strukture van nikkelsulfied, wat met die natuurlike mineraal heazlewoodiet ooreenstem. Die verskillende omsettermatte het ook die minerale strukture van kopersulfied, NiCu-allooi, spinel en OsRu-allooi bevat. Daar is bevind dat die verkryging van ’n spesifieke ystereindpunt tot meetbare mineralogiese verskille in die relatiewe volopheid van minerale, die eksterne morfologiese kenmerke sowel as minerale chemie lei. Die mineralogiese verskille was veral duidelik te sien tussen die minerale strukture van die ysterryke (5.17% Fe) en ysterarm (0.99% en 0.15% Fe) matte. Fyn mineralogiese verskille is ook tussen die minerale strukture van die ysterarm matte bespeur. Die 0.99% Fe-mat het tipies beduidend meer NiCu-allooi as die 5.17% Fe-mat bevat. Die NiCu-allooistrukture tree oënskynlik op as die hoofversamelaars van die ekonomies belangrike platinumgroepmetale. Mineralogiese waarnemings is gebruik om ’n begrip te ontwikkel van die onderliggende mineralisasiemeganisme van NiCuallooistrukture. Die gevolglike gemineraliseerde strukture is met behulp van driedimensionele rekonstruksies met hoë kleurgetrouheid sowel as in grysskaal voorgestel. Daar is teoreties aangetoon dat variasies in ystereindpuntspesifieke beginsamestellings van suurstofvrye vloeibare matstelsels die solidifikasieroete na die eutetikum wysig. Daarbenewens is die vloeifasesolidifikasie van die ysterryke en ysterarm matstelsels, wat suurstof insluit, op sowat ±2.5 oC gekwantifiseer. Die meeste van die spesifieke energie wat vir maling beskikbaar was, is gebruik om die nikkelsulfiedmatriks te breek, veral vir die ysterryke mat. Berekeninge toon dat die breektempo’s van die minerale strukture van kopersulfied by die 5.17% Fe-mat hoër was as by die 0.15% Fe-mat teen ’n spesifieke energie van 25 kWh/t. Die mate van kopersulfiedvrystelling was hoër by die 5.17% Fe-mat as by die 0.15% Fe-mat by dieselfde spesifieke energie vir maling. ’n Hoër mate van Ni-ekstraksie en Cu-sementasie is verkry toe ysterarm matdeeltjies geloog is. Wat eindpuntseleksiemaatstawwe betref, is die produksie van ’n omsettermat met ’n spesifieke ystereindpunt van 0,99% as die mees geskikte aangewys. ’n Praktiese ystereindpuntbestek van 1.6% tot 1.0% word aanbeveel vir die produksie van ’n omsettermat met ’n gevolglike mineralogiese gehalte wat binne die perke van die Lonmin-raffinadery vir onedel metale val. Hierdie studie bied ’n geïntegreerde begrip van die produksie van onedel en platinumgroepmetale as ’n funksie van ’n gewenste ystereindpunt by Lonmin. Hierdie inligting was nie voorheen in literatuur oor metaalproduksie beskikbaar nie. Nuwe tegnologie vir die monitering en konsekwente beheer van so ’n praktiese ystereindpuntbestek kan dus op grond hiervan in werking gestel word.

This thesis investigates the mode of action of cationic reagents in the recovery of platinum group metals (PGMs) by anion exchange solvent extraction. Industry uses a range of extractants to achieve efficient concentration and separation of PGMs in hydrometallurgical processes, but an understanding of the processes at a molecular level is limited and restricts the options to improve efficiency. The research, sponsored in part by Johnson Matthey and Anglo American, explores two different aspects of the mode of action of reagents used to recover chloride and platinum. Chapter 1 reviews the extraction of chloridometalates in hydrometallurgy and other methods used to recover PGMs. The chapter also covers current ideas on whether formation of outer-sphere anion-cation molecular assemblies or whether larger supramolecular aggregates are responsible for the extraction of PGMs. These two separate routes of study can be investigated by various computational and experimental methods, which are discussed in Chapter 2. In Chapter 3, the model systems chosen to develop the methodologies utilised throughout the thesis are presented. The development involves the extraction of chloride ions by tributyl-phosphate (TBP) and then is extended to extraction of PGM chloridometalates in Chapter 4. Computational methods are used to probe the atomistic and supramolecular theories in predicting the most likely assemblies which will be formed in the transfer of anions between the aqueous and organic phase. Slope analysis and the determination of the contents of the organic phase is used to validate computational models, along with spectroscopic techniques to determine shape and size of assemblies formed during extraction. The application of these methodologies to an amide extractant is discussed in Chapter 5. Computational methods predict the probability of formation of specific complex assemblies during the extraction of PtCl62- by protonated forms of the amide. Determination of the stoichiometry involved in formation of the complex assemblies by slope analysis is reported along with analysis of water, metal and chloride content to confirm the computational model. Final conclusions on all systems explored within the thesis and suggestions for future work are presented in the final chapter. The combination of experimental and computational methods are shown to be very efficient in defining mechanisms of extraction, involving determination of structures formed during the process and how and why they form.

Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: In this study, SiC reduction of Rowland and Easterns LG (Low Grade) concentrates was investigated. The purpose of the study was to investigate the feasibility of SiC as reductant with respect to metal fall, PGM grade in the alloy, slag composition, Cr solubility and overall PGM recovery. The integration of such process in the current matte-based collection process was also investigated. Currently, the matted-based collection process is most widely used for PGM recovery, but because PGM containing concentrates are becoming more enriched with UG2 (Upper Group 2) LG concentrates, it is expected to be integrated or replaced with an alloy collection process. This kind of process offers greater flexibility to the different types of ore that could be used. The process is chromium tolerant and environmentally friendly. For this purpose Rowland and Easterns UG2 LG Concentrate samples from Lonmin Western Platinum Limited were analysed with XRD, XRF and ICP-MS and it was found that SiO2 and MgO are the most abundant oxides and Pd is the most abundant element from the PGMs. Sulphide bearing minerals such as chalcopyrite were detected in low concentrations (below 1 %) and Cr2O3 concentrations are between 2 – 4 %. The FeO/SiO2 ratio was lower in Rowland LG concentrate. SiC reduction of Rowland and Easterns concentrate was done at 1600℃. Reductant to concentrate ratios for laboratory scale experiments were ranged from 2.5 to 3.5 kg SiC / 100 kg concentrate. SiC reduction of Rowland concentrate had different reduction times. The duration of reduction experiments ranged from 30 - 180 min. PGM recoveries from SiC reduction of Rowland concentrate were very poor (below 10 %) and Fe recoveries were lower than 50 %. A slag viscosity at the end of the melt of more than 4 poise was responsible for poor phase separation. SEM images revealed metal prills entrained in the slag phase instead of settling and combining to the alloy globule at the bottom of the crucible. However, PGM recoveries from SiC reduction of Easterns concentrate was significantly better. More than 85 % of Ir and Pd and almost 60 % of Pt were recovered in a test with a reductant to concentrate ratio of 3.5 kg SiC / 100 kg Easterns concentrate. Fe recovery was also the highest at 66%. Cr and Si concentrations were below 5 % in total. The slag viscosity at the end of melt was calculated to be less than 4 poise and a SEM image of a slag sample revealed few entrained metal prills. After the above findings on the importance of viscosity, it was decided to increase the FeO content in the initial concentrate charge in order to decrease slag viscosity, increase metal fall (PGM collecting phase) and further increase PGM recovery. Peirce-Smith converter slag was used for this purpose. A test was conducted with the addition of 10 kg converter slag / 100 kg Easterns concentrate. The reductant to concentrate ratio was kept at 3.5 kg SiC / 100 kg Easterns concentrate. The results revealed that Ir and Pd recoveries were more than 95%, while Pt recovery was almost 70%. Fe recovery increased to 76 %. On the basis of the results from the test, an optimum feed ratio between Easterns LG concentrate, Rowland concentrate and Peirce-Smith converter slag was calculated. Thermodynamic phase equilibrium calculations predicted that the concentrate charge should consist of 60 - 80% Easterns concentrate with a slag addition of 30 – 40 kg converter slag / 100 kg LG concentrate. SiC reduction of this optimum LG concentrate charge is expected to recover more than 90% of all PGMs. Cr and Si concentrations in the alloy will be below 1 % in total. The amount of converter slag as an addition will be however limited by final PGM grade in the alloy, furnace slag quantities recycled and slag resistivity required in the alloy furnace. The effectiveness of SiC as reductant was also compared to C reduction. C reduction of an optimum concentrate charge had a marginally higher metal fall at the same reductant to concentrate ratio than SiC reduction of an optimum concentrate charge. However, gas emissions are on average 3 times higher for C reduction of a concentrate charge and C reduction requires at least 300 MJ more to smelt 1 ton of LG concentrate than SiC reduction. This is mostly due to C reacting endothermically with FeO to produce Fe(l) and CO(g) in contrast to SiC reacting exothermically with FeO to produce Fe(l), SiO2(l) and CO(g). Integrating SiC reduction of LG concentrates into the existing smelting route at Lonmin was also proposed through a process flow diagram. From an economic point of view, it was found that SiC reduction of 1 ton of LG concentrate charge with a converter slag addition requires almost 700 MJ more than the smelting of a UG2 blended concentrate to produce a matte phase. However it must be taken into account that the sulphide rich layers in the Bushveld complex are being depleted rapidly and alternative processes such as SiC reduction and alloy collection process will be utilized faster than expected. Moreover, gas emissions from reductive smelting is considerably lower, hence it is a more environmentally friendly process. Finally, from the findings of this study, it could be said that base metals and PGMs could be recovered in an iron alloy from SiC reduction of LG concentrate with converter slag additions. Therefore integrating such a process into the matte-based collection process could be considered as a future alternative to smelting UG2 LG concentrates.
AFRIKAANSE OPSOMMING: In hierdie studie, word SiC reduksie met Rowland en Oostelikes LG (Lae Graad) konsentrate ondersoek. Die doel van die studie was om die doeltreffendheid van SiC as reduktant te ondersoek met betrekking tot metaalval, PGM graad in die allooi, slaksamestelling (spesifiek word daar gekyk na Cr oplosbaarheid) en algehele PGM herwinning. Die integrasie van die proses in die huidige mat-gebaseerde versamelingproses word ook ondersoek. Tans word die mat-gebaseerde versamelingproses die algemeenste gebruik om PGM'e te kollekteer, maar omdat PGM konsentrate al hoe meer verryk word met UG2 (Upper Group 2) LG konsentrate, word daar verwag dat dit geïntegreer of vervang gaan word met 'n allooi-versamelingproses. Hierdie tipe proses bied groter buigsaamheid om die verskillende reekse van erts wat gebruik kan word. Die proses kan ook chroom hanteer en is omgewingsvriendelik. Vir hierdie doel was Rowland en Oostelikes UG2 LG konsentraatmonsters van Lonmin Western Platinum Limited ontleed met XRD, XRF en ICP -MS en met die ontleding was daar gevind dat SiO2 en MgO die volopste oksides was en dat Pd die volopste elemente van die PGMe was. Sulfiedminerale soos chalkopiriet is in lae konsentrasies opgespoor (minder as 1%) en Cr2O3 konsentrasies is tussen 2-4 %. Die FeO/SiO2 verhouding was laer in Rowland konsentraat. SiC reduksie van Rowland en Oostelikes konsentrate is teen 1600 ℃ uitgevoer. Die reduktant tot konsentraat verhouding vir laboratoriumskaal eksperimente het gewissel van 2.5 – 3.5 kg SiC / 100 kg konsentraat. SiC reduksie van Rowland LG konsentraat het verskillende reduksie tye gehad. Die duur van die reduksie eksperimente het gewissel van 30-180 min. PGM herwinning van SiC reduksie met Rowland konsentreer was baie laag (onder 10 %) en Fe herwinning was minder as 50%. 'n Slakviskositeit aan die einde van die smelt was hoër as 4 poise en was verantwoordelik vir die swak skeiding van fases. SEM beelde het gewys dat fyn metaalstukkies opgehou was in die slakfase in plaas daarvan dat dit vestig en kombineer met die allooibolletjie aan die onderkant van die smeltkroes. In teenstelling was die PGM herwinning van SiC reduksie met Oostelikes konsentraat aansienlik beter. Meer as 85 % van Ir en Pd was herwin en byna 60% van Pt was herwin tydens 'n toets met 'n reduktant tot konsentraat verhouding van 3.5 kg SiC / 100 kg Oostelikes konsentraat. Fe herwinning was 66% en was ook die hoogste van al die eksperimente. Cr en Si konsentrasies was minder as 5 % in totaal. Die slakviskositeit aan die einde van smelt was bereken en is minder as 4 posie. 'n SEM beeld van 'n slakmonster het baie min vasgevangde metaalstukkies getoon. Na afloop van die bogenoemde bevindinge oor die belangrikheid van viskositeit, was daar besluit om die FeO inhoud van die aanvanklike konsentraat te verhoog. Dit was gedoen om die slakviskositeit te verminder, die metaalval (PGM kollektering fase) te verhoog en sodoende die PGM herwinning verder te verbeter. Vir die doel was Peirce -Smith omskakelaarslak gebruik. ʼn Toets was uitgevoer met die toevoeging van 10 kg omskakelaarslak / 100 kg Oostelikes konsentraat. Die reduktant tot konsentraat verhouding was behou by 3.5 kg SiC / 100 kg Oostelikes konsentraat. Die resultate het getoon dat meer as 95 % van Ir en Pd herwin was, terwyl byna 70 % Pt herwin was. Die Fe herwinning het toegeneem tot 76%. Op grond van die resultate van die toets, is 'n optimale verhouding tussen Oostelikes konsentraat, Rowland konsentraat en Peirce -Smith omskakelaarslak bereken. Termodinamiese modellering voorspel dat die begin LG konsentraat voer uit 60 – 80 % Oostelikes konsentraat moet bestaan, met 'n slak toevoeging van 30 – 40 kg omskakelaarslak / 100 kg LG konsentraat. Daar word verwag dat meer as 90 % van PGM'e herwin sal word vanaf SiC reduksie met ʼn optimum LG konsentraat voer. Cr en Si konsentrasies in die allooi sal minder as 1% in totaal wees. Die hoeveelheid slak wat bygevoeg kan word sal egter beperk word deur die finale PGM graad in die allooi, oond-slak hoeveelhede wat herwin kan word en slakweerstand wat benodig word in die allooi-oond. Die effektiwiteit van SiC as reduktant is ook vergelyk met C reduksie. C reduksie van ʼn optimale konsentraatvoer het 'n effens hoër metaalval wanneer dieselde reduktant tot konsentraat verhouding behou was vir SiC reduksie van 'n optimale konsentraatvoer. Gas hoeveelhede van C reduksie is gemiddeld 3 keer meer en vereis te minste 300 MJ meer om 1 ton LG konsentraat te smelt. Dit is hoofsaaklik te wydte aan C wat endotermies reageer met FeO om Fe (l) en CO (g) te produseer, in teenstelling met SiC wat eksotermies reageer met FeO om Fe (l), SiO2(l) en CO (g) te produseer. Integrasie van SiC reduksie met LG konsentrate in die bestaande smeltroete by Lonmin Western Platinum Limited is ook voorgestel deur 'n proses vloeidiagram. Uit 'n ekonomiese oogpunt, is daar gevind dat SiC reduksie van 1 ton LG konsentraatvoer met 'n omskakelaarslak byvoeging ongeveer 700 MJ meer benodig as om 1 ton UG2 gemengde konsentraat te smelt en 'n mat-fase te produseer. Dit moet wel in ag geneem word dat die sulfied ryk lae in die Bosveld-kompleks vinnig uitgeput word en dat hierdie alternatiewe prosesse soos SiC reduksie en ʼn allooiversameling proses vinniger as verwagtend benut sal word. Verder, gas hoeveelhede van SiC reduksie is laer en daarom is dit 'n meer omgewingsvriendelik proses. Ten slotte, vanaf die bevindinge van hierdie studie, kan dit gesê word dat basismetale en PGM'e in 'n ysterallooi herwin kan word deur middel van SiC reduksie met LG konsentrate en die toevoeging van omskakelaarslak. Daarom kan die integrasie van so 'n proses in die huidige mat-gebaseerde versameling proses beskou word as 'n alternatief vir die toekoms om UG2 LG konsentrate te smelt.

A consideration of pertinent aspects of general electro- chemistry and electrodeposition was followed by a review of the relevant literature relating to hard chromium plating technique and understanding (and problems and proposed improvements therein). Following the establishment and evaluation (using a Standard Solution at 55 0 C) of a reproducible technique for the measurement of (low current density) partial cathodic polarization data during plating, the Tafel regions of the resulting curves were analysed using the relationship - dn Cp -2.303 kT to provide an indication as to the nature of the rate-determining step in the plating and hydrogen evolution (cathodic) reactions. Information thus generated was used with a modified Arrhenius- type expression and further (experimentally determined) data to provide values of the thermodynamic constants of activation for the plating reaction. A series of experiments were undertaken to determine the effects upon various (physical) plate and plating parameters of three new inorganic additions (at selected concentrations) to a Standard Solution at 55 0 C. The results of these tests were commented upon with regard to potential industrial applications. The electrochemical investigative techniques referred to earlier were then employed with each new solution tested to determine the effect (if any) of the new additions upon those aspects of the deposition mechanism yielded, and to relate these effects to the observed (corresponding) changes in plate and plating parameters. The new additions were found to have profound effects upon a number of (physical) plate and plating parameters, and upon experimentally determined theoretical aspects of the deposition mechanism (the relationship between the two is discussed). Whilst no definite conclusion has been reached with regard to the precise mechanism of chromium plating, the techniques employed and the data generated have been used to provide significant pointers with regard to the direction future investigations might take.

Ion plating involves the transportation of vapour through a low pressure glow discharge to form solid coatings on negatively biased substrates. Although the method has gained commercial acceptance, particularly for engineering applications, much of the underlying science of the process is poorly understood. This work is concerned with investigating certain mechanisms occurring within the ion plating environment, and their role in process optimisation.The work has concentrated primarily on electron beam evaporation in thermionically enhanced discharges. Investigations have centred on various aspects of discharges used in ion plating and the influence of gas scattering mechanisms on the vapour species during deposition. This has been achieved by analysing the published literature and performing experiments involving cathode sheath thickness measurements, sputter weight loss determinations, optical emission spectroscopy and coating thickness evaluation.The main findings are:(i) Thermionically enhanced discharges can considerably reduce cathode sheath thickness, providing benefits in terms of bombardment uniformity and energy transportation. However, the influence of plasma bombardment is anisotropic and also falls off exponentially with distance from the thermionic emitter. This can be offset by a comparable reduction in coating flux arrival rates if the thermionic emitter is positioned close to the vapour source.(ii) The incorporation of nitrogen in (reactive) ion plating discharges may reduce the rate of ion generation, particularly in the presence of thermionic emitters. Nitrogen dissociative charge transfer collisions within the cathode sheath may be signif icant but their practical importance is questionable.(iii) There is evidence to suggest that the metal vapour in an argon ion plating discharge transports most of the ion current to the substrate and at least some of the material arrives as atomic clusters.(iv) A model which unifies coating thickness uniformity with source to substrate distance has been developed. This predicts the existence of a virtual source phenomenon.

Dans ce travail nous avons étudié des réactions chimiques sur la surface de deux métaux :le platine et l'or, en utilisant la microscopie ionique à effet de champ électrique (FIM) et la spectrométrie de masse de désorption par champ pulsé (PFDMS). En complément de ces données expérimentales, nous apportons des résultats obtenus par la théorie de la fonctionnelle de la densité (DFT). La taille et la morphologie de nos échantillons font qu’ils sont de bons modèles de grains de phase active dans un catalyseur réel.

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Doctorat en sciences, Spécialisation chimie
info:eu-repo/semantics/nonPublished

L'accroissement de la densité d'intégration des composants électroniques, engendre un certain nombre de contraintes qui se traduisent par une évolution des technologies. Le passage aux circuits multiniveaux entraine l'utilisation de diélectriques organiques (dont la stabilité thermique est limitée) et nécessite la mise en place de piliers assurant la connexion électrique des différents niveaux. La métallisation de tels piliers montre les limitations des techniques conventionnelles. Le procédé de dépôt par réaction chimique en phase gazeuse à basse pression, par son aspect sélectif permet de supprimer plusieurs étapes de photolithographie et de gravure toujours génératrices de risques de défauts dans les dispositifs. L'utilisation du silane comme réducteur de l'hexafluorure de tungstène, en augmentant très notablement la vitesse de dépôt, rend possible le remplissage des piliers dont la profondeur peut atteindre et dépasser le micron, en un temps relativement court. Dans ce mémoire, le procédé d'élaboration est étudié et optimisé par corrélation des paramètres expérimentaux et des caractérisations des dépôts obtenus. Notamment, ce travail montre la possibilité d'obtenir avec une sélectivité convenable des dépôts de tungstène de faible résistivité avec des vitesses supérieures au micron par minute à une température inférieure à 400C.

Etude dans l'approximation des liaisons fortes et de la methode des moments de la structure electronique et des proprietes d'adsorption de plusieurs types de surfaces de metaux de transition. Application a l'etude de la reconstruction de la surface (110) du tungstene. Interpretation du comportement surprenant des dimeres de la troisieme serie des metaux de transition sur la surface w (110) en prenant en compte les effets des correlations electroniques. Influence de la presence de marches sur les proprietes d'adsorption d'une surface d'un metal de transition

Les ateliers comportant des contraintes de temps de séjours sont assez répandus dans l'industrie manufacturière. Pourtant, les études les concernant sont peu nombreuses dans la littérature. Comme la qualité des produits finis dépend directement du respect des temps de séjours, on recherche une commande robuste vis-a-vis de ces spécifications, en présence de différentes variations. Dans un premier temps, on montre l’incapacité des méthodes graphiques de modélisation des systèmes à événements discrets de la littérature, à spécifier les contraintes de temps de séjour. Cela nous amène à proposer un cahier des charges pour l'introduction d'un nouvel outil. Ces spécifications ont servi de support aux travaux de thèse de W. Khansa pour la définition des RdP p-temporels kha97. Un nombre important de propriétés structurelles sont alors présentées en vue de l’évaluation de performance et du calcul des marges de fonctionnement. Dans un deuxième temps, la recherche d'une commande robuste vis-a-vis des objectifs est effectuée, en fonctionnement répétitif, pour un atelier à flots sans stocks comportant une unique ressource de transport. On présente d'abord une procédure de séparation et d’évaluation utilisant des contraintes, qui découlent de manière systématique des propriétés structurelles du modèle RdP p-temporels. Les résultats concernant la robustesse des commandes obtenues, vis-a-vis de diverses variations, sont ensuite développés. Enfin, les possibilités de généralisation de la démarche proposée sont discutées. Ainsi, l'approche s’avère applicable pour la plupart des ateliers à flots. Par ailleurs, les résultats théoriques sont confrontés à l’étude d'un atelier de galvanoplastie particulièrement complexe. La commande robuste se révèle alors intéressante pour décomposer le système en sous-modules et pour rechercher une architecture de commande capable de supporter plusieurs gammes. Bien plus, certains degrés de liberté sont nécessaires pour permettre le maintien de la qualité des produits par les experts. Dans ce cas, la spécification d'une commande ayant la robustesse indispensable vis-a-vis des paramètres critiques s’avère être la seule solution.

Grace a des mesures microgravimetriques et electrochimiques couplees in situ, la cinetique de reduction du nickel a ete analysee au voisinage du potentiel de depot chimique en presence de la reduction de l'hydrogene et de l'oxydation de l'ion hypophosphite. Un programme informatique a ete elabore pour determiner la distribution des complexes du nickel et des especes acides et basiques dans des solutions contenant plusieurs acides carboxyliques. Dans de tels milieux, faiblement acides, une forte interaction apparait entre les deux processus cathodiques : le depot de nickel est forme par reduction de l'intermediaire ni(i) par l'hydrogene en phase adsorbee. Ce mecanisme est inchange en presence d'ions hypophosphite, de sorte que les caracteristiques du depot chimique peuvent etre decrites par le modele d'evans. En revanche, il n'existe aucune interaction forte entre les ions nickel(ii) et l'oxydation de l'ion hypophosphite. Ces resultats ont permis d'analyser le role des especes qui, a faible teneur, sont dites acceleratrices du depot autocatalytique et ainsi d'elargir la famille des especes chimiques susceptibles de jouer ce role. Enfin, de nouveaux bains ont ete elabores par un choix rationnel d'acides carboxyliques permettant d'operer plus pres de la neutralite. Leur teneur a ete optimisee vis a vis de la complexation du nickel en prenant en compte les contraintes liees a leur utilisation industrielle.

Etude de certains aspects et parametres lies au traitement de conversion par phosphatation des toles d'aciers galvanises et electrozingues: temperature, composition, ph des bains. . . Caracterisation de la couche de conversion et examen de l'influence du vieillissement du bain de degraissage et du traitement final de passivation par des solutions de ticl::(3)

A Dissertation submitted to the Faculty of Engineering, University of the Witwatersrand Johannesburg, in fulfillment of the requirements for the Degree of Master of Science in Engineering
High extractions of the platinum group metals' from a refractory tailings concentrate (PGM Concentration : Pt 81.5ppm, Pd 21.5ppm, Rh 17.5ppm) was achieved after short. low-temperature roasting and subsequent leaching with a zinc chloride based leach reagent containing nitric acid under atmospheric pressure at temperatures from 105-C to 120-C. [Abbreviated Abstract. Open document to view full version]
AC2017

Extraction of platinum group elements (PGE) is a major source of revenue in South Africa and the reserves represent about 75 per cent of world reserves. Most of the remaining Platinum Group Mineral (PGM) reserves are located in the UG-2 chromitite layer of the Bushveld Igneous Complex. Platinum concentrators experience significant losses of PGE in their secondary milling circuits due to insufficient liberation of platinum-bearing particles. The chromium oxide (Cr2O3) content in UG-2 concentrates is typically 3%, which results in operational problems in the downstream smelting process. Ways of improving the design of the secondary milling circuit were investigated, with the purpose of improving PGE recovery and reducing Cr2O3 entrainment in the subsequent flotation stage. Batch-scale laboratory and pilot plant tests were carried out to investigate the optimal design of a secondary milling circuit configuration. The optimal design consisted of a conventional hydrocyclone to de-slime the feed, followed by gravity separation with a spiral concentrator circuit to separate the ore into lights (silicates-rich) and heavies (chromite-rich) fractions. Separate milling of the light and heavy fractions made it possible to grind the silicate-rich fraction finer and to avoid over-grinding of the chromite. The total milling energy was redistributed between the silicates and chromite ball mills with 88% of the energy input to the silicates mill and 12% to the chromite mill thus reducing chromite over-grinding. The effects on the recovery of PGE, and the entrainment of Cr2O3 were measured in combined batch rougher flotation tests. The results indicated a 2% improvement in the secondary rougher flotation PGE recovery for the densifier underflow sample as compared to the standard MF-2 circuit, and most significantly the Cr2O3 entrainment was reduced by over 30% overall. Attritioning of the chromite-rich heavies fraction and ball milling of the silicates-rich lights fraction resulted in a 52% reduction of Cr2O3 in the rougher flotation concentrate and a 0.4% increase in PGE recovery (0.4%) as compared to the standard circuit. The improved reduction in chromite entrainment may be attributed to the lower fines generation with attritioning (52.8%- 106μm) as compared to ball milling with a 12% energy input (83.6% -106μm). Over 50% of the chromite minerals remained in the +106μm of the attritioned heavies product as compared with 21% for the ball milled spiral heavies stream. This accounted for a significant proportion of the overall chromite reduction in the flotation concentrate and supported the motivation for the inclusion of a separate grinding circuit for the chromite and silicate particles. Pilot plant testwork on a VHG (very high grade) spiral concentrator circuit followed by laboratory milling and rougher flotation tests confirmed the above conclusions. A 3.7% improvement in PGE recovery was noted with a 32% Cr2O3 reduction in the secondary rougher flotation concentrate as compared to the standard circuit. The statistical reliability of the laboratory and pilot plant data were quantified at various stages of the testwork due to the heterogeneous nature of the feed material and representative sampling. The repeat analyses on selected flotation tests for the high grade ore revealed that the variances were below 0.5%, 4%, and 7% for the head grades, PGE and Cr2O3 recoveries respectively. The flotation results for the standard and significantly improved milling circuits had variances in the 4E recoveries for the low grade ore and pilot plant ore of below 5.5% and 1% respectively. Low variances (<1%) in the Cr2O3 recoveries were noted for the low grade and pilot plant ores. A preliminary cost estimate was undertaken based on the pilot plant data to determine what value the proposed circuit could add for an additional 3.7% PGE recovery. An additional revenue of approximately R50 000 per day could result based upon the platinum mineral recovery only. The other precious metals, i.e. palladium and rhodium were neglected and would further increase the overall revenue. The minimum payback period for the estimated capital investment would be approximately 4 years. This confirmed the benefit of this improved secondary milling circuit design as a viable option. A closed-circuit operation of the silicates mill should offer more significant benefits compared to the open circuit option; however, this was not considered in the current testwork. This project has confirmed the benefit of separate ball milling and the use of a spiral concentrator as an effective gravity separation device in the secondary milling circuit for a chromite-rich (>50%) UG-2 platinum ore.
Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.

A Research Report submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering (Mining) to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa, July 2017
The project investigated the application of geostatistical techniques in evaluating a mechanically deposited platinum tailings resource. The project was undertaken on one of the Anglo American Platinum tailings dams, the identity of which cannot be revealed, due to the agreement in place or permission given. Remnant unrecovered minerals of economic potential still exist in tailings dams. These unrecovered minerals have influenced several mining companies to turn their attention to the economic potential that still exists in tailings, making them a key strategic component of their resources and reserves. Geostatistics has been developed and thoroughly tested or improved to address challenges experienced in estimating in situ geological ore bodies. The main aim of this Research Project is to test whether these fundamental principles and theories of geostatistics are relevant and appropriate in evaluating man-made ore bodies, such as a Platinum tailings dam, without any significant changes needed on the underlying principles or estimation algorithms. The findings on the Case Study tailings resource can be applied in the evaluation of other tailings dams, as well as any other man-made structures such as low grade rock dumps, muck piles, with related characteristics. A standard approach (methodology) was followed to evaluate the Case Study tailings resource. Drilling and sampling was conducted through sonic drilling. It is a dry drilling technique that is suitable for sampling unconsolidated particles such as tailings. Thereafter, 2 samples were sent to the laboratory to establish grade (concentration) of Platinum Group Metals (Platinum, Palladium and Rhodium), Gold and Base Metals (Copper and Nickel). Density was also measured, and comprehensively analysed as part of variables of interest in this research. Statistical analyses were performed on all variables of interest contained in the dam: which are Platinum (Pt), Palladium (Pd), Gold (Au), 3E (two PGMs plus Gold), Copper (Cu), Nickel (Ni) and Density. The underlying statistical distributions of all metals and density were found to be non-symmetrical and slightly positive skewed. The skewness of the distributions was established to be marginal. Differences between raw data (untransformed) averages and the log-normal estimates were analysed and found to be insignificant. As such Ordinary Kriging of untransformed data was concluded to be the appropriate geostatistical technique for Case Study tailings resource. Analysis of mineralisation continuity (variography), a pre-requisite for geostatistical techniques such as Ordinary Kriging applied on the case study tailings resource, was also performed. Reasonable and sufficient mineralisation continuity was established to exist in the Case Study tailings resource. Although characterised by high nugget effect, these spatial correlations were established to be continuous with ranges of influence well beyond 450 m in all variables. Anisotropic variograms were modelled for all variables and are comprised of nested structures with two to three spherical models. Resource estimation was conducted through Ordinary Kriging in Datamine. All the seven variables were successfully interpolated into each cell of the 5m x 5m x 5m block model. Rigorous validation of the resource model was performed to establish the quality and reliability of the estimation carried out. Estimated resource model was analysed against the original borehole data, through comparison of grade profiles, statistical analysis, QQ Plots and histograms. The grade profile was recognised to be similar between boreholes (5 m composites) and the adjacent cells that have been estimated. Furthermore, statistical analyses revealed minimal differences between means of the estimated model and the original borehole data: the highest difference being 1.7% realised on 3E, followed by 1.1% on Density and Gold (Au). The rest of the variables (Pt, Pd, Cu, and Ni) have differences that are below 1%. 3 QQ plots and histogram were plotted from resource model with 5m x 5m x 5m cells and 5 m composited boreholes. Although these data sets are of different (slightly incompatible) supports, the intended purpose of comparing distributions was achieved. QQ plots and histograms revealed approximately identical shaped distributions of the two data sets, with some minor deviations noticeable in graphs of only two variables (Au and Density) that are underlain by two populations. The validation process carried out gave a compelling assurance on the quality and reliability of the resource model produced. The Case Study tailings resource therefore is successfully estimated by Ordinary Kriging. The results achieved on the Case Study tailings dam has successfully proved that geostatistical principles and theories can confidently be applied, in their current form or understanding, to any man-made tailings resource
CK2018

M.Tech.
The Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique showed very high uncertainties associated with the determination of the concentrations of minor elements in the Platinum Group Metal (PGM) smelting plant samples. This project reports on the work done for the identification of, and subsequent minimisation of the sources of uncertainties associated with the measurements of minor elements in the PGM Furnace Matte material by ICP-MS. To perform these studies, Elan 6000, Shimadzu ICPM-8500 and Finnigan Element 2 ICP-M spectrometers were employed. Synthetic Furnace Matte samples (SFMSs) were prepared and used to ascertain the uncertainties associated with the alleged sources at Mintek and Leo-Tech laboratories. The Element 2 spectrometer dominated the other two ICP-M spectrometers in terms of the accuracy for the determination of the concentrations of minor elements in SFMSs. The evidence of spectral interferences from the significant deviations in the measurement results between the isotopes of the same element was observed in the quantification of Zn, Se, Te and Sn in SFMS by the quadrupole Elan 6000 and the Shimadzu spectrometers. It also transpired that the accuracy of the quantitative determination of minor elements in the Furnace Matte (FM) matrix by ICP-MS was hampered by the matrix elements with the severity depending on the specific analyte and the make and model of the ICP-M spectrometer. The Anglo platinum FM material that was analysed in the second round robin was used as a Certified Reference Material (CRM) in the analysis of the Lonmin FM sample. It was revealed that the laboratory standard operating procedures for the preparation, dilution and subsequent analysis of the sample are potential sources of uncertainty in measurement results. The two-fold dilution of the sample for the lessening of the matrix effects was not effective. The use of multi-walled nanotubes for the alleviation of the matrix effects by removal was also not successful. Nevertheless standard addition method (SAM), combined with internal standardisation can be used as an effective calibration method in ICP-MS to achieve less matrix interfered results over the combination of the common external standardisation and internal standardisation methods.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfillment of the requirements for the degree of Doctor of Philosophy, Johannesburg, August 2017
Titanium aluminides Ti3Al (α2), γ-TiAl and TiAl3 have received much attention for potential applications where light weight for energy saving, room temperature corrosion resistance in aqueous solutions, high-temperature oxidation resistance, or where combinations of the above are needed. Gamma-TiAl of composition Ti-47.5 at.% Al with additions of platinum group metals (PGMs: Pt, Pd, Ru and Ir) was investigated for microstructure, hardness, room temperature aqueous corrosion, high-temperature oxidation resistance, mechanical alloying and consolidation by spark plasma sintering, and coating on titanium Grade 2 and Ti-6Al-4V substrates. Gamma-TiAl of Ti-47.5 at.% Al produced by melting and casting gave a microstructure consisting of γ grains and lamellar grains with alternating of α2 and γ phase lamellae. Additions of 0.2, 1.0, 1.5, and 2.0 at.% PGMs introduced new phases of high PGM contents. The γ and lamellar phases were still present. The additions of PGMs significantly improved the aqueous corrosion properties at room temperature, by improving the pitting corrosion resistance of the γ-TiAl alloy by modifying its hydrogen evolution of the cathodic reaction. The presence of PGMs also influenced the oxidation behaviour of γ-TiAl at 950°by forming the Z-phase which stabilized a continuous protective Al2O3 phase. However, Ti-47.5 at.% Al, being a two-phase alloy (α2+γ), PGMs could not sustain a stable Z-phase, as it transformed into an oxygen supersaturated Ti3Al, which subsequently led to the formation of TiO2+Al2O3, a non-protective oxide mixture. The optimal PGM addition to γ-TiAl was 0.5 at.%, with iridium giving the best room temperature corrosion and high-temperature oxidation resistance. Mechanical alloying of Ti and Al pure powders with PGM additions gave powders where α2 and γ were only identified after heat treatment. Consolidation of the mechanically alloyed powders by spark plasma sintering gave different microstructures from the cast alloys, with continuous α2 and γ phases and evenly distributed nanometer-sized alumina, and much higher hardnesses. Cold spraying the mechanically alloyed powders on to titanium Grade 2 and Ti-6Al-4V substrates gave coatings of irregular thickness, dense near the substrates with porosity at the top, giving poor oxidation protection.
CK2018

Dissertation submitted in compliance with the requirements for the Master's Diploma in Technology: Dental Technology, Technikon Natal, 1993.
The unpredictability of solder joints in dental base metal alloys constitute a major problem. This study aimed to establish whether gold plating the joint surfaces of a metal ceramic base metal alloy prior to postceramic soldering would enhance the predictability of the soldering method and joint strength. 150 standardised test specimens were prepared from 3 Oegussa dental alloys, viz Resistal P (Nier), Oegulor M (AUPt) and Realor (PdAU). The Resistal P specimens were subjected to 6 porcelain firing cycles and solder joint surfaces of 40 specimens gold plated prior to soldering, using gold plating equipment and solutions found in the jewellery industry. suitable fluxes were used and all soldering was done in a porcelain furnace. First the soldering method was validated by soldering 20 oegulor M specimens and determining the tensile strength of the 10 joints in an Instron testing machine. The data were then compared with the ISO minimum standards. The soldering method proved sound and a control was thus established. secondly, using 3 alloy combinations without gold plating, 30 solder joints were made and their tensile strengths determined. This established the level of predictability and strength and parameters for comparison. Thirdly, the above procedure was repeated, but the Resistal P specimen joint surfaces were gold plated prior to investing for soldering. The levels of predictability and strength were then compared with the parameters set. The fracture sites of broken joints were examined and photographed using a metallurgical microscope. The data were analysed using 4 statistical tests. The Oegulor M control group solder joints were the strongest and the Resistal P joints the weakest. The success rates for the non-plated joints were; oegulor M to oegulor M = 100%, Resistal P to oegulor M = 90%, Resistal P to Realor = 80% and Resistal P to Resistal P = 60%. The success rates for the gold plated joints were; Resistal P to oegulor M = 60%, Resistal P to Realor = 40% and Resistal P to Resistal P = 80%. This study found, under the circumstances of testing, that gold plating of the base metal alloy prior to investing for postceramic soldering did not enhance the strength, solderability and predictability of the solder joints to an extent that a flux that does not discolour porcelain can be used.
M