Tesi sul tema "Platinum Group Metals (PGM)"
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1
Zhang, Jingshu Ph D. Massachusetts Institute of Technology. "A bottom-up prospective dynamic materials flow assessment for platinum group metals (PGM) global demand forecast". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93048.
Abstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 71-77).
by Jingshu Zhang.
S.M.
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Machado, Norma Maria Pereira. "Rheological study of nuclear glass melts containing Platinum Group Metal aggregates". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0018.
Abstract (sommario):
En France, les produits de fission nucléaire issus du retraitement des combustibles usés sont conditionnés au sein de matrices de verres borosilicatés. Lors du processus de vitrification à haute température (1200 °C), les éléments à confiner réagissent chimiquement avec les additifs de vitrification pour former un verre homogène. Cependant, parmi ces éléments, les platinoïdes ne sont pas solubles dans le bain de verre et restent en suspension sous forme de particules de quelques microns. Ces particules présentent une forte tendance à l'agrégation et les suspensions peuvent alors présenter une viscosité apparente anormalement élevée. Ces systèmes sont caractérisés par un comportement rhéofluidifiant et thixotrope. La présente étude vise à fournir des données importantes sur le comportement rhéologique global de ces systèmes et leurs propriétés, grâce à la caractérisation d'un verre nucléaire simulé contenant 3,0 % massique (1,02 % en volume) de platinoïdes. Une modélisation mathématique du comportement thixotrope de ce verre est présentée pour la première fois en utilisant un modèle similaire à celui proposé par Houska (Houska, 1981). Ce modèle prédictif permet la description des résultats expérimentaux obtenus à partir de mesures en régimes permanent et transitoire. L'impact de la contrainte de cisaillement et du temps sur le degré d'agrégation et la cinétique de sédimentation des particules est déterminé à l'aide d'un rhéomètre à contrainte imposée opéré à haute température et d'analyses d'images obtenues par microscopie électronique à balayage (MEB). Pour la première fois, l'interaction entre le comportement rhéologique du système et le degré d'agrégation est analysé, tout comme le lien avec la sédimentation des particules. Sur la base des données expérimentales acquises, un calcul d'équilibre des forces est réalisé pour illustrer les différents scénarios d'agrégation. Ce travail fournit des nouvelles données pour la modélisation et le contrôle du processus de vitrificationIn France, borosilicate glass is used as a matrix to immobilize nuclear fission products resulting from spent fuel reprocessing. In the high-temperature vitrification process (1200 °C), most of elements to be contained react chemically with the vitrification additives to form a homogeneous glass melt. Platinum Group Metal (PGM) particles are not soluble in the melt and therefore are present as suspended particles of few microns. These particles exhibit an intense aggregation tendency and consequently the suspensions may present an anomalously high apparent viscosity. These systems are characterized by a shear-thinning and a thixotropic behaviors. The present study aims to provide important inputs for the overall rheological behavior of this system and its features through the characterization of a simulated nuclear glass melt containing 3.0 wt% (1.02 vol%) of PGM particles. A mathematical modeling of the thixotropic behavior of glass melts containing PGM particles is presented for the first time using a model similar to that proposed by Houska (Houska, 1981). This predictive model allow to describe experimental results obtained both in steady state and transient conditions. The impact of the shear stress and time on PGM aggregation degree and sedimentation kinetics is determined using an imposed-stress rheometer at high temperature and imaging analyses via Scanning Electron Microscopy (SEM). For the first time, the interplay between the rheological behavior of the system and the aggregation degree is provided, as well as the link with the particles settling. Based on the acquired experimental data, a force balance computation is executed to illustrate the different aggregation scenarios. The work provides a new input for the modeling and control of the vitrification process
3
Alshana, Usama Ahmed. "Separation And Quantitation Of Some Platinum Group Metals By Rp-hplc". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12605760/index.pdf.
Abstract (sommario):
In this study, a reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed to separate and determine Pt and Pd after formation of their chelates with N,N-diethyl-N'-benzoylthiourea (DEBT). With the aim of reducing the number of steps in treating the samples, the method developed does not require the elimination of excess chelating reagent before the analysis of metal chelates. The different physical and chemical parameters affecting separation were examined in details. The whole analysis was completed on a C18 column in 16 min at 280 nm, with the mobile phase of acetonitrile-methanol-water (80:10:10, v:v:v) containing 0.20 mol l-1 pH 5.0 acetate buffer at a flow rate of 0.8 ml min-1. Detection limits of the method, based on 3s, were found as 14.2 ug l-1 for Pd and 0.77 mg l-1 for Pt using a 20-ul sample loop. Reproducibility of the method for ten repeated measurements was found as 2.36 % for 0.60 mg l-1 Pd and 2.58 % for 10.0 mg l-1 Pt as % RSD. The proposed method is a rapid, simple and highly selective method for the simultaneous determination of Pt and Pd by HPLC without the need for any interference elimination process.
4
Kriek, R. J. "Leaching of selected PGMs : a thermodynamic and electrochemical study employing less aggressive lixiviants". Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5611.
Abstract (sommario):
Includes abstract.Includes bibliographical references (leaves 74-79).
Historically the platinum group metals (PGMs) have been, and are still being dissolved by means of rather aggressive methods, e.g. aqua regia. Limited research has been conducted into the dissolution of the PGMs using different oxidizing agents. The dissolution of gold on the other hand has been afforded extensive research, and numerous papers and review articles have been published on the subject. The last number of years has seen the biggest application by volume of the PGMs as part of autocatalysts towards the degradation of harmful motor vehicle exhaust gases. This has subsequently sparked research into the recovery of specifically platinum, palladium, and rhodium from spent autocatalysts. Currently pyrometallurgical recovery of PGMs is being employed predominantly. A hydrometallurgical process on the other hand is, based on current technology, still a rather aggressive process that makes for high maintenance costs and an unpleasant environment. Gold has traditionally been dissolved by making use of cyanide, which is still the major route for gold dissolution. Due to environmental concerns lixiviants such as thiosulphate (S2O3 2-), thiourea (H2NCSNH2), and thiocyanate (SCN-) are gaining acceptance due to them being more environmentally friendly and giving good recoveries. These ‘softer’ alternatives have however not been tested on the PGMs. It is therefore the aim of this study to obtain an improved understanding of the leaching of the PGMs using lixiviants less aggressive than aqua-regia. These lixiviants include (i) SCN-, (ii) S2O3 2-, (iii) H2NCSNH2, and (iv) AlCl3/HCl. A thermodynamic study highlighted the fact that thermodynamic data for platinum-, palladium- and rhodium complexes are basically non-existent. To therefore obtain a clearer thermodynamic understanding of the leaching of the platinum group metals by means of these alternative lixiviants, future detailed speciation and thermodynamic investigations need to be conducted. An exploratory electrochemical investigation focusing on open circuit potentials and potentiodynamic scans, showed AlCl3 / HCl / NaOCl to be a good candidate for the leaching of the platinum group metals followed by SCN- / Fe3+ and CS(NH2)2 / Fe3+. Actual leach results, employing virgin autocatalysts as sample material, again highlighted the potential of AlCl3 / HCl / NaOCl as being a good lixiviant system. The surprise package, however, has been SCN- / Fe3+ that rendered very good results for Pd and Pt.
5
Aiglsperger, Thomas Hans. "Mineralogy and geochemistry of the platinum group elements (PGE), rare earth elements (REE) and scandium in nickel laterites". Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/396340.
Abstract (sommario):
Ni laterites are considered worthy targets for critical metals (CM) exploration as rare earth elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this investigation geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s) (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits.
Two Ni laterite profiles from the Falcondo mining area have been compared for their platinum group element (PGE) geochemistry and mineralogy. One profile (Loma Peguera) is characterized by PGE-enriched (up to 3.5 ppm total PGE) chromitite bodies incorporated within the saprolite, whereas the second profile is chromitite-free (Loma Caribe). Total PGE contents of both profiles slightly increase from parent rocks (36 and 30 ppb, respectively) to saprolite (-50 ppb) and reach highest levels within the limonite zone (640 and 264 ppb, respectively). Chondrite-normalized PGE patterns of saprolite and limonite reveal rather flat shapes with positive peaks of Ru and Pd. Three types of platinum group minerals (PGM) were found by using an innovative hydroseparation technique: (i) primary PGM inclusions in fresh Cr-spinel (laurite and bowieite), (ii) secondary PGM (e.g., Ru-Fe-Os-Ir compounds) from weathering of preexisting PGM (e.g., serpentinization and/or laterization), and (iii) PGM precipitated after PGE mobilization within the laterite (neoformation). Results provide evidence that (i) PGM occurrence and PGE enrichment in the laterite profiles is independent of chromitite incorporation; (ii) PGE enrichment is residual on the profile scale; and (iii) PGE are mobile on a local scale leading to in situ growth of PGM within limonite, probably by bioreduction and/or electrochemical metal accretion.
Free grains of PGM with delicate morphologies were discovered in limonite hosted chromitite samples (“floating chromitites”) from highest levels in the Falcondo Ni laterite deposit (Dominican Republic). Textural and chemical evidence obtained via SEM and EMP analysis points to a multistage formation: (i) primary PGM formation at magmatic stage; (ii) transformation to highly porous secondary Os-Ru PGM during serpentinization; (iii) neoformation of Ir-Fe-Ni-(Pt) mineral phases during early stages of lateritization; (iv) neoformation of Pt-(Ir) mineral phases within the critical zone of the profile resulting in nugget shaped accumulation of rounded particulates during late stages of lateritization. The observation of accumulations of most likely biogenic mediated in situ growth of Pt rich nanoparticles in supergene environments could help to explain (i) why Pt bearing nuggets are the most abundant PGM found in surface environments, (ii) why Pt nuggets from placer deposits generally surpass the grain sizes of Pt grains found in parent rocks by several orders of magnitude (few micrometers vs. several millimeters) and (iii) how anthropogenic PGE contamination may affect our biosphere.
Osmium chromitite, saprolite and limonite (Falcondo mining area), suggest that serpentinization of the Loma Caribe peridotite has not significantly affected the Re-Os system in Os-rich PGM. This is noted by the fact, that primary PGM formed at magmatic stage and secondary Ru-Os-Mg- isotope characteristics from primary and secondary PGM, separated from Si PGM formed due desulphurization of primary PGM with significant incorporation of Mg silicates, have almost identical Os isotope characteristics, typical of the mantle. However, the Re-Os system can be significantly disturbed during stages of lateritization when porous secondary PGM react with Fe-rich fluids, thus forming hexaferrum and magnetite in the 187 188 interstices of secondary PGM. Here presented data indicate that more radiogenic ratios in higher levels of the weathering profile are linked to steady mobilization of PGE within secondary PGM resulting in subsequent loss of Os counterbalanced by the incorporation of Fe. Os/ Os
In this investigation presented data clearly states that PGE are neither noble nor inert in surface environments, at least in those related to tropical Ni laterites from the Northern Caribbean.
6
Van, der Horst Charlton. "Development of a bismuth-silver nanofilm sensor for the determination of platinum group metals in environmental samples". University of the Western Cape, 2015. http://hdl.handle.net/11394/4451.
Abstract (sommario):
Philosophiae Doctor - PhDNowadays, the pollution of surface waters with chemical contaminants is one of the most crucial environmental problems. These chemical contaminants enter rivers and streams resulting in tremendous amount of destruction, so the detection and monitoring of these chemical contaminants results in an ever-increasing demand. This thesis describes the search for a suitable method for the determination of platinum group metals (PGMs) in environmental samples due to the toxicity of mercury films and the limitations with methods other than electroanalytical methods. This study focuses on the development of a novel bismuth-silver bimetallic nanosensor for the determination of PGMs in roadside dust and soil samples. Firstly, individual silver, bismuth and novel bismuth-silver bimetallic nanoparticles were chemically synthesised. The synthesised nanoparticles was compared and characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transformed infrared spectroscopy (FT-IR), Raman spectroscopy, and transmission electron microscopy (TEM) analysis to interrogate the electrochemical, optical, structural, and morphological properties of the nanomaterials. The individual silver, bismuth, and bismuth-silver bimetallic nanoparticles in the high resolution transmission electron microscopy results exhibited an average particle size of 10-30 nm. The electrochemical results obtained have shown that the bismuth-silver bimetallic nanoparticles exhibit good electro-catalytic activity that can be harnessed for sensor construction and related applications. The ultraviolet-visible spectroscopy, Fourier-transformed infrared spectroscopy, and Raman spectroscopy results confirmed the structural properties of the novel bismuth-silver bimetallic nanoparticles. In addition the transmission electron microscopy and selected area electron diffraction morphological characterisation confirmed the nanoscale nature of the bismuth-silver bimetallic nanoparticles. Secondly, a sensitive adsorptive stripping voltammetric procedure for palladium, platinum and rhodium determination was developed in the presence of dimethylglyoxime (DMG) as the chelating agent at a glassy carbon electrode coated with a bismuth-silver bimetallic nanofilm. The nanosensor further allowed the adsorptive stripping voltammetric detection of PGMs without oxygen removal in solution. In this study the factors that influence the stripping performance such as composition of supporting electrolyte, DMG concentration, deposition potential and time studies, and pH have been investigated and optimised. The bismuth-silver bimetallic nanosensor was used as the working electrode with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. The differential pulse adsorptive stripping peak current signal was linear from 0.2 to 1.0 ng/L range (60 s deposition), with limit of detections for Pd (0.19 ng/L), Pt (0.20 ng/L), Rh (0.22 ng/L), respectively. Good precision for the sensor application was also obtained with a reproducibility of 4.61% for Pd(II), 5.16% for Pt(II) and 5.27% for Rh(III), for three measurements. Investigations of the possible interferences from co-existing ions with PGMs were also done in this study. The results obtained for the study of interferences have shown that Ni(II) and Co(II) interfere with Pd(II), Pt(II) and Rh(III) at high concentrations. The interference studies of Cd(II), Pb(II), Cu(II) and Fe(III) showed that these metal ions only interfere with Pd(II) and Pt(II) at high concentrations, with no interferences observed for Rh(III). Phosphate and sulphate only interfere at high concentrations with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. Based on the experimental results, this bismuth-silver bimetallic nanosensor can be considered as an alternative to common mercury electrodes, carbon paste and bismuth film electrodes for electrochemical detection of PGMs in environmental samples. Thirdly, this study dealt with the development of a bismuth-silver bimetallic nanosensor for differential pulse adsorptive stripping voltammetry (DPAdSV) of PGMs in environmental samples. The nanosensor was fabricated by drop coating a thin bismuth-silver bimetallic film onto the active area of the SPCEs. Optimisation parameters such as pH, DMG concentration, deposition potential and deposition time, stability test and interferences were also studied. In 0.2 M acetate buffer (pH = 4.7) solution and DMG as the chelating agent, the reduction signal for PGMs ranged from 0.2 to 1.0 ng/L. The detection limit for Pd(II), Pt(II) and Rh(III) was found to be 0.07 ng/L, 0.06 ng/L and 0.2 ng/L, respectively. Good precision for the sensor application was also obtained with a reproducibility of 7.58% for Pd(II), 6.31% for Pt(II) and 5.37% for Rh(III), for three measurements. In the study of possible interferences, the results have shown that Ni(II), Co(II), Fe(III), Na+, SO42- and PO43- does not interfere with Pd(II) in the presence of DMG with sodium acetate buffer as the supporting electrolyte solution. These possible interference ions only interfere with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) as the supporting electrolyte solution.
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Necib, Ammour Ouarda. "Effect of platinum group metal (PGM) additions on the stress corrosion cracking resistance of type 304 stainless steel in pressurised water reactors". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/effect-of-platinum-group-metal-pgm-additions-on-the-stress-corrosion-cracking-resistance-of-type-304-stainless-steel-in-pressurised-water-reactors(d7578933-6268-4fe8-819e-7b9b066f5c2e).html.
Abstract (sommario):
In pressurised water reactors (PWRs), hydrogen overpressure is used to keep the corrosion potential below the threshold for onset of intergranular stress corrosion cracking (IGSCC) in type 304 SS. However, some regions may contain higher oxygen levels resulting in an increase in the potential. These 'dead space' regions are difficult to access and during refuelling; oxygen may become trapped in these locations. The objective of this study was to investigate the influence of PGM additions on IGSCC susceptibility of type 304 stainless steels (SS) in the sensitised state within PWRs. The work presented herein investigates several aspects of the IGSCC problem. Virgin and platinum group metal (PGM)-modified (Ru and Pd) 304 SS have been studied. Material characterisation, including microstructural, tensile properties, hardness and grain size measurements, has been conducted. Crack initiation studies using U-bend samples in autoclaves simulating PWR environments have also been performed. In addition, crack propagation studies using circumferential cracked bar (CCB) specimens under constant extension in potassium tetrathionate solutions, a well-known medium to promote IGSCC on sensitised stainless steels, have been conducted in order to evaluate cracking resistance. Electrochemical studies using model solutions for PWR chemistry (containing boric acid and lithium hydroxide) and also potassium tetrathionate were carried out to look at the influence of the PGM on the kinetics of the main electrochemical reactions. The results revealed that PGM additions appeared to reduce crack initiation on sensitised type 304 SS under oxygenated conditions in high temperature water containing sulphate and chloride. PGM-doped and standard sensitised type 304 stainless steels revealed susceptibility to IGSCC propagation in 0.01 M K2S4O6, at pH=1.5 and 25°C. Electrochemical studies in potassium tetrathionate media showed smaller anodic dissolution peaks with PGM additions and metallography indicated less intergranular attack with PGM additions. In PWR model electrolytes, PGM additions, particularly 1 wt% Ru, were shown to catalyse the oxygen reduction reaction or hydrogen oxidation reaction, depending on the oxygen /hydrogen level. Overall findings showed that Ru additions can improve the IGSCC resistance of sensitised type 304 SS in PWR, while Pd additions are less effective.
8
Sýkora, Jiří. "Využití iontoměničů pro prekoncentraci platinových kovů". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-295670.
Abstract (sommario):
The aim of this thesis is the elaboration of a detailed literature review on the use of ion exchangers for the preconcentration of platinum group metals. This work contains an actual literature review on this issue. In this work you will find information about the current occurrence of platinum metals in the environment, their impact on health, properties, resources and the use. There are also described ways of decomposition, extraction and use of ion exchangers. In the experimental part this thesis deals with optimization of ion exchangers and following application of real samples from the city of Brno.
9
Gxoyiya, Babalwa Siliziwe Blossom. "Synthesis and evaluation of PGM-selective ligands". Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1007849.
Abstract (sommario):
A series of polydentate POM-selective, sulfur-containing amide ligands have been synthesized from ro-dibromoalkanes and mercaptoacetanilide, The resulting 3,6- dithiaoctanediamides and 3,7-dithianonanediamides, some of which contain a polymerisable group, were all characterized by high-resolution MS, IR, I Hand I3C NMR spectroscopic methods. Various approaches to the polymerisable ligands were explored, the most efficient proving to be the incorporation of an allyl ether moiety in the mercaptoacetanilide. The corresponding Pd(U) and Pt(II) complexes were also prepared from the metal chloride salts and characterized by elemental analysis and spectroscopic methods. The NMR data indicates that both the cis- and transcomplexes were formed, while the IR data indicates cis- coordination of the chlorine . ligands. Molecularly imprinted polymers (MIP's), prepared using platinum(II) mercaptoacetanilide and 3,6-dithiadiamide complexes, showed high selectivity for , , palladium(II) [in the presence of Pt(II), CoCII), Cu(II) and Ni(II)] as determined by . ICP-MS analysis. The more kinetically inert Pt(II) ions however, slowly displaced Pd(II), confirming the Pt(II) selectivity of the MIP's. Solvent extraction studies were conducted to explore the selectivity of the 3,6- dithiaoctanediamides and 3,7-dithianonanediamides for Pd(U) over CoCII), Cu(U) and Ni(II). The ICP-MS data indicate that, in general, equilibration was achieved within ten minutes and that the longer-chain amides were less selective than the shorter-chain analogues.KMBT_363
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Caddy, Irene. "A platinum life cycle assessment : potential benefits to Anglo Platinum / I. Caddy". Thesis, North-West University, 2011. http://hdl.handle.net/10394/6279.
Abstract (sommario):
There has been an increased awareness of the inter-dependence between man and the environment since the 1960’s. Environmental awareness has evolved from representing fairly radical views opposing all development, to a current emphasis on sustainable development between development and the environment.
Life Cycle Assessment (LCA) is defined as the identification and quantification of the environmental impacts of a product, process or service during the entire life cycle being studied. The life cycle starts at the extraction of raw materials and the production of energy used to create the product through the use and final disposal of the product. LCA therefore considers the production, use and disposal of a product, which constitutes the life cycle of the product.
LCA can be combined with methodologies that study other parameters such as costs in order to optimise the benefits from LCA. It is suggested that cost implications of processes to reduce environmental impacts should be included in a methodology used for a Platinum LCA.
A comment that is consistently raised in the case studies is that the minerals industry regards LCA as an effective tool to determine the impacts of the industry, however extraction & beneficiation of minerals are often grouped together, with accurate data not being available, and databases either not available or not updated.
The case studies indicated several benefits from the various LCA’s conducted. A Platinum LCA should clearly define and group the environmental impacts being studied into categories such as greenhouse gas emissions, global warming, acidification, and resource consumption.
A Platinum LCA will be resource- and time intensive due to the large scale of the processes involved. It is suggested that a Platinum LCA firstly focuses on the production phase, i.e. cradle-to-gate, with potential future work done on the use and end-of-life stages.
It is suggested that individual facility-based LCA’s for AMPLATS and other platinum producers are conducted in order to get a true reflection of the environmental burden of each company, and then selectively share technological improvements to reduce the environmental burden without disclosing sensitive information.
The benefit of LCA in the case of platinum will be optimised if it can be used to make business decisions, together with consideration of financial and production benefits in addition to anticipated environmental benefits of alterations to processes. It is essential that LCA is seen as a business tool that will assist the company to make informed business decisions about process improvements, as well as new projects and design of new facilities.
LCA on its own will not determine which product or process is the most cost effective or works best. The information developed in a LCA study should be used as one component of a more comprehensive decision making process assessing the trade-offs with cost and performance. The results from a LCA could be used to make informed decisions about optimisation between costs and reduced environmental impacts.Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2011.
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Tooze, R. P. "Organometallic compounds of platinum group metals". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37880.
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Isbilir, Amina. "Tridentate ligands with platinum group metals". Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42777.
Abstract (sommario):
In this thesis, a series of symmetrical and unsymmetrical pincer ligands are synthesised and explored as supports for platinum group metals, such as palladium, platinum and ruthenium. In Chapters 2 and 3, the synthesis and characterisation of novel pyridine-based dianionic aryl-containing [C,NPy,O] and phenol-containing [O,NPy,O] pincer pro-ligands and their reactivity towards palladium(II) and ruthenium(II) metal precursors is described. [C,NPy,O]-type pincer pro-ligands have been shown to promote sp2 C-H activations upon reaction with palladium(II) and ruthenium(II) metal salts. Phenol-containing [O,NPy,O] pincer pro-ligands demonstrated deprotonation of the phenolic oxygen, resulting in a tridentate coordination upon binding to palladium(II) and ruthenium(III) metal centres. In Chapter 4, six novel paramagnetic ruthenium(III) pincer complexes developed from aryl-containing [C,NPy,O] and phenol-containing [O,NPy,O] pincer pro-ligands, have been employed as efficient catalysts for the transfer hydrogenation of ketones. Chapter 5 describes the synthesis of mono(imino)pyridyl [N,NPy,O] pincer pro-ligands incorporating an ethyl ester group at 6-position and their ability to undergo hydrolysis to a carboxylic acid upon coordination to palladium. Use of platinum(II) metal precursor, on the contrary, did not promote hydrolysis resulting in a bidentate coordination mode in the corresponding complexes. Chapter 6 explores the reactivity of two dien [N,N,N] pincer pro-ligands towards palladium(II) salts. Preliminary investigations demonstrated the ability of the amine-NH donor moieties to promote NH···A (acceptor) hydrogen bond interactions with the acceptor atoms on their corresponding anions in the solid state.
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Roberts, Yvonne V. "Macrocyclic complexes of platinum group metals". Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/11897.
Abstract (sommario):
A series of half-sandwich complexes, [M([9]aneS3)*XY]n+ have been synthesised from MCl2 [M = Pd, Pt,X = Y = Cl-(n = 0), PPh30.5dppm, 0.5dppe,0.5x2, 2'-bipy(n = 2), X = Cl-, Y = PPh3(n&61 1); M = Pd, X = Y = 0.5oxytriphos, 0.5x1, 10-phen(n = 2), X = Cl-, Y = PCy3(n = 1)]. All but one of the crystal structures [M = Pd, X = Y = Cl-, PPh3, 0.5dppm, 0.5oxytriphos, 0.5x2,2'-bipy, 0.5x1,10-phen, X = Cl-, Y&61 PPh3; M = Pt, X = Y&61 PPh3, 0.5dppm] solved show the metal in a square-planar, S2XY co-ordination set, with a long-range apical interaction to the remaining S-atom of [9]aneS3; [Pt([9]aneS3)(PPh3)2]2+ is trigonal bipyramidal. The reductive electrochemistry of the Pd complexes shows the stabilisation of Pd(I) species by bidentate, π-acceptor X,Y ligands. A series of complexes [Ru([9]aneS_3)XYZ]^+ (X-Cl^-, Y = CO or PCy_3, Z&61 H or MeCN; X = H, Y = Z = 0.5x1,5-COD) and [Ru([n]aneS_4)*XY]^m+ (X = Cl^-, Y = PPh_3, n = 12,14,16, m&61 1; X = McCN, Y = PPh_3, n = 12,14, m&61 2; X = Y = McCN, n = 16, m = 2) have also been prepared. The crystral structures of [Ru([9]aneS_3)XYZ]^+ (X = Cl^-, Y = CO, Z&61 McCN; X = H, Y = Z = 0.5x1,5-COD) show the metal to be octahedrally co-ordinated. Such is also the case for [Ru([n]aneS_4)XY]^m+ (n = 14,16, X = Cl^-, Y&61 PPh_3; n = 16, X = Y = MeCN), with the non-macrocyclic ligands mutually cis. A study by nmr spectroscopy of the mechanism of formation of [Ru([9]aneS_3)Cl(PPh_3)(C_4H_3O)H^+ ]^- from [Ru([9]aneS_3)Cl_2(PPh_3)] and Et_2O/THF was undertaken. The former complex, and the dimeric intermediates [Ru([9]aneS_3)(PPh_3)Cl]_2^2+ and [Ru([9]aneS_3(PPh_3)(μ2-Cl)Tl(μ3-Cl)]_2^2+ were characterised by X-ray crystallography. Finally, the novel agostic species [Pd(H[9]aneN_3)Cl_2]_2(PF_6)_2.2([Pd(H[9]aneN_3)Cl_2]_2) is described. The X-ray structure of the dimer shows an unsupported Pd-Pd bond with mutally cis-Cl^- ligands. Only one of the two metal ions in the dimer forms an agostic M-H-N bond. The metal in each of the monomers also forms on M-H-N agostic bond. *[9]aneS_3 = 1,4,7-trithiacyclononane, [14]aneS_4 = 1,4,8,11-tetrathiacyclotetradecane [12]aneS_4 = 1,4,7,10-tetrathiacyclododecane, [16]aneS_4 = 1,5,9,13-tetrathiacyclohexadecane.
14
Fotheringham, John David. "Heterobimetallic complexes of the platinum group metals". Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/10906.
15
Shams, Leyla. "Accumulation of platinum group elements by the marine microalga, Chlorella stigmatophora". Thesis, University of Plymouth, 2010. http://hdl.handle.net/10026.1/309.
Abstract (sommario):
Very little information exists on the marine biogeochemistry of Rh, Pd and Pt, or the platinum group elements (PGE), an emerging group of contaminants whose principal emissions are associated with the abrasion of the catalytic converter in motor vehicles and chemotherapy drugs discharged in hospital wastes. In this study, Rh(III), Pd(II) and Pt(IV) were added individually and in combination to cultures of the marine microalga, Chlorella stigmatophora, maintained in coastal seawater at 15oC and under fluorescence lighting both in the presence and absence of trace nutrients (e.g. Fe, Co, Zn and EDTA). The accumulation of PGE was established under varying conditions (pH, algal biomass, PGE concentration, time) by ICP-MS analysis of seawater and nitric acid digests and EDTA washes of the alga, the latter giving a measure of PGE adsorption by C. stigmatophora. Under all conditions the extent of accumulation was in the order: Rh > Pd >> Pt. In short-term (24-h) exposures, accumulation isotherms were quasi-linear up to PGE concentrations of 30 ug L-1, although Pd displayed convexity, hence saturation of available binding sites, at greater concentrations. The pH, adjusted between about 5.5 and 9.5 by addition of acid or base, did not have a great impact on PGE accumulation, with Rh displaying a moderate increase in accumulation and Pd a moderate reduction with increasing pH. More important, all PGE displayed a significant reduction in accumulation on a weight-normalized basis with increasing concentration of algae, an effect not reported for metal-marine algal interactions previously in the literature. Longer-term experiments showed that the rates of both overall accumulation and internalization were greatest for Pd and least for Pt. Consistent with this observation, the toxicity to C. stigmatophora evaluated by both pigment content and growth rate, was significantly greater for Pd than for Pt. Differences in the biogeochemical behaviours among the PGE are attributed to differences in their aqueous speciation in seawater, different affinities for the algal surface, different tendencies to cross the cell membrane, and especially with regard to Pd and Pt, differences in the rates of these interactions. Thus, although the equilibrium chemistries of Pd and Pt are very similar, their differential biogeochemistries are the result of kinetic constraints on reactions involving the latter. Because the environmental concentrations of PGE are predicted to increase with increasing emissions from vehicles and hospitals, the results of this study make an important contribution to an improved understanding of the likely effects and fates of these emerging contaminants in the marine environment. The results are also more generally important to an improved understanding of the interactions of trace metals with microalgae in seawater.
16
Harding, Nigel Anthony. "β-thia-alkyl complexes of platinum group metals". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283721.
17
Auer, Derek. "Flow-injection analysis of the platinum-group metals". Doctoral thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/17511.
Abstract (sommario):
Includes bibliographical references.To date the principle methods for the determination of the platinum-group metals (PGMs) use an "off-line" assay with flame-atomic absorption spectrometry and visible spectrometry. Both suffer numerous interferences and involve time-consuming and arduous laboratory separation methods prior to analysis. An "on-line" method for the rapid assay of the PGMs is indeed a lacking component in the analysts' repertoire of methods. This study describes the development of spectrophotometric methods for the determination of the PGMs using flow-injection analysis (FIA). The principle of exploiting the remarkably specific and selective reaction of stannous halides with the PGMs to yield a series of intensely coloured complexes in acidic solutions forms the basis of these methods. The reaction is subject to relatively few interferences from other transition metals. A high speed scanning spectrophotometer is employed to obtain second order data. The successful manipulation of the data enables the determination of PGMs as single components and also simultaneously in mixtures. Attention is focused on the establishment of principles for successful multi-component analysis of PGMs. The development of a software program for multi-wavelength data manipulation was mandatory and is described. Criteria for successful selection of analytical wavelengths are discussed. The usefulness of multi-dimensional graphical data representation is demonstrated in a stop-flow study of the palladium reaction with tin (II) chloride. Qualitative information is provided regarding the nature of complexes and their interactions. Correlation of spectrophotometric data with complex solution colour changes is made. The requirements for future progress in multi-component FIA determinations as well as the direction for future research conclude the study.
18
Bradley, Ena. "Electrochemistry of platinum group metals in ionic liquids". Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705896.
19
Harlow, Karsten James. "Imidazolidene and alkylidene complexes of the platinum group metals". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313729.
20
Rioche, Cyrille Christophe. "An investigation of platinum group metals for environmental catalysis". Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492038.
Abstract (sommario):
Environmental concerns and more stringent regulations have stimulated the development of new cleaner technologies to decrease the emissions of greenhouse gases and other hazardous gas emissions. In this study, the steam reforming of biooil as well as NOx storage and reduction catalysts were investigated. The production of hydrogen by steam reforming of bio-oils obtained from the fast pyrolysis of biomass requires the development of efficient catalysts able to cope with the complex chemical nature of the reactant. Steam reforming of a few model compounds and that of an actual bio-oil was investigated in the temperature range 650-900°C over Pt, Pd and Rh supported on alumina and a ceria-zirconia sample. The use of ceria-zirconia led to higher H2 yields. The supported Rh and Pt catalysts were the most active, while palladium-based catalysts performed poorly. Temperatures close to, or higher than, 800°C were required to achieve significant conversions to COx and H2 (e.g., H2 yields around 70%) ofthe bio-oil. NOx Storage and Reduction (NSR) catalysts are considered to be one of the most promising solutions to meet the upcoming NOx exhaust emission regulations. However, despite the high level of activity in this area, it is surprising that most studies have been conducted under conditions that are far from realistic. A fast transient apparatus has been developed to study these catalysts under realistic temporal conditions. The performance of a typical Pt/Ba/y-Ah03 NSR catalyst was studied as a function ofthe temperature, rich phase duration, reductant concentration, the type of reductant and the space velocity and the importance of the regeneration step in the NSR process was highlighted. The regeneration step was further investigated over Pt and/or Rh based catalysts by coupling of fast transient kinetic switching and the use of 15NO. An unexpected double peak in the evolution of nitrogen was revealed. The first peak occurred immediately on switching from lean to rich conditions, while the second peak started at the point at which the gases switched from rich to lean. Rh/Ba/Ah03 trap was found to be dependent on the rate of NOx storage, since the rate of regeneration was sufficient to remove the NOx stored in the lean phase. pt/Ba/Al203 was found to be limited by the rate of regeneration.
21
Heaton, Stephen Nicholas. "Vinylsilane and silyl hydride complexes of platinum group metals". Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295650.
22
Totland, Marina. "Determination of the platinum group metals in geological materials". Thesis, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390298.
23
Savage, Paul David. "Organometallic compounds of rhenium and the platinum group metals". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46494.
24
Arnold, Philip M. "Coordination chemistry of platinum group metals with sulphur-containing ligands". Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249298.
25
Jeffery, Edward. "Hydrogenation of ketones over platinum group metals : a DFT study". Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54642/.
Abstract (sommario):
The enantioselective hydrogenation of a-ketoesters over a platinum surface modified by cinchona alkaloids has been studied using accurate computational modelling. A series of small prototype compounds were used to interact with the metal surface, leading to the study of acetone adsorption on a platinum surface. It was found that the enol and enolate isomers of acetone may play a crucial role in the surface chemistry. The enol form of acetone was significantly more stable than the keto-form, and the enolate form was also more stable. Vibrational frequency analysis suggests that the enolate form may prove to be a better fit to some of the experimental data than the commonly-accepted ketone form. The interaction of an a-ketoester, methyl pyruvate, with a platinum surface was then studied using the same techniques. The enol form was again the most stable surface species compared to the enolate and ketone forms. Additionally, the cis form of methyl pyruvate was generally more stable than the trans form. A full vibrational analysis was performed, allowing comparison with future experimental work. In order to investigate the conversion between the different types of isomer, an eigenvector following scheme is under development to find reaction barriers and transition states. To date, this has been applied to simpler systems with success and is in the process of being extended to more complicated applications. Concurrently, a technique to study the whole enantioselective reaction system was also being developed. This involves a modified simple QM/MM scheme containing a model for the surface, the substrate and modifier. This was successfully applied to a simple system (methyl pyruvate interacting with the surface and modifier) and yielded predicted ees in agreement with experimental observation. This was extended to a more complex system under study at Cardiff University and reproduced the experimental enantioselectivity this was then used to suggest possible improvements to enhance the ee of this system.
26
Freestone, Timothy. "Some aspects of the biocompatibility of the platinum group metals". Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316572.
27
McKenzie, S. G. "The effect of platinum group metals on duplex stainless steel". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37782.
28
Morton-Fernández, Brian. "Synthesis and characterisation of dithiolato complexes with platinum group metals". Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3556.
Abstract (sommario):
The interest in biosensors can be attributed to the first described enzyme containing sensor used to detect levels of glucose in 1962. Although research into biosensors was initially slow to pick up, the field has become increasingly popular and research has been widespread for the last 20 years. The continuing research into biosensors is crucial as this will improve current devices to become smaller, faster and more economical and yield new biosensors. This thesis is mostly concerned with the development of an integral component of a biosensor, the redox mediator. Complexes of ruthenium incorporating electron rich sulfur-donor ligands such as naphthalenedithiol should possess interesting redox qualities which could be used to produce better mediators. A second area covered in this thesis is in the structural studies of a series of iridium and rhodium complexes. Two classes of ruthenium complexes with sulfur-donor ligands have been prepared. The first class incorporates the ruthenium bis-bipyridine moiety while the second contains pentamethylcyclopentadienyl ruthenium. Most complexes synthesised exhibited reversible oxidation waves in the region of -0.1 to 0.2 V vs. Ag/Ag⁺. Their possible use as redox mediators was hindered by several factors, particularly difficulties in purification. They also exhibited oxygen sensitivity and low stability when in solution.The second area covered in this thesis is to further understand the bonding of the ligands used in the above study. A series of pentamethylcyclopentadienyl iridium and rhodium complexes were synthesised with three different dithiolato ligands. Two of the three ligands studies produced structures that included more than one metal centre leading to straining of the ligand. In order to study the monomeric form, the clusters were opened with a neutral phosphine ligand. Both the Ir…S and Rh…S bond lengths of all the complexes were within expected parameters.
29
Wilson, Andrew Matthew. "Ditopic reagents for the solvent extraction of platinum group metals". Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/16864.
Abstract (sommario):
This work aims to develop solvent extractants to recover platinum and palladium from highly acidic chloride solutions bearing other platinum group metals (PGMs). In general, metal values can be recovered by solvent extraction through three different mechanisms: metal cation extraction (1); metalate anion extraction (2); or metal salt extraction (3). Mn- + n(LH)(org) ⇌ [M(L)n](org) + nH+ (1) MClx n- + nL(org) + nH+ ⇌ [MClx(LH)n](org) (2) MClx + nL(org) ⇌ [MClxLn](org) (3) The main objective of this thesis is to establish whether ditopic extractants can be developed which have chemical functionalities that allow both mechanisms (2) and (3) to operate, co-extracting Pt(IV) and Pd(II) as their chloridometalates in an outer sphere binding site (2) and allowing their separation by raising pH to transfer the more kinetically labile Pd(II) to an inner sphere binding site (3) and releasing H2PtCl6 to the aqueous strip solution. A review of the literature is presented in Chapter 1, noting current commercially available extractants and the processes in which they are, or have been, applied. Particular attention is paid to the mode of action of the reported extractants and whether they extract metal cations, anions or metal salts. This chapter also outlines the proposed solvent extraction circuit in which new reagents developed in this thesis would be incorporated and the methods applied during the screening of candidate extractants. Chapter 2 deals exclusively with the use of reagents with inner-sphere binding sites for the selective extraction of palladium over platinum. Work on a series of oxime reagents synthesised for palladium extraction as part of preliminary MSci research (Andrew M. Wilson, MSci Thesis, University of Edinburgh, 2011) is reviewed. Studies of the hydrolytic stability of oximes indicate that they are unsuitable for incorporation into ditopic reagents for use in a circuit with a highly acidic feed solution. Thioethers were studied as alternatives as they show high kinetic selectivity for palladium over platinum and are more stable under acidic conditions. The synthesis and extraction properties of model reagents (largely arylalkyl thioethers) are reported and compared with those of the commercially available di-n-hexylsulfide. Incorporation of a polar group such as an amide provides phase transfer catalysis, accelerating the rate of transport of Pd(II) into the organic phase, but reducing selectivity over Pt(IV). The identification of functionalities that operate as receptors for chloridometalates by forming outer-sphere assemblies is explored in Chapter 3. The synthesis of amine, amide and amino-amide extractants from acid chloride streams and the effects of variations of functional groups on the extraction of PtCl6 2− are described. Secondary amides were found to be stronger extractants than tertiary amides, and aliphatic amides also show better metalate extraction than aromatic amides. The interactions between protonated aminoamide reagents and PtCl6 2− werre analysed by X-ray crystallography, noting that C-H∙∙∙Cl interactions with the “soft” chloridometalate anion are more common than with the “hard” chloride ion which shows a preference for more conventional N-H∙∙∙Cl interactions. Chapter 4 combines the reagent types explored in Chapters 2 and 3, in ditopic extractants that have both inner- and outer sphere binding sites. The synthesis and characterisation of a series of thioether amide reagents are reported and the selective extraction of platinum and palladium over other PGMs are discussed. In-house screenings of aryl- and alkylthioetheramide extractants showed selective co-extraction of Pd(II) and Pt(IV), rejecting Ir(III). Pt(IV) can be selectively water-stripped followed by ammonia-stripping of Pd(II). Industrial screenings at Johnson Matthey Technology Centre further exemplified the selectivity of these extractants over Ru(III) and Rh(III), although third phases were formed when the reagents were used for recovery from highly concentrated metal-feed solutions. The mode of action of the ditopic extractants is discussed, based on DFT calculations, crystal structure determinations and NMR studies, which support the formation of outersphere metalate assemblies and inner-sphere palladium complexes. Chapter 5 describes new difunctional (inner + outer sphere complexation) extraction by a single chemical entity, in this case an unsaturated N-heterocycle (an azole). The synthesis and characterisation of a series of hydrophobic azoles are described. These have basicities which allow protonation when contacted with strongly acidic solutions (2), but can be deprotonated in contact with water to allow their neutral forms to form inner-sphere complexes with Pd(II). Triazole-based reagents show the selective co-extraction of Pt(IV) and Pd(II) and, as with the ditopic thioetheramide reagents reported in Chapter 4, allow the selective water stripping of Pt(IV) and subsequent ammonia stripping of Pd(II).
30
Flynn, Allison. "Transition metals as anti-tumoral agents : some structure-function relationships of the platinum group metals /". Master's thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-03022010-020016/.
31
Kaukonen, R. (Risto). "Sulfide-poor platinum-group element deposits:a mineralogical approach with case studies and examples from the literature". Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514289545.
Abstract (sommario):
Abstract
Sulfide-poor deposits of platinum-group elements (PGE) occur in two main types: silicate-type and oxide-type. In the silicate-type mineralization PGE form discrete platinum-group minerals (PGM) that occur as inclusions in various silicate minerals. In the oxide-type mineralization PGM may have different modes of occurrence. They may be associated with silicates or they may occur as inclusions in chromite, magnetite or ilmenite, for example. In some cases they may even be associated with base metal sulfides.
The approach chosen in this work is mainly a mineralogical one. PGM parageneses, their modes of occurrence and associations with other minerals were studied from different deposits. These are then compared to some well-recorded examples of PGE deposits.
The case studies presented, the Duluth Complex in Minnesota, U.S.A., the Hanumalapur Complex in Karnataka, India, and the Penikat Layered Intrusion in northern Finland, are examples that illustrate the multitude of possibilities regarding PGE mineralization versus the traditional approach where any significant quantities of PGE are supposed to occur only in association with base metal sulfides.
As the traditional orthomagmatic and hydrothermal models cannot explain the genesis of some sulfide-poor PGE occurrences, a new theory of PGE mineralization was developed. This “redox theory” is an attempt at explaining the association of PGE with various oxide minerals, most importantly chromite.
32
Shi, Peipei. "Geochemical assessment of the bioavailability of platinum group metals for phytomining". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57880.
Abstract (sommario):
Phytomining is suggested as a novel technology to obtain platinum group metals (PGMs) nanoparticles from plants grown on the mineralized soil, rock, or on mine wastes. The primary determinant of metal uptake by a plant is the bioavailability of the metal in the soil-plant system. In this thesis project, the bioavailability of PGMs of several PGM-rich materials is assessed with respect to phytomining. Notably, feed, concentrate and tailings from North American Palladium (NAP) in Canada, and two gossan samples from Broken Hill (BH) mineral complex in Australia are assessed in the context of phytomining. Geochemical techniques are used to obtain the mineralogy, the total concentration of PGMs, and concentrations of PGMs extracted by chemicals. These methods assess the bioavailability of PGMs in the samples and enable the estimation regarding the available concentrations of Pd, Pt, Au and Cu to plants. Soil-associated factors such as pH, salinity (EC), and cation exchange capacity (CEC) have been shown to influence indirectly the bioavailability of PGMs. Thus, soil-associated factors were analyzed. Additionally, a selection model for the substrate of phytomining is proposed. The criteria for choosing substrate for the phytomining of Pd include available Pd concentration, pH, EC, CEC and available Cu concentration. This thesis concludes that the PGM species that can be extracted by ammonium acetate are the best indicators of their natural availability to plants. Those PGMs that can be extracted by fulvic acid and citrate-dithionite are good indicators as they can be soluble in soils. According to the selection model, the available Pd concentration of BH gossan 1 is higher than 2 mg/kg. Its low EC, high CEC, and proper pH make it a suitable substrate for plant growth. It is the best “one” of the five samples for phytomining of Pd. One thing to note is that high Cu-tolerant plant species should be chosen to grow on BH gossan 1 due to its high Cu concentration available to plants.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
33
Wright, Edward Anthony. "A study of the hydrogen evolution reaction on platinum group metals". Thesis, University of Exeter, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414258.
34
Morales-Morales, David. "New sulphur complexes of platinum group metals as potential homogeneous catalysts". Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242265.
35
Javu, Bulelwa Patricia. "Multi-component Platinum Group Metals for the methanol electro-oxidation process". University of the Western Cape, 2018. http://hdl.handle.net/11394/6571.
Abstract (sommario):
>Magister Scientiae - MScThe purpose of this study was to develop a high performance-lower cost catalyst to be applied in Direct Methanol Fuel Cells (DMFC). The study also aimed to prepare plurimetallic supported platinum (Pt), platinum-ruthenium (PtRu), platinum-ruthenium-vanadium (PtRuV) and platinum ruthenium-vanadium-iron (PtRuVFe) upon multi-walled carbon nanotube (MWCNT) as well as upon multiwalled carbon nanotube-titanium oxide (MWCNT/TiO2) supports. Platinum is very active but prone to poisoning by carbon monoxide (CO), which may be present in the fuel used in fuel cells. The focus on the use of methanol was because of its better reaction kinetics, and better performance in direct methanol fuel cells (DMFC) better than proton exchange membrane fuel cell (PEMFC). When Pt is alloyed with another platinum group metals (PGM) the alloying decreases the over-potential for reactions critical in the fuel cells. Proton exchange membrane fuel cell (PEMFC) performance may be improved at low metal loading, when supported pluri-metallic catalysts are applied since the trimetallic catalysts may promote high catalyst utilisation. In practice, DMFC require electrodes with a Pt loading to achieve acceptance fuel cell (FC) power performance. The aim of this study was therefore the reduction of the catalyst loading through further improvement of mass activity of Pt based catalysts by partial substitution of the noble metal/metals, and the use of a carbon support that will provide high surface area, good electrical conductivity and high stability. MWCNT supported pluri-metallic (PtRuVFe,) and bimetallic (PtRu) nanoparticles possessed characteristic of increased surface area, improved electron transfer rate, enhance electro-catalytic activity and promoted stability.
36
McInnes, Eric J. L. "Physico-chemical studies of coordination complexes of the platinum group metals". Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/12617.
Abstract (sommario):
This thesis is concerned with the electrochemistry and spectroscopy of redox-active late transition metal complexes of the 2,2'-bipyridine ligand (bpy) and their reduction products. Complexes of general formula [Ph(4,4'-X2-bby)L2] (where L is a non redox-active ligand and X = NH2, OEt, Me, H, Ph, C1, CO2Me) undergo two one-electron reductions as revealed by cyclic voltammetry. The absorption spectra of the one-electron reduction products reveal the first of these reductions to be localised on the bpy ligand giving rise to radical anion ligand complexes of Pt(II). Epr spectra of the reduced, seventeen-electron species indicate a significant (ca. 10%) admixture of metal 5d orbitals in the SOMO, in good agreement with EHMO calculations. Both the E1/2 value of the first reduction process and the MLCT νmax value vary linearly with the Hammett parameter of the substituent X. The second reduction electron spin-pairs with the first in the same π* orbital. The LUMO of [Pd(4,4'-X2-bpy)C12] is Pd 4d based and these complexes undergo irreversible two-electron reductions. Complexes of the 4,4'-(NO2)2-bpy ligand undergo up to four one-electron reductions. Epr spectroscopy of the di-reduction products of [M(4,4'-(NO2)2-bpy)L2] (M = Pd, Pt, L = C1; M = Rh, L2 = 1,5-cod) shows that spin-triplet species are formed on di-reduction and consequently that the LUMO-SLUMO gap is smaller than the spin-pairing energy for these complexes. The redox-active orbitals are highly localised on the nitro-groups. EHMO calculations are in good agreement. [Pt)bpy)2]2+ undergoes a redox-induced dimerisation reaction at room temperature. Low-temperature cyclic voltammetry reveals the redox-active orbital to be bpy-based. The single-crystal structures of [Pt(4,4'-(NO2)2-bpy)C12] and [Au(bpy)C12]BF4 are reported.
37
Zhou, Yi. "Platinum group metals catalyzed steam methane reforming via micro-channel reactor". Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/8703.
Abstract (sommario):
Includes bibliographical references.Steam methane reforming is a well-established industrial process used for generating hydrogen and synthesis gas. By performing this reaction in micro-channel reactors it is possible to take advantage of increased heat and mass transfer rates, allowing equipment size and residence times to be decreased by an order of magnitude which, in turn, leads to the possible utilisation of small scale steam reformers for portable fuel cell power systems. In this study, two commercial steam reforming catalysts, namely catalysts YR and XR, and a single in-house synthesised Rh/Al2O3 catalyst were studied in both packed bed and microchannel reactor configurations. All these catalysts exhibited stable activity in the packed bed reactor experiments.
38
Surakitbanharn, Yosyong. "The efficient separation of platinum group metals using centrifugal partition chromatography". Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186074.
Abstract (sommario):
Centrifugal Partition Chromatography (CPC) is a multistage liquid-liquid countercurrent distribution technique which utilizes rotating teflon cartridges to hold a liquid phase stationary while the other liquid phase is pumped at a constant flow rate. It has been demonstrated to be a valuable technique for the base line separations of families of metal ions such as the platinum group metals (PGM)--Pt, Pd, Rh and Ir. The separations of these metals as their anionic chloro complexes were achieved using the heptane-water phase pair with a stable and relatively inexpensive extractant trioctylphosphine oxide (TOPO) functioning as a ligand in its neutral form and as a cation in its protonated form. A striking feature of the chromatograms of the complexes and ion pairs were their much poorer efficiencies compared to the efficiency of an organic analyte like 3-picoline under identical distribution rations. The inefficiencies of the PGM separations were also a function of the concentrations of the aqueous and organic phase components. These inefficiencies could be attributed to slow kinetics of the back extraction of the complexes and ion pairs and could be used to derive the mechanisms of these slow chemical kinetic steps. A correlation was established for the Pd(II) system between the CPC inefficiencies and the half lives of the slow reactions measured independently by stopped flow in micelles. This correlation was utilized to derive the rate constants for the back extraction of the TOPO complexes and ion pairs of Pt and Ir. The mechanisms of the extraction reactions were derived using the principle of microscopic reversibility based on the mechanisms of the back extraction reactions. This was then used to obtain estimates for the rate constants for the extraction reactions as well. The PGM were thus separated and their equilibrium and kinetics (extraction and back extraction) completely characterized using CPC. This is a significant development with CPC because such complete equilibrium and kinetic characterizations are hard to achieve with conventional liquid chromatographic techniques.
39
Wang, Sherrie Fang. "The coordination chemistry of tripodal phosphine chalcogenide ligands with platinum group metals". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ34289.pdf.
40
Mwase, James Malumbo. "Hydrometallurgical extraction of platinum group metals from a low-grade ore concentrate". Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/8966.
Abstract (sommario):
Includes bibliographical references (leaves 143-153).The aim of this study is to investigate the economic and technical feasibility of processing platinum group metals (PGMs) and base metals (BMs) from a low-grade ore concentrate produced in the concentrator plant at Lonmin Pic. The PGMs of particular interest are platinum, palladium, ruthenium and rhodium, while the BMs of interest are copper and nickel. The ore concentrate, as a by-product, represents only 5 % of the total PGM value but as much as 70 % of the total tonnage of material processed in the concentrator plant. Further upgrading this material is not considered a viable route. However, even this low PGM content in the concentrate material accumulates to appreciable value on an annual basis motivating the need to develop alternative methods of extracting value from it. Initial estimates indicate that extraction levels of at least 50 % of the PGMs and 50 % of the BMs would need to be achieved, using low cost hydrometallurgical processes, to make the venture economically viable. These methods would exclude treatment via the smelter and pressure leaching: which are costly. energy intensive and result in leaching of large quantities of non-valuable elements. Previous studies revealed that organic acids had the potential to economically extract the PGMs under alkaline conditions, and BMs under acidic conditions, from various ores and concentrate materials. A literature survey confirmed that certain organic acids can be used to leach metals from ores and concentrates via chemical complexation. It further revealed that other chemical agents. namely cyanide, thiosulphate and bisulphide, were similarly capable of strongly complexing PGMs under various conditions of pH and temperature. The survey also revealed industrially established methods for extracting BMs from low-grade ores and concentrates. Based on this material, this study experimentally evaluated these options with the intent to propose a flowsheet to treat the concentrate material. This was conducted in two phases of experimental work.
41
Chatterjee, Sayandev. "Cooperative Two-Electron Reagents of Lower Transition Metals of Group 10". University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250266435.
42
Nassar, Roger Abdo. "Coordination of some monodentate and hybrid multidentate phosphine ligands to platinum group metals". Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30050.
Abstract (sommario):
A range of low-valent late transition-metal triarylphosphine complexes have been prepared and characterised by a combination of 1H, 31P and 19F (as appropriate) NMR and IR spectroscopies and mass spectrometry. Some of these complexes have been isolated as single crystals and characterised by X-ray diffraction. The triarylphosphine ligands used in this study were P(4-CH3OC6H4)3, P(4-HOC6H4)3, P(2-CH3OC6H4)3, PPh2(2-CH3OC6H4), P(2-HOC6H4)3 and PPh2(2-C2H3C6H4) whilst the transition-metals were platinum(II), palladium(II), rhodium(I), rhodium(III), osmium(II) and ruthenium(II). This work has shown that the former four phosphine ligands act as monodentate ligands whilst the last two ligands act as hybrid multidentate ligands. The metal complexes of the ortho-hydroxy substituted ligand exhibit fluxional behaviour in solution, where the phosphine is interchanging between mono- and bi-dentate modes of coordination. In contrast, fluxionality has not been observed in the case of the ortho-vinyl substituted ligand. A set of platinum(II)-, osmium(II)- and ruthenium(II)-fluoride triarylphosphine complexes have been prepared and characterised. The electron-donating substituents in the phosphine strengthen the metal-phosphine and metal fluoride bonds as compared to those for the non-substituted triarylphosphine ligand, PPh3. Furthermore, these substituents affect the geometry at the metal centre in these complexes. In the reactions of P(2-HOC6H4)3 with [Pt(-F){P(4-CH3OC6H4)3}2]2 or [M(-F)F(CO)3]4 (M = Os, Ru), metal chelates are formed by the displacement of fluoride by phenoxide and liberation of HF, whereas, in the related reactions, the ortho-vinyl substituted ligand acted in a monodentate mode.
43
Bernardis, Francesco Luigi. "Development of novel chromatographic media for the separation of the platinum-group metals". Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410220.
44
Murray, Angela Janet. "Recovery of platinum group metals from spent furnace linings and used automotive catalysts". Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/7210/.
Abstract (sommario):
The availability of finite resources is uncertain due to the worldwide increase in population growth and global industrialisation. Consequently, there is a pressing need for substitutive replacements and methods of replenishing stocks by recycling. The platinum group metals (PGMs) are rare, expensive elements with an unpredictable supply chain and a wide range of industrial applications for which there are often no substitutes. Mining from primary ores is environmentally damaging; hence recycling is vital to minimise losses and maintain stock at sustainable levels. This work investigates the feasibility of recovering PGMs from secondary waste sources and bioconverting them into new catalysts, circumventing the current environmentally polluting and energy expensive pyrometallurgical processing. Two secondary sources of PGMs were examined: scrap automotive catalysts and spent furnace refractory lining. This study shows a route to improve PGM recycling from secondary waste sources and, further, the potential to produce a catalytically active end product without the need for traditional refining.
45
Tsoureas, Nikolaos. "Synthesis of phosphine - and pyridine - functionalised N-heterocyclic carbene complexes of platinum group metals". Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494717.
46
Brothwood, Susan. "Vehicle related emissions of platinum group elements and other heavy metals in the urban environment". Thesis, Aberystwyth University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289175.
47
Mulwanda, James. "Recovery of dissolved platinum group metals from a pregnant copper sulphate leach solution by precipitation". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86538.
Abstract (sommario):
Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: In Base Metal Refineries (BMRs), the copper sulphate leach solution produced during the final pressure leaching stage contains impurities such as selenium and tellurium, as well as other precious metals (OPMs, namely Rh, Ru, and Ir). Se and Te are removed by precipitation with sulphur dioxide prior to electrowinning of Cu. While a small percentage of the dissolved OPMs precipitate with the Se and Te, the largest portion remains in solution and is recycled to the first stage leach. If a larger portion of the OPMs in solution can be recovered in the Se/Te precipitation stage, OPM losses and the OPM inventory of the plant can be reduced. The aim of this project was to determine operating conditions that would allow maximum OPM recovery with minimal Cu and Ni co-precipitation in the Se/Te removal section of a BMR. The effects that the operating temperature, pressure, stirring rate, reagent type, and reagent quantity have on the metal precipitation behavior and precipitate characteristics were determined experimentally. Thio-urea and sulphurous acid were evaluated as precipitation reagents for temperatures of 80°C and 160°C, stirring rates of 250 rpm and 500 rpm, and pressures equal to ambient pressure and 7 bar. 200 % and 320 % excess thio-urea and 720 % and 960 % excess sulphur dioxide were used. The precipitation of OPMs with sulphur dioxide was generally poor; the maximum percentage Rh, Ru, and Ir precipitated were 35 %, 18 %, and 20 %, respectively. It was, however, found that the OPM precipitation increased as the reagent amount was increased. Increasing the temperature further increased Rh and Ir precipitation but affected the Ru precipitation negatively. Thio-urea precipitated virtually all of the Rh contained in the solution irrespective of the values of the process variables studied. As was the case with sulphur dioxide, increasing the amount of thio-urea added resulted in increased Ru and Ir precipitation, while higher temperatures favored Ir precipitation but not Ru precipitation. The maximum percentage Ru and Ir precipitation achieved with thio-urea were 87 % and 60 %, respectively. Complete Se precipitation was observed at all process conditions, while Te precipitation increased as the operating temperature and the reagent quantity were increased. Maximum Te precipitation of 98 % and 90 % were achieved when using 320 % excess thio-urea and 960 % sulphurous acid quantities, respectively, at 160°C and a stirring rate of 250 rpm. Increasing the reagent quantity and temperature did, however, also result in increased copper and nickel precipitation. The statistical analysis of the results allowed regression models to be fitted to predict the percentage metal precipitation as a function of the investigated process variables. These models were used to define an objective function to determine the optimal operating conditions. A temperature of 80oC, a pressure of 7 bar, and 200 % excess thio-urea were proposed as the optimum operating conditions that would yield 98 % Rh, 75 % Ru, and 48 % Ir precipitation with less than 5 % Cu and Ni co-precipitation. Experimental validation tests confirmed the model predicted values and proved repeatability of the experimental data.
AFRIKAANSE OPSOMMING: Die kopersulfaat logingsoplossing wat tydens die finale drukloging stadium in Basis Metaal Raffinaderye (BMRe) produseer word, bevat onsuiwerhede soos selenium en tellurium sowel as ander edelmetale (AEMe, naamlik Rh, Ru, en Ir). Se en Te word voor Cu elektrowinning verwyder deur middel van presipitasie met swaweldioksied. Alhoewel ʼn klein persentasie van die opgeloste AEMe saam met die Se en Te presipiteer, bly die grootste gedeelte in oplossing en word gevolglik na die eerste loging stadium hersirkuleer. AEM verliese en die AEM inventaris van die aanleg kan verminder word indien ʼn groter gedeelte van die AEMe in die Se/Te presipitasie stadium herwin kan word. Die doel van hierdie projek was om bedryfstoestande te bepaal om maksimum AEM herwinning met minimale Cu en Ni kopresipitasie in die Se/Te verwyderingseksie van ʼn BMR te behaal. Die effekte wat bedryfstoestande soos temperatuur, druk, roerder tempo, tipe reagens, en hoeveelheid reagens op die metaal presipitasiegedrag en presipitaat eienskappe het, is eksperimenteel bepaal. Tio-ureum en swaweligsuur is evalueer as presipitasie reagense vir temperature van 80°C en 160°C, roerder tempo’s van 250 rpm en 500 rpm, en drukke gelyk aan omgewingsdruk en 7 bar. 200 % en 320 % oormaat tio-ureum en 720 % en 960 % oormaat swaweldioksied is gebruik. Die presipitasie van AEMe met swaweldioksied was swak in die algemeen; die maksimum persentasie Rh, Ru, en Ir presipitasie wat behaal is, is 35 %, 18 %, en 20 %, onderskeidelik. Daar is egter gevind dat die AEM presipitasie toeneem indien die hoeveelheid reagens toeneem. ʼn Toename in die temperatuur het verder tot ʼn toename in Rh en Ir presipitasie gelei, maar dit het Ru presipitasie negatief affekteer. Tio-ureum het basies al die Rh in oplossing laat presipiteer, ongeag die waardes van die ander prosesveranderlikes wat ondersoek is. Soos wat die geval vir swaweldioksied was, het ʼn toename in die hoeveelheid tio-ureum ʼn toename in die Ru en Ir presipitasie tot gevolg gehad, terwyl hoër temperature Ir presipitasie bevoordeel en Ru presipitasie benadeel het. Die maksimum persentasie Ru en Ir presipitasie wat met tio-ureum behaal is, is 87 % en 60 %, onderskeidelik. Volledige Se presipitasie is by alle proses toestande waargeneem, terwyl Te presipitasie toegeneem het soos wat die temperatuur en die hoeveelheid reagens toegeneem het. Maksimum Te presipitasie van 98 % en 90 % is behaal toe 320 % oormaat tio-ureum en 960 % oormaat swaweligsuur, onderskeidelik, by 160°C en ʼn roerder tempo van 250 rpm gebruik is. ʼn Toename in die hoeveelheid reagens en die temperatuur het egter ook meer koper en nikkel presipitasie tot gevolg gehad. Die statistiese analise van die resultate het dit moontlik gemaak om regressie modelle te pas om die persentasie metaal presipitasie as ʼn funksie van die ondersoekte veranderlikes te voorspel. Hierdie modelle is gebruik om ʼn doelfunksie te definieer ten einde die optimale bedryfstoestande te bepaal. ʼn Temperatuur van 80°C, ʼn druk van 7 bar, en 200 % oormaat tioureum is voorgestel as die optimale bedryfstoestande wat 98 % Rh, 75 % Ru, en 48 % Ir presipitasie met minder as 5 % Cu en Ni kopresipitasie tot gevolg sal hê. Eksperimentele geldigheidsbepalingtoetse het die waardes wat deur die modelle voorspel is bevestig en die herhaalbaarheid van die eksperimentele data bewys.
48
Hyman, Matthew P. "A theoretical study of the electrocatalytic oxygen reduction reaction and related reactions on platinum group metals". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273680.
49
Monahan, Jennifer L. "Skeletal Pathology of Tibiotarsi in Chick Embryos Exposed to Platinum Group Metals by Micro-Raman Spectroscopy". Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1278554763.
50
Mack, Cherie-Lynn. "Screening of technologies for the recovery of rhodium (III) metal ions from a precious metal refinery wastewater". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1004046.
Abstract (sommario):
The selective recovery of rhodium from wastewaters, in which the metal would be otherwise lost, would be highly profitable if the process were suitably low-cost. Current recovery processes are generally high maintenance and high-cost, whereas biological processes can be engineered to run with little external input in terms of cost and maintenance. Three emerging technologies were chosen based on their reported efficiency when removing base metals from wastewaters. The first technology screened, the sulphide-extraction membrane bioreactor (SEMB), consists of a sulphate-reducing prokaryote (SRP) anaerobic digester, in which a silicone membrane is submerged. Wastewater is passed through the membrane and metal ions are precipitated as metal sulphides by the hydrogen sulphide gas, which is capable of permeating the membrane. The second technology screened was a fluidized sand bed reactor in which metal ions are removed from solution via induction of nucleated precipitation by sodium carbonate onto the sand grains. The third, and most well established removal technology screened was a biosorption system using immobilized Saccharomyces cerevisiae biomass as the biosorbent. Experimental trials with each technology highlighted drawbacks with each; the SEMB system proved to be largely ineffective when challenged with the removal of rhodium from the wastewater as the rhodium precipitate fouled the membrane within hours, the fluidized bed system seemed unable to overcome the acidity of the wastewater and thus could not precipitate out the rhodium metal, and the efficiency of the biosorption process was hampered by the diversity of rhodium species present in the wastewater, which reduced the amount recovered. The outcomes of the trials with each technology indicated that further optimization of the technology or pretreatment of the wastewater is necessary before any of these options can be implemented. It could be concluded, however, that despite further optimization, both the SEMB and the fluidized bed system were not applicable in this case as precipitation would be non-specific, resulting in the necessity for further steps in order to purify the rhodium ions. Hence, the biosorption system was shown to be most applicable, and further optimization of the system could yield a highly efficient rhodium recovery process.