Página 1 dos resultados de 95 itens digitais encontrados em 0.009 segundos

‣ Platinum Group Minerals in Eastern Brazil GEOLOGY AND OCCURRENCES IN CHROMITITE AND PLACERS

Angeli, Nelson
Fonte: Johnson Matthey Publ Ltd Co Publicador: Johnson Matthey Publ Ltd Co
Tipo: Artigo de Revista Científica Formato: 41-53
Português
Relevância na Pesquisa
48.57862%
Brazil does not have working platinum mines, nor even large reserves of the platinum metals, but there is platinum in Brazil. In this paper, four massifs (mafic/ultramafic complexes) in eastern Brazil, in the states of Minas Gerais and Ceara, where platinum is found will be described. Three of these massifs contain concentrations of platinum group minerals or platinum group elements, and gold, associated with the chromitite rock found there. In the fourth massif, in Minas Gerais State, the platinum group elements are found in alluvial deposits at the Bom Sucesso occurrence. This placer is currently being studied.

‣ New extractants for separation of platinium-group metals from chloride solutions and their application to recycling processes

Paiva, A. P.; Carvalho, G. I.; Schneider, A. L.; Costa, M. Clara; Costa, A. M.; Assunção, A. F.; Nogueira, C. A.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 10/09/2012 Português
Relevância na Pesquisa
88.82605%
In this paper some results on the application of four N,N’-tetrasubstituted malonamide derivatives for the extraction and separation of platinum-group metals (PGMs) are presented. The above mentioned extractants were specifically synthesized in order to evaluate their efficiency for the extraction of a specific metal, or group of metals, from aqueous chloride matrices. Different behaviours were obtained towards platinum(IV) and/or palladium(II) extraction, all the N,N’-tetrasubstituted malonamide derivatives allowing the mutual separation of the two metal ions, depending on the HCl concentration. Generally, extraction experiments were carried out involving initial aqueous phases containing 100 mg/L of each metal isolate, in varying 1M to 8M HCl concentration ranges, and 0.05M extractant in 1,2- dichloroethane solutions. From the preliminary results obtained, one can conclude that HCl concentrations and the structure of the malonamide derivative play a crucial role on the efficiency shown for Pt(IV) and/or Pd(II) extraction. The efficiency of the stripping stage of the loaded organic phases is variable, depending on the N,N’-tetrasubstituted malonamide derivative, as well as on the metal ion involved; for Pt(IV), distilled water and 1M HCl were generally successful...

‣ Recovery of platinum(IV) and palladium(II) from complex hydrochloric acid matrices by a thiodiglycolamide derivative

Paiva, A. P.; Carvalho, G. I.; Costa, M. Clara; Costa, Ana M. Rosa da; Nogueira, C. A.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2014 Português
Relevância na Pesquisa
57.94592%
The solvent extraction performance of N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) towards Pt(IV) and Pd(II) in HCl solutions has recently been published. It was shown that these two platinum-group metals (PGMs) are efficiently extracted from 8 M HCl aqueous phases, being subsequently separated by sequential strippings: 1 M HCl allows Pt(IV) recovery, whereas Pd(II) is only back-extracted by thiourea in HCl. In this work, selectivity tests were carried out to evaluate the performance of DMDCHTDGA towards the recovery of both PGMs, from 8 M HCl aqueous phases, when in presence of Rh(III), Fe(III), Ni(II), Zn(II), Al(III), Ce(III) and Zr(IV), simulating the leaching solutions that may result from the hydrometallurgical treatment of spent automobile catalytic converters. It was generally observed that the additional metal ions do not affect the recovery of Pd(II) and Pt(IV) by DMDCHTDGA. Fe(III), Zn(II) and Zr(IV) are co-extracted with Pt(IV) and Pd(II); Fe(III) and Zn(II) were efficiently scrubbed with water, whereas Zr(IV) was removed by an acidified aqueous solution. Inversely, Ni(II) is not extracted, and Rh(III) and Ce(III) appear only traceably in the loaded organic phase. Al(III) is a concern, as it is appreciably extracted...

‣ IgE antibody responses to platinum group metals: a large scale refinery survey.

Murdoch, R D; Pepys, J; Hughes, E G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1986 Português
Relevância na Pesquisa
48.663325%
All 306 South African platinum refinery workers (116 white, 190 coloured) accepted for employment on grounds of absence of evidence of atopy were investigated using the skin prick test and RAST to detect sensitivity to platinum, palladium, and rhodium salts. RAST studies were made for these, together with HSA and DNP-HSA RAST. Of the 306 workers, 38 had a positive skin prick test to the platinum halide salts; of these, one gave a positive reaction to the palladium salt and six to the rhodium salt. There were no isolated positives to the rhodium and palladium halide salts. Total IgE levels were raised in 24 of the 38 (63%) platinum salt prick test positive workers compared with only 43 of the 268 (16%) prick test negative group (p less than 0.001). Positive RASTs were obtained in 62% of those with positive skin tests to the platinum salts. Four of the six giving positive rhodium salt skin tests gave a positive RAST to rhodium salt. Of these, two gave positive RASTS to HSA and all four to DNP-HSA. The palladium salt RAST was negative in the single skin test reactor. In the platinum salt skin test positive group a raised HSA RAST was obtained in 10.5% compared with only 2.5% in the skin negative group. Twenty one per cent of the platinum salt skin positive group had a raised RAST score to DNP-HSA with only 3.5% (4/116) in the skin test negative group...

‣ Part I. Pseudomonas aeruginosa apo azurin and its mutants as mononuclear metal scaffolds. Part II. A stable nickel phosphine catalyst for homogeneous photogeneration of hydrogen from aqueous solutions; Pseudomonas aeruginosa apo azurin and its mutants as mononuclear metal scaffolds. Part II. A stable nickel phosphine catalyst for homogeneous photogeneration of hydrogen from aqueous solutions; Part II. A stable nickel phosphine catalyst for homogeneous photogeneration of hydrogen from aqueous solutions; A Stable nickel phosphine catalyst for homogeneous photogeneration of hydrogen from aqueous solutions

McLaughlin, Matthew P. (1983 - ); Holland, Patrick L.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xv, 142 leaves; Illustrations:ill. (some col.)
Português
Relevância na Pesquisa
48.888457%
Thesis (Ph. D.)--University of Rochester. Dept. of Chemistry, 2012.; In the first part of the thesis, wild type and mutant versions of Pseudomonas aeruginosa apo azurin were expressed, purified, and explored as mononuclear metal scaffolds. Despite the prolific success of non-heme iron in bioinorganic and organometallic chemistry, utilizing proteins as an artificial scaffold for iron is a largely unexplored area. Chapter 1 describes using wild type and M121A apo azurin as low-coordinate iron scaffold. The 1:1 iron complexes were characterized by a combination of electronic absorption, Mössbauer, and NMR spectroscopies, and X-ray crystallography. The available characterization indicated that both have a high-spin iron(II) in a distorted tetrahedral environment. Uncharacteristically, the iron(II) complexes do not react with chemical redox agents to undergo oxidation or reduction. The cavity created by the M121A mutant creates space for reversible binding of azide and cyanide anions to the iron(II) center. These studies indicate that protein engineering is a viable strategy for introducing a reactive iron(II) binding site in azurin. Chapter 2 was motivated by the unparalleled catalytic activity of the platinum group metals and the surprisingly limited amount of work with platinum group protein complexes. The work describes the H117G apo azurin mutant as a mononuclear scaffold for palladium(II) and platinum(II). Both metals show strong 1:1 binding to the apo protein at the copper site. Each complex has strong metal binding at the vacant copper site...

‣ The role of late sulfide saturation in the formation of a Cu- and Au-rich Magma: Insights from the Platinum Group Element Geochemistry of Niuatahi-Motutahi Lavas, Tonga Rear Arc

Park, Jung-Woo; Campbell, Ian H.; Kim, Jonguk; Moon, Jai-Woon
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
68.167666%
Magmas enriched in Cu and Au are likely to be the most prospective for magmatic–hydrothermal deposits of these metals. However, the mechanism that leads to the formation of metal-rich magmas is not well constrained. We report major, trace and platinum group element (PGE) data for the Niuatahi–Motutahi lavas, Tonga rear arc, with the aim of studying their petrogenesis with special emphasis on the evolution of chalcophile elements during magmatic differentiation. Major and trace element contents, including S and Cl, were also measured in glasses, phenocrysts and melt inclusions to complement the whole-rock data. The Niuatahi–Motutahi lavas are associated with Cu and Au mineralization and therefore provide an opportunity to investigate the characteristics of an ore-associated magmatic system. They show a wide compositional variation from basalts to dacites with MgO contents that vary between ∼14 and 1 wt %. The dacites can be subdivided into high-K and low-K dacites. Geochemical modeling and their mineralogy suggest that the low-K dacites are comagmatic with the basalts and evolved by fractional crystallization. Copper, Au and Pd behave incompatibly in the basalts and andesitic glasses, whereas they become compatible in the low-K dacite. In contrast...

‣ Proposta de método para determinação de Pt em sangue total visando o uso como biomarcador de exposição ambiental por veículos automotivos; A method for determination of Pt in whole blood in order to use as biomarker of environmental exposure by automotive vehicles.

Santos, Leandro Mota
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/06/2015 Português
Relevância na Pesquisa
48.422656%
Reflexo de um modo de vida que exige locomoção rápida e com um mínimo de conforto, atualmente, nas grandes metrópoles, há um grande número de veículos em circulação que emitem gases poluentes (hidrocarbonetos, CO e óxidos de nitrogênio - NOx). Para minimizar a emissão desses gases, os carros atuais são dotados de conversores catalíticos, formados pelos metais do grupo da platina, com a finalidade de converter gases nocivos em gases menos agressivos ao ambiente e ao homem. Porém, esses elementos constituintes dos conversores catalíticos podem ser expelidos para o ambiente, na forma de materiais particulados em suspensão, por volatilização ou junto com os gases da combustão. Desta forma, esses elementos podem acumular-se nos mais diversos ambientes. A utilização de amostras biológicas, tal como sangue, na investigação e no controle à exposição de elementos nos seres humanos vem sendo praticada há muito tempo. Estudos com materiais biológicos apontam que as concentrações de metais do grupo da Platina estão na ordem de ng/kg. Tais níveis de concentração representam um grande desafio para a Química Analítica, pois são muito baixos para que se tenham resultados com boa precisão e exatidão nas análises...

‣ Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal–nitrogen coordination

Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 10/06/2015 Português
Relevância na Pesquisa
58.49888%
Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon–nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

‣ Noble metals in oncology

Markowska, Anna; Kasprzak, Bartosz; Jaszczyńska-Nowinka, Karolina; Lubin, Jolanta; Markowska, Janina
Fonte: Termedia Publishing House Publicador: Termedia Publishing House
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.422656%
Worldwide research groups are searching for anticancer compounds, many of them are organometalic complexes having platinum group metals as their active centers. Most commonly used cytostatics from this group are cisplatin, carboplatin and oxaliplatin. Cisplatin was used fot the first time in 1978, from this time many platinum derivatives were created. In this review we present biological properties and probable future clinical use of platinum, gold, silver, iridium and ruthenium derivatives. Gold derivative Auranofin has been studied extensively. Action of silver nanoparticles on different cell lines was analysed. Iridium isotopes are commonly used in brachyterapy. Ruthenium compound new anti-tumour metastasis inhibitor (NAMI-A) is used in managing lung cancer metastases. Electroporation of another ruthenium based compound KP1339 was also studied. Most of described complexes have antiproliferative and proapoptotic properties. Further studies need to be made. Nevertheless noble metal based chemotherapheutics and compounds seem to be an interesting direction of research.

‣ A high-throughput ab initio review of platinum-group alloy systems

Hart, Gus L. W.; Curtarolo, Stefano; Massalski, Thaddeus B.; Levy, Ohad
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
58.67238%
We report a comprehensive study of the binary systems of the platinum group metals with the transition metals, using high-throughput first-principles calculations. These computations predict stability of new compounds in 38 binary systems where no compounds have been reported in the literature experimentally, and a few dozen of as yet unreported compounds in additional systems. Our calculations also identify stable structures at compound compositions that have been previously reported without detailed structural data and indicate that some experimentally reported compounds may actually be unstable at low temperatures. With these results we construct enhanced structure maps for the binary alloys of platinum group metals. These are much more complete, systematic and predictive than those based on empirical results alone.; Comment: 24 pages, 12 figures

‣ Recovery of precious metals from exhausted automotive catalysts by leaching and solvent extraction

Nogueira, C. A.; Carvalho, G. I.; Costa, M. Clara; Costa, Ana M. Rosa da; Paiva, A. P.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Relevância na Pesquisa
78.775244%
Platinum group metals (PGM’s) are precious and rare metals used in many existing and emerging technologies such as electronics, catalysts, energy and medical appliances, among others. PGM’s applications and demand are growing rapidly, and their supply is short and considered critical. Recycling of residues containing PGM’s is therefore mandatory, in order to allow the continuity of supplying. The main market share of PGM´s are catalysts, specially automotive catalytic converters. When exhausted, these wastes constitute important secondary resources that cannot be neglected. Therefore, the recycling of autocatalysts has been taken growing attention. Although some refiners operating plants for PGM’s recovery from residues are already known, the processes are complex, involve many operations and are highly reagent-consuming. Research in this domain is increasing, trying to develop new technologies and processes, more efficient and selective, and less consuming. Hydrometallurgy, and specifically solvent extraction with new reagents, can play an important role in achieving those objectives. In this context, a research has been carried out aiming at developing hydrometallurgical technologies to recover PGM's from spent autocatalysts. This paper presents some results of this investigation...

‣ Ion exchange technology for the efficient recovery of precious metals from waste and low-grade streams

Yahorava,V.; Kotze,M.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2014 Português
Relevância na Pesquisa
58.18867%
Efficient recovery of precious metals from process solutions is essential for improving process economics. Traditionally, precious metals are relatively effectively recovered from waste streams via precipitation or cementation. However, these approaches have a number of drawbacks, including poor water balance, creation of environmentally unfriendly waste streams, and losses of precious metals. Ion exchange technology is an alternative for the recovery of precious metals from waste or low-grade streams. This technology allows the recovery of the precious metals to extremely low levels (micrograms per litre) with relatively high upgrade ratios from the solution onto the resin without major water balance concerns, while the impact on the environment could be minimized or avoided. Research was conducted on the recovery of platinum group metals and gold from different low-grade and waste streams from one of the precious metals refineries in South Africa by means of ion exchange. Various functionalities and matrices (granular and fibrous) of ion exchange materials were evaluated. The results from these studies indicated that in some cases ion exchange could be very effective for the recovery of precious metals, and that the PGM concentration could be reduced to < 1 mg/L. The upgrading ratios of the various PGMs onto the specific fibres were relatively high for the specific streams evaluated...

‣ Novel redesign of a pressure leach autoclave by a South African Platinum producer

Roux,J.O.; du Toit,M.; Shklaz,D.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2009 Português
Relevância na Pesquisa
48.72145%
The Impala Platinum Limited Base Metals Refinery in Springs, South Africa, refines convertor matte containing base metals and PGM's (platinum group metals) using a hydrometallurgical process. In addition to a PGM-rich concentrate that is further refined, the Base Metals Refinery produces nickel (in powder or briquette form), copper cathodes and cobalt powder. Five leaching stages are utilized to remove the base metals and impurities from the PGM concentrate. The project described in this paper involves a radical redesign of the second stage leach autoclave with the aim of reducing maintenance costs and downtime, increasing throughput and ensuring a safer working environment. The second stage leach process at the Base Metals Refinery, produces a PGM-rich residue through the extraction of copper and any remaining base metals from the first stage leach solid residue material. Leaching is performed in an autoclave operating at a pressure of 600 kPaG and a temperature of 140°C to 150°C. Concentrated H2SO4 is added to the feed to produce a solution with a free acid content between 10 and 30 g/L and a pH of less than 2. Oxygen is passed into the 1st and 2nd compartments of the autoclave. As a result of the aggressive, highly oxidizing conditions within the autoclave...

‣ A comparative assessment of Ti-47.5 at.%Al cathodically modified by precious metal addition

Mwamba,LA.; Cornish,L.A.; van der Lingen,E.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 Português
Relevância na Pesquisa
48.579443%
Plain and alloyed titanium aluminides of composition Ti-47.5 at.% Al were prepared by melting commercial-purity titanium and aluminium with additions of 1 at.% precious metal. The as-cast alloys were subjected to potentiodynamic scans in 5, 15, and 25 wt% HCl aqueous solutions at room temperature and compared for their abilities to spontaneously passivate. Addition of precious metals resulted in a general improvement of corrosion resistance by increasing the open circuit potential to more noble values. Addition of 1 at.% gold or silver to titanium aluminide did not significantly increase the corrosion potential (e corr) above that of the plain titanium aluminide alloy, indicating that gold and silver are not sufficient cathodic modifiers to improve the corrosion resistance of titanium aluminide in all the solutions tested. However, platinum, palladium, and iridium additions shifted the corrosion potentials to the position of the passive region of plain TiAl for all solution concentrations. This indicated that TiAl alloyed with these platinum group metals would passivate spontaneously by cathodic modification. TiAl alloyed with palladium performed the best in 5 wt% HCl solution with the most positive corrosion potential. In 15 wt% HCl solution...

‣ The use of Dowex-M43 ion-exchange resin in the determination of Pt and Pd in converter matte by ICP-OES

Dyosi,Zolani; McCrindle,Robert I.; Wondimu,Tadesse; Botha,Barend M.; Ndibewu,Peter P.
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 Português
Relevância na Pesquisa
68.493594%
The method of choice for the separation of platinum group metals (PGMs) from base metals and easily ionizable elements (EIEs) is usually ion-exchange. This paper describes an anion-exchange procedure using Dowex-M43 for the separation of EIEs in geological samples (converter matte) from PGMs and Au. Aqueous commercial standards were used to study the adsorption capacity of the Dowex-M43 resin for both Pd and Pt metals (0-1000µg mL-1). The concentrations of Pd and Pt were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The results from the analysis of solutions prepared from commercial standards after ion-exchange treatment showed quantitative recoveries of both Pt (97%) and Pd (99%) from Dowex-M43 resin using 0.1 mol L-1 thiourea solution. Good agreement was observed between results obtained in this method and those obtained with the use of the conventional acid dissolution method for the determination of Pd and Pt in converter matte.

‣ Assessing the blue-water footprint of an opencast platinum mine in South Africa

Ranchod,Nikita; Sheridan,Craig M.; Pint,Neville; Slatter,Kerry; Harding,Kevin G.
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 Português
Relevância na Pesquisa
58.07473%
South Africa's extensive mineral resources have resulted in mining activities dispersed across the country, playing a critical role in its socio-economic development. In contrast to this abundance of mineral wealth, water resources are generally limited, and vulnerable to environmental impacts from the mining industry. These circumstances make tailored management of water resources in the mining sector essential. To achieve this, detailed information on water use throughout a mine operation as well as an accurate water balance account is required. Blue-water footprints have the potential to contribute to this task as they allow for quantification of direct and indirect water use across the supply chain of a process, while incorporating both spatial extension and temporal duration. As defined by the Water Footprint Network's (WFN) globally acknowledged water footprint assessment methodology, a blue-water footprint is determined by calculating the net consumptive use of water by an operation. According to the WFN, this includes water which is evaporated, incorporated into a product, or lost to outflows which do not return to the same catchment area in the same period.The applicability of this tool in the mining sector has not been fully explored. Therefore...

‣ Application of fundamentals in optimizing platinum concentrator performance

Valenta,M.M.; Mapheto,H.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
Relevância na Pesquisa
58.07473%
A number of challenges face platinum concentrator plant operators. These challenges include the increase in operating costs, the increase in smelter cost for the processing of concentrate, the shortage and cost of power, and the tightening of specifications on concentrate quality by the toll-smelting operations. Over the years the focus has moved from extracting the platinum group metals (PGM) from the Merensky Reef to the UG2 reef. This has a number of advantages, including the higher 'basket price' for UG2 concentrate, reduced mining cost per unit volume as a result of the higher density of UG2, and the reduction in overall concentrate tonnage to be smelted. In many cases the Merensky ore has been fully exploited and it makes sense for the focus to shift to the UG2 ore that can be accessed through the Merensky shaft infrastructure. The presence of relatively high levels of chromite in UG2 concentrate is, however, a major disadvantage due to the problems associated with smelting such a concentrate in conventional submerged arc furnaces. In addition to increasing the specification on the minimum PGM grade of concentrates, smelters have had to impose strict specifications on the levels of chromite in the concentrate. The threat of high penalties has forced concentrators to change their modus operandi...

‣ Kell hydrometallurgical process for extraction of platinum group metals and base metals from flotation concentrates

Liddell,K.S.; Adams,M.D.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 Português
Relevância na Pesquisa
78.991323%
The Kell Process has been developed for the extraction of platinum group metals (PGMs)and base metals from sulphide flotation concentrates. The process has been successfully tested on several different sulphide flotation concentrates, including those from the UG2 chromitite horizon and the Platreef mafic/ultramafic layer. It has been shown to provide high (>95 per cent) and selective extraction efficiencies for the key valuable metals, i.e. Pt, Pd, Rh, Au, Ni, Co, and Cu. The Kell Process consists of several commercially proven unit operations. S, Ni, Co, and Cu are first selectively removed by use of a pressure oxidation step during which the dissolution of PGMs is minimized. The residue from pressure oxidation is subjected to a thermal treatment to ensure efficient PGM recovery by subsequent chlorination. All the core steps are very similar to well-proven conventional unit operations in common use, as are the subsequent metal recovery steps to provide marketable end products. Typical metallurgical responses of flotation concentrates from UG2 and Platreef to the Kell Process are provided, and key outcomes of an energy comparison study with smelting are summarized in this paper. Kell presents a potentially substantial improvement in PGM concentrate processing technology...

‣ The application of activated carbon for the adsorption and elution of platinum group metals from dilute cyanide leach solutions

Snyders,C.A.; Mpinga,C.N.; Bradshaw,S.M.; Akdogan,G.; Eksteen,J.J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2013 Português
Relevância na Pesquisa
99.11979%
The research presented in this paper investigated the practical aspects of the recovery of platinum group metals (PGMs) from a dilute cyanide leach solution containing base metals, in a manner similar to that used for gold extraction in a typical CIP process, and focuses on both the adsorption and elution stages. The carrier-phase extraction of precious metals using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs. As a sorbent, activated carbon is still by far the most important material because of its large surface area, high adsorption capacity, porous structure, negligible environmental toxicity, low cost, and high purity standards. Adsorption tests were conducted on a pregnant alkaline leach solution (0.15 ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) resulting from cyanide extraction performed in column leach tests. The initial adsorption rates of Pt, Pd, and Au were very fast and recoveries of these three metals were approximately 90 per cent after 2 hours, and 100 per cent for Pt, 97.4 per cent for Pd, and 99.9 per cent for Au after 72 hours. The parameters that influence the extraction of PGMs and Au were examined to assess their relative importance during the adsorption process in order to provide the basis for process optimization. The concentration of thiocyanate was not identified as significant factor for PGMs adsorption...

‣ Applicability of analytical protocols for the characterisation of carbon-supported platinum group metal fuel cell electrocatalysts

Williams,M.; Khotseng,L.; Naidoo,Q.; Petrik,L.; Nechaev,A.; Linkov,V.
Fonte: South African Journal of Science Publicador: South African Journal of Science
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2009 Português
Relevância na Pesquisa
57.882114%
The nanoparticulate size of fuel cell electrocatalysts raises significant challenges in the analytical techniques used in their structural and electrochemical characterisation. For this reason, the applicability of analytical protocols in the qualitative and quantitative characterisation of nanophase fuel cell electrocatalysts was investigated. A set of structural and chemical properties influencing the performance of the electrocatalysts was identified. A large range of analytical tools was employed in characterising the electrocatalysts of interest. High accuracy and precision in the quantitative and qualitative structural and electrochemical characterisation of Pt/C and Pt-Ru/C nanophase electrocatalysts was demonstrated. Certain techniques were deemed to be highly applicable in discriminating between high- and low-performance electrocatalysts based on their structural and electrochemical properties. The goal of this effort is to contribute to the development of South Africa's capabilities in the emerging hydrogen economy.