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The dissolution of platinum-group metals (PGMs) requires a high chloride ion concentration in an acidic solution and a suitable oxidant. At Impala Platinum Refinery, the concentrate is leached in a hydrochloric acid solution using chlorine gas as the oxidant. The goal of this leaching step is a total dissolution of the PGMs and gold. The silver precipitates as silver chloride. The efficiency of this stage is crucial for the performance of the precious metals refinery. The aim of this project is to investigate the factors that influence the efficiency of the PGM leaching operation and to model for the results obtained. In order to investigate and evaluate the total dissolution of the PGt;~; in HClICl2 leach system, it is necessary to establish the effective conditions for the dissolution of chlorine gas in hydrochloric acid solution. The results showed that the solubility of chlorine gas increases with an increase in the acid concentration and chlorine gas concentration but decreases as the temperature increases. The HCI solution is almost saturated with chlorine after about 50 minutes. The chlorine mass' msfer coefficient is dependent on the temperature, the stirrer speed, the concentration of the HCI solution and that of the chlorine. [Abbreviated abstract. Open document to view full version] / GR 2016

Since the industrialization of platinum group metals (PGMs), particularly platinum (Pt), palladium (Pd) and rhodium (Rh), the control of trace impurities in these metals has become vital. Reliable analysis of impurities in these metals is, however a difficult task. Nobel metals are difficult to dissolve quickly and quantitatively. Thus, analytical techniques which determine samples in liquid form have become less favourable. They require time consuming digestions and are prone to contamination both from the chemicals and equipment used for the preparation. Direct-analysis techniques are increasingly being used in the platinum group metal (PGM) industry for the determination of impurities in the final products. Spark-optical emission spectroscopy (Spark-OES) for the analysis of metals offers rapid turnaround times. Since the technique is almost non-destructive, little of the product is lost during analysis. The technique is also well established in the PGM industry. It is routinely used by two of the three largest platinum producing companies for the determination of impurities in their products. It is also used for the determination of PGMs after Fire Assay procedure by Anglo American Platinum. The greatest challenge for this technique remains the availability of certified reference materials (CRM) and calibration standards. This study investigates the use of the Spark-OES for the determination of impurities in PGMs (notably gold (Au), silver (Ag), iron (Fe), nickel (Ni), copper (Cu), lead (Pb), magnesium (Mg), manganese (Mn), silicon (Si), aluminium (Al), antimony (Sb), chromium (Cr), tin (Sn), titanium (Ti), zirconium (Zr), calcium (Ca), zinc (Zn), boron (B), cobalt (Co), vanadium (V), molybdenum (Mo), bismuth (Bi), arsenic (As), selenium (Se), tellurium (Te), cadmium (Cd) in refined platinum, palladium and rhodium metals). It is to be used at Anglo American Platinum’s final metal’s laboratory. A method to be used routinely in the laboratory is also developed. The concentration of the impurities determined is used to quantify the overall purity of the PGMs. PGMs, other than the matrix (the metal whose purity is being quantified), are also determined. The use of Spark-OES was evaluated as an alternative to inductively coupled plasma-optical emission spectroscopy (ICP-OES). Due to the lack of CRMs and calibration standards, the study included the preparation of in-house reference material (IRM) for calibration and quality control purposes. The standards were prepared by spiking pure PGM metal sponges (produced by Anglo Platinum) with the metal oxides of the elements of interest. These were melted together using a vacuum induction furnace to produce metal disks. The disks were ground and analysed after dissolution using ICP-OES. The metal disks, and the shavings, were distributed to three other independent laboratories and analyzed by ICP-OES, inductively coupled plasma-mass spectroscopy (ICP-MS) and Spark-OES. The assigned consensus values were used for the calibration of the Spark-OES. The method was validated for linearity, accuracy, precision, robustness, bias and the measurement uncertainty of the method. The metal disks were first tested for homogeneity. It was found that the bottom surface of the rhodium metal was not homogenous. Rapidly cooled moulds, will facilitate almost instantaneous cooling of the metal. This eliminates the migration of elements during cooling. This could assist with homogenizing the metal. Limits of detections (LODs) achieved for the methods ranged from 0.1 mg.kg-1 to 4 mg.kg-1. The highest LOD was for silicon, which was caused by contamination from the crucibles used. The precision for all impurity elements, except ruthenium (Ru), of the three methods (analysis of platinum, palladium and rhodium) was satisfactory. Ru showed poor precision in all the matrices due to the channel installed in the spectrometer. Due to the lack of CRMs, the traceability of the method could not be validated and the accuracy could only be validated by comparing it to in-house reference material. Although the method met the validation criteria, it cannot be used to certify the purity of the product as the traceability could not be validated. It suggests that the method be used for twin stream analysis in conjunction with a primary method. Because of its rapid turnaround time, and its non-destructive nature, the method can be used for plant control purposes, where the level of accuracy required is not as stringent as required on a certificate of analysis.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

Wong Hoi Chun = Fe3O4和 ZnxFe3-xO4薄膜的制備及其熱處理效應 / 黃凱俊. / On t.p. "x" is subscript / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Wong Hoi Chun = Fe3O4 he ZnxFe3-xO4 bo mo de zhi bei ji qi re chu li xiao ying / Huang Kaijun. / Acknowledgement --- p.i / Abstract --- p.ii / 論文摘要 --- p.iii / Table of contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.xiii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction to magnetite and zinc ferrite / Chapter 1.1.1 --- Structure and properties --- p.1-1 / Chapter 1.1.2 --- Deposition methods of magnetite and zinc ferrite --- p.1-5 / Chapter 1.1.3 --- Review of Verwey transition --- p.1-7 / Chapter 1.1.4 --- Development of magnetic tunneling junction --- p.1-11 / Chapter 1.2 --- Research motivation --- p.1-13 / Chapter 1.3 --- Scope of this thesis --- p.1-14 / References --- p.1-15 / Chapter Chapter 2 --- Instrumentation / Chapter 2.1 --- Thin film deposition / Chapter 2.1.1 --- Facing-target sputtering technique --- p.2-1 / Chapter 2.1.2 --- Vacuum system --- p.2-3 / Chapter 2.1.3 --- Asymmetric bipolar pulsed DC power source --- p.2-4 / Chapter 2.2 --- Annealing / Chapter 2.2.1 --- Vacuum annealing system --- p.2-8 / Chapter 2.2.2 --- Oxygen annealing system --- p.2-8 / Chapter 2.3 --- Characterization / Chapter 2.3.1 --- Profilometer --- p.2-10 / Chapter 2.3.2 --- X-ray diffractometer --- p.2-10 / Chapter 2.3.3 --- X-ray fluorescence spectrometer --- p.2-12 / Chapter 2.3.4 --- Rutherford backscattering spectrometer --- p.2-12 / Chapter 2.3.5 --- X-ray photoelectron spectroscopy --- p.2-13 / Chapter 2.3.6 --- Resistance measuring system --- p.2-15 / References --- p.2-17 / Chapter Chapter 3 --- Fabrication and characteristics of epitaxial Fe304 and ZnxFe3-xO4 single layer thin film / Chapter 3.1 --- Sample preparation / Chapter 3.1.1 --- Targets for reactive sputtering --- p.3-1 / Chapter 3.1.2 --- Substrates --- p.3-2 / Chapter 3.1.3 --- Deposition procedure --- p.3-4 / Chapter 3.2 --- Characterization of Fe3O4 thin films / Chapter 3.2.1 --- Effects of oxygen partial pressure --- p.3-5 / Chapter 3.2.2 --- Effects of substrate temperature --- p.3-10 / Chapter 3.2.3 --- Effects of deposition power --- p.3-17 / Chapter 3.2.4 --- Effects of deposition pressure --- p.3-19 / Chapter 3.2.5 --- Other factors --- p.3-19 / Chapter 3.3 --- Characterization of ZnxFe3-x04 thin films / Chapter 3.3.1 --- Effects of oxygen partial pressure --- p.3-22 / Chapter 3.3.2 --- Effects of substrate temperature --- p.3-28 / Chapter 3.3.3 --- Effects of thickness --- p.3-46 / Chapter 3.4 --- Fabrication and Characterization of ZnxFe3-x04 and Fe3O4 thin films on magnesium oxide(MgO) --- p.3-49 / References --- p.3-56 / Chapter Chapter 4 --- Annealing of epitaxial Fe304 and ZnxFe3-x04 thin films / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- Vacuum annealing of ZnxFe3-x04 thin film / Chapter 4.2.1 --- Enhancement in magnitude of the Verwey transition --- p.4-1 / Chapter 4.2.2 --- Reduction in resistivity --- p.4-5 / Chapter 4.2.3 --- Improvement of crystallinity --- p.4-5 / Chapter 4.2.4 --- Characterizations after high-temperature annealing --- p.4-11 / Chapter 4.2.5 --- Oxygen diffusion in atmosphere --- p.4-16 / Chapter 4.3 --- Oxygen annealing of ZnxFe3-x04 thin film --- p.4-18 / References --- p.4-22 / Chapter Chapter 5 --- Conclusions / Chapter 5.1 --- Conclusions --- p.5-1 / Chapter 5.2 --- Future outlook --- p.5-2

Queenie Wai Yan Ip. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 91-94). / Abstracts in English and Chinese. / Acknowledgements --- p.ii / Abstract --- p.iii / 摘要 --- p.v / List of Abbreviations --- p.xii / List of Compounds Synthesized --- p.xiii / Chapter CHAPTER 1 --- Syntheses and Characterizations of Pyrazyl-Linked Bis(l-Aza-Allyl) Alkali-Metal Complexes / Chapter 1.1. --- Introduction --- p.1 / Chapter 1.1.1. --- A General Review of 1-Aza-Allyl Ligands --- p.1 / Chapter 1.1.2. --- A General Review of Group 1 Alkali-Metal Complexes Containing Bis(l-Aza-Allyl) Ligands --- p.6 / Chapter 1.2. --- Objective --- p.9 / Chapter 1.3. --- Results and Discussion --- p.11 / Chapter 1.3.1. --- Preparation and Characterization of Pyrazyl-Linked Bis(l-Aza-Allyl) Di-Lithium Complex --- p.11 / Chapter 1.3.1.1. --- "A Modified Synthesis of Pyrazyl-Linked Bis(l-Aza-Allyl) Di-Lithium Complex [Li2{{N(SiMe3)C(But)C(H)}2C4H2N2-2,3}(THF)2]2 (1)" --- p.11 / Chapter 1.3.1.2. --- Physical and Spectroscopic Properties of Complex 1 --- p.11 / Chapter 1.3.1.3. --- Molecular Structure of Complex 1 --- p.12 / Chapter 1.3.2. --- Preparation and Characterization of Pyrazyl-Linked Bis(l-Aza-Allyl) Di-Sodium and Di-Potassium Complexes --- p.15 / Chapter 1.3.2.1. --- "Preparation of Pyrazyl-Linked Bis( 1 -Aza-Allyl) Di-Sodium complex [Na2{{N(SiMe3)C(But)C(H)}2C4H2N2-2,3}(THF)2]2 (2) and Di-Potassium Complex [K2{{N(SiMe3)C(But)C(H)}2C4H2N2-2,3}- (THF)3]2 (3)" --- p.15 / Chapter 1.3.2.2. --- Physical and Spectroscopic Properties of Complexes 2 and 3 --- p.15 / Chapter 1.3.2.3. --- Molecular Structures of Complexes 2 and 3 --- p.16 / Chapter 1.4 --- Experimental Section --- p.23 / Chapter 1.5 --- References --- p.25 / Chapter CHAPTER 2 --- Syntheses and Characterizations of Pyrazyl-Linked Bis(l-Aza-Allyl) Group 2 and 12 Metal Complexes / Chapter 2.1 --- Introduction --- p.29 / Chapter 2.1.1. --- A General Review of Group 2 Metal Complexes containing Bis(l-Aza-Allyl) Ligands --- p.29 / Chapter 2.1.2. --- A General Review of Group 12 Metal Complexes containing Bis(l-Aza-Allyl) Ligands --- p.32 / Chapter 2.2 --- Results and Discussion --- p.34 / Chapter 2.2.1. --- Preparation and Characterization of Pyrazyl-Linked Bis(l-Aza-Allyl) Di-Magnesium Complex --- p.34 / Chapter 2.2.1.1. --- "Preparation of Pyrazyl-Linked Bis(l-Aza-Allyl) Di-Magnesium Complex [Mg2{{N(SiMe3)C(But)C(H)}2C4H2N2-2,3}Br2(THF)4] (4).……" --- p.34 / Chapter 2.2.1.2. --- Physical and Spectroscopic Properties of Complex 4 --- p.34 / Chapter 2.2.1.3. --- Molecular Structure of Complex 4 --- p.35 / Chapter 2.2.2. --- Preparation and Characterization of Pyrazyl-Linked Bis(l-Aza-Allyl) Lithium Zincate Complex --- p.38 / Chapter 2.2.2.1. --- "Preparation of Pyrazyl-Linked Bis(l-Aza-Allyl) Lithium Zincate Complex [Zn2{{N(SiMe3)C(But)C(H)}2C4H2N2-2,3}Cl2(u-Cl)2Li2(THF)6] (5)" --- p.38 / Chapter 2.2.2.2. --- Physical and Spectroscopic Properties of Complex 5 --- p.39 / Chapter 2.2.2.3. --- Molecular Structure of Complex 5 --- p.39 / Chapter 2.2.3. --- Preparation and Characterization of Unexpected Cyclization Compound --- p.42 / Chapter 2.2.3.1. --- "Preparation of Unexpected Cyclization Compound [{Me2Si{NC(But)C(H)}}2C4H2N2-2,3] (6)" --- p.42 / Chapter 2.2.3.2. --- Physical and Spectroscopic Properties of Complex 6 --- p.43 / Chapter 2.2.3.3. --- Molecular Structure of Complex 6 --- p.44 / Chapter 2.2.4. --- Attempted Synthesis of Analogous Mercury Complex --- p.45 / Chapter 2.2.5. --- Comparison on Structures and Reactivities of Compounds 4-6 --- p.46 / Chapter 2.3. --- Experimental Section --- p.48 / Chapter 2.4. --- References --- p.50 / Chapter CHAPTER 3 --- Syntheses and Characterizations of Bis(Phosphoranoimido) Magnesium and Group 14 Metal Complexes / Chapter 3.1 --- Introduction --- p.52 / Chapter 3.1.1. --- A General Review of Functionalized Phosphoranoimine Ligands --- p.52 / Chapter 3.1.2. --- A General Review of Group 14 Metal Complexes Containing Bis(Phosphoranoimines) Ligands --- p.59 / Chapter 3.2. --- Objective --- p.61 / Chapter 3.3. --- Results and Discussion --- p.64 / Chapter 3.3.1. --- Preparation and Characterization of Bis(Phosphoranoimido) Magnesium Complexes --- p.64 / Chapter 3.3.1.1. --- "Preparation and Characterization of Bis(Phosphoranoimido) Magnesium Complexes [Mg{(Me3SiN=PR2CH)2C5H3N-2,6}THF] (R = Pri, 9; R = Ph, 10)" --- p.64 / Chapter 3.3.1.2. --- Physical and Spectroscopic Properties of Complexes 9 and 10 --- p.64 / Chapter 3.3.1.3. --- Molecular Structures of Complexes 9 and 10 --- p.65 / Chapter 3.3.2. --- Preparation and Characterization of Bis(Phosphoranoimido) Tin(II) and Lead(II) Complexes --- p.70 / Chapter 3.3.2.1. --- "Preparations and Characterizations of 1,3-Distannacyclobutane with Chlorotin(II) Alkyl Complex [{2-{Sn{C(Pri2P=NSiMe3)}}-6- {Sn{CH(Pri2p=NSiMe3)}Cl}}C5H3N]2 (11) and 1,3-Diplumbacyclobutane with bis(trimethylsilyI)amido Lead(II) Alkyl Complex [{2-{Pb{C(Pri2P=NSiMe3)}}-6-{Pb{CH(Pri2P=NSiMe3)}N(SiMe3)2}}- C5H3N]2 (12)" --- p.70 / Chapter 3.3.2.2. --- Physical and Spectroscopic Properties of Complexes 11 and 12 --- p.73 / Chapter 3.3.2.3. --- Molecular Structures of Complexes 11 and 12 --- p.74 / Chapter 3.3.3. --- Preparation and Characterization of Bis(Phosphoranoimido) Germanium(II) Enamido and Alkyl Complex --- p.79 / Chapter 3.3.3.1. --- Preparation and Characterization of Bis(Phosphoranoimido) Germanium(II) Enamido and Alkyl Complex [{2-CH(Pri2P=NSiMe3)-6-CH(Pri2P=NSiMe3)}C5H3NGe{2-{C(Pri2P=NSi Me3)Ge} -6-CH2(Pri2P=NSiMe3)} C5H3N] (13) --- p.79 / Chapter 3.3.3.2. --- Physical and Spectroscopic Properties of Complex 13 --- p.81 / Chapter 3.3.3.3. --- Molecular Structure of Complex 13 --- p.81 / Chapter 3.3.4. --- Comparison on Structures and Reactivities of Compounds 11-13 --- p.85 / Chapter 3.4. --- Experimental Section --- p.87 / Chapter 3.5. --- References --- p.91 / APPENDIX I / Chapter A --- General Experimental Procedures and Physical Measurement --- p.95 / Chapter B --- X-Ray Crystallography --- p.96 / APPENDIX II / Tables of Crystallographic Data and Refinement Parameters --- p.98

No description available.

Thesis (M.Sc) -- University of Limpopo, 2008. / The National Water Act (Act No. 36 of 1998) requires effective use of our water resources for protection of the environment and provision of safe water for current and future generations. Previous studies in the study area have shown that there are certain heavy metals occurring at elevated concentrations. These metals are cadmium, lead,zinc, copper and chromium. Metals tend to increase in concentrations in organisms at higher trophic levels through a process called bioaccumulation and this was assessed during the study. There is very little data on the tributaries of this system because the streams flow intermittently. Less attention has in the past been given to these smaller streams yet they contribute a great deal to larger rivers of interest. This study focused on Naboom Spruit and Tobias Spruit, both tributaries of the Mogalakena River. The study was to determine the levels of certain selected metals within the system and to prove the hypothesis that wetlands act as pollutant filters. The study was also undertaken to further assess levels of those metals which have been recorded to be occurring at high concentration in certain areas within the Mogalakwena River system. A supplementary fish exposure laboratory experiment to determine the rate of uptake of cadmium and zinc by Clarias gariepinus in vitro under controlled conditions was also undertaken.Both the high and low flow surveys were conducted where physico-chemical parameters were recorded on sites and water, fish, aquatic macro-invertebrates, sediment and aquatic plants were collected. These samples were analysed for cadmium, lead, zinc,copper and chromium content using methods described in chapter 3 of the study. The laboratory fish exposure experiment followed the analytical protocol described in Chapter 7 of this document. Results obtained were statistically analysed and recorded and of the five metals studied in this project, the mean concentrations in all samples at the studied reaches of the subcatchment ranked: Zinc>Copper>Chromium>Lead>Cadmium. The ranking for samples is generally: sediment>invertebrates>fish>plants. The hypothesis that sediment tend to have increased free and compound heavy metals was clearly depicted in this study. There was increase in metal concentrations in sediment samples also increased on sites where there was less or no flow as a result of lower turbulence. In general, metal contents between sites ranked: Driefontein>Mine>Tobias>Bergland>Sacchariasboom. Metal concentrations were low at Bergland, increasing downstream and after the vlei area decreasing to as little as in the headwater at Sacchariasboom. It was then deduced that the vlei area plays its important role as a filter for pollutants in the natural system as the Sacchariasboom site is downstream of a wetland area after confluence of the Tobias Spruit with the Nylsvley. All concentrations of the five metals studied were higher in the other fish species as compared to values measured in C. gariepinus. These seem to relate perfectly to the low concentration of all the metals in Sacchariasboom site, where the C. gariepinus analysed for metals were collected. It is often difficult to determine in the natural environment, which factor/s in the system affects concentrations of other metals and substance, and which one causes a problem,because of multiple occurrences. Laboratory tests such as metals exposure to biota under set conditions was used in this study to determine synergistic and or additive effects of all components in a natural system. Under conditions of the experiment performed in this study, zinc showed to have higher affinity and or was taken up much quicker by C. gariepinus than cadmium, both in pure metal (zinc or cadmium alone) and combination of metal(zinc/cadmium solution), under similar conditions. Zinc has therefore proved to have higher binding affinity to proteins of the fish than cadmium under the set condition in this experiment. / University of Limpopo,and the University of Johannesburg

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