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1
Smit, Timotheus Servaas. "Hydrodesulphurization of thiophenes using transition metal sulphides". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28084.
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Mulligan, David John. "Reduction of sulphur dioxide over transition metal sulphides". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61916.
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Harrison, Mark Robert. "One-dimensional, mixed-metal sulphides – structural and physical properties". Thesis, University of Hull, 2011. http://hydra.hull.ac.uk/resources/hull:5281.
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New one-dimensional sulphides based on Ba2CoS3 have been synthesised and their structural and electronic properties investigated. The starting point was the one-dimensional sulphide Ba2CoS3, which shows one-dimensional anti-ferromagnetism, metallic-like behaviour and a small negative magnetoresistance. Cationic substitutions were carried out on both the barium and cobalt sites of Ba2CoS3. The substitution of zinc for cobalt into Ba2CoS3 resulted in the formation of the series Ba2Cox1−xZnxS3 (x = 0.0-1.0). Ba2Co1−xZnS3 compounds maintain the one-dimensional structure but become paramagnetic and show semiconducting properties. Interestingly significant values of magnetoresistance (up to −25%) are found in the series. The origin of the magnetoresistance is currently unknown although it is suspected that there is some extrinsic contribution. The compound Ba2Co0.75Fe0.25S3 has also been successfully synthesised although attempts to form compounds with higher iron content were not successful. A large number of compounds in the series Ba2Zn1–xMxS3 (M = Fe, Mn, Cr, Ni) have also been synthesised and initial investigations into the properties of these materials show that again they exhibit negative magnetoresistance. Finally Ba1.9K0.1CoS3 has been synthesised although no investigation into the properties has yet been carried out.
4
Green, Pamela Rose. "The synthesis and structure of ternary transition metal sulphides". Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284056.
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David, Lorraine. "MBE growth and characterisation of metastable transition metal sulphides". Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/197.
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Engin, Tahir. "Structural, magnetic and electron transport properties of mixed metal sulphides". Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2059.
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The construction of cells that enables the electrical resistance of a material to be measured simultaneously with the collection of powder neutron diffraction data at a range of temperatures (4.2 :5 TIK:5 1000) is described. The cells have been used to investigate the origin of the anomalous electron-transport properties of the ternary sulphides, TICu6.ssS4, BaCu4S3 and CuFeS2. Data for TICu6.ssS4 reveal that the anomaly observed at 255 K is associated with a structural change from P41n to 141m on cooling due to a distortion involving a doubling of the e-axis of the unit cell. There,are .~/ two resistance anomalies observed in BaCu4S3. The first at 523 K is associated' with a phase transition from a two-phase mixture (Pllma + Cmem) to a Cmem phase, whilst the second anomaly can be correlated with the decomposition of the 'sample at 923 K. Variable temperature powder neutron diffraction reveals that CuFeS2 adopts a tetragonal antiferromagnetically ordered structure up to 748 K, above which it consists of a mixture of two phases until TN = 823 K, where a loss of magnetic order is coincident with a transformation to a cubic structure. Resistance anomalies are observed at each of those temperatures. A new family of vanadium-substituted chromium sulphides (VxCr2-xS3, 0 < x < 2) has been prepared and characterized by powder X-ray and neutron diffraction, SQUID magnetometry, electrical resistivity, and Seebeck coefficient measurements. Vanadium substitution leads to a single-phase region with a rhombohedral Cr2S3 structure over the composition range 0.0 < x:5 0.75, while at higher vanadium contents (1.6 :5 x < 2.0) a second single-phase region, in which materials adopt a cation-deficient Cr3S4 structure, is observed. Materials with the Cr2S3 structure all exhibit semiconducting behavior whilst those adopting Cr3S4-type structure exhibit metallic behavior. Materials in both single phase regions undergo a magnetic ordering transition at temperatures in the range 90 - 118 K. Materials with the Cr2S3 structure undergo a transition to a ferrimagnetic state, the nature of which has been determined by low-temperature neutron diffraction measurements. Structural studies of the mixed-metal sulphides, FexMnl_xS (0 :5 x :5 0.4) were performed using powder neutron diffraction. Rietveld refinements show that all samples adopt a cubic rock-salt structure (F'm3m) at room temperature. The Feo.2Mno.sS sample is essentially pure phase whilst materials with higher Fe content contain 3CFe7SS (21.3% in Feo.4Mno.6S). Low-temperature neutron diffraction reveals that all materials are magnetically ordered at temperatures in the range 180 - 185 K, below Which they show a structural distortion. The magnetic structure consists of ferromagnetically aligned layers, with antiferromagnetic coupling of adjacent layers. Electron-transport property measurements reveal that all the samples are Arrhenius semiconductors with activation energies that decrease with increasing Fe content.
7
d'Arbeloff-Wilson, Sarah. "Reactions of the phosphaalkyne, PCBu't with metal sulphides, selenides and tellurides". Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324201.
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Poole, Mark Charles. "Synthetic and spectroscopic studies of organic sulphides, sulphoxides, sulphones, and their metal complexes". Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332281.
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Szkoda, Iwona. "Phase relations, structural studies and physical properties of mixed metal oxides and sulphides". Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2212.
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The phase relations in three oxide systems; ZnO–BiVO4, Pb2V2O7–BiVO4 and PbO– BiVO4, have been studied and their phase diagrams over the whole component concentration range up to 1273 K have been established. As a result of solid-state reaction between ZnO and BiVO4 mixed at a molar ratio of 2:1 or among ZnO, V2O5 and Bi2O3, mixed at a molar ratio of 4:1:1, a new double vanadate BiZn2VO6 has been obtained. Its crystallographic system was determined, its unit cell parameters were calculated and its incongruent melting temperature was established. A new compound is also formed in the Pb2V2O7–BiVO4 system. It has been shown that BiVO4 and Pb2V2O7 react with each other forming a compound of the formula Pb2BiV3O11, when their molar ratio is equal to 1:1, or between PbO, Bi2O3 and V2O5, mixed at a molar ratio of 4:1:3. This material melts congruently and it crystallises in the triclinic system. A new series of non-stoichiometric sulphides Ga1-xGexV4S8 (0 x 1) has been synthesised by standard solid-state reaction. The samples have been characterised by powder X-ray and neutron diffraction, SQUID magnetometry and electrical transportproperty measurements. Structural analysis reveals that a solid solution is formed throughout this composition range. Magnetic measurements suggest that the ferromagnetic behaviour of the end-member phase GaV4S8 is retained at x 0.7. By contrast Ga0.25Ge0.75V4S8 appears to undergo antiferromagnetic ordering at ca. 15 K. All materials with x ¹ 1 are n-type semiconductors whose resistivity falls by almost six orders of magnitude with decreasing gallium content, whilst the end-member phase GeV4S8 is a ptype semiconductor. Powder neutron diffraction studies show that the cubic unit cell is retained for non-stoichiometric materials to the lowest temperatures studied. Single crystals of five erbium-chromium sulphides have been grown by chemical vapour transport using iodine as the transporting agent. Single-crystal X-ray diffraction reveals that in Er3CrS6, octahedral sites are occupied exclusively by Cr3+ cations, leading to onedimensional CrS4 5- chains of edge-sharing octahedra, whilst in Er2CrS4, Er3+ and Cr2+ cations occupy the available octahedral sites in an ordered manner. By contrast, in Er6Cr2S11, Er4CrS7 and Er8Cr3S15, Er3+ and Cr2+ ions are disordered over the octahedral sites. In Er2CrS4, Er6Cr2S11, Er4CrS7 and Er8Cr3S15, the network of octahedra generates an anionic framework constructed from M2S5 slabs of varying thickness, linked by onedimensional octahedral chains. This suggests that these four phases belong to a series in which the anionic framework may be described by the general formula [M2n+1S4n+3]x-, with charge balancing provided by Er3+ cations located in sites of high-coordination number within one-dimensional channels defined by the framework. Er4CrS7, Er6Cr2S11, Er8Cr3S15 ii and Er2CrS4 may thus be considered as the n = 1, 2, 3 and members of this series. Whilst Er4CrS7 is paramagnetic, successive magnetic transitions associated with ordering of the chromium and erbium sub-lattices are observed on cooling Er3CrS6 (TC(Cr) = 30 K; TC(Er) = 11 K) and Er2CrS4 (TN(Cr) = 42 K, TN(Er) = 10 K) whereas Er6Cr2S11 exhibits ordering of the chromium sub-lattice only (TN = 11.4 K). These four materials have been studied using neutron diffraction which allowed magnetic ordering to be examined.
10
Coimbatore, Dhandayuth Venkatesh. "Cerium chloride inhibition for high strength low alloy steel exposed to sulphide polluted seawater". University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0134.
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[Truncated abstract] Corrosion of steel structures caused by sulphide is a common engineering problem encountered by many industries, such as the petroleum, chemical processing, mining and mineral processing industries. The control of sulphide corrosion is still a controversial topic among corrosion engineers. There is an absence of guideline for a reliable acceptable limit of sulphide level in service and each processing industry has its own empirical values. Selection of inhibitors in the sulphide environment depends on laboratory testing before its actual application in pipelines and reaction vessels. Many investigators have postulated the corrosion mechanisms due to sulphide based on operating envelopes such as pH, chloride, manganese, hydrogen sulphide, sulphate reducing bacteria levels and inhibitor concentration. It is recommended in the literature that the batch dosing of inhibitor and biocide needs to be evaluated in regards to sulphide reducing bacteria (SRB) level, which may produce sulphide concentrations up to 2000 ppm. Although sulphide scale formation may protect the base metal by providing a physical barrier, the detrimental effects of sulphide are often inevitable, such as stress corrosion cracking, hydrogen embrittlement, etc. Currently, there are many chemicals that are used as inhibitors to prevent corrosion by scavenging the sulphide from the environment. Cerium, a rare-earth element, is not used as inhibitor in the sulphide environment. Also, there are no previous research findings on the effects of compounds of rare-earth metals, such as cerium chloride (CeCl3), in sulphide environment. This research examines the corrosion behaviour of 0.4Mo-0.8Cr steel, a High Strength Low Alloy (HSLA) steel, in sulphide-polluted artificial seawater with the addition of CeCl3 and glutaraldehyde. ... It is postulated that the moderate inhibiting effect of CeCl3 is due to the scavenging effect thereby forming Ce2S3 complex. Further reaction of sulphide with steel resulted in ferrous sulphide, leading to an increased corrosion rate. It is also concluded that the CeCl3 interferes with both anodic and cathodic reactions in deaerated conditions. Addition of glutaraldehyde in the sulphide-polluted seawater was found to decrease the corrosion rate. According to the electrochemical measurements conducted, the concurrent addition of glutaraldehyde and CeCl3 appeared to have an added effect on reducing the corrosion of the steel, as evidenced by the increase of the open circuit potential during the short-term testing. From the weight loss measurements after 60 days, sulphide pollution in deaerated seawater was found to increase corrosion rate. This is attributed to the increase of sulphide activity whereby continual dissolution of steel was encountered. From the weight loss tests, it was found that the addition of CeCl3 and glutaraldehyde reduced the corrosion rate of the steel in the solutions containing 0-10 ppm sulphide. There is no noticeable corrosion rate decrease for the solution containing 100 ppm sulphide. The added effect of CeCl3 and glutaraldehyde to the SRB medium has resulted in lower corrosion rates. Further detailed experimentation is required to elucidate the corrosion reduction mechanism in glutaraldehyde-containing environments.
11
Jordan, Mark Adrian. "The oxidation of base metal sulphides and pyritic gold concentrates with particular reference to mechanism and preferential release of ferrous iron". Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357977.
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Grobler, Willem Adriaan. "A study into the use of fatty acid and xanthate collector combination in the recovery of base metal sulphides : a holistic approach". Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/50910.
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In this study, a collector combination between xanthate and a fatty acid
collector (Betacol 364) is tested on an ore containing chalcopyrite, pentlandite and
pyrrhotite. An increase in the rate of pentlandite and pyrrhotite recovery was
measured when the fatty acid and xanthate combination was tested against the
baseline (xanthate as sole collector), using the standard laboratory scale batch
flotation test procedure.
The rate of mineral recovery in a batch flotation test is not only influenced by
particle floatability, but also by the amount of air bubble surface area available in
the pulp and the recovery of value mineral from the flotation froth. This is given
as = . . where k is the rate constant (min-1), P is a parameter which
represents the floatability of a mineral, Rf is the froth recovery factor and Sb bubble
surface area flux.
A test unit developed for this study (based on the Bikerman foam test) indicated
that the fatty acid collector used (Betacol 364) has froth stabilising characteristics
and thus may have increased the froth recovery ( Rf) during the batch flotation test.
The increase in the rate of pyrrhotite recovery measured can therefore not only be
explained by an increase in pyrrhotite floatability. In a case where the batch
flotation tests are followed by plant testing and the rate of flotation increase
measured during the batch test was only or partially as a result of an increase in
froth recovery ( Rf), the batch test would be an unreliable test to predict plant
performance.
Plant operators have many variables available to manage froth recovery ( Rf), for
example pulp level and frother dosing rate. For a laboratory scale batch test to be
a reliable test for predicting a rate increase in plant recovery, it is necessary that an
increase in the rate of recovery will be as a result of an increase in particle
floatability ( P). It is recommended that a collector batch flotation test campaign must include a test to measure if the collector has frothing characteristics. The
Bikerman froth stability column is demonstrated as a possible test to measure if a
collector has froth stabilising characteristics.
The Bikerman froth stability column test method confirmed that the fatty acid
collector tested (Betacol 364) has froth stabilising properties. Additional tests are
therefore recommended to confirm that the rate of recovery increase measured is
as a result of an increase in pyrrhotite and pentlandite floatability (P ). Micro
flotation tests performed on pyrrhotite mineral specimens confirmed that a
combination between Xanthate and Betacol 364 increases the particle floatability
(P ) of pyrrhotite. Laboratory scale flotation tests performed on artificial ores,
consisting of a mixture of quartz and pyrrhotite mineral specimens, confirmed that
the combination of Betacol 364 and xanthate increases the floatability of pyrrhotite
(P ).Dissertation (MEng)--University of Pretoria, 2015.
tm2015
Materials Science and Metallurgical Engineering
MEng
Unrestricted
13
Masenya, Mamago Adolphina. "Computational modelling studies of precious mixed metals sulphides". Thesis, University of Limpopo, 2016. http://hdl.handle.net/10386/1725.
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Thesis (MSc. (Physics)) -- University of Limpopo, 2016The stabilities of PtS to PdS and PdS to PtS were investigated using density functional theory within the generalized gradient approximation. Their structural, electronic and mechanical properties were determined to show their stability and the effect of pressure on different compositions. We found good correlation of calculations with available ex-perimental data. The lattice parameters were observed to fluctuate with increasing con-centration for both systems. Furthermore, heats of formation were calculated to deter-mine the relative structural stability of the systems. They predict that the most stable structure is Pd50S50 P42/mmc and Pt25Pd25S50 P42/mmc being the least stable. Pd12.5Pt37.5S50 P42/m is the most stable and Pd50S50 P42/m being the least stable struc-ture. The Pt37.5Pd12.5S50 P1 was said to be the most stable structure and Pd50S50 P1 be-ing the least stable. The phonon dispersion calculations show that Pt50S50 P42/mmc, Pd50S50 P42/mmc, Pd12.5Pt37.5S50 P42/m and Pt50S50 P1 (derived from P42/mmc) are me-chanically stable, consistent with calculated elastic constants. The Pt25Pd25S50 P42/mmc show soft modes, which are due to vibrations of Pt and Pd atoms in the x - y plane which suggests the instability of the structure, in agreement with C66 being negative, and consistent with heats of formation. The lattice parameters decreased steadily with increasing pressure. An anomaly was observed in Pt50S50 P1 (derived from P42/mmc), where the c lattice parameter was found to increase with increasing pressure. The elec-tronic density of states (DOS) were performed on all compositions. The DOS were sub-jected to pressure and it was generally noted that the band gap increases with increas-ing pressure. It was observed that the smaller the band gap, the more stable the struc-ture. Furthermore, phonon dispersions under pressure show that compounds with the P42/mmc and P1 (from P42/mmc) symmetries display the mixing of lower and upper en-ergy bands at pressures above 30 GPa.
National Research Foundation
14
Thangwane, Selaelo Christabel. "Synthesis and characterization of substituted dithiocarbamates ligands and complexes as a source of metal (Pb, Ni & Co) sulphide nanoparticles". Thesis, Vaal University of Technology, 2017. http://hdl.handle.net/10352/396.
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M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology.Lead, nickel and cobalt dithiocarbamates complexes were synthesized using methanol and water as solvents. All complexes were refluxed at 60 °C, cooled at room temperature, washed with methanol to remove the impurities and dried under the fume hood. A combination of Fourier transformer infrared (FTIR), elemental analysis (EA) and thermogravimetric analysis (TGA) were used to characterize these complexes. There was shifting of bands from low to high frequencies of the dithiocarbamates complexes compared to benzimidazole derivatives. The absence of the N-H band and the presence of new C=S bands confirmed that the complexes can be used in the preparation of metal sulphide nanoparticles. Elemental analysis showed that there was a percentage mismatch for the complexes I, III, IV and V. Complexes II and VI calculated percentages were within the limits with the found percentages except for sulphur which was low. The TGA curves decomposed to form a mixture of metal and metal sulphides for complex I, II, III and IV except for complex VI which gave metal sulphide only. All benzimidazole complexes decomposed at higher temperatures and were considered as stable complexes. Lead sulphide (PbS) is an important group IV-VI metal chalcogenide semiconductor. It has a direct narrow band gap of 0.41 eV at 300K and a large excitonic Bohr radius of 18 nm. Lead sulphide absorption band can be tuned to anywhere between near IR to UV (0.4μm) covering the entire visible spectrum, while achieving the quantum confinement region. The synthesis of lead sulphide nanoparticles was conducted by varying the effect of the reaction conditions such as the type of capping agents and temperature. Lead dithiocarbamate complex derived from benzimidazole, [Pb(S2N2C8H5)2] was thermolysed in hexadecylamine (HDA) and trioctylphosphine oxide (TOPO) at different reaction temperatures (140, 160 and 180 °C) to produce HDA and TOPO capped PbS nanoparticles. The nanoparticles were characterized using X-ray diffraction (XRD) for structural analysis, transmission electron microscopy (TEM) for shape and size, Ultraviolet visible (UV/Vis) and Photoluminescence (PL) spectroscopy for optical properties. An increase in temperature gave a decrease in the sizes of the nanoparticles when using the HDA capped lead benzimidazole dithiocarbamate complex. The observed morphology was cubes. TOPO capped lead benzimidazole dithiocarbamate complex gave no specific trend when temperature was varied. A cross-like layer with quasi spherical particles on top was observed at 160 °C. At 180 °C, the cross-like layer decomposed into rods- like materials with quasi spherical particles on top for TOPO capped PbS nanoparticles. For lead 2-methylbenzimidazole [Pb(S2N2C9H7)2] dithiocarbamate complex, TOPO capped PbS produced agglomerated cubic morphology at low temperature but as the temperature was increased agglomerated cylindrical shapes were observed. HDA capped PbS produced polydispersed nanocubes which were increasing in size when the temperature was increased. Nanoparticles displayed a blue shift in band edges with good photoluminescence behaviour which was red shifted from their respective band edges all temperatures and capping agents. XRD confirmed the crystal structure of cubic phase (galena) of PbS at all temperatures except for HDA capped PbS nanoparticles at 140 °C from lead benzimidazole dithiocarbamate complex which confirmed the crystal structure of face-centred cubic phase of PbS nanoparticles. Nickel sulphide has much more complicated phase diagram than cobalt sulfides and iron sulfides. Their chemical composition has many crystalline phases such as α-NiS, β=NiS, NiS2, Ni3S2, Ni3S4, Ni7S6 and Ni9S8. Ni3S2 phase has shown potential as a low-cost counter electrode material in dye sensitised solar cells, while the α-NiS phase has been applied as a cathode Material in lithium-ion batteries. The synthesis of nickel sulphide nanoparticles was done by varying the effect of the reaction conditions such concentration and temperature. Nickel benzimidazole dithiocarbamate [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni (S2N2C9H7)2] dithiocarbamates complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) and precursor concentrations (0.30, 0.35 and 0.40 g) to produce HDA capped NiS nanoparticles. It was observed that increasing both temperature and precursor concentration increased the size of the nanoparticles. Anisotropic particles were observed for both complexes when varying precursor concentration and temperature. Nickel benzimidazole dithiocarbamate complex produced stable shapes (spheres and cubes) of nickel sulphide nanoparticles. Nickel 2-methylbenzimidazole dithiocarbamate complex produced a mixture of spheres, cubes, triangles and rods nickel sulphide nanoparticles at all concentrations. But when varying temperature, it only produced that mixture at 160 °C. The optical measurements supported the presence of smaller particles at all temperatures and concentrations. XRD showed the presence of C7OS8 and pure nickel as impurities. However, the crystal structure of cubic Ni3S4 was observed at low temperatures and an introduction of monoclinic NixS6 at high temperature (180 °C) when varying temperature for both complexes. When varying concentration using nickel benzimidazole dithiocarbamate complex, XRD showed the presence of NiSO4.6H2O impurities at high temperatures. At 160 °C a mixture of hexagonal NiS and cubic Ni3S4 was observed. At low temperatures only nickel as a metal was found as an impurity and the crystal structure of cubic Ni3S4 was observed. When nickel 2-methylbenzimidazole complex was used, C7OS8 and pure nickel were found as impurities but the crystal structure of cubic Ni3S4 was observed. Cobalt sulphide (CoS) belongs to the family of group II-IV compounds with considerable potential for application in electronic devices. They have a complex phase diagram and their chemical composition have many phases such as Co4S3, Co9S8, CoS, Co1-xS, Co3S4, Co2S3 and CoS2. The synthesis of cobalt sulphide nanoparticles was conducted by varying the effect of temperature on size and shape of the nanoparticles. Nickel benzimidazole dithiocarbamate, [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni(S2N2C9H7)2] complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) to produce HDA capped CoS nanoparticles. Cobalt benzimidazole dithiocarbamate complex produced close to spherical shapes nanoparticles at all temperatures. The images showed that as temperature was increased, the size of the particles decreased. All the main reflection peaks were indexed to face-centred cubic Co3S4 and there were some impurities of C7OS8 at all temperatures. The optical measurements supported the presence of smaller particles at all temperatures. Cobalt 2-methylbenzimidazole dithiocarbamate complex produced big and undefined morphology. The optical properties were also featureless and XRD only showed impurities of C7OS8. The impurity is thought to be generated from a side reaction between benzimidazole and carbon disulphide to give this persistent organic moiety.
15
Alakangas, Lena. "Sulphide oxidation, oxygen diffusion and metal mobility in sulphide-bearing mine tailings in Northern Sweden". Doctoral thesis, Luleå : Division of Applied Geology, Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1544/2006/27/.
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Fredriksson, Andreas. "Adsorption of heptyl xanthate at the metal sulphide/aqueousinterface". Licentiate thesis, Luleå, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16791.
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In sulphide mineral flotation a sufficient hydrophobicity of the mineral surfaces is obtained by the adsorption of collector chemicals at the metal sulphide/aqueous interface. This surface alteration is of fundamental and applied interest. In this thesis, attenuated total reflection infrared spectroscopy has been used to monitor the adsorption kinetics and the orientation of heptyl xanthate when adsorbed onto three solid surfaces - germanium, zinc sulphide and lead sulphide in-situ. The choice of using the ATR technique is because it is very suitable when working with water as solvent, and the choice of germanium as internal reflection element is because of its small penetration depth due to a high refraction index. The Chemical Bath Deposition method has been used to deposit metal sulphides onto germanium internal reflection elements. For determining the adsorption of heptyl xanthate onto lead sulphide a novel method has been tested, and verified as capable in recovering information about surface reactions at a lead sulphide/aqueous interface. In the study of surface reactions the substrate is of vast importance, implying that the chemistry of the surface has to be well characterised. This work has utilized X-ray Photoelectron spectroscopy, and ATR spectroscopy, in the characterisation of the different surfaces. The adsorption kinetics has been followed to adsorption equilibrium at different concentrations. In the case of heptyl xanthate adsorbed at the zinc sulphide/aqueous interface, an adsorption isotherm has been calculated from the equilibrium data. On the assumption that the adsorption step was rate controlling a second order rate equation was derived and adsorption rate data tested according to this equation. In addition, an orientation study of the heptyl xanthate molecule at the different interfaces was performed, which requires polarised infrared light. In the case of heptyl xanthate adorbed onto germanium, both surface excess and a degree of alignment of the alkyl chain from the surface normal has been calculated.Godkänd; 2004; 20070127 (ysko)
17
Healy, J. "Some metal sulphide interactions governing copper solubility and availability". Thesis, Robert Gordon University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379262.
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Fredriksson, Andreas. "Adsorption of heptyl xanthate at the metal sulphide/aqueous interface /". Luleå, 2004. http://epubl.luth.se/1402-1757/2004/01.
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Horton, Joseph Hugh. "Surface photo-oxidation and metal film growth processes on amorphous GeSâ†2". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337978.
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Knipe, Stephen William. "The role of sulphide surfaces on the deposition of precious metals from hydrothermal fluids". Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260201.
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Sui, Chihyu Caroline. "Metal ion transfer between sulphide minerals and effect on xanthate interaction with pyrite". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40263.
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Metal ion production by minerals alone and in pairs was studied by solution analysis, extraction with ethylene diamine tetraacetate (EDTA) and laser ion mass spectroscopy (LIMS) for combinations of pyrite, pyrrhotite, galena, and sphalerite. The effect of grinding, pH, and the presence of xanthate was studied. Metal ion transfer between sulphide minerals was determined.Metal ion production with minerals in pairs was different from that for single minerals. The amount of metal ion in solution followed a galvanic interaction model, increasing for the anodic mineral and decreasing for the cathodic mineral. However, from the EDTA extraction technique, the concentration of metal ions on the mineral surface increased for both minerals. The mechanism of additional metal ion production on the cathodic mineral is unclear, but may be related to reaction between the mineral and OH ions formed on the surface as a result of galvanic interaction.
Metal ions transferred between two minerals in contact. In the case of pairing with pyrite, the larger proportion of Fe remained on pyrite, while 50% or more of Zn (from sphalerite) and Pb (from galena) transferred to pyrite.
The effect of Pb ions on pyrite in the presence of xanthate, and diethylene triamine (DETA) was investigated by cyclic voltammetry, ex situ spectroelectrochemical analysis and zeta potential measurements.
Once pyrite was contaminated by Pb ions, uptake of xanthate was promoted at pHs 9.2 and 10.5 with lime as pH modifier. The source of Pb--from solution or from contact with galena--was not a factor, and the effect was evident at Pb concentrations as low as 1 ppm. With soda ash as pH modifier, the effect of Pb was suppressed, perhaps due to formation of lead carbonate. The only xanthate product detected was dixanthogen, unless an initial potential less than $-$800 mV/SCE was imposed (when Pb$ sp{2+}$ is reduced to Pb$ sp0)$ and lead xanthate formed.
Xanthate adsorption on Pb-contaminated pyrite was suppressed by DETA, but relatively large concentrations were required. DETA decreased the potential at the mineral/solution interface, which retarded oxidation of xanthate to dixanthogen.
A mechanism of Pb "activation" of pyrite was proposed: adsorption of Pb(OH)$ sp+$ on pyrite provided sites for xanthate adsorption forming Pb(OH)X, on which xanthate ions were attached by hydrophobic interaction and oxidised to dixanthogen.
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Khalid, Muhammad. "Gold cyanidation : gold associated with silver minerals embedded within base-metal sulphide matrices". Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27893.
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Les problématiques dans le traitement des minerais aurifères deviennent de plus en plus significatives avec la déplétion des gisements à haute teneur autour du monde. L’or est trouvé principalement sous forme métallique dans la nature et est fréquemment associé avec des minéraux d’argent ou des sulfures métalliques. Dans la présente thèse, le rôle des minéraux d’argent sur la cyanuration de l’or au sein de sulfures métalliques est étudié en détail relativement aux interactions galvaniques et aux phénomènes de passivation de surface. Puisque les contacts galvaniques permanents naturellement présents à l’intérieur des grains des minéraux sont difficiles à répliquer en utilisant des montages standards d’électrodes à disques rotatifs ou de la pulpe de minerais riches en sulfures, une stratégie utilisant un réacteur à lit fixe (PBR) a été adoptée afin d’isoler et de quantifier les contributions des interactions galvaniques et des réactions de passivation sur les taux de lixiviation de l’or et de l’argent au sein de sulfures métalliques. Des mélanges d’or, de minéraux d’argent et d’autres sulfures métalliques ont été placés dans le réacteur à lit fixe afin de créer des contacts galvaniques inter-particules permanents parmi les constituants. La pyrite, la sphalérite et la stibnite ont été choisis comme sulfures métalliques modèles. De l’argent métallique (Ag), de l’acanthite Ag₂S) et de la pyrargyrite (Ag₃SbS₃) sont pour leur part les minéraux d’argent qui ont été étudiés. Les interactions galvaniques entre l’or, l’argent et la pyrite ainsi que la sphalérite ont résulté en un comportement complexe de la lixiviation de l’or et de l’argent sous l’impact direct des contacts galvaniques ainsi que sous l’impact des effets de passivation. Les minéraux d’argent ont pour leur part démontré un effet amoindrissant pour la lixiviation de l’or dans de la chalcopyrite et de la stibnite. Des stratégies ont été investiguées pour améliorer la cinétique de lixiviation de l’or en présence de minéraux d’argent et de sulfures métalliques. Des solutions de cyanure contant des sels de plomb ont augmenté la récupération de l’or et ont permis une neutralisation des effets négatifs issus de la présence des sulfures métalliques, particulièrement dans le cas de la chalcopyrite. De plus, l’addition de plomb a augmenté les cinétiques de lixiviation de l’or de manière significative pour l’or et l’argent associé à de la pyrite, de la chalcopyrite et de la sphalérite. Un prétraitement à l’aide d’une solution alcaline d’acétate de plomb a été étudié pour les mêmes couples de minéraux et il a été démontré que cette stratégie augmente la récupération de l’or dans le cas de la pyrite, de la chalcopyrite et de la sphalérite. D’autre part, la stibinite a démontré un effet net de réduction de la dissolution de l’or avec des minéraux d’argent. Des films recouvrant la surface des particules d’or dans le cas de la cyanuration de l’or en présence des sulfures métalliques ont aussi été observés dans le cas de la chalcopyrite et de la stibnite.Numerous non-idealities in gold processing are becoming increasingly significant with the depletion of free-milling oxide ores around the globe. Gold is mostly found in nature in metallic form and is associated with silver minerals and bae-metal sulphides. In the present thesis work, the role of silver minerals on gold cyanidation with base-metal sulphides was elucidated in detail on the relative importance of galvanic interactions and passivation phenomena. As the permanent galvanic contacts, inherently present within the ore grains, are hard to achieve between gold rotating disk electrode and slurried base-metal sulphide-rich ores, a packed-bed reactor (PBR) strategy was thus adopted to single out and quantify the virtual contributions of galvanic interaction and passivation effect on the gold and silver leaching rates during gold cyanidation with silver minerals and base-metal sulphides. The mixtures of gold, silver-minerals and sulphides were filled in the PBR to ensure the permanent particle-particle micro-electrical contacts among all ore constituents. Pyrite, chalcopyrite, sphalerite and stibnite were the sulphidic minerals investigated in the present gold-silver cyanidation study. Metallic silver (Ag), acanthite (Ag₂S) and pyrargyrite (Ag₃SbS₃), were the silver-minerals taken into account. Galvanic interactions were found to alleviate the leaching of gold and silver to various extents, for gold and silver minerals associated with pyrite and sphalerite, both under galvanic and passivation impact from the sulphide minerals. Silver minerals were found retarding to the gold leaching for chalcopyrite and stibnite minerals. Strategies were investigated to enhance the gold leaching kinetics in the presence of silver minerals and base-metal sulphides. Lead containing cyanide solution enhanced gold recovery and was found to neutralize significantly the negative effect of sulphidic minerals, particularly for chalcopyrite. Moreover, lead addition enhanced gold leaching kinetics significantly for gold and silver minerals associated with pyrite, chalcopyrite and sphalerite. Pre-treatment with alkaline lead acetate tested on sulphide associated mixtures of gold and silver minerals affirmed enhanced gold recovery in case of pyrite, chalcopyrite and sphalerite minerals. Stibnite found severely retarding towards gold dissolution with silver minerals. Surface obstructing films were observed on gold particles for gold cyanidation with silver minerals and base-metal sulphides in case of chalcopyrite and stibnite.
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Mokone, Thebe Phillip. "Metal sulphide precipitation : effect of operational parameters on particle characteristics and process efficiency". Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/13429.
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Includes bibliographical references (p. 127-141).Acid mine drainage (AMD) is one of the major, long-term environmental challenges facing the minerals processing industry. Uncontrolled discharges have polluted thousands of kilometres of rivers, as well as surface and groundwater bodies with acidic effluents high in dissolved metals and sulphate. Conventional treatment technologies rely on oxidation, neutralisation and precipitation. While these may be effective they are expensive and not sustainable in the long term. Several biological treatment technologies, based on the activity of sulphate reducing bacteria (SRB), have been successfully developed and applied at both laboratory and industrial scale. The SRB uses sulphate as the terminal electron acceptor and with a suitable electron donor produce bicarbonate alkalinity and sulphide. These can be used to neutralise acidic effluents and effect precipitation of dissolved metal ions as metal sulphides. However, a number of challenges exist around the precipitation step, particularly where the recovery of valuable metals is desired. Metal sulphide precipitation reactions are inherently driven by extremely high levels of supersaturation. As a result, metal sulphide precipitation reactions are difficult to control and a large number of small particles are formed during the process. This leads to significant technical challenges with respect to solid-liquid separation and subsequent recovery of the precipitate. Despite the theoretically high metal removal, related to the low solubility of metal sulphides, practical efficiency is often significantly lower. Previous studies have shown that metal precipitation reactions require controlled physico-chemical conditions and the control of high levels of supersaturation to achieve optimum efficiency. The objective of this study was to extend this approach to metal suphide systems.Initial data indicated that conventional techniques to manage supersaturation were not effective and subsequent work focused on characterising the effect of reaction conditions on particle properties and investigating downstream processing options. The intention of this research was to bridge the gap between highly fundamental studies and practical application of sulphide precipitation technologies.
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Haring, Peter G. "The nature of heavy metal contamination in organic lake sediments near the Buchans massive sulphide base metal mines, Central Newfoundland /". Internet access available to MUN users only, 2002. http://collections.mun.ca/u?/theses,25133.
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Naylor, Chris. "An investigation of the interactions of metals and sulphide in anoxic sediments". Thesis, Lancaster University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525312.
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Fredriksson, Andreas. "Kinetics of collector in-situ adsorption on metal sulphide surfaces studied by ATR-FTIR spectroscopy". Doctoral thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26680.
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In sulphide mineral flotation, a sufficient hydrophobicity of the mineral surfaces is obtained by the adsorption of collector chemicals at the metal sulphide/aqueous interface. This surface alteration is of fundamental and applied interest. In this thesis, attenuated total reflection infrared spectroscopy has been used to monitor the adsorption kinetics and the orientation of heptyl xanthate when adsorbed onto three solid surfaces - germanium, zinc sulphide and lead sulphide in-situ. The Chemical Bath Deposition method has been used to deposit metal sulphides onto germanium internal reflection elements, and verified as capable in synthesizing metal sulphide surfaces for adsorption studies recovering information about surface reactions at metal sulphide/solution interfaces. In the study of surface reactions the substrate is of great importance, implying that the chemistry of the surface has to be well characterised. This work has utilized X-ray photoelectron spectroscopy in the characterisation of the different surfaces. The adsorption kinetics has been followed to monitor the adsorption equilibria at different concentrations. In the case of heptyl xanthate adsorbed at the zinc sulphide/aqueous interface, an adsorption isotherm has been calculated from the equilibrium data. On the assumption that the adsorption step was rate controlling a pseudo-first order equation was derived and adsorption rate data, in all the three studied systems, tested according to this equation. In addition, an orientation study of the heptyl xanthate molecule at the different interfaces was performed, which requires polarised infrared light. Density Functional calculations of a free heptyl xanthate molecule, and a heptyl xanthate molecule adsorbed on a pure Ge(111) were utilized to get more information about the in-situ adsorption of heptyl xanthate on a germanium surface. The important vibration bands were assigned to different vibrations, and the theoretical infrared spectra were compared with the experimentally analyzed spectra. This study shows the strengths of using advanced first-principle Density Functional Theory in the interpretation of real surface adsorption systems.Godkänd; 2006; 20070314 (evan)
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McElhinney, Rob. "Style and genesis of base metal sulphide mineralisation of Angas prospect - Strathalbyn area, South Australia /". Title page, table of contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09S.B/09s.bm141.pdf.
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Hamuyuni, Joseph. "Measurement of surface tension in base metal sulphide mattes by an improved sessile drop method". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71651.
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Gqebe, Sibongiseni Yamkela. "Improving the settleability of a metal sulphide suspension by the application of a magnetic field". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20053.
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Gravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. More especially in sulphide precipitation, where high levels of supersaturation dominate and nucleation is favoured. This results in a large number of colloidal particles with a highly negative surface charge, which remain suspended in solution. The high surface charge of the suspension results in strong attraction/interaction between the ions on the particle surface and counter-ions in solution. Moreover, this strong interaction between ions on the particle surface and counter-ions in solution results in a charge build-up that renders the suspension stable. In order to induce gravitational sedimentation of these particles, a redistribution of ions close to the particle surface is required. This study therefore seeks to redistribute ions close to the particle surface by applying a magnetic field. This results in the reduction of inter-particle electrostatic repulsive forces and subsequent increase in the zeta potential of a suspension. For the purposes of this study, a copper sulphide suspension was used. A T-mixer was used as the reaction zone for the precipitation of each suspension. Subsequent to this, the suspended copper sulphide particles were exposed to a range of field strengths for set exposure times and their zeta potential was measured before and after exposure to the magnetic field. The effect of magnetic field strength, exposure time and particle speed on the zeta potential were tested. All particles had an initial zeta potential value equal to or less than - 40 mV prior to magnetic field exposure. A significant increase in zeta potential was observed with values reaching a maximum of - 16.5 mV when exposed to a 2 T field strength for 40 minutes. An increase in the zeta potential corresponds to a reduction in repulsive electrostatic forces between suspended particles due to the Lorentz force exerted by a magnetic field on the particle surface. DLVO plots were used to quantify this reduction in repulsive electrostatic forces.
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Lin, Qingyang. "Use of X-ray computed microtomography to measure the leaching behaviour of metal sulphide ores". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/25274.
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Heap leaching is an important hydrometallurgical method to extract valuable metals from ores, especially low grade ores. The main disadvantages of heap leaching are the long processing time and low extraction efficiencies. Currently, a major barrier in fully understanding the leaching process is the study of the mass transport and surface chemistry at individual ore particle and mineral grain scale. This thesis describes a combined experimental and modelling approach to visualise, quantify and predict the leach behaviour based on X-ray Computed Microtomography (XMT, or micro-CT). An automatic image processing package was developed to process the 3D volume data. Individual ore particles as well as individual mineral grains can be tracked using a centroid tracking algorithm and a novel fast tracking algorithm respectively. The systematic and random errors and uncertainties in the image volume measurements were quantified. It was found that both the systematic and random errors are a strong function of the grain size relative to the voxel size. The random error can be reduced by combining the results from either multiple scans of the same object or scans of multiple similar objects while the systematic error can be eliminated by using volume standards. The leach performance for a leaching column was quantified at different scales and it was found that the leach behaviour and its variability were difficult to quantify at large scales (column and individual ore particle scale), but can be quantified at mineral grain scale by using a novel statistical analysis method. The tracked grains were divided into different size-distance categories to analyse the average leach performance and the variation for each category. Both grain size and distance dependencies were observed. The size dependency is more dominant at the early stage of leaching whereas the distance dependency can significantly influence the ultimate recovery. A method for using the data to estimate the variability in the in-situ surface kinetics was also developed. A model for simulating the grain dissolution and the resultant kinetics based directly on XMT based 3D volume is introduced. The simulations were able to accurately predict both the overall leaching trends, as well as the leaching behaviour of mineral grains in classes based on their size and distance to the particle surface.
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Shaw, Alan. "Synthesis and reactivity studies on oxo and sulphide compounds of the early transition metals". Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6554/.
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This thesis describes studies directed towards the preparation of new oxo compounds of the early transition metals with a view to delineating some of the complex factors which govern their stability and reactivity. For a number of the types of compound studied, the work has also been extended to analogous sulphide systems in order to provide a contrast with another chalcogenide element and further aid an understanding of the bonding and reactivity of both of these elements in a transition metal enviroment. Chapter 1 highlights the areas of transition metal oxo chemistry of relevance to the general theme of the thesis. Chapter 2 describes the use of the commercially available reagents Me(_3)SiYR (R = alkyl, SiMe(_3); Y = O, S), for rapid, convenient, solution syntheses of transition metal oxohalide and sulphidohalide compounds of molybdenum, tungsten, niobium and tantalum. In addition, this methodology allows the preparation of mixed oxosulphidohalide materials and, in certain cases, intermediate alkoxo(siloxo) halide compounds have been isolated. Chapter 3 describes the synthesis, characterisation and reactivity of a series of mononuclear mono-oxo complexes of molybdenum and tungsten including M(O)(OAr)(_4) [M=W, Ar=2,6-Me(_2)C(_6)H(_3) (DMP), 2,4,6-Me(_3)C(_6)H(_2) (TMP), 2,6-Pr(^i)C(_6)H(_3) (DIPP); M=Mo, Ar=(DMP)], M(_2)(O)(_3)(DMP)(_6) and Mo(O)C1(_2)(DMP)(_2). Attempts to synthesise related mononuclear complexes containing the cis di-oxo moeity are also discussed. Chapter 4 describes the synthesis and reactivity of seven coordinate oxo and sulphidohalide derivatives of niobium and tantalum which exhibit the phenomenon of bond-stretch isomerism. Compounds prepared include Nb(O)Br(_3)(PMe(_3))(_3), Nb(S)X(_3)(PMe(_3))(_3) (X=C1, Br) and Ta(S)C1(_3)(PMe(_3))(_3). The latter three have been characterised by X-ray crystallography. Chapter 5 describes the synthesis and reactivity of half-sandwich oxo compounds of niobium and tantalum. Some of the derivatives prepared include[CpNbC1(_3)](_2)(µ(_2)-O), [CpTaC1(_3)](_2)(|µ(_2)-O) and [Cp*TaC1(_3)](_2)(µ(_2)O). The stability of [Cp*Ta(O)Cl(_2)](_2) has been investigated and the X-ray structure of the trinuclear decomposition product Cp*(_3)Ta(_3)O(_4)C1(_4) is described. Chapter 6 describes the use of alkali metal aryloxides as intercalating agents and the preparation of a series of novel intercalation compounds, of the type W(O)(_2)C1(_2)xM (M = Li, Na and K) which display the properties characteristic of tungsten bronzes. Chapter 7 gives experimental details for chapters 2 6.
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Ghavami-Riabi, Reza. "Geochemical exploration for base metal sulphide deposits in an arid environment (eastern Namaqua Metamorphic Province), South Africa". Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-06192007-100552.
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Lazarevic, David Andrew. "In-situ Removal of Hydrogen Sulphide from Landfill Gas : Arising from the Interaction between Municipal Solid Waste and Sulphide Mine Environments within Bioreactor Conditions". Thesis, KTH, Industriell ekologi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32770.
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This project was compiled in co-operation with the Royal Institute of Technology, Stockholm and Veolia Environmental Services (Australia) at the Woodlawn Bioreactor in NSW, Australia. Hydrogen sulphide is an unwanted component of landfill gas, raising occupational health and safety concerns, whilst leading to acid gas corrosion of power generation equipment and increased emissions of SOx, a primary constituent of acidification. Australian governmental requirements to place a periodic cover over the unused proportion of the tipping surface of landfills and bioreactors create an interesting opportunity for the removal of the hydrogen sulphide component of landfill gas. Using waste materials containing a high concentration of metals as waste cover can enhance the precipitation of sulphur in the form of metal sulphides. The reduction of sulphate via sulphate reducing bacteria is prevalent in sites that have a sizeable inflow of sulphate. The Woodlawn Bioreactor is located in an area where the influence of sulphate has a critical influence of bioreactor performance and production of hydrogen sulphide. Through a series of experimental bioreactors it was established that from the use of metalliferous periodic waste covers, the hydrogen sulphide component of landfill gas was maintained at an extremely low level when compared to the levels of hydrogen sulphide produced in waste under the influence of high sulphate loads with no waste cover.www.ima.kth.se
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Kiventerä, J. (Jenni). "Stabilization of sulphidic mine tailings by different treatment methods:heavy metals and sulphate immobilization". Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223964.
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Abstract Millions of tons of mine tailings are generated worldwide annually. Since many valuable metals such as Ag, Cu, Pb, Zn, Au and Ni are usually incorporated into sulphidic minerals, a large proportion of the tailings generated contain high amounts of sulphates and heavy metals. Some of these tailings are used as paste backfill material at mining sites, but large amounts are still being deposited into the tailings dams under water coverage. Sulphidic minerals are stable underground but after mining of the ore and several processing steps these minerals can be oxidized when they come into contact with water and air. This oxidation generates acid and thus reduces the pH of the surrounding environment. Furthermore, the heavy metals present in the mine tailings can be leached into the environment. This phenomenon, called Acid Mine Drainage (AMD), is one of the most critical environmental issues related to the management of sulphidic-rich tailings. Since AMD generation can still occur hundreds of years after closure of the mine, the mine tailings need stable, sustainable and economically viable management methods in order to prevent AMD production in the long term. The aim of this PhD thesis was to study various solidification/stabilization (S/S) methods for the immobilization of sulphidic mine tailings. The main focus was to develop a suitable chemical environment for achieving effective heavy metal (mainly arsenic) and sulphate immobilization while simultaneously ensuring good mechanical properties. Three treatment methods were tested: alkali activation, stabilization using hydrated lime (Ca(OH)2) and blast furnace slag (GBFS), and calcium sulphoaluminate-belite (CSAB) cement stabilization. The mine tailings used in this study contained large amounts of sulphates and heavy metals such as Cr, Cu, Ni, Mn, Zn, V and As. The leaching of arsenic and sulphates from powdered tailings exceeded the legal limits for regular and inert waste. All treatment methods were found to generate a hardened matrix that was suitable for use as a backfilling or construction material, but the calcium-based binding system was the most suitable for effective immobilization of all the heavy metals (including arsenic) and the sulphates. Precipitation in the form of calcium sulphates/calcium arsenate and the formation of ettringite are the main stabilization methods employed in calcium-based stabilization/solidification (S/S) systems. Some evidence of physical encapsulation occurring simultaneously with chemical stabilization was noted. These results can be exploited further to develop more sustainable mine tailing management systems for use in the future. The tailings could be stored in a dry landfill area instead of in tailing dams, and in this way a long-term decrease in AMD generation could be achieved, together with a high potential for recyclingTiivistelmä Monet arvometallit kuten kulta, kupari ja nikkeli ovat sitoutuneena sulfidipitoisiin mineraaleihin. Louhittaessa ja rikastettaessa näitä sulfidimineraaleja syntyy miljoonia tonneja sulfidipitoisia rikastushiekkoja vuosittain. Rikastushiekat voivat sisältää myös runsaasti erilaisia raskasmetalleja. Osa rikastushiekoista hyödynnetään kaivostäytössä, mutta suurin osa rikastushiekoista läjitetään edelleen ympäristöön rikastushiekka-altaisiin veden alle. Kun sulfidipitoinen malmi kaivetaan ja käsitellään, sulfidiset mineraalit hapettuvat ollessaan kosketuksissa veden ja hapen kanssa. Hapettuessaan ne muodostavat rikkihappoa, laskien ympäristön pH:ta jolloin useimmat raskasmetallit liukenevat ympäristöön. Muodostuvia happamia kaivosvesiä voi syntyä vielä pitkään kaivoksen sulkemisen jälkeen ja ovat näin ollen yksi suurimmista kaivosteollisuuteen liittyvistä ympäristöongelmista. Lisäksi suuret rikastushiekka-altaat voivat aiheuttaa vaaraa myös ihmisille, mikäli altaan rakenteet pettävät. Rikastushiekkojen kestäviä ja ympäristöystävällisiä varastointimenetelmiä täytyy kehittää, jotta näitä ongelmia voidaan tulevaisuudessa ehkäistä. Tässä työssä tutkittiin menetelmiä, joilla kultakaivoksella syntyvät sulfidipitoiset vaaralliseksi jätteeksi luokitellut rikastushiekat saataisiin stabiloitua tehokkaasti. Työssä keskityttiin kolmeen erilaiseen menetelmään: alkali-aktivointiin, stabilointiin kalsiumhydroksidin ja masuunikuonan avulla ja stabilointiin CSAB sementin avulla. Valmistettujen materiaalien mekaanisia ja kemiallisia ominaisuuksia arvioitiin. Tavoitteena oli ymmärtää, miten eri menetelmät soveltuvat raskasmetallien (erityisesti arseenin) ja sulfaattien sitoutumiseen ja mikä on eri komponenttien rooli reaktioissa. Alkali-aktivoimalla rikastushiekkaa sopivan sidosaineen kanssa saavutettiin hyvät mekaaniset ominaisuudet ja useimmat haitta-aineet sitoutuivat materiaaliin. Ongelmia aiheuttivat edelleen sulfaatit ja arseeni. Kalsiumpohjaiset menetelmät sitoivat raskasmetallit (myös arseenin) ja sulfaatit tehokkaimmin. Sulfaatit ja arseeni saostuivat muodostaen niukkaliukoisia komponentteja kalsiumin kanssa. Samanaikaisesti rakenteeseen muodostui ettringiittiä, jolla on tutkitusti hyvä kyky sitoa erilaisia raskasmetalleja rakenteeseensa. Raskasmetallit myös kapseloituivat rakenteen sisään. Työn tuloksia voidaan hyödyntää, kehitettäessä rikastushiekkojen turvallista varastointia. Kun materiaalille saavutetaan riittävän hyvä lujuus ja kemiallinen stabiilius, rikastushiekat voitaisiin läjittää tulevaisuudessa kuivalle maalle altaan sijaan. Näin vältyttäisiin rikastushiekka-altaiden rakentamiselta ja voitaisiin vähentää happamien kaivosvesien muodostumista pitkällä ajanjaksolla. Saavutettujen tulosten perusteella rikastushiekkoja voidaan mahdollisesti tulevaisuudessa hyödyntää myös erilaisissa betonin tapaisissa rakennusmateriaaleissa
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Sheridan, Liam A. "Alternative cadmium source precursors for the growth of cadmium sulphide and cadmium selenide by metal-organic chemical vapour deposition". Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339511.
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Beer, Michael P. "A study of volatile precursors for the growth of cadmium sulphide and cadmium selenide by Metal Organic Vapour Deposition". Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303986.
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Chetty, Deshenthree. "Geochemical fingerprinting of carbonate wall rock alteration at major base metal sulphide deposits in the Otavi Mountain Land, Namibia". Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/9555.
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Bibliography: leaves 134-147.The Otavi Mountain Land is a base metal ore province in which base metal sulphide deposits are hosted by platform carbonates in a foreland fold-and-thrust belt on the northern edge of the PanAfrican Damara Belt. Deposits have been classified as the Berg Aukas- and Tsumeb- types, based on differences in ore association, stratigraphic position and geochemistry of ores and gangue carbonates. Mineralisation at each of these deposits is accompanied by carbonate alteration in the form of dolomite and calcite veins, carbonate recrystallisation, calcitisation and carbonate silicification. Optical cathodoluminescence imaging, electron probe micro analysis, X-ray fluorescence spectrometry, X-ray diffraction, high performance ion chromatography, proton probe micro analysis, stable isotope techniques, and fluid inclusion microthermometry were employed (i) to differentiate between carbonate generations associated with the alteration and mineralisation, particularly for the more economic Tsumeb-type deposits, represented by Tsumeb and Kombat, as well as in comparing between Berg Aukas- and Tsumeb-type deposits; (ii) to set constraints on the fluids effecting such alteration and associated mineralisation; (iii) to determine the relationship of the Khasib Springs deposit, for which little geochemical data exists, to deposits of the Tsumeb-type, and (iv) to identify those parameters which are diagnostic of Tsumeb-type mineralisation.
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Markström, Jimmy. "Is mercury mobilized from acid sulfate soils? : Interpreting the mercury record from lake- and marine sediments in Persöfjärden and adjacent sea bay". Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-171611.
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Acid sulfate (AS) soils are characterized by a large pool of sulfates which may provide significant amounts of acidity and heavy metals – commonly nickel (Ni), Cobolt (Co), Zinc (Zn) and Arsenic (As) - to surrounding surface waters. The occurrence of AS soils is widespread, covering 17 million ha globally, and they are known for threatening freshwaters in Australia, North America as well as in many tropical regions. Mobilization of mercury (Hg) from AS soils is however poorly studied and could potentially be an environmental problem of concern due to its toxicity and capacity of bioaccumulating in food webs. In this study I investigated whether Hg is mobilized from AS soils by conducting chemical analyses on sediment samples from a 1,6 m deep lake core and a transect of surficial sediment samples in an adjacent sea bay. Here, I used zircon (Zr) and zinc (Zn) as proxies for silicate sources and sulfide soil sources, respectively. I found that Zn and Hg concentrations normalized to the organic matter content (LOI) showed a significant correlation in the lake core; hence, Hg in the sediment co-varied with my sulfide proxy and showed no correlation to my silicate proxy, and I then conclude that a considerable fraction of mercury in the studied sediment has a likely origin from AS soils.
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Cherico, Lia. "Development of a geometallurgical data set for the prediction of operating conditions to beneficiate base metal sulphide ore via flotation". Thesis, Cherico, Lia (2017) Development of a geometallurgical data set for the prediction of operating conditions to beneficiate base metal sulphide ore via flotation. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40454/.
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The optimisation and process development surrounding the beneficiation of nickelcopper sulphide ores is of fundamental importance when considering the continued rise in global demand for base metals. The selective sequential flotation of these ores is accompanied with various processing challenges due to the low-grade and mineralogical complexity associated with such deposits.
One of the greatest challenges faced during the flotation stage is the successful separation of the nickel and copper valuable minerals from the pyrrhotite gangue, significantly decreasing the grade and recovery of the final products. Utilisation of the TETA/sulphite depressant system has proven to significantly improve the flotation process, however its dosage requirements have been found to vary extensively between ore types. The investigations undertaken throughout this thesis project and the subsequent findings discussed in this report have allowed for a greater insight involving this system and its influence on the selective sequential flotation process.
The research undertaken throughout this project focuses on the mineralogy of nickelcopper sulphide ores and their subsequent concentration. Mineralogical and metallurgical analysis of this work has found that the individual mineral compositions within an ore have a large impact of its response to flotation processes and the successful separation of copper and nickel concentrates.
This thesis paper emphasises the fundamental importance of a holistic approach in order to understand the interactions and mechanisms involved in the selective flotation of nickel-copper sulphides. This will allow for the optimisation and development of operations with improved process control systems and the ability to predict mineral flotation behaviours with variations in ore type.
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Syrovetnik, Kristina. "Long-term metal retention processes in a peat bog : Field studies, data and modelling". Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-460.
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De, Beer Deon Johan. "The relationship of weld metal hardness residual stress and susceptible to stress corrosion cracking in hydrogen sulphide environment in A516 Grade 70 carbon steel shielded metal arc welded joint". Diss., University of Pretoria, 2002. http://hdl.handle.net/2263/71679.
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In the petrochemical industry, carbon steels exposed to H2S environments may be susceptible to stress-corrosion cracking. A tensile residual stress and high hardness increases the risk of cracking in H2S environments. NACE SP 0472 limits weld metal hardness to 210 HV10 (200 HB) and heat-affected zone hardness to 250 HV10 to prevent stress-corrosion cracking of carbon steel welds in H2S. The hardness is controlled by the weld thermal cycle or by a post-weld heat treatment. In this project, the effect of hardness on the susceptibility to stress-corrosion cracking was investigated by increasing electrode strength systematically and measuring residual stress in the weld metal in the as-welded state. Samples were manufactured from SA 516 Gr 70, a carbon steel used extensively in the petrochemical industry. Heavily clamped plates were welded to minimise distortion and to maximise residual stress. The weld metal hardness was increased by using E6013, E7018-1, E8018-B2 and E9018-B3 electrodes without a post-weld heat treatment. Mechanical tests included all-weld and transverse tensile tests, impact strength and hardness testing. As the nominal strength of the weld metal increased, the all-weld tensile strength increased from 512 to 829 MPa, while the yield strength increased from 443 to 659 MPa. The average weld metal hardness increased from 177 to 317 HV10. The transverse tensile strength was between 511-517 MPa, while the yield strength (in the transverse direction) was between 360 and 382 MPa. Residual stresses of the welded joint were measured by neutron diffraction in the through-thickness, longitudinal and transverse direction. The Von Mises theorem evaluated the principle residual stress. Results indicate that the residual stress in the weld metal may be up to 99% of the yield strength. For stress-corrosion cracking, the samples were submerged in the standard TM0177-2005 test solution for 30 days. The only sample to crack was the E9018, with an average weld metal hardness of 317 HV10. The study results were consistent with the NACE SP0472 specification and earlier publications.Dissertation (MEng)--University of Pretoria, 2017.
TM2019
Materials Science and Metallurgical Engineering
MEng
Unrestricted
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Lopes, Mariângela Vieira. "Desenvolvimento de procedimentos e sistemas automatizados para controle de qualidade de carnes e produtos cárneos". Instituto de Química, 2005. http://repositorio.ufba.br/ri/handle/ri/20507.
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Neste trabalho, foram desenvolvidos procedimentos e sistemas automatizados para o controle de qualidade de carnes e produtos cárneos quanto à presença de aditivos (NO2- e NO3-), degradação (evolução de H2S), presença de adulterante (SO3-) e riscos de contaminação pela capacidade sortiva de metais. O desenvolvimento destes procedimentos vem contrapor as metodologias clássicas recomendadas pelos órgãos oficiais brasileiros. Os métodos e procedimentos aqui desenvolvidos obedecem às recomendações da Química Analítica moderna, as quais priorizam precisão, exatidão, sensibilidade, custos operacionais, versatilidade, robustez, rastreabilidade, minimização de resíduos e produtividade analítica. O sistema de analise por injeção em fluxo (FIA), para análise seletora e discriminatória de H2S evoluído pela carne, foi desenvolvido baseado no método do azul de metileno. O emprego da multicomutação, associado à câmara de pervaporação, conferiu versatilidade ao sistema com produtividade analítica de 30 determinações h-1. Paralelo a isto, foi realizada uma avaliação da degradação de carnes empregando a espectroscopia no infravermelho próximo (NIR) para averiguação das condições de conservação de carnes. Os resultados foram concordantes para as duas metodologias (NIR e FIA), sendo possível detectar indícios de deterioração após 30 min de exposição da carne à atmosfera em temperatura ambiente. O desenvolvimento de sistema em fluxo para análise seqüencial de NO2- e NO3-, em produtos cárneos, utilizando câmara de tubos concêntricos (CTC) foi baseado no método de Greiss. A CTC proporcionou a divisão da zona da amostra, facilitando as determinações seqüenciais de NO2- e NO3-. A subzona da amostra que passava pelo tubo central da CTC resultava apenas na determinação do NO2-. A amostra que passava pelo tubo externo (coroa) da CTC, percolava grãos de cádmio coperizado, resultando na redução do NO3- existente à NO2-. Este sistema ofereceu boa sensibilidade para a quantificação dos analitos, apresentando limites de detecção de 0,018 e 0,036 mg L-1 para NO2- e NO3-, respectivamente. O procedimento proposto atingiu produtividade analítica de 120 determinações h-1. O desenvolvimento de sistema automatizado em fluxo para análise discriminatória de sulfito em carnes foi baseado no método da p-rosanilina. Foi empregado câmara de permeação gasosa, onde o SO3- presente na amostra, permeava através de membrana de PTFE para a reação com o reagente cromogênico. O sistema foi satisfatório para screening analysis, com produtividade analítica de 12 determinações h-1. A capacidade sortiva de metais pela carne bovina foi também avaliada. Foi avaliado o contato estático da carne com soluções de referência de Cd e Pb, preparadas com água de torneira, a pH 6. Foi empregada válvula multiportas, com oito canais para execução dos experimentos, enquanto que metais foram determinados por ICP OES. Os resultados indicaram um elevado poder sortivo, cerca de 80% para ambos os metais, evidenciando risco potencial de contaminação para as carnes submetidas a práticas inadequadas de abate e comercialização
In the present work automated systems and procedures to control the quality of meats and meat products had been developed, in concern to the additive presence (NO2- and NO3-), degradation (H2S evolution) and presence of adulterating species (SO32-). Also the metal sorption capacity on meat was evaluated. The development of these methods comes to oppose classical methods recommended by brazilian official agencies. The developed procedures follow the recommendations of the modern Analytical Chemical, which prioritizes the precision, exactness, sensitivity, traceability, robustness, reduced operational costs, lesser production of residue and raised analytical productivity. The flow analysis (FIA) procedure to discriminate H2S in meat sample was developed based on methylene blue method. Multicommutation, associated to gas permeation conferred versatility to the system with analytical throughput of 30 determinations h-1. Parallel to this, the spectroscopy in the near infrared region (NIR) was carried out to evaluate meat degradation. A flow system for sequential NO2- and NO3- analysis in meat products, using concentric tubes chamber (CTC) was based on the Greiss method. The CTC provides the division of sample zone, permitting the sequential analysis. The sample sub zone that passed for the central pipe of the CTC resulted in the determination of the NO2-. The sample that passed through external CCP pipe, percolated the cadmium column, allowing the reduction of the NO3- to NO2-. This system offers sensitivity in the quantification of anilities with detection limits of 0.036 for NO3- and 0.018 mg L-1 for NO2-, reaching 120 determinations h-1. The flow system for the screening analysis of SO32- in meat sample was based on p-rosanilne method. Chamber for gas permeation was employed. The system revealed efficient for screening analysis with analytical throughput of 12 determination h-1. The metal sorption capacity on meat was evaluated. The investigated species comprised Cd and Pb from solutions prepared with tap water at pH 6. In the experimental set, it was employed an eight channels multiport valve in order to prepare part of the samples, while the metal determinations was carried out by using ICP OES technique. The results obtained demonstrated an expressive retention capacity of meat for Cd2+ and Pb2+ ions with percentages ca. 80% (m/m) for both metals, indicating the potential risks related to the consumption of meat submitted to inappropriate conditions of abattoir, handling, storage and commercialization.
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Mattisson, Emmy. "Increased leaching of metals as a result of foundation work". Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232049.
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Heavy metal contamination in the environment is a global issue that is likely to increase in the future. This report investigates a construction area in which increased concentrations of the heavy metals cadmium, cobalt, copper, nickel and zinc and a decreased pH-value has been observed in the surface water recipient. The focus is on assessing contamination characteristics and identifying suitable remediation methods to avoid a river protected by environmental quality standards further downstream from getting contaminated. The bedrock in the area is sulphide containing and releases acidic leachate when oxidising, which is assumed to have occurred due to plane blasting and filling of residual rock. The contamination characteristics were assessed with the statistical methods modified double mass analysis and principal components analysis. A water balance was established to obtain the flowrates, discharge volumes and to determine the masses of the released metals in the surface water. Identification of suitable remediation methods was performed through a literature study of available remediation methods and using the findings of the assessments as basis. The results showed that there was a significant increase in metal concentrations and decrease in pH-value roughly around the same time as blasting and filling of residual rocks in the area was begun and that there were elevated levels of sulphide and sulphur, but they could not be specifically linked to any media. The yearly masses of metals released from the area into the surface water were between 77-98 % higher than allowed by the established guidelines. By separating the water assumed to carry the majority of the contaminants from the remaining natural water in the watershed, the volume that needs to be treated can be halved. As the contamination is so extensive, a mixture of remediation methods was proposed, including installing green roofs to decrease the runoff from the area, confining the crushed rock with bentonite and installing a filter for fast, efficient reduction. For long-term remediation, it is suggested to optimise the existing sedimentation basins and wetlands. The conclusions were that it will be very expensive to remediate the contamination, due to the extent and magnitude, and that handling sulphide containing bedrock for construction purposes should be legally regulated in order to avoid negative environmental and economic impacts.Förorening av tungmetaller i naturen är ett globalt problem som troligtvis kommer öka i framtiden. Den här rapporten undersöker en byggarbetsplats där ökade koncentrationer av metallerna kadmium, kobolt, koppar, nickel och zink samt ett minskat pH-värde har observerats i ytvattenrecipienten. Fokus ligger på att analysera föroreningskaraktärer och identifiera lämpliga åtgärdsmetoder för att undvika att en å nedströms som är skyddad av miljökvalitetsnormer ska förorenas. Berggrunden i området är sulfidförande och släpper ut surt lakvatten när den oxiderar, vilket är antaget har hänt till följd av plansprängning och utfyllnad av överblivet bergmaterial. Föroreningskaraktärerna analyserades med de statistiska metoderna modified double mass analysis och principalkomponentsanalys. En vattenbalans etablerades för att ta fram flöden, volymer och för att bestämma massorna av de frigjorda metallerna i ytvattnet. Identifiering av lämpliga åtgärdsmetoder gjordes med en litteraturstudie av tillgängliga metoder som grund. Resultaten visade att det är en signifikant ökning av metallkoncentrationer och minskning i pH-värde runt samma tid som sprängning och utfyllning av bergmaterial påbörjades samt att det är förhöjda halter av sulfid och svavel, men de kunde inte bli associerade med ett specifikt media. De årliga massorna av frigjorda metaller som släpps ut från området i ytvattnet är mellan 77-98 % högre än tillåtet av de etablerade riktlinjerna. Genom att separera vattnet som kan antas innehålla majoriteten av föroreningarna från det naturliga vattenflödet i avrinningsområdet kan volymen som behöver renas halveras. Eftersom föroreningen är så omfattande föreslås en kombination av åtgärdsmetoder; installation av gröna tak för att minska avrinningen från området, inneslutning av utfyllnadsmaterialet med bentonit och installation av ett filter för snabb, effektiv reduktion. För mer långsiktig rening föreslås det att optimera de existerande sedimentationsdammarna och våtmarken. Slutsatsen är att det kommer bli väldigt dyrt att åtgärda föroreningen på grund av dess omfattning, och hantering av sulfidförande berg för exploateringssyfte borde vara lagstadgat för att undvika miljömässiga och ekonomiska kostnader.
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Bonel, Kevin Anthony. "The mode of occurrence, recovery characteristics and petrogenesis of platinum-group and base metal sulphide minerals in the UG2 chromitite at Northam Platinum Mine, South Africa". Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297790.
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Robinson, Oliver B. "A critical review of the phenomenon of bond-stretch and distortional isomerism in oxo and sulphido complexes of transition metals". Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5758/.
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This thesis describes studies directed towards the preparation of oxo compounds of the early transition metals with a view to assessing their potentials for exhibiting distortional and bond-stretch isomerism. Analogous sulphido complexes in the case of the M(E)X(_3)(PMe(_3))(_3) system (M= Nb, Ta; X= CI; E= S) have also been investigated in detail to provide a contrast with another chalcogenide element and further aid an understanding of the phenomenon of bond-stretch isomerism. Chapter 1 reviews the body of evidence to date on the phenomena of distortional and bond-stretch isomerism, and considers possible theoretical origins for the phenomena. Chapter 2 describes the detailed study of distortional isomerism in the six coordinate series of complexes Mo(O)X(_2)(PMe(_2)Ph)(_3) (X= CI, Br, I) and confirms the existence of two pure blue forms for the chloro and bromo cases. Chapter 3 assesses the evidence for further examples of distortional isomerism in the complexes W(O)Cl(_2)(PMe(_2)Ph)(_3), Mo(O)(NCS)(_2)(PMe(_2)Ph)(_3) and Mo(O)Cl(_2)(Pet(_2)Ph)(_3). Structural characterisation by X-ray crystallography has indicated the existence of a link between the orientation of the aikyl and aryl substituents on the phosphine ligands and the general features observed in their infrared spectra. Chapters 4 and 5 describe the seven coordinate oxo and sulphido-halide derivatives of niobium and tantalum which exhibit the phenomenon of bond-stretch isomerism. Compounds studied include M(E)X(_3)(PMe(_3))(_3) (M= Nb, E= O, S, X=C1, Br; M= Ta, E= S, X=Cl). The structures of these compounds have been re-investigated by X-ray crystallography in order to assess the significance of the co-crystallised isostructural NbCl(_4)(PMe(_3))(_3) contaminant. Chapter 6 summaries the evidence for and against distortional and bond-stretch isomerism. Chapter 7 gives experimental details for chapters 2-5.
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Parker, Andrew Donald. "Oxidative dissolution of chalcopyrite in ferric media: an x-ray photoelectron spectroscopy study". Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/140.
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The oxidative dissolution of chalcopyrite in ferric media often produces incomplete copper recoveries. The incomplete recoveries have been attributed to inhibition caused by the formation of a metal deficient sulphide and the deposition of elemental sulphur and jarosite. Although these phases have been qualitatively identified on the surface of chalcopyrite, none have been quantitatively identified. The aim of the project was to quantitatively analyse the surface before and after oxidative dissolution, with X-ray photoelectron spectroscopy (XPS), and to use the phases identified as the basis for mechanisms of dissolution and inhibition.XPS analysis was performed on chalcopyrite massive fractured under anaerobic atmosphere and chalcopyrite massive and concentrate oxidised in 0.1 M ferric sulphate (pH 1.9) and 0.2 M ferric chloride (pH 1.6) at 50, 65 and 80ºC. Quantitative XPS analysis of the chalcopyrite surfaces required the development of programs that accounted for the observed XPS spectra. The output of these programs was used to construct profiles of the chalcopyrite surfaces and the deposited phases. These surface profiles were correlated with copper recoveries determined for chalcopyrite concentrate dissolution under the same conditions.The surface of chalcopyrite before oxidative dissolution reconstructs to form a `pyritic' disulphide phase. This phase is oxidised in ferric media to form thiosulphate via the incorporation of oxygen atoms from the hydration sphere. The thiosulphate reacts in the oxidising conditions of low pH to form elemental sulphur, sulphite and sulphate. The sulphate complexes with ferric to produce hydronium jarosite. This reaction occurs at the surface during the initial stages of dissolution and in the bulk solution during the latter stages. This precipitation of hydronium jarosite during the latter stages of dissolution corresponds to inhibition of the dissolution reaction. It is therefore concluded hydronium jarosite is responsible for inhibiting the oxidative dissolution of chalcopyrite in ferric media.The identification of hydronium jarosite as the inhibiting phase is consistent with the industrial practice of removing `excess' iron from the ferric solution before oxidative dissolution. However, additional iron and sulphate are generated at the chalcopyrite surface during oxidative dissolution. These high iron and sulphate concentrations combine with the low pH and high temperatures favoured for the oxidative dissolution of chalcopyrite to produce ideal conditions for jarosite precipitation. Therefore, pH must be lowered further to prevent jarosite precipitation and enhance copper recoveries from chalcopyrite in ferric media.
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Parker, Andrew Donald. "Oxidative dissolution of chalcopyrite in ferric media: an x-ray photoelectron spectroscopy study". Curtin University of Technology, School of Science and Computing, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=118673.
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The oxidative dissolution of chalcopyrite in ferric media often produces incomplete copper recoveries. The incomplete recoveries have been attributed to inhibition caused by the formation of a metal deficient sulphide and the deposition of elemental sulphur and jarosite. Although these phases have been qualitatively identified on the surface of chalcopyrite, none have been quantitatively identified. The aim of the project was to quantitatively analyse the surface before and after oxidative dissolution, with X-ray photoelectron spectroscopy (XPS), and to use the phases identified as the basis for mechanisms of dissolution and inhibition.XPS analysis was performed on chalcopyrite massive fractured under anaerobic atmosphere and chalcopyrite massive and concentrate oxidised in 0.1 M ferric sulphate (pH 1.9) and 0.2 M ferric chloride (pH 1.6) at 50, 65 and 80ºC. Quantitative XPS analysis of the chalcopyrite surfaces required the development of programs that accounted for the observed XPS spectra. The output of these programs was used to construct profiles of the chalcopyrite surfaces and the deposited phases. These surface profiles were correlated with copper recoveries determined for chalcopyrite concentrate dissolution under the same conditions.
The surface of chalcopyrite before oxidative dissolution reconstructs to form a `pyritic' disulphide phase. This phase is oxidised in ferric media to form thiosulphate via the incorporation of oxygen atoms from the hydration sphere. The thiosulphate reacts in the oxidising conditions of low pH to form elemental sulphur, sulphite and sulphate. The sulphate complexes with ferric to produce hydronium jarosite. This reaction occurs at the surface during the initial stages of dissolution and in the bulk solution during the latter stages. This precipitation of hydronium jarosite during the latter stages of dissolution corresponds to inhibition of the dissolution reaction. It is therefore concluded hydronium jarosite is responsible for inhibiting the oxidative dissolution of chalcopyrite in ferric media.
The identification of hydronium jarosite as the inhibiting phase is consistent with the industrial practice of removing `excess' iron from the ferric solution before oxidative dissolution. However, additional iron and sulphate are generated at the chalcopyrite surface during oxidative dissolution. These high iron and sulphate concentrations combine with the low pH and high temperatures favoured for the oxidative dissolution of chalcopyrite to produce ideal conditions for jarosite precipitation. Therefore, pH must be lowered further to prevent jarosite precipitation and enhance copper recoveries from chalcopyrite in ferric media.
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Cuthbert, Edwin. "The synthesis of metal chalcogenide volatile precursors in the formation of antimony and bismuth sulphide thin films and the synthesis of amine adducts for the formation of gallium nitride by MOCVD". Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250737.
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Mariga, Valentina. "Sustainability analysis in the mining sector: a case study on new recycling technologies for sulphidic mine residues valorisation". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23270/.
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Research has demonstrated that mining activities can cause serious impacts on the environment, as well as the surrounding communities, mainly due to the unsafe storage of mine tailings.
This research focuses on the sustainability assessment of new technologies for the recovery of metals from mine residues. The assessment consists in the evaluation of the environmental, economic, and social impacts through the Life Cycle based methods: Life Cycle Assessment (LCA), Life Cycle Costing (LCC), and Social Life Cycle Assessment (SLCA). The analyses are performed on the Mondo Minerals bioleaching project, which aim is to recover nickel and cobalt from the Sotkamo and Vuonos mine tailings.
The LCA demonstrates that the project contributes to the avoided production of nickel and cobalt concentrates from new resources, hence reducing several environmental impacts.
The LCC analysis shows that the company’s main costs are linked to the bioleaching process, caused by electricity consumption and the chemicals used.
The SLCA analyses the impacts on three main stakeholder categories: workers, local community, and society. The results demonstrated that a fair salary (or the absence of it) impacts the workers the most, while the local community stakeholder category impacts are related to the access to material resources. The health and safety category is the most impacted category for the society stakeholder.
The environmental and economic analyses demonstrate that the recovery of mine tailings may represents a good opportunity for mine companies both to reduce the environmental impacts linked to mine tailings and to increase the profitability. In particular, the project helps reduce the amounts of metals extracted from new resources and demonstrates that the use of the bioleaching technology for the extraction of metals can be economically profitable.
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Stalder, Marcel. "Petrology and mineral chemistry of sulphide ores and associated metalliferous rocks of the Gamsberg Zn-Pb deposit, South Africa : implications for ore genesis and mineral exploration". Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16072.
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Thesis (PhD)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The Gamsberg Zn-Pb deposit is a metamorphosed and multiply deformed sediment-hosted base metal deposit in the central Namaqua Province of South Africa. The deposit is hosted by the Bushmanland Group, a late Palaeoproterozoic (2000-1600 Ma) supracrustal succession of quartzite, metapelitic schist and interbedded metavolcanic rocks. Mineralisation occurs within the central part of the Gams Formation, a heterogeneous sequence of metamorphosed metalliferous sediments and fine-grained organic-rich shales. The ore horizon is subdivided into a lower unit of metapelite-hosted ore, an intermediate layer of phosphorite-hosted ore, and an upper unit of banded garnet-apatite ore. The ore body is enveloped by unmineralised silicate-, carbonate- and oxide-facies metalliferous rocks, which originally represented mixtures of Fe-Mn-rich hydrothermal precipitates, authigenic carbonate, and variable concentrations of detrital material. Based on mineralogical and geochemical characteristics, the metalliferous host rocks are subdivided into iron formations, coticules, Fe-Mn silicates, impure marbles and barite/Ba-rich quartzite. Minerals of the Gams Formation mostly represent solid solution between the Fe and Mn end-members of garnet, pyroxene, pyroxenoid, amphibole, olivine, spinel and ilmenite. Calcium-rich rock types are a typical feature and characterized by the occurrence of manganoan calcite, clinopyroxene, andradite-rich garnet and titanite. A successive increase in the (Mn+Ca):Fe value of rocks and minerals is evident with increasing distance from the ore horizon. Amphibole is restricted to Fe-rich ore-bearing assemblages, whereas orthopyroxene, clinopyroxene, Fe-rich pyroxenoid and olivine are present in intermediate assemblages, and Mn-rich rhodonite and pyroxmangite in the most manganiferous assemblages. These variations are mimicked by an increase in the Mn:Fe value of coexisting garnet and ilmenite group minerals with increasing distance from ore. LA-ICP-MS analyses have been used to constrain the REE patterns of garnet and apatite. In the ore-body, these minerals display a positive Eu anomaly, which is interpreted to reflect a distinct hydrothermal signature. In contrast, garnet and apatite in unmineralised metalliferous rocks display nil or a negative Eu anomaly. Primary features of the Gams Formation, such as REE patterns, the banded nature of garnet-apatite ore, the presence of diagenetic apatite nodules, and the distribution of the redox-sensitive elements Ba and Mn have been used to constrain palaeo-environmental conditions. The results indicate that metapelitehosted ore has been deposited in a stratified ocean that was characterised by anoxic bottom waters and precipitation of Fe and Zn sulphides into organic matter-rich shales. These rocks were superceded by phosphorite-hosted ore, garnet-apatite ore and metalliferous host rocks that developed in a suboxic to oxic environment. The large size of the deposit, the internal lamination of the ores and the predominance of sphalerite and barite are consistent with a vent-distal setting and precipitation of the ore-forming constituents from dense and reduced hydrothermal fluids, which originated due to reactivation of dormant growth faults. Collectively, the geological evidence indicates that Gamsberg is bridging the gap betweenthe SEDEX and BHT classifications. The relationships demonstrate that differences between these two classes of sediment-hosted Zn-Pb deposits are predominantly related to environmental conditions within localised third order basins and not to fundamental differences in ore-forming processes.
AFRIKAANSE OPSOMMING: Die Gamsberg Zn-Pb afsetting is ‘n meerfasig vervormde en gemetamorfiseerde sedimentgesetelde onedel metaal afsetting in die sentrale Namakwa Provinsie van Suid Afrika. Die afsetting word geherberg deur die Boesmanland Groep, ‘n laat Paleoproterosoïse (2000 – 1600 Ma) bokors-opeenvolging van kwartsiet, metapelitiese skis en tussengelaagde metavulkaniese gesteente. Mineralisasie word gevind in the sentrale deel van die Gams Formasie. Die Gams Formasie is ‘n heterogene opeenvolging van gemetamorfiseerde metaalhoudende sediment en fynkorrelrige organiese skalie. Die erts horison word onderverdeel in ‘n onderste laag van metapeliet-gesetelde erts, n sentrale laag van fosforiet-gesetelde erts, en ‘n boonste laag van gebande granaat-apatiet erts. Die erts-liggaam word omhuls deur ongemineraliseerde silikaat-, karbonaat- en oksied-fasies metal-ryke rotse. Hierdie gesteentes word geinterpreteer as oorspronklike mengsels van Fe-Mn-ryke hidrotermale partikels, outigeniese karbonaat, en verskeie hoeveelhede detritale materiaal. Gebaseer op mineralogiese en geochemiese kenmerke word hierdie rotse onderverdeel in ysterformasies, „coticules“, Fe-Mn silikate, onsuiwer marmer en barite/Ba-ryke kwartsiet. Minerale van die Gams Formasie form meestal soliede oplossingsreekse tussen die Fe en Mn endlede van granaat, pirokseen, piroksenoid, amfibool, olivien, spinel en ilmeniet. Kalsium-ryke rots tipes is ‘n tipiese kenmerk van die Gams Formasie en word gekenmerk deur mangaan-ryke kalsiet, klinopirokseen, andradiet-ryke granaat en sfeen. Daar word ‘n stapsgewyse vergroting van die (Mn+Ca):Fe verhouding in gesteentes en minerale gevind met toeneemende afstand van die erts horison. Amfibool is beperk tot Fe-ryke ertsdraende gesteentes, ortopirokseen, klinopirokseen, Fe-ryke piroksenoid en olivien tot intermediêre gesteentes, en Mn-ryke rodoniet en piroksmangiet tot Mn-ryke gesteentes. Hierdie variasies gaan gepaard met vergroting van die Mn:Fe verhouding in granaat en ilmeniet-groep minerale met toeneemende afstand van die erts. LA-ICP-MS analises was gebruik om die skaars-aarde element patrone van granaat en apatiet te bepaal. In die erts-liggaam wys hierdie minerale ‘n positiewe Eu anomalie, wat geinterpreteerd word as ‘n hidrotermale kenmerk. In ongemineraliseerde gasheer gesteentes wys granaat en apatiet geen of ‘n negatiewe Eu anomalie. Primêre kenmerke van die Gams Formasie, soos skaars-aarde patrone, the gebande voorkoms van granaat-apatiet erts, die teenwoordigheid van diagenetiese apatiet knolle, en die verspreiding van die redox-sensitiewe elemente Ba en Mn, was gebruik om afleidings oor die paleo-omgewing te maak. Die resultate het gewys dat metapeliet-gesetelde erts afgeset was onder anoksiese bodem water deur presipitasie van Fe en Zn sulfiedes in organiese skalie. Hierdie erts gaan oor in fosforiet-gesetelde erts, granaat-apatiet erts en metaal-ryke gasheer gesteente wat in ‘n suboksiese tot oksiese omgewing ontstaan het. Die grootte van die afsetting, die interne gelaagdheid van die erts, asook die teenwoordigheid van sfaleriet en bariet dui op ‘n distale omgewing relatief tot die hidrotermale bron en presipitasie van die ertsuit digte en gereduseerde hidrotermale vloeistowwe, wat ontstaan het deur die heraktiveering van rustende groeiverskuiwings. Gesaamentlik bewys die geologiese kenmerke van Gamsberg dat gemetamorfiseerde SEDEX en Broken Hill-tipe mineralisasie binne die perke van ‘n enkele afsetting kan voorkom. Die geologiese verhoudings dui aan dat verskille tussen hierdie twee tipes van sedimentgesetelde afsettings meestal veroorsaak word deur omgewings-toestande binne in gelokaliseerde derde orde komme en nie deur fundamentele verskille in ertsvormende prosesse nie.