No description available.

It was the purpose of this investigation to study the effect of addition agents on the electrodeposition of aluminum on copper from a fused bath of 80 per cent aluminum chloride and 20 per cent sodium chloride. The agents added and the concentrations studied were lead chloride, 0.5 and 1.0 per cent; aluminum thiocyanate, 0.5 and 1.0 per cent; chromic oxide, 0.5 per cent; sodium cyanide, 0.1 and 0.5 per cent; and vanadium pentoxide, 0.1 per cent. The electrolysis was carried out in a 1000-millimeter beaker in a furnace heated by a 1000-watt element. The plating cell was fitted with a tight lid through which the electrodes could be adjusted. The optimum current density range while plating from a bath of 80 per cent aluminum chloride and 20 per cent sodium chloride was 8.2 to 21.0 amperes per square foot. When aluminum was electroplated from a bath of 75 per cent aluminum chloride, 20 per cent sodium chloride, and 5 per cent lithium chloride, the plates did not adhere to the base metal. Also, the plates corroded to the base metal in a few days. The optimum temperature was found to be 356 °F. Lead chloride, when added at a concentration of 0.5 and 1.0 per cent, produced a smoothening effect. The plates obtained at the former concentration were smoothest. However, the plates were rather easily corroded by the atmosphere. In contrast, chronic oxide at 0.5 per cent did not improve the smoothness of the plate but did improve considerably the corrosion resistance of the plate. Addition of aluminum thiocyanate caused formation of a black powder which was non-adherent. Sodium cyanide at 0.1 and 0.5 per cent did not improve the ductility and corrosive resistance of the plate to any extent. Vanadium pentoxide gave corrosive resistance and ductility to the deposit at lower current densities of 10 to 100 amperes per square foot and thin mirror plates at current densities between 100 and 500 amperes per square foot. The vanadium pentoxide was used at a concentration of 0.1 weight per cent. In attempts to protect the plates from corrosion, applications of chemical treatment to the aluminum plate failed, as also did an application of lacquer. The results obtained with the addition of lead chloride, chromic oxide, and vanadium pentoxide warrant further study to determine optimum operating conditions and limits. / Master of Science

Industrial activities of mankind are feared to damage the environment irretrievably. Especially the release of huge amounts of harmful gases causes concern. In this regard the environmental pollution caused by the one billion motor vehicles on earth is particularly important. The platinum-group metals (PGM) are well known for their catalytic activity. They are used extensively for reducing the amounts of hydrocarbons, carbon monoxide and nitrogen oxides from the exhausts gas emitted by automobiles. In 2012 20% of platinum and 27% of palladium produced were used in the manufacture of catalytic converters. With the increasing use of PGM-containing autocatalysts, the reclaiming of PGMs from spent catalysts has become essential. Particularly attractive hydrometallurgical methods are those based on the use of halide ions e.g. sodium chloride, as complexing agent in conjunction with nitric acid as oxidant. The chemical reactions between mixtures of aluminium chloride and nitric acid have been studied, but the electrochemical reactions have received little attention. The research reported in this dissertation is aimed at providing data relating to the electrochemical behaviour of platinum in mixtures of aluminium chloride and nitric acid. The construction of Pourbaix diagrams of platinum in chloride environments confirmed that the stable chloro-complexes [PtCl4]2- and PtCl6]2-, as well as platinum oxides (PtO and PtO2) could play a role under the experimental conditions employed in this study. From the thermodynamic results it can be concluded that the systems deserving consideration favour high chloride concentrations and high temperatures. Notable anodic reactions found were the adsorption of chloride on the platinum surface and the gradual formation of [PtCl6]2-, followed by the formation of platinum oxides at 1.00 to 1.01 V. The results show that anodic currents diminished with lower chloride concentrations. A seemingly anomalous anodic behaviour at 35 °C and 45 °C could be explained in terms of a competition between platinum oxide formation and the formation of platinum chloro-complexes. Evidence for the following cathodic reduction reactions was found: hydrogen evolution, reduction of dissolved oxygen to hydrogen dioxide (-1.3 V SHE), nitrate ion reduction to nitrite ions (-0.01 V SHE), nitrite ion reduction to nitric oxide (-0.85 V SHE) and reduction of PtO and PtO2 to Pt (at -1.00 V and 1.01 V SHE, respectively). A brief study was undertaken in an attempt to relate the electrochemical results to the leaching of platinum from a virgin automotive exhaust catalyst. The recovery was low for mixtures with low chloride concentrations, which could be expected from the electrochemical polarisation curves obtained in electrolytes with different chloride concentrations. The maximum platinum recovery attained, was 60% at 45 °C in a mixture containing 0.6 M AlCl3 and 0.9 M HNO3. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

Industrial activities of mankind are feared to damage the environment irretrievably. Especially the release of huge amounts of harmful gases causes concern. In this regard the environmental pollution caused by the one billion motor vehicles on earth is particularly important. The platinum-group metals (PGM) are well known for their catalytic activity. They are used extensively for reducing the amounts of hydrocarbons, carbon monoxide and nitrogen oxides from the exhausts gas emitted by automobiles. In 2012 20% of platinum and 27% of palladium produced were used in the manufacture of catalytic converters. With the increasing use of PGM-containing autocatalysts, the reclaiming of PGMs from spent catalysts has become essential. Particularly attractive hydrometallurgical methods are those based on the use of halide ions e.g. sodium chloride, as complexing agent in conjunction with nitric acid as oxidant. The chemical reactions between mixtures of aluminium chloride and nitric acid have been studied, but the electrochemical reactions have received little attention. The research reported in this dissertation is aimed at providing data relating to the electrochemical behaviour of platinum in mixtures of aluminium chloride and nitric acid. The construction of Pourbaix diagrams of platinum in chloride environments confirmed that the stable chloro-complexes [PtCl4]2- and PtCl6]2-, as well as platinum oxides (PtO and PtO2) could play a role under the experimental conditions employed in this study. From the thermodynamic results it can be concluded that the systems deserving consideration favour high chloride concentrations and high temperatures. Notable anodic reactions found were the adsorption of chloride on the platinum surface and the gradual formation of [PtCl6]2-, followed by the formation of platinum oxides at 1.00 to 1.01 V. The results show that anodic currents diminished with lower chloride concentrations. A seemingly anomalous anodic behaviour at 35 °C and 45 °C could be explained in terms of a competition between platinum oxide formation and the formation of platinum chloro-complexes. Evidence for the following cathodic reduction reactions was found: hydrogen evolution, reduction of dissolved oxygen to hydrogen dioxide (-1.3 V SHE), nitrate ion reduction to nitrite ions (-0.01 V SHE), nitrite ion reduction to nitric oxide (-0.85 V SHE) and reduction of PtO and PtO2 to Pt (at -1.00 V and 1.01 V SHE, respectively). A brief study was undertaken in an attempt to relate the electrochemical results to the leaching of platinum from a virgin automotive exhaust catalyst. The recovery was low for mixtures with low chloride concentrations, which could be expected from the electrochemical polarisation curves obtained in electrolytes with different chloride concentrations. The maximum platinum recovery attained, was 60% at 45 °C in a mixture containing 0.6 M AlCl3 and 0.9 M HNO3. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

No description available.

Thesis (Ph. D.)--University OF MICHIGAN.

Thesis (Ph. D.)--University of Chicago, 1938. / Reproduced from type-written copy. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois." eContent provider-neutral record in process. Description based on print version record. Bibliographical foot-notes.

Thesis (Ph. D.)--University of Chicago, 1938. / Reproduced from type-written copy. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois." eContent provider-neutral record in process. Description based on print version record. Bibliographical foot-notes.

Thesis (Ph. D.)--University OF MICHIGAN. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University OF MICHIGAN.