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Increasing attention has been given to the preparation and study of compounds with linear chains of metal atoms surrounded by four ligands. The majority of linear trimetal complexes are supported by dpa, the anion of dipyridylamine, having the general formula M3(dpa)4X2, where X is typically a monoanion. It has been shown that the behavior of the trinuclear system is far more complicated than might have been expected. Specifically, both symmetrical and unsymmetrical chains can occur and the interpretation of the magnetic properties of certain compounds has been a challenging task. Present in this dissertation is the bulk of work completed on an exploration of syntheses and characterizations of linear trichromium and trinickel compounds with different types of tridentate ligands. These ligands include 2,6-bis(phenylamino)pyridine,H2BPAP, (the corresponding dianion of this is denoted by BPAP) and a set of five unsymmetrical formamidines with different organic substituents ranging from strong electron-donating groups, such as -OCH3, to electron-withdrawing groups, e.g., F. Ligands impact on the trimetal chain in various ways. In the case of the M3(BPAP)42- ions, there are no axial interactions because these anionic species do not attract electron donating ligands. Thus they have properties which are different from those of M3(dpa)4X2 molecules. Most notably, the Ni3(BPAP)42- ion is diamagnetic and all three nickel ions can be described as square-planar, low-spin NiII centers. ivWhen unsymmetrical formamidines are used to support linear trichromium chains with a Cl anion at each end, the separation between terminal chromium atoms is significantly longer (ca. 0.15 - 0.25) than those in trichromium compounds reported earlier. Moreover, the unsymmetrical formamidinates tend to support symmetrical trichromium chains, while the rest of the known tridentate ligands typically yield unsymmetrical Cr36+ chains. The synthesis and structural studies of trinickel compounds with unsymmetrical formamidines are also presented.

The sulphation and sulphate decomposition occurring during the oxidation of nickel concentrates were studied by thermal analysis. Samples of industrial nickel concentrates were heated in inert gas to temperatures between 400°C and 850°C and oxidized isothermally in air or in a 4%O2-96%N2 mixture. During isothermal oxidation of the concentrates, SO2 evolved from the roasting reactions led to partial formation of metal sulphates. Following the oxidation and sulphation of the sample, the decomposition of the formed sulphates was studied. This was completed either by heating the sulphated sample to 950°C to thermally decompose the sulphates, or by lowering the partial pressure of oxygen while holding the sample at the isothermal oxidation temperature. The sulphation of the sample was found to follow the parabolic rate law, implying diffusion as the rate controlling-step. The thermal decomposition of the sulphates occurred at a near constant rate, implying zero-order kinetics.

The sulphation and sulphate decomposition occurring during the oxidation of nickel concentrates were studied by thermal analysis. Samples of industrial nickel concentrates were heated in inert gas to temperatures between 400°C and 850°C and oxidized isothermally in air or in a 4%O2-96%N2 mixture. During isothermal oxidation of the concentrates, SO2 evolved from the roasting reactions led to partial formation of metal sulphates. Following the oxidation and sulphation of the sample, the decomposition of the formed sulphates was studied. This was completed either by heating the sulphated sample to 950°C to thermally decompose the sulphates, or by lowering the partial pressure of oxygen while holding the sample at the isothermal oxidation temperature. The sulphation of the sample was found to follow the parabolic rate law, implying diffusion as the rate controlling-step. The thermal decomposition of the sulphates occurred at a near constant rate, implying zero-order kinetics.

This thesis investigates the stabilization of divalent germanium using substituted diethanol amine ligands. Germylenes of type RN(CH2CH2OH)2Ge were obtained from N-heterocyclic germylenes and N-alkyl diethanol amines in yields of up to 94%. Single crystal X-ray diffraction confims the presence of a transannular Ge-N dative bond in all cases. In addition, intermolecular dimers containing Ge2O2 rings are formed for R = Me and Et. Reaction of the four germylenes L with nickel carbonyl yielded the respective germylene complexes L2Ni(CO)2 and LNi(CO)3. The germylenes and their complexes were investigated with DFT methods. Only four methods, SVWN, BB1K, MPWB1K and M062x gave acceptable Ge-N distances. Dimerization energies of the germylenes were examined with the thermochemically accurate M062x method. At the M062x/Def2-TZVP level, the dimerization energies of the germylenes are very small (ΔG° ≈ 0 kcal/mol). The experimentally observed dimerization or lack thereof may accordingly be determined by packing effects in the solid state or solvation energies in solution.

As more contaminated sites are being discovered, new in situ remediation techniques need to be developed. Chemically treating soil with lime to increase soil pH is a method that may decrease the bioavailability of the contaminant. To test the usefulness of rendering metal-contaminated soils alkaline with dolomitic lime, to improve crop performance, field trials at a site in Port Colborne, ON, with soil nickel concentration (as high as 5000 mg/kg) from refinery emissions were completed. Oat and soybean yield, as well as plant uptake and bioavailabilty of nickel in soil were evaluated. Liming Ni-contaminated soils decreased soybean foliar Ni concentrations from 36.68 µg/g in unlimed fields to 19.98 µg/g in 50 t/ha limed fields in the 2007 growing season; yield of both oat and soybean in unlimed soils was the same (p>0.05) as at a reference site, suggesting that for these soils, remediation is not necessary for yield.

Filter Cake, which contains leachable nickel and vanadium above the criteria in the Alberta Waste Control Regulation, is produced at an oil sands facility operated by Nexen Inc. and is currently being disposed in a landfill. Bench scale and field tests were performed with stabilization/solidification (S/S) treatment reagents such as Portland cement, fly ash, elemental sulphur, and CETCO Oilfield Service’s proprietary reagents to assess their efficacy at reducing leachable metals in Filter Cake. The CETCO reagents were the most effective treatment for reducing leachable nickel and vanadium in Filter Cake. Treatments with Portland cement were successful in bench scale tests, but inconsistent in field tests. The inconsistent results obtained for Portland cement may have been due to interferences of the cement reactions from factors such as fine particulates. S/S treatments of Filter Cake present a viable waste management option. However, the associated reduced cost and environmental impacts were not substantial.

Hydrochloric acid leaching of saprolite nickel ores has been proposed as an effective means of recovering nickel and cobalt. However, the leach produces a concentrated brine of magnesium chloride which must be hydrolyzed to recover the HCl lixiviant. The processing of carnallite similarly produces a concentrated MgCl2 brine; converting this brine into HCl and MgO provides an attractive way of adding value while effectively disposing of this waste product. Direct pyrohydrolysis of magnesium chloride brines by the reaction, MgCl2,a + H2Oa  MgOs + 2HClg is energy-intensive as large volumes of water must be evaporated. The energy cost is high, and the HCl stream produced is limited to approximately 20 wt% HCl. This thesis explores alternative methods of obtaining HCl from aqueous magnesium chloride solutions. Two methods are considered: the hydrolysis, under autogenous pressure, of concentrated MgCl2 molten salt hydrates; and the precipitation of magnesium hydroxychloride compounds such as 2MgO·MgCl2·6H2O and 3MgO·MgCl2·11H2O, which are subsequently decomposed at high temperature. Considerable experimental difficulties were encountered in studying pressure hydrolysis of molten salt hydrates, despite extensive equipment modifications. Ultimately, the work moved on to precipitation and decomposition of hydroxychlorides. This was found to bear promise, and conceptual flowsheets based on these reactions are presented. A phase stability diagram giving the areas of predominance of the different hydroxychloride phases is presented, and fundamental thermochemical data are derived. The results of a kinetic study on magnesium hydroxychloride thermal decomposition are also presented. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2011-03-11 10:14:53.455

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