The aim of this study was to investigate the removal of cobalt from zinc sulfate solution by cementation with the help of conventional and new type of additives that were 4% Sn-zinc alloy powder and 10% Sn-zinc alloy powder, respectively. Synthetic leach solutions containing 150 g/l Zn and 75 mg/l Co were prepared and used in all of the experiments. The parameters researched with the conventional method were the amount of arsenic trioxide and the effect of copper sulfate on cementation of cobalt. While using the alloys, the parameters studied were the amounts of arsenic trioxide, copper sulfate and tin containing zinc alloy powder additions, cementation duration and temperature. The difference in the optimization of alloy additions was in the amount of addition of arsenic trioxide. The amount of 4%Sn-zinc alloy powder was tried to be optimized with the addition of arsenic trioxide whereas the optimization was tried to be done without any arsenic addition while using 10%Sn-zinc alloy. The XRD and SEM studies of the cementates were also performed. The obtained results indicated that tin containing alloys were much better than pure zinc. With the additions of 4 g/l 4%Sn-Zn alloy dust, 1.2 g/l CuSO4.5H2O, 0.12 g/l As2O3 and in 2 hours of cementation duration at 85-90oC, the maximum amount of cobalt cementation efficiency was achieved. The experiments indicated that cobalt in the solution could be reduced to about 2 mg/l by using 10%Sn-zinc alloy powder with an initial Sn/Co weight ratio of 13.25:1 without the addition of arsenic trioxide at 85oC in 2 hours of cementation duration.

Thesis (M.Sc)(Chemical Technology, Engineering and Technology Management)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references (leaves 75-80).

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M.Tech. (Homoeopathy) / The ability to consume oxygen during exercise relies on the functionality of the cardiorespiratory system to deliver oxygen to the working muscles and therefore generate ATP or energy (Astrand et al., 2003). Performance enhancement drugs are becoming increasingly popular as athletes are under extreme pressure to enhance their performance (Shermer, 2008). The purpose of this study was to look for a safe alternative to increase oxygen consumption during exercise. The aim included determining whether the homeopathic remedy Arsenicum album 200CH had an effect on oxygen consumption during submaximal cycling. The study consisted of 32 healthy participants who were randomly divided into a control (placebo) or experimental (treatment) group. Two baseline tests were performed where no medication (remedy or placebo) was given two days apart and the average of the two were taken as the baseline average. After a further two days, the first medication test was conducted after participants were given the treatment 5 minutes prior to testing to ascertain the immediate effect of the medication. The last test was performed after one week of administering where the medication was given twice daily to distinguish what the prolonged effect of the medication was on oxygen consumption. The test consisted of a warm-up at 25-Watts for women and 50-Watts for men, the test included cycling at 3 minute increments where the wattage was increased every 3 minutes by 25-Watts until the participants reached their age-predicted maximum. When this maximum was reached, the wattage was decreased to the warm-up wattage and a cool-down commenced. Heart rate was recorded every minute and documented. The participant was also asked to rate their perceived rate of exertion at the end of every 3minute stage, as a subjective measurement. Although the time periods of administration yielded different results, both were statistically insignificant. The immediate administration showed a negative trend whereas the prolonged administration showed a positive trend in the treatment group after one week. Despite not showing statistical significance, it warrants additional research over a longer period of time.

The Giant Mine near Yellowknife, NWT generated 237 000 tonnes of arsenic-trioxide (As₂O₃)-rich dust as a by-product of gold mining during its years of operation (1948 - 2004). Arsenic trioxide is a relatively soluble form of arsenic (As) and is currently stored in the mine, posing a threat of contamination to the adjacent Great Slave Lake. This research investigates the potential for permanent remediation of the As₂O₃ using sulfidation to transform it to arsenic trisulfide (As₂S₃). Knowing that aqueous As₂O₃ readily reacts with sulfide (Ostermeyer, 2021), it was determined that the most practical and effective method to achieve sulfidation of the Giant Mine dust is to first dissolve the As₂O₃ and then conduct the reaction with sulfide. The optimal conditions at which to dissolve As₂O₃ were investigated. The solubility and dissolution rate in water were shown to increase with temperature, with solubility increasing from 185.7 g As₂O₃/kg water at 140 °C to 250.6 g As₂O₃/kg water at 180 °C. Qualitative demonstrations of the rate of dissolution show that ≥ 90 % of the As₂O₃ dissolved within 5 minutes at 140 °C, and 4 minutes at 180 °C; previous research indicates that time to equilibrium is > 24 hours at 60 °C (CANMET, 2000). Reaction of Giant-Mine material in water at elevated temperatures (140 °C - 200 °C) for 10 to 30 minutes consistently resulted in dissolution of approximately 80 wt. % of the initial solid-phase As concentrations, representing almost all the As₂O₃, yielding undissolved residues (≈ 40 wt. % of initial mass). The persistence of As in these residues is likely due to it being hosted in As₂O₃ - Sb₂O₃ solid solutions and low-solubility Fe-oxide phases in the initial sample (CANMET, 2000; Poirier, 2004).

This Thesis extends the chemistry of group VII transition metal oxide fluorides, namely ReO3F and MnO3F. The fundamental chemistry of ReO3F has been significantly extended with the development of its high-yield and high-purity synthesis. This has been achieved by solvolysis of Re2O7 in anhydrous HF (aHF) followed by reaction of the water formed with dissolved F2 at room temperature. The improved synthesis has allowed the Lewis acid and fluoride-ion donor-acceptor properties of ReO3F to be further investigated. The Lewis acid-base complex, (HF)2ReO3F·HF, was obtained by dissolution of ReO3F in aHF at room temperature and was characterized by vibrational spectroscopy with aid of quantum-chemical calculations and single-crystal X-ray diffraction at −173 °C. The HF molecules are F-coordinated to rhenium, representing the only known example of an HF complex with rhenium. The study of the fluoride-ion acceptor properties of ReO3F resulted in the syntheses and characterization of the [{ReO3(μ-F)}3(μ3-O)]2−, [ReO3F3]2−, and [ReO3F2]− anions. The [{ReO3(μ-F)}3(μ3-O)]2− anion was obtained as the [N(CH3)4]+ salt by the reaction of stoichiometric amounts of ReO3F and [N(CH3)4]F in CH3CN solvent. The anion was structurally characterized in CH3CN solution by 1D and 2D 19F NMR spectroscopy and in the solid state by Raman spectroscopy and a single-crystal X-ray structure determination of [N(CH3)4]2[{ReO3(μ-F)}3(μ3-O)]·CH3CN. The structure of the [{ReO3(μ-F)}3(μ3-O)]2– anion consists of three ReO3F units linked to each other through dicoordinate bridging fluorine atoms (F) and a central tricoordinate bridging oxygen atom (O3). Calculated vibrational frequencies and Raman intensities of the [{MO3(μ-F)}3(μ3-O)]2− (C3v) and [{MO3(μ-F)}3(μ3-F)]− (C3v) anions (M = Re, Tc) have been used to assign the Raman spectrum of [N(CH3)4]2[{ReO3(μ-F)}3(μ3-O)]·CH3CN. The fac-[ReO3F3]2− and [ReO3F2]− anions have been synthesized by the reactions of ReO3F with CsF and KF in aHF, and by reaction of ReO3F with NOF. Additionally, the [ReO3F2]− anion has been synthesized by the reaction of ReO3F with [NH4]F in aHF. Both anions were characterized by Raman spectroscopy in the solid state and single-crystal X-ray diffraction. The calculated vibrational frequencies of the fac-[ReO3F3]2− (C3v) and [(µ-F)4(ReO3F)4]4− (C4v) anions were used to assign the Raman spectra of fac-[ReO3F3]2− and [ReO3F2]−, respectively. The rhenium atoms in the open-chain, fluorine-bridged [ReO3F2]− anion and the monomeric fac-[ReO3F3]2− anion are six-coordinate with a facial arrangement of the oxygen ligands. The fluoride-ion donor properties were established by the reactions of ReO3F with excess AsF5 and SbF5/SO2ClF. Both reactions resulted in the formation of white friable solids, µ-O(ReO2F)(AsF5)∙2AsF5 and [ReO3][Sb3F16]. The [ReO3][Sb3F16] salt is stable at room temperature and decomposes to [ReO2F2][SbF5], when maintained at 45 oC under dynamic vacuum. The µ-O(ReO2F)(AsF5)∙2AsF5, however, slowly decomposes at 0 oC to ReO3F and AsF5. Both products were characterized by Raman spectroscopy in the solid state with aid of quantum-chemical calculations. The vibrational analyses revealed that the geometry of [ReO3][Sb3F16] is consistent with a trigonal pyramidal arrangement of oxygen atoms around rhenium, whereas in µ-O(ReO2F)(AsF5)∙2AsF5, ReO3F interacts with one of the AsF5 molecules through an O-bridge, which represents the first example of such type of bonding. The reactions of µ-O(ReO2F)(AsF5)∙2AsF5 and [ReO3][Sb3F16] with CH3CN resulted in the formation of the white salts, [O3Re(NCCH3)3][PnF6] (Pn = As, Sb), which were characterized by Raman spectroscopy. The reactivity of ReO3F has been extended to the synthesis of a new Re(VII) oxide fluoride, (μ-F)4{[μ-O(ReO2F)2](ReO2F2)2}, which was synthesized by the reaction of 1:3 molar ratio of ReO3F and ReO2F3. The compound, (μ-F)4{[μ-O(ReO2F)2](ReO2F2)2}, a rare example of an O-bridged rhenium oxide fluoride, has been characterized by single-crystal X-ray diffraction and solid-state Raman spectroscopy. The vibrational assignments of (μ-F)4{[μ-O(ReO2F)2](ReO2F2)2} were confirmed by 18O-enrichment and quantum-chemical calculations. The improved synthesis of ReO3F has also led to the synthesis and characterization of the novel [XeOXeOXe]2+ cation as its [μ-F(ReO2F3)2]− salt by the low-temperature reaction of ReO3F and XeF2 in aHF. The [XeOXeOXe]2+ cation provides an unprecedented example of a xenon(II) oxide and a noble-gas oxocation as well as a rare example of a noble-gas dication. The crystal structure of [XeOXeOXe][µ-F(ReO2F3)2]2 consists of a planar, zigzag-shaped [XeOXeOXe]2+ cation (C2h symmetry) that is fluorine bridged through its terminal xenon atoms to two [µ-F(ReO2F3)2]– anions. The Raman spectra of the natural abundance and 18O-enriched [XeOXeOXe]2+ salts are consistent with a centrosymmetric (C2h) cation geometry. Quantum-chemical calculations were used to aid in the vibrational assignments of [Xe16/18OXe16/18OXe][µ-F(Re16/18O2F3)2]2 and to assess the bonding in [XeOXeOXe]2+ by NBO, QTAIM, ELF, and MEPS analyses. Ion pair interactions occur through Re–Fμ---Xe bridges, which are predominantly electrostatic in nature and result from polarization of the Fμ-atom electron densities by the exposed core charges of the terminal xenon atoms. Each xenon(II) atom is surrounded by a torus of xenon valence electron density comprised of the three valence electron lone pairs. The positive regions of the terminal xenon atoms and associated fluorine bridge bonds correspond to the positive σ-holes and donor interactions that are associated with “halogen bonding”. The reactions of MnO3F with noble-gas fluorides, KrF2 and XeF6, have been studied as the possible synthetic routes to MnOF5 and MnO2F3. The reaction of MnO3F with KrF2 yielded a red solid, which was isolated as a crystalline solid at room temperature and its crystal structure was assigned to manganese(V) fluoride, MnF5. The crystal structure of polymeric MnF5 consists of MnF6-octahedra which are trans-coordinated through fluorine bridges. The geometrical parameters of MnF5 could not be reliably determined due to unresolved twinning issues. The reaction of MnO3F with KrF2 in the presence of K[HF2] yielded a red-orange solid mixture of K[MnF6] (soluble in HF) and MnF3 (insoluble in HF). The HF solution of the solid mixture was characterized by 19F NMR spectroscopy and the resonance observed in the 19F NMR spectrum was preliminary assigned to [MnF6] by comparison with the chemical shift observed in the 19F NMR spectrum of MnO3F. Additionally, MnO3F was characterized by 19F−55Mn COSY NMR and 55Mn NMR spectroscopies, the latter provided the first 1J(19F−55Mn) coupling constant. The K[MnF6] salt was also characterized by single-crystal X-ray diffraction. The resulting octahedral geometry is imposed by symmetry, therefore, the anticipated Jahn-Teller distortion, which would result in D4h symmetry for the [MnF6] anion, could not be observed. The reaction of MnO3F with XeF6 resulted in the isolation of [Xe2F11]2[MnF6] and [XeF5]2[MnF6]. Both salts were characterized by low-temperature single-crystal X-ray diffraction. The [Xe2F11]2[MnF6] salt was additionally characterized by low-temperature Raman spectroscopy with the aid of quantum-chemical calculations, whereas the assignment of the known Raman spectrum of [XeF5]2[MnF6] has been improved in the present work. / Thesis / Doctor of Philosophy (PhD)

Graduation date: 2003

The material used in retrofilling is among others a decisive factor for the success in parendodontic surgeries; therefore they should have investigated their biocompatible characteristics since they remain in direct contact with the periapical bone tissue. This study investigated the inflammatory response of bone tissue when in contact with four types of MTAs available on the market, through intraosseous implants in guinea pigs, using for that purpose, the methodology recommended by the International Dental Federation (1980) which is internationally accepted (ADA, 1982). Forty guinea pigs were used in experimental periods of four and twelve weeks. Each animal received an implant in each side of the mandibular symphysis region. From each implant it was made 24 blades with 144 histological cuts, stained with hematoxylin-eosin and reviewed by two independent observers. There was similarity between the materials tested, since after 4 weeks all the implants with MTAs ProRoot ® gray and white as well as the ones with MTAs Angelus ® gray and white presented an absent/mild inflammatory reaction evolving into a process of scar repair with affixing of mineralized matrix. Thus, through the methodology employed it was possible to conclude that all types of MTAs, regardless the trademark, were biocompatible promoting similar tissue responses when in contact with the bone tissue. / O material utilizado na retro-obturação é, entre outros, um fator determinante do sucesso na cirurgia parendodôntica, dessa forma estes devem ter investigadas suas características de biocompatibilidade uma vez que permanecem em contato direto com o tecido ósseo periapical. Neste estudo, investigou-se a resposta inflamatória do tecido ósseo frente aos quatro tipos de MTAs disponíveis no mercado, através de implantes intra ósseos em cobaias guinea pigs, usando para isso, a metodologia recomendada pela Federação Dentária Internacional (1980) e aceita internacionalmente (ADA, 1982). Quarenta cobaias foram utilizadas nos períodos experimentais de quatro e doze semanas. Cada animal recebeu um implante em cada lado da região sinfisária da mandíbula. De cada implante foram confeccionadas 24 lâminas com 144 cortes histológicos, coradas com hematoxicilina-eosina e analisadas por dois observadores independentes. Verificou-se similaridade entre os materiais testados, uma vez que em todos os períodos de avaliação, tanto os MTAs ProRoot® cinza e branco quanto os MTAs Ângelus® cinza e branco apresentaram uma reação inflamatória ausentes/suaves evoluindo para um processo de reparo cicatricial com aposição de matriz mineralizada. Assim, através da metodologia empregada foi possível concluir que todos os tipos de MTAs, independentemente da marca comercial, foram biocompatíveis promovendo resposta tecidual similar quando em contato com o tecido ósseo. / Mestre em Odontologia

The use of Mineral Trioxide Aggregate (MTA) is gaining popularity among clinicians. Despite the many ideal qualities it possesses, it is often difficult to manipulate and often requires a second appointment for placement of a restoration to allow for setting. If the time to set of MTA can be accelerated to a single appointment time frame without significantly altering its properties, then MTA may gain even wider acceptance. The purpose of this study is to identify the percentage of a Portland Cement Accelerator (PCA), that when added to MTA, will decrease the time to set of MTA towards a single appointment time frame. Ten Teflon sample molds were prepared to hold 20 standardized chambers in each. Three sample molds were prepared with a 5.0% (by weight of MTA) accelerator, 3 with 10.0% accelerator and 3 with 15.0% accelerator mixed with MTA and water. Another sample mold contained a mixture of MTA and water only and acted as the control. Samples were tested using a dial indicator microgauge apparatus that measured the depth of needle penetration starting at 2 minutes and then every minute up to 15 minutes. Samples were also tested at 3, 4, 24, 48 and 72 hours. A mixed-model repeated measures ANOVA showed the four accelerator groups were significantly different and there was a significant time trend. The 5.0% accelerator group set significantly faster compared to the 15.0% and the control at 15 minutes or less (p<0.05). In conclusion, it appears that 5.0% PCA when added to MTA can accelerate the setting reaction.