Background Vanadium is an economically important mineral that is mined and processed at several international locations, including South Africa and the USA. Vanadium exists in several oxidative states, of which the pentavalent compounds are usually the most toxic. Vanadium pentoxide (V205) is pentavalent and is generated during various processing and metal alloy manufacturing processes. Occupational exposure may occur via inhalation of V205 fumes and particles, resulting primarily in adverse effects to the respiratory system. Currently, there is no evidence that vanadium is carcinogenic in humans, and it has never been reported in exposed humans. The International Agency for Research in Cancer (IARC) has classified V205 as possibly carcinogenic to humans, based on the increased incidence of bronchiolo-alveolar neo¬plasms observed in male and female mice and male rats in a study by the National Toxicology Program (NTP) of the US Department of Health and Human Services. The NTP study has prompted the international vanadium industry, embodied by Vanitec, the international association of vanadium producers, to request an epidemiological study with the aim of determining the potential association between cancer and occupational V205 exposure. Aim The aim of the study was to conduct a pilot retrospective case-control study to investigate the relationship between cumulative occupational exposure to V2O5 and the risk of developing cancer at two representative vanadium processing plants, one in SA and one in the USA. Methods All cases and controls were sourced from the industry’s current and past employee corps. Employees that could potentially have been exposed to V2O5 in the workplace for a period of at least 5 years were included in the study. Ethics approval for the study was obtained from the Ethics Committee of the University of Pretoria. Participation was on a voluntary basis, and all potentially eligible current workers were invited to participate. As many retirees and former employees as possible were traced and invited to participate, and eligible deceased employees that conformed to the inclusion and exclusion criteria were identified from lists provided by the companies involved. Potential participants were asked to grant informed consent to participate in the study. Health and lifestyle information, information on fuel use in the family home, and a personal job history were obtained by use of a structured questionnaire during a personal interview with a trained interviewer. Interviews were conducted from April to July 2004. The main inclusion criterion for both cases and controls was current or previous employment at the South African, or the USA vanadium processing facility included in the study. The disease case definition was histologically confirmed cancer. Exclusion criteria were: refusal of interview; less than 5 years in employment when V2O5 was produced at the plant; cause of death not ascertained, employment elsewhere in the vanadium industry, and exposure to a known carcinogenic agent during a period of employment elsewhere. Males and females were included and participants were not excluded on the basis of race or ethnicity. Employees of all ages were eligible. Exposure assessment at both plants was based on recorded V2O5 concentrations in personal air samples, the participant’s job history, the history of vanadium processing, the physical structure and work organisation at the processing plants. Historical V2O5 concentrations in air in the workplace were retrospectively estimated for those periods during which personal air sampling was not conducted. Historical concentrations were estimated by extrapolation from current (known) air concentrations, in conjunction with data on annual production volumes, personal experiences of occupational hygienists and plant managers at the plant, and historical records of plant upgrades, controls on emissions, changes in production processes and industrial incidents and accidents, where available at the plants. Exposure was expressed as the cumulative exposure (mg-years/m3) and the mean air concentration (mg/m3) of V2O5 to which participants had been exposed. Study participants were also classified into exposure categories based on their mean exposure concentrations. Results In total, 196 questionnaires were collected from eligible participants. The majority (94.4 per cent) were males. Smoking and the consumption of alcohol was fairly common amongst the study group, with 61 per cent of the participants being current or previous smokers, and 59.5 per cent indicating that they were drinking alcoholic drinks or beverages. The mean age (± SD) of the study group was 52.4 ± 10.2. The annual mean exposure of the study group during the period of employment was 0.02 ± 0.03 mg/m3 V2O5, and the mean cumulative exposure to V2O5 was 0.17 ± 0.46 mg-years/m3. Four (4) cancer cases were confirmed at the South African plant, and 6 at the USA plant: four adenocarcinomas (three each in the prostate and one in the colon); three squamous cell carcinomas (two each in the lung and one skin cancer); one renal cell cancer of the kidney, one seminoma of the testis, and one papillary urothelial cancer of the bladder. The occurrence of prostate and lung cancers were not unusual, giving the presence of risk factors such as relatively advanced age (for prostate cancer) and smoking (for lung cancer). The other types of cancer, and the ages at which cancer was most frequently diagnosed (the mean age at diagnosis of cancer was 58.5) were not remarkably different from those that were prominent in the cancer literature. An unusual cluster of specific types of cancer, or of any prominent and unusual organ involvement not associated with known non-occupational risk factors, was therefore not found in the case group. Conclusion The results of this study fail to indicate a statistically significant association between cancer and various indices of exposure to vanadium pentoxide. This conclusion is subject to a number of limitations and uncertainties arising from the small number of cases available for study, and limited follow-up of some participants. The potential association between exposure and cancer should be tested in a larger study group with more cancer cases, allowing more powerful statistical analyses, ideally multivariate logistic regression analysis. The study has confirmed the feasibility of the retrospective assessment of exposure to vanadium compounds in the vanadium processing industry, providing that the processing plant history covers detail of processing methodologies, physical structures, production volumes and work organisation, and providing that a detailed job history should be available for all potential participants. Confirmation of the cause of death and cancer status of previous employees was not practical in the South African scenario. An open case-control design nested in a prospective cohort should be more successful in the South African scenario, but also more expensive and results will only be available after an extended follow-up period. In the USA scenario tracing of previous employees, and access to cancer registries and death certificates should be more practical, and a retrospective case-control study should be possible. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / School of Health Systems and Public Health (SHSPH) / Unrestricted

This semestral thesis deals with problematics of redox flow batteries, especially vanadium batteries. The first part is focused on describing basic terms, describes redox batteries and explains chemical processes. It also deals with vanadium batteries properties and construction. The second part of the thesis describes diagnostic method of spectroscopy, which seems to be very perspective for examining attributes of vanadium redax batteries.

The quadrupolar interaction in sodium orthovanadate dodecahydrate, calcium orthovanadate, vanadinite, descloizite, zirconium divanadate, cadmium divanadate, potassium metavanadate and vanadium pentoxide, was studied by nuclear magnetic resonance. The v51 quadrupole coupling constants in these compounds show a strong correlation with the distortion of the tetrahedral symmetry around the vanadium ion. Vanadium pentoxide is an exception and shows a surprisingly small coupling constant. The point multipole model was found to be inadequate for the calculations of the electric field gradients in these compounds. A covalent model provides an explanation of the small magnitude of the coupling constant of vanadium pentoxide. However, because of the numbers of approximations in this model, only a qualitative correlation with the experimental results was achieved. In addition, the chemical shift tensor of the v51 resonance line in a single crystal of vanadium pentoxide was measured to be very large. This result was correlated with a large Van Vleck term in the magnetic susceptibility of vanadium pentoxide. / Thesis / Doctor of Philosophy (PhD)

Vanadium Redox Flow Batteries VRFBs are promising energy storage systems with highly recyclable electrolytes. The recycling of these systems usually involves ammonium-based salt precipitation steps, which produce toxicgases and contaminated water as waste. In this study, a novel method has been developed to recycle vanadiumdirectly from VRFB electrolyte solutions. The purity and characteristics of the final product have been analyzedusing X-ray Diffraction and Cyclic Voltammetry analysis. The method developed in this study has a precipitationrecovery of 98%. However, further investigation is needed to improve product purity and method optimization. / Sammanfattning på svenska: Vanadium Redox Flödes Batterier VRFB är lovande energilagringssystem medmycket återvinningsbara elektrolyter. Återvinningen av dessa system innefattar vanligtvis ammoniumbaseradesaltutfällningssteg som producerar giftiga gaser och förorenat vatten som avfall. I denna studie har en ny metodutvecklats för återvinning av vanadium direkt från VRFB elektrolytlösningar. Renheten och egenskaperna hosslutprodukten har analyserats med X-ray diffraktion och cyclic voltammetry analys. Metoden som utvecklats idenna studie har återvinnings kapacitet på 98 %. Ytterligare utredning behövs inom förbättring av produktensrenhet samt metods optimering.

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Darbo tikslas yra susintetinti natrio-vanadžio oksidinę bronzą Na0.33V2O5 zolių-gelių sintezės būdu bei nustatyti jos cheminį sąstatą Rentgeno fotoelektronų spektroskopijos metodu. Darbe aprašyti zolių-gelių technologijos pagrindai, vanadžio pentoksido ir jo hidratuotų junginių struktūra, vanadžio oksidinių bronzų savybės ir sintezės būdai bei Rentgeno fotoelektronų spektroskopijos metodo pagrindai. Pateiktas išsamus vanadžio – natrio oksidinės bronzos sintezės zolių-gelių metodu technologijos aprašymas. Aprašyti eksperimentiniai bronzos ir vanadžio – natrio kserogelio Rentgeno fotoelektronų spektrai. Gautas rezultatas: nustatyta, kad zolių – gelių technologija leidžia paprastais metodais, nenaudojant sudėtingos aparatūros, susintetinti norimos cheminės sudėties vanadžio – natrio oksidines bronzas; Rentgeno fotoelektronų spektroskopijos metodas įgalina atlikti bronzų kokybinę bei kiekybinę cheminę analizę ir nustatyti metalų jonų valentines būsenas bronzoje; sintetinant bronzą iš V2O5 ir Na2SO4 galutiniame produkte nėra sieros pėdsakų; susintetintoje bronzoje vanadžio jonai yra dviejose valentinėse būsenose – V4+ ir V5+. / The main aim of the present work was the synthesis of vanadium – sodium oxide bronze by using sol-gel technology and the study of the bronze chemical composition by X-Ray photoelectron spectroscopy. The bases of sol-gel technology, the structure of vanadium pentoxide and its hydrated compounds, the properties and the structure of vanadium oxide bronzes and the bases of X-Ray photoelectron spectroscopy are described in the work. The detailed description of technological process of vanadium – sodium oxide bronze synthesis by sol-gel technology is resulted. The experimental results of the study of X-Ray photoelectron spectra of vanadium - sodium bronze ant its hydrate are described and discussed. As a result of work, it is established that sol-gel technology allows a synthesis of bronzes of necessary structure by simple methods, without using difficult equipment; X-Ray photoelectron spectroscopy method allows making a quantitative and qualitative analysis of the composition of the bronzes and an establishment of the valence of metals ions; when the bronze was synthesized V2O5 and Na2SO4, the sulphur presence was not observed in the bronze; vanadium ions in the bronze are in V4+ and V5+ states.

Industrial catalysts used in commercial processes for the production of maleic anhydride are mainly Vanadium Phosphorous Oxide (VPO) catalysts. The VPO catalyst used is Vanadyl Pyrophosphate (VO)2P207 made from its precursor Vanadium Phosphorous Hemi-Hydrate VOHP04.O.5H20 in an non-aqueous medium. In order for the VPO catalyst to perform optimally, a metal promoter, Ru, was selected as the doping agent in this study. Four catalysts of different metal doping concentrations (undoped, 0.2%, 0.6% and 1%) were subjected to the oxidation of n-butane. Promoters are added to facilitate the oxidation of n-butane to maleic anhydride. n-Butane gas is now being used in many industrial processes, in fixed bed reactors to convert the gas to maleic anhydride. Catalysts were calcined under high temperatures under a nitrogen atmosphere. It was found that with an increase in reaction temperature, there was an increase in conversion of n-butane to maleic anhydride. Selectivity of the product also showed an increase with an increase in temperature at a Gas Hourly Space Velocity (GHSV) of 1960-2170hr-1. Catalysts were characterized using different techniques such as Electron Dispersive X-Ray Spectroscopy, Inductively Coupled Plasma-Atomic Emission Spectroscopy, Fourier Transform - Infra Red, Average Oxidation State, Brunauer Emmett and Teller (surface area), X-Ray Diffraction and Scanning Electron Microscopy. The 0.6% Ru promoted VPO catalyst showed to be most effective in terms of conversion, selectivity and yield, at a temperature of 450°C as compared to the other catalysts studied. The catalysts degenerated after being subjected to higher temperatures. The selectivity obtained by this catalyst was at 70.2% and the yield obtained was 37%. This study showed that with an increase in Ru up to a certain concentration (0.6%), an increase in selectivity and yield was observed, thereafter, with additional Ru doping, a decrease in selectivity and yield was obtained. / Thesis (M.Sc.)-University of Natal, 2003.

Co promoted and unpromoted vanadium-phosphorous-oxide (VPO) catalysts were synthesized via an organic route. The catalyst precursor was calcined and then conditioned in a reactor, forming the active vanadyl pyrophosphate, (VO)2P2O7, phase. Different promoter loaded catalysts were synthesized and their effect on the yield of maleic anhydride (MA) from n-butane oxidation was examined at different temperatures and gas hourly space velocities (GHSV). The catalysts were tested as a powder. The catalysts were examined in the oxidation of n-butane gas, over air as an oxidant, in a specially designed and constructed continuous flow, fixed-bed catalytic micro-reactor equipped with an on-line gas chromatography (GC) monitoring system. A thermal conductivity detector (TCD) was employed for carbon oxide monitoring and a flame ionization detector (FID) for all other products. The catalysts were characterised by X-ray diffraction (XRD) to determine the phases present in the precursor, calcined and used catalysts. The Brunauer-Emmet-Teller (BET) surface area was calculated for the different promoter loaded catalysts. Fourier transform infrared (FT-IR) spectra, via the KBr pellet method, and attenuated total reflectance (ATR) spectra were recorded to determine the anions present in the bulk and surface of the catalyst respectively. Energy dispersive X-ray (EDX) and inductively couple plasma-atomic emission spectroscopic (ICP-AES) techniques were employed to determine the elemental composition on the surface and in the bulk of the catalyst respectively. Scanning electron microscopic (SEM) images of the catalysts during different stages of their investigation were recorded. The average vanadium oxidation state (AV) in the bulk of the catalyst was determined via a titrimetric method. The catalysts were optimized to a high yield and selectivity of MA. The operating temperature, GHSV and promoter loading on the catalyst were the parameters that were changed during the testing of the catalyst. Different stages of the catalyst's life were characterised via the techniques mentioned above. The catalysts were monitored over a 200-hour period on average, usually taking approximately 24 hours to equilibrate. One such Co promoted catalyst yielded 45 % MA at 275°C and GHSV of 2878 hr-1 on equilibration, with an n-butane conversion of 73 %, whilst all previously reported VPO catalysts produce far lower MA yields at this temperature. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

A series of five, tetradentate Schiff-base ligands were synthesised and chelated to vanadyl to form oxovanadium(IV) complexes. The ligands, 4,4’-{benzene-1,2-diylbis[nitrilo(1E)phen-1-yl-1ylidene]}- dibenzene-1,3-diol (H2L1), 4,4’-{ethane-1,2-diylbis[nitrilo(1E)phenyl-1-yl-1-ylidene]}dibenzene-1,3-diol (H2L2), 4,4’-{propane-1,2-diylbis[nitrilo(1E)phen-1-yl-1-ylidene]}dibenzene-1,3-diol (H2L3), 4,4’-{(2- hydroxypropane-1,3-diyl)bis[nitrilo(1E)phen-1-yl-1-ylidene]}dibenzene-1,3-diol (H2L4) and 4,4’-{2,2- dimethylpropane-1,3-diyl)bis-[nitrilo(1E)phen-1-yl-1-ylidene]}-dibenzene-1,3-diol (H2L5), characterised by TOF-MS, IR, electronic absorption, 1H and 13C NMR spectroscopy. The ligand H2L5 was also characterised by XRD. The ligands were shown to have a bis-zwitterionic structure in the solid state, and possibly also in solution. Complexes were characterised by Elemental Analysis, TOF-MS, IR, electronic absorption spectra, EPR and 51V NMR spectroscopy. They form mononuclear complexes, with one ligand binding a single vanadyl ion. EPR spectroscopy was performed on both the powdered form and solutions of the complexes. All the complexes displayed axial symmetry, with increasing distortion from an ideal square pyramidal geometry as the size and bulk of the central chelate ring was increased. Isotropic g0 values suggest solvent interaction with the vanadium ion for the coordinating solvent DMSO. Additional distortion on the coordination geometry, presumably from the benzyl groups of the compounds, causes the isotropic hyperfine coupling constants to be greater than expected. Furthermore, the ability of the complexes to bind peroxide species was investigated by following the addition of H2O2 to the complexes using 51V NMR spectroscopy to observe shielding changes at the vanadium nucleus, and 1H NMR spectroscopy to monitor the bulk magnetic susceptibility, via a modified Evan’s NMR method. Similar experiments were done with sodium hydroxide for comparison. As expected, the oxoperoxovanadium(V) complexes were more stable than their progenitor oxovanadium(IV) complexes. Additionally, increasing the distortion from the ideal pseudo square-pyramidal coordination geometry for the vanadyl ion resulted in a greater increase in the apparent stability of the peroxocomplexes. This latter effect is further enhanced by the addition of a hydrogen-bonding group in close proximity to the vanadium nucleus. DFT calculations of the optimized geometries, natural bond orbitals, electronic absorption and infra-red frequencies were performed for both the ligands and the complexes; nuclear magnetic resonance calculations were performed for the ligands as well. The B3LYP/6-311G (d,p) and B3LYP/LANL2DZ level of theories were used for the ligands and complexes respectively, except for electronic transitions, which were calculated using TD-SCF methods for both ligands and complexes. Calculated and experimental results were compared where possible, and showed reasonable agreement for all calculations performed. The exception to this was for the NMR calculations for the ligands, which were poorly simulated. Finally, the in vitro biological activity of the complexes was evaluated for cytotoxicity against the human tumour cell lines: A549, U251, TK-10 and HT29, via an MTT assay. All complexes showed promising anticancer activity, as evidenced by their low IC50 values for the cell lines A549, U251 and TK-10, which are in general, lower than that observed for cisplatin. They did, however, express negligible activity against the HT29 colon adenocarcinoma cell line; showing an apparent selectivity for certain cell lines. These oxovanadium(IV) complexes, thus warrant further evaluation as chemotherapeutic agents. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.