Ph.D. (Chemistry) / In this study, carbon based electrode materials such as glassy carbon, graphene, diamond and exfoliated graphite were explored as suitable electrode materials for electrochemical detection, electrochemical and photoelectrochemical degradation of organic water pollutants. Graphene modified glassy carbon electrode sensor was developed for bisphenol A. Cyclic voltammetry was used to study the electrochemical properties of the prepared graphene- modified glassy carbon electrode using potassium ferricyanide as a redox probe. The prepared graphene- modified glassy carbon electrode exhibited more facile electron kinetics and enhanced current of about 75% when compared to the unmodified glassy carbon electrode...

The complex Fe2(TIED)4+ (compound I) [see PDF] has a characteristic intense low energy electronic absorption band (λ = 874 nm, ε = 24,600 M-1cm-1). This band is assigned as a metal to ligand charge transfer, MLCT, and it exhibits a very large solvent dependence which is attributed to replacement of the axial ligands on the iron atoms by solvent. The complex has two reversible oxidation and two reversible reduction steps in the cyclic voltammogram in dry CH3CN. The oxidation involves the iron atoms while the reduction places electrons on the conjugated part of the ligand. The cyclic voltammogram shows a single, apparently, two-electron reduction process in DMF and in H2O. A mixed-valence FeII/FeIII (Fe2(TIED)5+) compound has been obtained by electrochemical oxidation of Fe2(TIED)4+. The mixed-valence compound has an intense near-infrared band (λ = 940 nm, ε = 28,000 M-1cm-1). Analysts of this band using the Hush equations for an intervalence transition indicates that the system is delocalized. The difference in oxidation potentials, ΔE1/2 = ΔE1/2 (FeIII/FeIII) - ΔE1/2 (FeII/FeIII), is 500 mV and this corresponds to a comproportionation constant of 2.8 x 108. This large value indicates the mixed-valence species is stabilized by delocalization. The Mössbauer spectrum of the mixed-valence compound consists of a single quadrupole-split doublet at 90 K and 4.2 K. This establishes that the iron atoms are equivalent of the Mössbauer time scale, and the mixed-valence compound is classified as valence-average, ((Fe2.5/Fe2.5).

The object of this research was to develop an arsenic(V) selective electrode. The electrode is based on a solid state membrane prepared by pressing a precipitate of silver arsenate-silver sulfide into a pellet. After the electrode was made, experiments were designed to check for three general characteristics of the electrodes: dependence of potential on pH for constant arsenic(V) concentration; dependence of potential on arsenic(V) concentrations at constant pH and extent of interference due to phosphate and arsenic(III) ions. From these measurements, it was found that Ag2HAs04 was formed originally in the membranes containing a small fraction of arsenic(V) and that this compound was converted to Ag3As04 on the electrode surface in alkaline solutions.

The problem taken for investigation was discovered when a cryostat needed for use in polarography in liquid ammonia (the original problem) was found broken. For experience it was decided to turn to another form of nonaqueous polarography while the parts were on order. Materials remaining from a previous diamine investigation by Foss (21) were found in the laboratory. After reading the dissertation in which they had been used, it was decided to reproduce some of the results that had been previously obtained. Following preparation of the chemicals and several polarographic runs, a previously unreported wave was persistently observed. Further perusal of the dissertation found no such wave reported and only one other similar wave had been noted by Robert Burrus (12), as was revealed in a thorough search of the literature. It was the study of this new wave that was taken for the problem to be investigated.

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The purpose of this investigation was to determine the products of the electrolysis of dimethyl lithium amide. / Master of Science

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M. Tech. Metallurgical Engineering. / Investigate the dissolution behaviour of sphalerite minerals in sulphuric acid using ferric ions as oxidants. The specific objectives are to study the following: 1. the mineralogical characteristics of sphalerite ores ; 2. mineralogical effects on dissolution kinetics in sulphuric acid and 3. Effect of ferric ion concentration on the dissolution kinetics of sphalerite ores in sulphuric acid. Mineralogy is a critical area in mineral processing and has to be considered during process design stage, and during each processing stage. The type and concentration of oxidizing agent depend on the mineralogical composition of the ore. Many researchers investigations and test-works have been reported on leaching of sphalerite using both ferric sulphate and ferric chloride (Al-Harahsheh and Kingman, 2007; Rath et al., 1981). However, little or no studies have been reported on the combined oxidants.

published_or_final_version / Chemistry / Master / Master of Philosophy