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Nanowires and nanotubes with single component such as gold and nickel were fabricated by electrochemical deposition method directed by the Anodic Alumina Membrane (AAO) as a template. A so called "polymer-free" method has been investigated to make striped nanowires with superlattice structure. Various methods have been used to characterize these nanomaterials, including SEM, FESEM TEM, STM and Optical Microscope. The aggregation of the nanowires and their alignment under the magnetic force were observed under the optical microscope.

Student Number : 9900280X - MSc (Eng) dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / The flow characteristics of an on-line analyser were measured using a stimulus – response technique. The analyser was developed for monitoring homogeneous catalyst concentrations in a non-aqueous solution and it was considered important to limit dispersion effects between sample injection and measuring points. Various tube lengths between these points were used and the system was operated over a range of flow rates. The detectors employed were electrochemical in nature and of two different designs. The residence time distributions of the system were determined experimentally and analysed by the method of moments and frequency techniques. As expected dispersion of the sample decreased as tube length decreased and flow rate increased. An attempt was made to fit the experimental results to the axially dispersed plug flow model. This was only successful over a limited range of the variables.

Degree: Master of Science Department: Science / Metal-ligand models and complex stability constants of newly synthesised chelating ligands, N,N’-bis(2-hydroxycyclopentyl)-ethylenediamine (Cyp2EN) and N,N’-bis(2-hydroxycyclohexyl)-ethylenediamine (Cy2EN), with metal ions Cd2+, Cu2+, Ni2+, Pb2+ and Zn2+ were established in this work. Stability constants were determined by Glass Electrode Potentiometry (GEP) and polarography as electrochemical techniques. A new concept, termed Virtual Potentiometry (VP), was also used for the evaluation of stability constants. In this concept, polarographic or polarographic + potentiometric data were evaluated using potentiometric computer software (ESTA). This concept assisted in obtaining a final model for Cd–Cyp2EN and Pb–Cyp2EN systems. It could refine M(HL) complex inaccessible via polarographic study of Pb–Cyp2EN system and refined the hydroxo–complex ML2(OH) that in turn was inaccessible using GEP for Cd– Cyp2EN system. For all metals studied, the complexes ML formed with the ligand Cy2EN were found more stable than the complexes ML formed with the ligand Cyp2EN. The complex M(HL) was obtained for all systems studied, but it seemed to be a minor species. The complex ML2 was obtained in different systems studied with the ligand Cy2EN while this complex was only found in Cd–Cyp2EN system. In several systems potentiometric (ESTA) and voltammetric (3D–CFC) software could not distinguish which hydroxo–complexes were present as these species were formed in the pH range where the ligand was fully deprotonated. Selectivity trends for Cyp2EN and Cy2EN were compared and related to DHEEN as a function of metal ion radius. It was observed that the large metal ions were favoured by the addition of cyclopentyl bridges in DHEEN while the small metal ions were favoured when cyclohexyl bridges were added.

Master of Science in Engineering - Engineering / The employment of an electrochemical process is an attractive alternative for the treatment of effluents. When dealing with solutions of low metal ion concentrations mass transport limitations are significant and large electrode surfaces are required. The use of a reactor containing a three-dimensional electrode is preferable as the surface area per unit volume is orders of magnitude greater than that of the familiar plate type reactor. A benchscale electrochemical reactor was designed and constructed to incorporate a cylindrical packed bed cathode. The flow of electrolyte is perpendicular to the direction of the flow of the current and the system is operated galvanostatically in a batch recirculation mode. The industrial stream selected for examination contains palladium and copper ions and a small concentration of platinum in a chloride medium containing ammines. The evolution of chlorine gas at the anode by the oxidation of the chloride ions is prevented by the inclusion of a cation exchange membrane and a separate anolyte, namely sulphuric acid, is introduced to the outer anodic chamber. Tests were conducted on both synthetic and industrial solutions and a simplified model which was derived was used to estimate the mass transfer coefficients. The concentrations of the palladium, copper and platinum in the plant effluent were approximately 150, 200 and 10 ppm respectively. The results show that the metal ions can be rapidly reduced to well below 1 ppm in each case. The separation of the palladium and copper ions is shown to occur to a limited degree during electrodeposition, with the extent of separation increasing for lower current densities. Enhanced separation may be possible during the removal of the deposited metals from the cathode either by anodic stripping or chemical treatment. A further method for the recovery of the metals is the combustion of the graphite particles. The high value of palladium, coupled with the significant recoveries shown to be achievable, suggest economic viability in addition to the environmental benefits.

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