Master of Science

The present study involves the determination of traces of thallium and mercury in aqueous solution by forming ion-association complexes of these metals with rhodamine 6G (R6G) in the presence of iodide. Thallium(lll) and mercury(Il) are able to quench the fluorescence of R6G in the presence of iodide by forming ion—association complexes, and the degree of quenching correlates with the thallium(III) or mercury(II) concentrations . By using this method, the minimum amount of thallium- (III) that can be determined in aqueous solutions is approximately 4.00 X 10-6m, while the minimum amount of mercury(II) is approximately 3.00 X 10-6m. Thallium(I) cannot be determined by this method because it is not possible to form ion-association complexes under similar experimental conditions therefore, this method can be used to differentiate between Tl(I) and Tl(III) in aqueous solution. To elucidate the composition of the ion-association complexes in aqueous solutions two spectrophotometric methods are used: the mole-ratio method and the continuous- variation method. The experimental results seem to indicate that two complexes are formed for the mercury(II)-R6G-iodide system. The empirical compositions of these complexes are tentatively determined to be [(R6G)HgI3] and [(R6G)2HgI4).

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Recently concern has been raised regarding effluent from wine cellars, as it often does not comply with environmental legislation. It was with this in mind that the effluent problem at Ashton Cellars was addressed. After carrying out a water audit of the plant, described in Chapter 3, it was concluded that the ion exchange plant is a significant contributor to the low pH and high conductivity of the effluent dam. Decreasing the effluent from the ion exchange plant should therefore help in improving the total effluent quality. During the water audit opportunities to improve the effluent by making small process changes in the cellar were identified. The primary objective of this study was to provide guidelines to improve the quality and decrease the volume of the effluent from the ion-exchange plant to more environmentally acceptable levels, whilst maintaining product specifications and production rates. This was achieved by studying the operation of the plant (Chapter 4) and testing the characteristics of the current and alternative resins (Chapter 5). Auditing of the ion exchanges plant included a detailed analysis of the regeneration and loading of the ion exchange columns. It was concluded that the operation of the plant can only be optimised once pH and/or conductivity meters, and preferably an automated control system, are installed on the plant. The results given in this thesis can be used as a guide when setting up such a control system. Laboratory testing of the resins revealed that the cation resin currently being used on the plant has been fouled and loads at a slow rate. When the resins are replaced, the use of Purolite CISO and Purolite A103S should be considered as these resins gave the most favourable results. Some alternative treatment methods for the processing of grape must, have been mentioned in Chapter 6. / AFRIKAANSE OPSOMMING: Al meer kornrner word deesdae uitgespreek oor wynkelders se afvalwater, omdat dit meerendeels nie aan die vereistes van omgewingswetgewing voldoen nie. Dit was met hierdie probleem in die oog dat die afvalwater probleem by Ashton Kelders ondersoek IS. Nadat 'n wateroudit van die fabriek, soos beskryf in Hoofstuk 3, uitgevoer is, is daar tot die slotsom gekom dat die ioonuitruilsisteem 'n groot bydra tot die lae pH en hoe konduktiwiteit van die afvaldam lewer. Indien die ioonuitruilsisteem se uitvloeisel verminder kon word, sou dit tot 'n groot mate bydrae tot 'n verbetering van die totale uitvloei kwaliteit. Gedurende die wateroudit is verskeie moontlikhede vir die verbetering van die uitvloei deur klein prosesveranderinge aan te bring, geidentifiseer. Hierdie studie het as hoof oogmerk die daarstelling van riglyne vir die verbetering van die kwaliteit en grote van die afvalstrome van die ioonuitruilsisteem om sodeende aan omgewingswetgewing te voldoen, maar ter selfder tyd die produk spesifikasies en tempos te handhaaf. Dit is gedoen deur die huidige bedryf van die fabriek te bestudeer (Hoofstuk 4) en die eienskappe van die huidige en altematiewe ioonuitruilharse te toets (Hoofstuk 5). Die oudit van die ioonuitruilsisteem het 'n gedetaileerde anaIiese van die hergenerasie en lading van die ioonuitruilkolornrne ingesluit. Daar is tot die slotsom gekom dat die bedryf van die sisteem alleenlik geoptirniseer kon word indien pH en/of konduktiwiteitsmeters, en verkieslik 'n automatiese kontrolesisteem geinstalleer word. Die resultate van hierdie tesis kan as basis vir so 'n kontrole sisteem gebruik word. Die laboratoriumtoetse op die harse het aan die lig gebring dat die katioonhars wat tans in gebruik is, baie vervuil is en net teen 'n lae tempo belaai kan word. Wanneer die harse vervang word, word die gebruik van Purolite el50 en Purolite A103S aangeraai, aangesien hierdie harse die beste resultate gelewer het. Altematiewe behandelingsmetodes van druifmos is in Hoofstuk 6 genoem.

Magister Scientiae - MSc / The objective of this study was to investigate the feasibility of the application of low cost high capacity inorganic ion exchange material, synthesized form collected fly ash and acid mine drainage solid residues, for the decontamination of secondary co-disposal process waters, with emphasis on investigating the processes governing the solid/solution interface. / South Africa

The article presents the results of experimental tests of the liquid exchange level in a new design of a hydraulic cylinder in comparison with the classic one. Comparative results are presented, as well as the influence of the stroke range on the degree of liquid exchange. The results allow the empirical determination of the degree of real improvement of the process of liquid exchange in the cylinder during operation, and thus allow the initial determination of the reliability level increase in hydraulic cylinders. It should be emphasized that the presented results are a part of a research and implementation project carried out in cooperation between a university and an industrial partner. In addition, the presented test method of hydraulic cylinders is, in the opinion of the authors, an interesting proposition, which can be used by manufacturers of this type of components in the world.

Controlled Auto Ignition (CAI) combustion is a new combustion principle in internal combustion engines which has in recent years attracted increased attention. In CAI combustion, which combines features of spark ignition (SI) and compression ignition (CI) principles, air/fuel mixture is premixed, as in SI combustion and auto-ignited by piston compression as in CI combustion. Ignition is provided in multiple points, and thus the charge gives a simultaneous energy release. This results in uniform and simultaneous auto-ignition and chemical reaction throughout the whole charge without flame propagation. CAI combustion is controlled by the chemical kinetics of air/fuel mixture with no influence of turbulence. The CAI engine offers benefits in comparison to spark ignited and compression ignited engines in higher efficiency due to elimination of throttling losses at part and idle loads. There is a possibility to use high compression ratios since it is not knock limited, and in significant lower NOx emission (≈90%) and particle matter emission (≈50%), due to much lower combustion temperature and elimination of fuel rich zones. However, there are several disadvantages of the CAI engine that limits its practical application, such as high level of hydrocarbon and carbon monoxide emissions, high peak pressures, high rates of heat release, reduced power per displacement and difficulties in starting and controlling the engine. Controlling the operation over a wide range of loads and speeds is probably the major difficulty facing CAI engines. Controlling is actually two-components as it consists of auto-ignition phasing and controlling the rates of heat release. As CAI combustion is controlled by chemical kinetics of air/fuel mixture, the auto-ignition timing and heat release rate are determined by the charge properties such as temperature, composition and pressure. Therefore, changes in engine operational parameters or in types of fuel, results in changing of the charge properties. Hence, the auto-ignition timing and the rate of heat release. The Thesis investigates a controlled auto-ignition (CAI) combustion in internal combustion engines suitable for transport applications. The CAI engine environment is simulated by using a single-zone, homogeneous reactor model with a time variable volume according to the slider-crank relationship. The model uses detailed chemical kinetics and distributed heat transfer losses according to Woschini's correlation [1]. The fundamentals of chemical kinetics, and their relationship with combustion related problems are presented. The phenomenology and principles of auto-ignition process itself and its characteristics in CAI combustion are explained. The simulation model for representing CAI engine environment is established and calibrated with respect to the experimental data. The influences of fuel composition on the auto-ignition timing and the rate of heat release in a CAI engine are investigated. The effects of engine parameters on CAI combustion in different engine concepts fuelled with various fuels are analysed. The effects of internal gas recirculation (IEGR) in controlling the auto-ignition timing and the heat release rate in a CAI engine fuelled with different fuels are investigated. The effects of variable valve timings strategy on gas exchange process in CAI engine fuelled with commercial gasoline (95RON) are analysed.

The objective of this study was to investigate the feasibility of the application of low cost high capacity inorganic ion exchange material, synthesized form collected fly ash and acid mine drainage solid residues, for the decontamination of secondary co-disposal process waters, with emphasis on investigating the processes governing the solid/solution interface.

No description available.

The objective of this study was to investigate the feasibility of the application of low cost high capacity inorganic ion exchange material, synthesized form collected fly ash and acid mine drainage solid residues, for the decontamination of secondary co-disposal process waters, with emphasis on investigating the processes governing the solid/solution interface.

No description available.