https://commons.ru.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://commons.ru.ac.za/vital/access/manager/Repository/vital:2587 Wed 12 May 2021 23:06:18 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3895 Wed 12 May 2021 22:51:27 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:10894 Wed 12 May 2021 21:06:54 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:2595 Wed 12 May 2021 19:54:50 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5404 Wed 12 May 2021 18:57:22 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3976 Wed 12 May 2021 18:46:00 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5755 Wed 12 May 2021 18:13:50 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5506 Wed 12 May 2021 17:56:29 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4222 Wed 12 May 2021 17:42:24 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5262 Wed 12 May 2021 17:39:21 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3100 Wed 12 May 2021 16:49:40 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5618 Wed 12 May 2021 16:27:43 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4418 Wed 12 May 2021 16:25:06 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:10816 Wed 12 May 2021 16:11:41 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3894 Wed 12 May 2021 16:06:52 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:21049 Cu > Zn >>Fe. The binding capacity of the Spirulina for each of the metals was relatively low when compared to a range of other biosorbents. The toxicity thresholds of the algae was determined for copper and zinc. These were low (10umoles/g) and as such, the algae were not suitable for application in a treatment system in which they came into direct contact with the toxic metals. The algae were able to increase the pH of the surrounding medium. This occurred as a result of the accumulation of inorganic carbon, from bicarbonate, as a response to low concentrations of carbon dioxide in the medium. The resulting release of a hydroxide ion into solution led to the increase in pH. The increase in pH was shown to be due to a reduction in acidity, rather than an increase in alkalinity. The enzyme carbonic anhydrase was shown to be pivotal in this system. Attempts to determine the enzyme activity directly were unsuccessful, due to the inherent inaccuracy of the assay system. An indirect method of determining enzyme activity, by measuring changes in the carbonate species equilibrium, was developed. Under optimal conditions Spirulina was able to reduce the acidity by an amount equivalent to the addition of 3670umoles NaOH g·' h·'. Predictive modelling showed that this enhanced the potential of the medium to effect metal precipitation. For the algal system to be sustainable, a readily available source of bicarbonate was needed. This was achieved by the oxidation of organic carbon, under sulphidogenic conditions, by a bacterial consortium isolated from the anaerobic component of a facultative pond. The consortium was shown to consist of sulphate reducing (most likely Desulvovibrio and Desulfotomaculum)and acetogenic bacteria. Sulphate removal rates of 500mg 1·' day·' and 135mg 1·' day·' were achieved in a 21 agitated and 281 upflow reactor respectively. The bicarbonate generation rate in the 281 reactor was calculated as 4033umoles 1·' day·', which proved sufficient to act as a feed for the algal system. Sparging the anaerobic digester overflow with air and nitrogen resulted in a reduction in the aqueous sulphide concentration. Using nitrogen, a 70% recovery of sulphide, as H2S gas, was achieved in 60 minutes, while with air, this dropped to 40%, due to the oxidation of the aqueous sulphide. The stripping ofH2S resulted in an increase in pH. The H2S gas was used for the selective precipitation of copper and lead in the integrated system. The dynamics of metal precipitation was investigated. For simple reactions, between individual IV metal and base species, it was possible to generate an accurate predictive model and confirm the precipitating species using wavelength dispersive X-ray spectroscopy (WDS). In more complex systems, where precipitation of the artificial acid mine drainage was examined, the predictive modelling and WDS could not accurately describe the system. The addition of aqueous sulphide to copper and iron resulted in the formation of metastable, amorphous precipitates, which remained in suspension. Ageing of the copper precipitate resulted in the evolution of a stable crystalline structure (covellite) and the aggregation and settling of the precipitate. In the case of iron, the amorphous precipitate underwent oxidation before a stable iron sulphide could evolve and the settled precipitate was an iron oxide or oxyhydroxide. The artificial acid mine drainage was treated with sulphide, hydroxide, anaerobic digester overflow and algal overflow. The best metal removal was achieved with the sulphide and hydroxide, while the algal overflow outperformed the anaerobic digester overflow. The precipitate generated by the addition of sulphide was the most compact, followed by the algal overflow, the anaerobic digester overflow and the hydroxide. Efficient precipitation of all the heavy metals, except manganese, was achieved using the algal overflow at an acidity to alkalinity ratio of 1 :2. This ratio was selected for use in the pilot system. The Spirulina based pilot system was effectively used to treat an effluent from the Black Mountain base metal mine. The necessity to maintain the algae in suspension and avoid biomass washout were practical considerations which counted against this system. The replacement of the Spirulina by Oscillatoria, which adhered to a solid support, overcame these problems. The integrated biological system was able to effectively treat an artificial acid mine drainage for 90 days, reducing the concentration of all metals, except manganese, to below the acceptable environmental risk levels. The treatment of the final effluent in a second anaerobic digester reduced the manganese concentration to 4.5uM and proved that the sulphate reducing bacteria could be cultivated on enriched, partially treated acid mine drainage. The integrated biological treatment system performed well, effectively treating an effluent modelled closely on the quality of the water being discharged from the East Rand Basin. The cost of such a system would be considerably less than a "high tech" physico-chemical system. This, coupled with the potential long term sustainability of a biological system, would make it a potentially attractive option for the treatment of future acid mine drainage discharges.]]> Wed 12 May 2021 16:00:34 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:1854 Wed 12 May 2021 15:53:13 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4553 600 nm) in dimethylsulphoxide solution. All the ligands were transformed into the dihydroxy silicon octaphenoxyphthalocyanine with varying degrees of phototransformation quantum yields ranging in order from 10⁻³ to 10⁻⁵ depending on the axial ligand involved. During and after axial ligand transformations a photodegredation of the dihydroxy silicon octaphenoxy phthalocyanine was observed upon continued irradiation. The oligomers were found to undergo the same axial ligand transformation process with a phototransformation quantum yield of 10⁻⁵ The singlet oxygen quantum yields of the unaggregated monomeric silicon octaphenoxy phthalocyanines were all found to be approximately 0.2 with the exception of a compound with two (trihexyl)siloxy axial substituents that had a singlet oxygen quantum yield of approximately 0.4 in dimethylsulphoxide solutions. The oligomers showed a surprising trend of an increase in singlet oxygen quantum yield with an increase in phthalocyanine ring number up to the pentamer and then a dramatic decrease to the nonamer. The triplet quantum yield and triplet lifetime were determined by laser flash photolysis for selected compounds and no correlation was observed with any of these properties and the singlet oxygen quantum yields. These selected compounds all fluoresce and a very good correlation was found between the fluorescence lifetimes determined experimentally by laser photolysis and the Strickler-Berg equation for the non-aggregated compounds. Electrochemical measurements also indicate the importance of the axial ligands upon the behaviour of the phthalocyanines as cyclic voltammetric behaviour was determined by the nature of the axial ligand.]]> Thu 13 May 2021 14:52:35 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:11023 Thu 13 May 2021 07:07:36 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4554 SnPc>ZnPc. Triplet lifetimes of the GePc (168-340μs) are very similar to that of the ZnPc (197 - 366μs), but the triplet lifetimes of the SnPc are ten fold shorter (10 - 32μs ). Triplet quantum yields are higher for the GePc (0.20 - 0.50) and SnPc (0.08 - 0.45) than for the ZnPc (0.02 - 0.25). Fluorescence lifetimes of GePc ( 4.0 - 5.1 ns) are significantly longer than that of ZnPc (1.9 - 3.0 ns) and SnPc (0.2 - 0.4 ns). Fluorescence quantum yields decrease in the following order: GePc(0.21-0.31)>ZnPc(0.02-0.21)>SnPc(0.02- 0.06). Ring-substituted cobalt phthalocyanine complexes of the form CoPc(R)4 (R= NH2, N02, C(CH3)3, S03H and COOH) are compared for their catalytic activities towards the oxidation of cysteine. The potential for the electrocatalytic oxidation of cysteine is closely related to the Com/Co11 couple of the CoPc(R)4 complexes in acidic media and to the Con/Co1 couple in basic media. The catalytic current and the oxidation potential for cysteine are dependent on the pH of the solution, the potential becoming less positive and the currents increasing with increase in pH.]]> Thu 13 May 2021 06:41:11 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4061 Thu 13 May 2021 05:54:49 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3917 Thu 13 May 2021 05:04:53 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4079 Thu 13 May 2021 04:31:19 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5305 0.05) apparent nutrient (protein, fat, fiber, starch) digestibility. Using the above digestibility protocol amino acid availability of all plants ingredients currently used in the South African animal industry was evaluated for H. midae. Soybean meal (96.86 %) and lupins (96.51 %) presented the highest apparent mean amino acid availability of all plant protein ingredients evaluated with H. midae. Canola meal (94.21 %), faba beans (92.87 %) sunflower meal (92.77 %), peanut meal (87.39 %) and cottonseed meal (85.15 %) presented higher apparent mean amino acid availability values than fish meal (82.75 %). Apparent protein digestibility was highly correlated (r = 0.99) with mean apparent amino acid availability, while true amino acid availability was 1.88 % units higher than apparent amino acid availability for all ingredients tested. Predicted apparent protein digestibility in compound diets was within 1.1-6.5 % of determined values. Calcium phosphate mono dibasic presented the lowest (P < 0.05) dietary phosphorus leaching (51.51 % maximum) and highest apparent phosphorus digestibility (66.27 %) in comparison to other inorganic phosphorus sources. Based on the method of direct experimentation to determine the optimal dietary protein level using graded levels of dietary protein 28.1-35.9 % dietary protein from good quality sources is recommended for maximum growth of juvenile H. midae. This study provides a scientifically sound research tool including a faecal collection technique, suitable marker and assay technique that could be use in further studies to improve least-cost diet formulation for H. midae. Future nutritional studies in H. midae should primarily concentrate on reducing dietary nutrient leaching and improving the intake of nutrients in order to properly evaluate responses of this species to different dietary regimes.]]> Thu 13 May 2021 04:20:05 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:2803 Thu 13 May 2021 04:17:12 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4626 Thu 13 May 2021 04:05:20 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:5703 Thu 13 May 2021 03:25:08 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3916 Thu 13 May 2021 03:16:52 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4434 Thu 13 May 2021 02:00:59 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4207 Thu 13 May 2021 01:26:22 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4435 Thu 13 May 2021 00:36:20 SAST ]]>