The development of amine-based extractants for separation of base metals in a sulfate medium
- Authors: Magwa, Nomampondo Penelope
- Date: 2015
- Subjects: Extraction (Chemistry) , Sulfates , Ligands , Benzimidazoles , Infrared spectroscopy , Nuclear magnetic resonance spectroscopy , Metal ions , Metals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4559 , http://hdl.handle.net/10962/d1020010
- Description: Tridentate benzimidazole-based ligands, bis((1H-benzimidazol-2-yl)methyl)sulfide (BNSN) and bis((1H-benzimidazol-2-yl)methyl)amine (BNNN), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, were investigated as potential selective extractants for Ni2+ from base metals in a solvent extraction system using 2-octanol/Shellsol 2325 (8:2) as diluent and modifier. However, extraction studies show a lack of pH-metric separation of the later 3d metal ions with bis((1-octylbenzimidazol-2-yl)methyl)sulfide (BONSN) and bis((1- decylbenzimidazol-2-yl)methyl)amine (BDNNN) as extractants, but extractions occurred in the low pH range with an opportunity for back extraction. This investigation suggested that tridentate ligands (at least those of the nature investigated here) are not feasible extractants for separation of base metal ions due to their lack of stereochemical “tailor-making.”
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- Date Issued: 2015
Investigation into the biological removal of sulphate from ethanol distillery wastewater using sulphate-reducing prokaryotes
- Authors: Smuts, Lizl
- Date: 2005
- Subjects: Sewage -- Purification -- Biological treatment , Prokaryotes , Sulfates , Distilleries -- Waste disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3941 , http://hdl.handle.net/10962/d1004000 , Sewage -- Purification -- Biological treatment , Prokaryotes , Sulfates , Distilleries -- Waste disposal
- Description: Ethanol production wastewater is known to be toxic, and is not easily biodegradable. It also consists of a variety of coloured components adding to the complex composition of this wastewater. Disposal of this wastewater into water courses is not recommended and yet is performed all over the world. Investigation of this wastewater found that there was a high concentration of sulphate which, in the presence of sulphate-reducing prokaryotes can cause sulphide corrosion of cement. The concentration of sulphate in the wastewater was approximately 2770 mg/L. It was also found that the wastewater pH was very low and discharge of the wastewater into the wastewater treatment works caused a negative impact on the overall quality of the final wastewater discharged to sea. It was found using FISH techniques that there were no sulphate-reducing prokaryotes present in the wastewaters but that a sulphate-reducing population existed on the sewer wall. An anaerobic contact process was designed to treat this wastewater targeting sulphate reduction to sulphide, to be converted into elemental sulphur and to increase the wastewater pH. The process did not achieve this aim and only approximately 20-30 % reduction in sulphate from the wastewater was achieved with little to no change in the pH. A 95 % reduction in sulphate concentration was needed in order to reach acceptable discharge limits. Sulphate reduction could not be carried out, even under ideal laboratory conditions. It was found that the barrier causing the digester failure was the high concentration of phenols present in the wastewater (3.3 g/L) together with the production of high concentrations of volatile fatty acids (on average 13 g acetic/L). These two components are known to cause digester failure, especially phenols, and phenols are usually only degraded by fungal species. It was concluded that the wastewater itself was not amenable to this method of biological treatment.
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- Date Issued: 2005
The role of cellulases and glucohydrolases in the solubilisation of primary sewage sludge
- Authors: Ngesi, Nosisa
- Date: 2002 , 2013-05-09
- Subjects: Sewage sludge , Sewage sludge digestion , Cellulase , Glucosidase inhibitors , Hydrolases , Sulfates
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4080 , http://hdl.handle.net/10962/d1007454 , Sewage sludge , Sewage sludge digestion , Cellulase , Glucosidase inhibitors , Hydrolases , Sulfates
- Description: Biological sulph ate reduction has been identi fied as a potentially valuable process for removing sulphate and heavy metals from indllstrial effluents. The role of sulphate reducing bacteria (SRB) in this process has attracted the attention of biotechnologists and recently of enzymologists due to its fundamental properties and possible role in AMD bioremediation. These obligatory anaerobic sulphate-reducing bacteria are commonly known to dissimilate sulphate for energy. Under anaerobic conditions SRB oxidize simple organic compounds such as lactic acid with the sulphate and thereby generate hydrogen sulphide (a stTong reducing agent) and bicarbonate ions. The hydrogen sulphide in turn reacts with contaminant metals contained in AMD and precipitates them out of solution as metal sulphides. Bicarbonate ions neutralize AMD by reaction with protons to form carbon dioxide and water. Organic matter in the municipal sewage sludge has been identified as a potential source of electron donors for su lphate reduction. However, this organic matter is in the polymeric form that cannot be util ised by SRB. The latter depend on the activities of other hydrolytic bacteria for the degradation of complex polymers. Hence the availability of these monomeric substrates is a major factor, which may constrain further process development and is considered a rate-limiting step. Thi s study is therefore undertaken to investigate the bacterial glucohydrolase enzymes involved in the digestion of the polysaccharides present in the sewage sludge with specific interest in cellulases and/or p-glucosidase enzymes. The goals of the research are to: isolate, identify, purify and quantify these enzymes; study their distribution with respect to time, pH, and temperature; maximize and quantify the hydrol ys is products; study whether sulphide and sulphate have an enhancing or an inhibitory effect on the activity of enzymes; optimize the enzyme activity against substrate and/or product inhibition and soluble heavy metal salts. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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- Date Issued: 2002
Investigation of the formation of complexes between selected organic compounds and the chlorides and sulphates of chromium
- Authors: Ellis, Melville John
- Date: 1961
- Subjects: Organic compounds , Chromium compounds , Chlorides , Sulfates
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4466 , http://hdl.handle.net/10962/d1011744 , Organic compounds , Chromium compounds , Chlorides , Sulfates
- Description: Some properties of soluble chromium complexions containing coordinated aliphatic acids have been studied. The work falls naturally into two sections. In the first, the coordination of a series of ⊄, β and⊁amino acids by chromium chloride has been studied by physical methods. The tanning action of chromium chloride in the presence of these amino acids has also been studied. The absorption spectra of the complexes were similar to those reported previously for trivalent chromium solutions, having two pronounced maxima in the visible region. From the variations in these absorption maxima, it is suggested that the absorption maximum in the 580 m u region is influenced by coordination of the chromium with the ligand, while the maximum in the 420 m u region is also affected by the olation of the basic chromium salts. The spectrophotometric evidence indicates that raising the pH or the concentration of the ligand in the solution increases the amount of coordination, and further, that the tendency for coordination increases as the hydrocarbon chain separating the carboxyl and amino groups becomes longer. This suggests that tho stability of the complex is not dependent on chelate ring formation, but is influenced by the pK₁ value of the carboxyl group of the . ligand. Potentiometric titrations support the hypothesis that only the carboxyl group is coordinated, to an extent depending on its pK₁ value, since the curves have shown that the amino group is still free to titrate. Paper electrophoresis has shown that all the complexes prepared were cationic, indicating that the amino acids were coordinated as dipolar ions. The tanning action of the masked chromium solutions has confirmed the deductions made from the physical measurements. Increasing the amount of amino acid added to the solution lowered the chromium fixation and the hydrothermal stability of the leather, and further, that for solutions at the same pH containing the same amount of masking agent, tanning action was least for the ⊁ amino acid and greatest for the ⊄ amino acids. Comparison of the present data with the corresponding results obtained with chrome alum solutions showed that coordination of the amino acids was greater in the case of the chromium chloride solutions. The second section of the experimental work was an investigation of the coordination of substituted acetic and propionic acids by chromium chloride and chromium sulphate. Spectrophotometric and potentiometric methods were applied and the various solutions were also used in miniature tanning experiments. Certain difficulties were encountered in the preparation of some of the complexes, and it was not possible to carry the work to a point where conclusive results could be obtained. Nevertheless, the work reported suggests that chelate ring formation occurs in the coordination of hydroxy-carboxylic acids, resulting in exceptionally high stability of the complex. In the case of the other ligands, containing amino, chloro and bromo groups, as well as with acetic and propionic acids, the results suggest that coordination involves the carboxyl group only, and that the pY value of this group is an important factor determining the stability of the complexes.
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- Date Issued: 1961