Micellar-enhanced ultrafiltration of palladium and platinum anions
- Authors: Gwicana, Sakumzi
- Date: 2007
- Subjects: Micelles , Ultrafiltration , Palladium catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10414 , http://hdl.handle.net/10948/518 , Micelles , Ultrafiltration , Palladium catalysts
- Description: The project was concerned with studying the capability of a micellar-enhanced ultrafiltration system (MEUF) to remove platinum group metal ions namely Pt (lV) and Pd (ll) chloro anions from aqueous industrial waste effluents. South Africa has the world’s largest reserves of platinum group metals (PGMs) and other valuable metals such as manganese, chrome ores, titanium minerals etc. which are required for new automotive and other technologies, including fuel cells, catalytic converters and lighter components. The consistent loss with the industrial waste stream and the toxicological effects of these precious metals led to the need to develop new and effective methods to recover them from industrial waste effluents. With such a wide variety of fields where these PGMs are used and the failure of the traditional techniques namely sedimentation, fermentation etc. to effectively reduce or recover these highly toxic and precious metal ions prior to discharging industrial waste effluents, it is necessary to explore other techniques such as membrane technology that can be used to recover these valuable species from industrial waste streams. The present study involved the use of a cationic surfactant, viz cetylpyridinium chloride, which was introduced into an aqueous solution containing palladium and platinum metal anions. The surfactant forms charged micelles above a certain critical concentration value. The metal anions adsorb onto the available oppositely charged sites on the micelle surfaces and are then able to be retained by a suitable membrane. Hollow fibre ultrafiltration membranes with the MWCO of +/- 10 kD and +/-30nm pore size were used as a filter component in this study. For this MEUF system to be effective, it was vital that the anionic metal ion species adsorbed sufficiently onto the available oppositely charged sites of the micelles and that the micelles were retained efficiently by the membrane. Results obtained during the investigation made it possible to make certain predictions about the micellisation process. It was also found that, it was not only the metal ion: surfactant (M:S) ratio that was critical, but the presence of other electrolytes in the aqueous stream proved to have a huge impact on the capability of the MEUF system. Findings of this research study showed that the MEUF system using cetylpyridinium chloride (CPC) can be used to recover or retain Pt (lV) and Pd (ll) anions from industrial waste effluents. It was also found that PtCl6 2-, due to its greater adsorption capabilities onto the micelle surface than PdCl4 2- or PdCl3(H2O)-, was preferentially retained in neutral medium. This may be exploited as a possible means of separating the two metal ions. The developed system offers the following advantages over some traditional and current methods: simplified unit operation line flow process, smaller amounts of chemical usage and no solid toxic sludge to be disposed of. Applications of this work could be of vital importance in catalytic converter recycling, especially in Port Elizabeth where extensive automobile parts manufacturing occurs.
- Full Text:
- Date Issued: 2007
- Authors: Gwicana, Sakumzi
- Date: 2007
- Subjects: Micelles , Ultrafiltration , Palladium catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10414 , http://hdl.handle.net/10948/518 , Micelles , Ultrafiltration , Palladium catalysts
- Description: The project was concerned with studying the capability of a micellar-enhanced ultrafiltration system (MEUF) to remove platinum group metal ions namely Pt (lV) and Pd (ll) chloro anions from aqueous industrial waste effluents. South Africa has the world’s largest reserves of platinum group metals (PGMs) and other valuable metals such as manganese, chrome ores, titanium minerals etc. which are required for new automotive and other technologies, including fuel cells, catalytic converters and lighter components. The consistent loss with the industrial waste stream and the toxicological effects of these precious metals led to the need to develop new and effective methods to recover them from industrial waste effluents. With such a wide variety of fields where these PGMs are used and the failure of the traditional techniques namely sedimentation, fermentation etc. to effectively reduce or recover these highly toxic and precious metal ions prior to discharging industrial waste effluents, it is necessary to explore other techniques such as membrane technology that can be used to recover these valuable species from industrial waste streams. The present study involved the use of a cationic surfactant, viz cetylpyridinium chloride, which was introduced into an aqueous solution containing palladium and platinum metal anions. The surfactant forms charged micelles above a certain critical concentration value. The metal anions adsorb onto the available oppositely charged sites on the micelle surfaces and are then able to be retained by a suitable membrane. Hollow fibre ultrafiltration membranes with the MWCO of +/- 10 kD and +/-30nm pore size were used as a filter component in this study. For this MEUF system to be effective, it was vital that the anionic metal ion species adsorbed sufficiently onto the available oppositely charged sites of the micelles and that the micelles were retained efficiently by the membrane. Results obtained during the investigation made it possible to make certain predictions about the micellisation process. It was also found that, it was not only the metal ion: surfactant (M:S) ratio that was critical, but the presence of other electrolytes in the aqueous stream proved to have a huge impact on the capability of the MEUF system. Findings of this research study showed that the MEUF system using cetylpyridinium chloride (CPC) can be used to recover or retain Pt (lV) and Pd (ll) anions from industrial waste effluents. It was also found that PtCl6 2-, due to its greater adsorption capabilities onto the micelle surface than PdCl4 2- or PdCl3(H2O)-, was preferentially retained in neutral medium. This may be exploited as a possible means of separating the two metal ions. The developed system offers the following advantages over some traditional and current methods: simplified unit operation line flow process, smaller amounts of chemical usage and no solid toxic sludge to be disposed of. Applications of this work could be of vital importance in catalytic converter recycling, especially in Port Elizabeth where extensive automobile parts manufacturing occurs.
- Full Text:
- Date Issued: 2007
Cleaning of fouled membranes using enzymes from a sulphidogenic bioreactor
- Authors: Melamane, Xolisa L
- Date: 2004
- Subjects: Membrane filters , Membrane filters -- Fouling , Enzymes -- Biotechnology , Enzymes -- Purification , Water -- Purification -- Membrane filtration , Ultrafiltration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4133 , http://hdl.handle.net/10962/d1015764
- Description: Maintenance of membrane performance requires inevitable cleaning or defouling of fouled membranes. Membrane cleaning using enzymes such as proteases, lipases, α-glucosidases from a sulphidogenic bioreactor was investigated. At first, dilute and concentrated enzyme extract were prepared form the sulphidogenic pellet. Enzyme assays on 0.5 % azocaisen, 1 % triacetin and 1 mg/ml ρ-nitrophenyl-α-D-glucopyranoside were performed using the concentrated enzyme extract (0 – 200 mg/ml). For membrane fouling, an abattoir effluent was obtained from Ostritech Pty (Ltd), Grahamstown, South Africa. The effluent was characterised for presence of potential foulants such as lipids, proteins, amino acids and carbohydrates. Static fouling of polysulphone membranes (0.22 μm, 47 mm) was then performed using the abattoir effluent. Cleaning of the fouled membranes was also performed using at first the dilute and then the concentrated form (200 mg/ml) of enzyme extracts. Qualitative and quantitative biochemical analysis for proteins, lipids and carbohydrates was performed to ascertain the presence of foulants on polysulphone membranes and their removal by dilute or concentrated enzyme extracts. The ability of dilute enzyme extracts to remove proteins lipids, and carbohydrates fouling capillary UF membrane module; their ability to restore permeate fluxes and transmembrane pressure after cleaning/defouling was also investigated. Permeate volumes from this UF membrane module were analysed for protein, amino acids, lipids, and carbohydrates concentrations after fouling and defouling. Fouling was further characterized by standard blocking, cake filtration and pore blocking models using stirred UF cell and polyethersulphone membranes with MWCO of 30 000, 100 000 and 300 000. After characterization of fouling, polyethersulphone membranes with MWCO of 30 000 and 300 000 were defouled using the concentrated enzyme extract (100 mg ml). Enzyme activities at 200 mg/ml of enzyme concentration were 8.071 IU, 86.71 IU and 789.02 IU for proteases, lipases and α-glucosidases. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Proteins, lipids and carbohydrates fouling polysulphone membranes after a day were removed by 23.4 %, when a dilute enzyme was used. A concentrated enzyme extract of 200 mg/ml was able to remove proteins, lipids and carbohydrates up to 5 days of fouling by 100 %, 82 %, 71 %, 68 % and 76 % respectively. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 hour. Sulphidogenic proteases activity was 2.1 U/ml and flux Recovery (FR %) was 64. Characterization of fouling revealed that proteins and lipids were major foulants while low concentration of carbohydrates fouled polyethersulphone membranes. Fouling followed standard blocking for 10 minutes in all the membranes; afterwards fouling adopted cake filtration model for membranes with 30 000 MWCO and pore blocking model for membranes with 300 000 MWCO. A concentration of 100 mg/ml of enzyme extract was able to remove fouling from membranes with MWCO of 30 000. Defouling membranes that followed pore blocking model i.e. 300 000 MWCO was not successful due to a mass transfer problem. From the results of defouling of 30 000 and 300 000 MWCO it was concluded that defouling of cake layer fouling (30 000 MWCO) was successful while defouling of pore blocking fouling was unsuccessful due to a mass transfer problem. The ratio of enzymes present in the enzyme extract when calculated based on enzymatic activity for proteases, lipases and α-glucosidases was 1.1 %, 11 % and 87.9 %. It was hypothesized that apart from proteases, lipases, α and β-glucosidases; phosphatases, sulphatases, amonipeptidases etc. from a sulphidogenic bioreactor clean or defoul cake layer fouling by organic foulants and pore blocking fouling provided the mass transfer problem is solved. However, concentration of enzymes from a sulphidogenic bioreactor has not been optimized yet. Other methods of concentrating the enzyme extract can be investigated for example use of organic solvents.
- Full Text:
- Date Issued: 2004
- Authors: Melamane, Xolisa L
- Date: 2004
- Subjects: Membrane filters , Membrane filters -- Fouling , Enzymes -- Biotechnology , Enzymes -- Purification , Water -- Purification -- Membrane filtration , Ultrafiltration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4133 , http://hdl.handle.net/10962/d1015764
- Description: Maintenance of membrane performance requires inevitable cleaning or defouling of fouled membranes. Membrane cleaning using enzymes such as proteases, lipases, α-glucosidases from a sulphidogenic bioreactor was investigated. At first, dilute and concentrated enzyme extract were prepared form the sulphidogenic pellet. Enzyme assays on 0.5 % azocaisen, 1 % triacetin and 1 mg/ml ρ-nitrophenyl-α-D-glucopyranoside were performed using the concentrated enzyme extract (0 – 200 mg/ml). For membrane fouling, an abattoir effluent was obtained from Ostritech Pty (Ltd), Grahamstown, South Africa. The effluent was characterised for presence of potential foulants such as lipids, proteins, amino acids and carbohydrates. Static fouling of polysulphone membranes (0.22 μm, 47 mm) was then performed using the abattoir effluent. Cleaning of the fouled membranes was also performed using at first the dilute and then the concentrated form (200 mg/ml) of enzyme extracts. Qualitative and quantitative biochemical analysis for proteins, lipids and carbohydrates was performed to ascertain the presence of foulants on polysulphone membranes and their removal by dilute or concentrated enzyme extracts. The ability of dilute enzyme extracts to remove proteins lipids, and carbohydrates fouling capillary UF membrane module; their ability to restore permeate fluxes and transmembrane pressure after cleaning/defouling was also investigated. Permeate volumes from this UF membrane module were analysed for protein, amino acids, lipids, and carbohydrates concentrations after fouling and defouling. Fouling was further characterized by standard blocking, cake filtration and pore blocking models using stirred UF cell and polyethersulphone membranes with MWCO of 30 000, 100 000 and 300 000. After characterization of fouling, polyethersulphone membranes with MWCO of 30 000 and 300 000 were defouled using the concentrated enzyme extract (100 mg ml). Enzyme activities at 200 mg/ml of enzyme concentration were 8.071 IU, 86.71 IU and 789.02 IU for proteases, lipases and α-glucosidases. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Proteins, lipids and carbohydrates fouling polysulphone membranes after a day were removed by 23.4 %, when a dilute enzyme was used. A concentrated enzyme extract of 200 mg/ml was able to remove proteins, lipids and carbohydrates up to 5 days of fouling by 100 %, 82 %, 71 %, 68 % and 76 % respectively. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 hour. Sulphidogenic proteases activity was 2.1 U/ml and flux Recovery (FR %) was 64. Characterization of fouling revealed that proteins and lipids were major foulants while low concentration of carbohydrates fouled polyethersulphone membranes. Fouling followed standard blocking for 10 minutes in all the membranes; afterwards fouling adopted cake filtration model for membranes with 30 000 MWCO and pore blocking model for membranes with 300 000 MWCO. A concentration of 100 mg/ml of enzyme extract was able to remove fouling from membranes with MWCO of 30 000. Defouling membranes that followed pore blocking model i.e. 300 000 MWCO was not successful due to a mass transfer problem. From the results of defouling of 30 000 and 300 000 MWCO it was concluded that defouling of cake layer fouling (30 000 MWCO) was successful while defouling of pore blocking fouling was unsuccessful due to a mass transfer problem. The ratio of enzymes present in the enzyme extract when calculated based on enzymatic activity for proteases, lipases and α-glucosidases was 1.1 %, 11 % and 87.9 %. It was hypothesized that apart from proteases, lipases, α and β-glucosidases; phosphatases, sulphatases, amonipeptidases etc. from a sulphidogenic bioreactor clean or defoul cake layer fouling by organic foulants and pore blocking fouling provided the mass transfer problem is solved. However, concentration of enzymes from a sulphidogenic bioreactor has not been optimized yet. Other methods of concentrating the enzyme extract can be investigated for example use of organic solvents.
- Full Text:
- Date Issued: 2004
Evaluation of a 'defouling on demand' strategy for the ultrafiltration of brown water using activatable enzymes
- Authors: Buchanan, K
- Date: 1999
- Subjects: Water -- Purification , Ultrafiltration , Enzymes , Membranes (Technology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3904 , http://hdl.handle.net/10962/d1003963 , Water -- Purification , Ultrafiltration , Enzymes , Membranes (Technology)
- Description: New approaches to the application of membranes for the production of potable water are constantly being sought after in anticipation of future demands for increasingly rigorous water quality standards and reduced environmental impact. A major limitation, however, is membrane fouling, which manifests itself as a continual reduction in flux over time and thus restricts the practical implementation to restore flux. Mechanical and chemical methods have been implemented to restore flux to ultrafiltration systems, but these either result in a break in the process operation or lead to membrane damage or additional pollution problems. This project was aimed to develop a 'defouling on demand' stategy for cleaning membranes used during brown water ultrafiltration. The process involves the use of activatable peroxidase enzymes, which were immobilised onto flat sheet polysulphone membranes. Following flux decline which reaches a critical level with the build-up of the foulant layer, the immobilised enzyme layer was activated by the addition of a chemical activator solution, in this case hydrogen peroxidase and manganous sulphate. Manganese peroxidase was found to be the most effective enzyme at alleviating fouling by degrading the foulant layer formed on the membrane surface and hence restored flux to the ultrafiltration system. A 93% flux improvement was observed when manganese peroxidase was activated when 800uM manganous sulphate, 100mM hydrogen peroxide were added in the presence of a manganese chelator, lactate. The concept and the potential benefits this system holds will be discussed in further detail.
- Full Text:
- Date Issued: 1999
- Authors: Buchanan, K
- Date: 1999
- Subjects: Water -- Purification , Ultrafiltration , Enzymes , Membranes (Technology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3904 , http://hdl.handle.net/10962/d1003963 , Water -- Purification , Ultrafiltration , Enzymes , Membranes (Technology)
- Description: New approaches to the application of membranes for the production of potable water are constantly being sought after in anticipation of future demands for increasingly rigorous water quality standards and reduced environmental impact. A major limitation, however, is membrane fouling, which manifests itself as a continual reduction in flux over time and thus restricts the practical implementation to restore flux. Mechanical and chemical methods have been implemented to restore flux to ultrafiltration systems, but these either result in a break in the process operation or lead to membrane damage or additional pollution problems. This project was aimed to develop a 'defouling on demand' stategy for cleaning membranes used during brown water ultrafiltration. The process involves the use of activatable peroxidase enzymes, which were immobilised onto flat sheet polysulphone membranes. Following flux decline which reaches a critical level with the build-up of the foulant layer, the immobilised enzyme layer was activated by the addition of a chemical activator solution, in this case hydrogen peroxidase and manganous sulphate. Manganese peroxidase was found to be the most effective enzyme at alleviating fouling by degrading the foulant layer formed on the membrane surface and hence restored flux to the ultrafiltration system. A 93% flux improvement was observed when manganese peroxidase was activated when 800uM manganous sulphate, 100mM hydrogen peroxide were added in the presence of a manganese chelator, lactate. The concept and the potential benefits this system holds will be discussed in further detail.
- Full Text:
- Date Issued: 1999
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