Development & evaluation of modified lignocellulose-clinoptilolite composites for water treatment
- Authors: Vala, Mavula Kikwe Remy
- Date: 2012-12
- Subjects: Lignocellulose , Lignocellulose -- Biotechnology
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24521 , vital:63051
- Description: Municipalities, mining, textile and many other industries release wastewater into water bodies. Thus, the entire ecosystem (biota and abiota) including drinking water is affected by polluted effluents. The growing environmental concern over water pollution (due to inorganic and persistent organic compounds) attracts a significant amount of research in the removal of pollutants from water. In this study, lignocellulose and clinoptilolite were modified for the preparation of composites, with high adsorption properties, suitable for the removal of pollutants. Grass (Kikuyu grass) material was first treated with boiling water in order to remove soluble compounds and then with sulfuric acid in order to free functional groups within lignocellulose. The lignocellulose obtained was then chemically modified with three different siloxanes (3-aminopropyl-terminated poly (di)methylsiloxanes) of different molecular weights. For clinoptilolite, impurities were removed by reflux in hydrochloric acid before chemical modification with siloxanes. Grafting of siloxanes onto lignocellulose and clinoptilolite as well as the preparation of composites were successfully achieved by means of dibutyltin dilaurate (catalyst) after reflux under nitrogen. The modified materials were characterized by FT-IR, XRD, SEM and TGA and results confirmed successful modification of the materials. Solid state 29Si and 13C NMR were used to investigate the nature of the composite prepared with siloxane NH40D (CNH40D). The investigation revealed a possible bond between the modified lignocellulose and the modified clinoptilolite in the composite. The sorptive and/or ion exchange properties of the materials prepared for the removal of pollutants from water were then investigated. Phenol red, used motor (engine) oil and cyanide were used (with regard to textile, oil spill and gold mining effluents respectively) to simulate water pollution in the laboratory. It was found that adsorption properties of lignocellulose were significantly increased after sulfuric acid treatment, suggesting the availability of lignocellulose functional groups as adsorption sites. When further modified with siloxanes, lignocellulose showed less efficiency in adsorbing phenol red. The general mechanism of phenol red uptake onto lignocellulose and clinoptilolite modified with siloxane or composites was: rapid initial adsorption, slow uptake, small rate increase and then equilibrium. The mechanism of phenol red uptake could be well represented by the pseudo second-order kinetic model with equilibrium being reached after a period of time, ranging between 1-5 hours. The linear Langmuir model was the best model for describing adsorption of phenol red onto lignocellulose modified with siloxanes and composites while the Freundlich model appeared to be best for clinoptilolite modified with siloxanes. The general mechanism of used motor oil uptake onto lignocellulose and clinoptilolite modified with siloxane or composites was: rapid uptake, equilibrium and the process occurs over a short period (10 min). The pseudo second-order kinetic model appeared to be the best representation of this adsorption. The linear Langmuir isotherms are the best fitted model for used motor oil uptake onto the adsorbents prepared. Adsorption of cyanide occurred very quickly (10 to 30 min). For lignocellulose and clinoptilolite modified with siloxanes, desorption occurred soon after adsorption and thus no kinetic model nor isotherms of adsorption were deduced. However, adsorption of cyanide onto composites could be represented by the pseudo second-order kinetic model. Nanofibres were fabricated by electrospinning of the modified lignocellulose and composites by blending them with PAN in a solvent mixture of DMF-DMSO. Nanofiltration was achieved by packing the nanofibres prepared into a pipette and filtering polluted water. Nanofiltration was assessed by measurement of the turbidity of water which dropped from 63 NTU for polluted water to 3.06 NTU for filtered water. , Thesis (PhD) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Authors: Vala, Mavula Kikwe Remy
- Date: 2012-12
- Subjects: Lignocellulose , Lignocellulose -- Biotechnology
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24521 , vital:63051
- Description: Municipalities, mining, textile and many other industries release wastewater into water bodies. Thus, the entire ecosystem (biota and abiota) including drinking water is affected by polluted effluents. The growing environmental concern over water pollution (due to inorganic and persistent organic compounds) attracts a significant amount of research in the removal of pollutants from water. In this study, lignocellulose and clinoptilolite were modified for the preparation of composites, with high adsorption properties, suitable for the removal of pollutants. Grass (Kikuyu grass) material was first treated with boiling water in order to remove soluble compounds and then with sulfuric acid in order to free functional groups within lignocellulose. The lignocellulose obtained was then chemically modified with three different siloxanes (3-aminopropyl-terminated poly (di)methylsiloxanes) of different molecular weights. For clinoptilolite, impurities were removed by reflux in hydrochloric acid before chemical modification with siloxanes. Grafting of siloxanes onto lignocellulose and clinoptilolite as well as the preparation of composites were successfully achieved by means of dibutyltin dilaurate (catalyst) after reflux under nitrogen. The modified materials were characterized by FT-IR, XRD, SEM and TGA and results confirmed successful modification of the materials. Solid state 29Si and 13C NMR were used to investigate the nature of the composite prepared with siloxane NH40D (CNH40D). The investigation revealed a possible bond between the modified lignocellulose and the modified clinoptilolite in the composite. The sorptive and/or ion exchange properties of the materials prepared for the removal of pollutants from water were then investigated. Phenol red, used motor (engine) oil and cyanide were used (with regard to textile, oil spill and gold mining effluents respectively) to simulate water pollution in the laboratory. It was found that adsorption properties of lignocellulose were significantly increased after sulfuric acid treatment, suggesting the availability of lignocellulose functional groups as adsorption sites. When further modified with siloxanes, lignocellulose showed less efficiency in adsorbing phenol red. The general mechanism of phenol red uptake onto lignocellulose and clinoptilolite modified with siloxane or composites was: rapid initial adsorption, slow uptake, small rate increase and then equilibrium. The mechanism of phenol red uptake could be well represented by the pseudo second-order kinetic model with equilibrium being reached after a period of time, ranging between 1-5 hours. The linear Langmuir model was the best model for describing adsorption of phenol red onto lignocellulose modified with siloxanes and composites while the Freundlich model appeared to be best for clinoptilolite modified with siloxanes. The general mechanism of used motor oil uptake onto lignocellulose and clinoptilolite modified with siloxane or composites was: rapid uptake, equilibrium and the process occurs over a short period (10 min). The pseudo second-order kinetic model appeared to be the best representation of this adsorption. The linear Langmuir isotherms are the best fitted model for used motor oil uptake onto the adsorbents prepared. Adsorption of cyanide occurred very quickly (10 to 30 min). For lignocellulose and clinoptilolite modified with siloxanes, desorption occurred soon after adsorption and thus no kinetic model nor isotherms of adsorption were deduced. However, adsorption of cyanide onto composites could be represented by the pseudo second-order kinetic model. Nanofibres were fabricated by electrospinning of the modified lignocellulose and composites by blending them with PAN in a solvent mixture of DMF-DMSO. Nanofiltration was achieved by packing the nanofibres prepared into a pipette and filtering polluted water. Nanofiltration was assessed by measurement of the turbidity of water which dropped from 63 NTU for polluted water to 3.06 NTU for filtered water. , Thesis (PhD) -- Faculty of Science and Agriculture, 2012
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Synthesis of bioethanol from lignocellulosic materials: A focus on grass and waste paper as raw materials
- Authors: Vala, Mavula Kikwe
- Date: 2009-12
- Subjects: Ethanol as fuel , Biomass energy , Lignocellulose -- Biotechnology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24499 , vital:63049
- Description: Biofuels are currently recognized as not only a necessity, but an inevitable pathway to secure the planet future energy needs. Food crops have been used (so far) as the biomass for bioethanol and biodiesel production. This has increased concerns over food security and led to the search for diversification and alternative feedstocks for biofuel production. The use of lignocellulosic materials, the most abundant, low cost and easy feedstock to harvest for bioethanol purpose, involves challenging production processes. Several approaches have been used to facilitate the breakdown of the biopolymer structure to produce fermentable sugars that can be converted to ethanol. Most of the approaches have used high temperatures and pressures and have often led to the production of inhibitors of fermentation. In this study, lignocellulosic materials from grass and newsprint were investigated as sources of biomass for bioethanol production using a chemical route (sulfuric acid hydrolysis) which made use of temperatures below 100°C at normal atmospheric pressure. Fermentation of toxic lignocellulosic hydrolyzates was possible after the development of a method for inhibitors removal. The method used treated wood chips as a stationary phase in a chromatographic column to remove inhibitors. This method is expected to be extended to applications such as in municipal wastewater treatment. Sugar yields of 22.26 and 8.9 g/L of hydrolyzate; and an ethanol yield of 184.5 and 130.4 mg/mL of must were achieved for 5g grass and newsprint respectively using optimum conditions of 2percent H2SO4 at 97.5°C for grass and 0.5percent H2SO4 at 97.5°C for newsprint during the hydrolysis process. Pure cellulose was used as a control for the biomass where 254.1 g/L of fermentable sugars were recovered from soluble cellulose and the yield of ethanol was 201.8 mg/mL. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
- Full Text:
- Authors: Vala, Mavula Kikwe
- Date: 2009-12
- Subjects: Ethanol as fuel , Biomass energy , Lignocellulose -- Biotechnology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24499 , vital:63049
- Description: Biofuels are currently recognized as not only a necessity, but an inevitable pathway to secure the planet future energy needs. Food crops have been used (so far) as the biomass for bioethanol and biodiesel production. This has increased concerns over food security and led to the search for diversification and alternative feedstocks for biofuel production. The use of lignocellulosic materials, the most abundant, low cost and easy feedstock to harvest for bioethanol purpose, involves challenging production processes. Several approaches have been used to facilitate the breakdown of the biopolymer structure to produce fermentable sugars that can be converted to ethanol. Most of the approaches have used high temperatures and pressures and have often led to the production of inhibitors of fermentation. In this study, lignocellulosic materials from grass and newsprint were investigated as sources of biomass for bioethanol production using a chemical route (sulfuric acid hydrolysis) which made use of temperatures below 100°C at normal atmospheric pressure. Fermentation of toxic lignocellulosic hydrolyzates was possible after the development of a method for inhibitors removal. The method used treated wood chips as a stationary phase in a chromatographic column to remove inhibitors. This method is expected to be extended to applications such as in municipal wastewater treatment. Sugar yields of 22.26 and 8.9 g/L of hydrolyzate; and an ethanol yield of 184.5 and 130.4 mg/mL of must were achieved for 5g grass and newsprint respectively using optimum conditions of 2percent H2SO4 at 97.5°C for grass and 0.5percent H2SO4 at 97.5°C for newsprint during the hydrolysis process. Pure cellulose was used as a control for the biomass where 254.1 g/L of fermentable sugars were recovered from soluble cellulose and the yield of ethanol was 201.8 mg/mL. , Thesis (MSc) -- Faculty of Science and Agriculture, 2009
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