Conducting nanocomposites for the removal of heavy metals from wastewater
- Authors: Kera, Nazia Hassan
- Date: 2018
- Subjects: Heavy metals - Absorption and adsorption , Sewage - Purification - Heavy metals removal , Water - Purification , Nanocomposites (Materials) , Water chemistry
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366683 , http://hdl.handle.net/10210/278783 , uj:29923
- Description: Ph.D. (Chemistry) , Abstract: Hexavalent chromium, Cr(VI), is a toxic heavy metal pollutant that occurs in wastewater produced from mining and industrial activities such as leather tanning, chrome plating, wood preservation and alloy manufacture. Cr(VI) released into the environment is of concern due to its high mobility in water and soil and harmful effects on human health. The treatment of wastewater is necessary to prevent Cr(VI) contamination of water bodies in the environment. Conducting polymers, such as polypyrrole (PPy) and polyaniline (PANI), have the potential to be used as adsorbents for Cr(VI) in wastewater due to their abundant nitrogen-containing functional groups, anion-exchange sites and capacity to reduce Cr(VI) to the significantly less toxic, trivalent chromium, Cr(III). However, conducting polymers have shown low adsorption capacities for Cr(VI) due to agglomeration of particles and are also difficult to separate from treated water. The focus of this study was on the development of conducting polymer composites for the treatment of wastewater containing Cr(VI). In particular, the aim of the research carried out was the modification of conducting polymers to obtain adsorbents with high adsorption capacities for Cr(VI) that are well-suited towards water treatment applications. Three novel conducting polymer composites were prepared in this study, namely, polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, polypyrrole-polyaniline/iron oxide (PPy-PANI/Fe3O4) magnetic nanocomposite and polypyrrole-m-phenylenediamine (PPy-mPD) polymer for the desired application of removing Cr(VI) from industrial wastewater. The composites were synthesized easily and effectively by in situ chemical oxidative polymerization and their physicochemical properties characterized using various techniques including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. Batch studies were carried out to investigate the effect of parameters such as initial solution pH, adsorbent dose, initial Cr(VI) concentration, temperature and co-existing ions in solution on Cr(VI) removal by the different composites...
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- Authors: Kera, Nazia Hassan
- Date: 2018
- Subjects: Heavy metals - Absorption and adsorption , Sewage - Purification - Heavy metals removal , Water - Purification , Nanocomposites (Materials) , Water chemistry
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366683 , http://hdl.handle.net/10210/278783 , uj:29923
- Description: Ph.D. (Chemistry) , Abstract: Hexavalent chromium, Cr(VI), is a toxic heavy metal pollutant that occurs in wastewater produced from mining and industrial activities such as leather tanning, chrome plating, wood preservation and alloy manufacture. Cr(VI) released into the environment is of concern due to its high mobility in water and soil and harmful effects on human health. The treatment of wastewater is necessary to prevent Cr(VI) contamination of water bodies in the environment. Conducting polymers, such as polypyrrole (PPy) and polyaniline (PANI), have the potential to be used as adsorbents for Cr(VI) in wastewater due to their abundant nitrogen-containing functional groups, anion-exchange sites and capacity to reduce Cr(VI) to the significantly less toxic, trivalent chromium, Cr(III). However, conducting polymers have shown low adsorption capacities for Cr(VI) due to agglomeration of particles and are also difficult to separate from treated water. The focus of this study was on the development of conducting polymer composites for the treatment of wastewater containing Cr(VI). In particular, the aim of the research carried out was the modification of conducting polymers to obtain adsorbents with high adsorption capacities for Cr(VI) that are well-suited towards water treatment applications. Three novel conducting polymer composites were prepared in this study, namely, polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, polypyrrole-polyaniline/iron oxide (PPy-PANI/Fe3O4) magnetic nanocomposite and polypyrrole-m-phenylenediamine (PPy-mPD) polymer for the desired application of removing Cr(VI) from industrial wastewater. The composites were synthesized easily and effectively by in situ chemical oxidative polymerization and their physicochemical properties characterized using various techniques including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. Batch studies were carried out to investigate the effect of parameters such as initial solution pH, adsorbent dose, initial Cr(VI) concentration, temperature and co-existing ions in solution on Cr(VI) removal by the different composites...
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Removal of heavy metals from aqueous acidic mineral effluents by reductive precipitation
- Authors: Sithole, Nastassia Thandiwe
- Date: 2015
- Subjects: Sewage - Purification - Heavy metals removal , Heavy metals - Absorption and adsorption , Hydrazine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/56204 , uj:16342
- Description: Abstract: The removal of heavy metals from acidic mineral effluents (pH<3) is among the most important issues for many industrialized countries. Removal of Fe3+, Al3+ and Mn2+ from acidic mineral effluents was studied using reductive precipitation as an alternative method. A comparative study of using different reducing agents (hydrazine, dimethylamine borane (DMAB) and glyoxylic acid) and different seeding materials (Nickel powder, Fe powder, Granulated Blast Furnace Slag (GBFS) and Basic Oxygen Furnace Slag (BOFS) respectively) was done. Reductive precipitation batch experiments were conducted where metal ions solution, seeding material and a reducing agent were added to a batch reactor. The volume of acidic mineral effluents was 500 ml and 30g of the seeding materials and stoichiometric amounts of the different reducing agents. The obtained BOFS before and after reductive precipitation was characterized for particle size distribution using MPAM, surface morphology and surface functional groups were done using SEM and FTIR respectively. Identification of phases was done using XRD while elemental composition was performed using XRF. using SEM and surface functional groups using FTIR, identification of phases using XRD, elemental composition using XRF. BOFS was the only seeding material characterized since it was found to be more effective and efficient than other seeding materials... , M.Tech. (Chemical Engineering)
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- Authors: Sithole, Nastassia Thandiwe
- Date: 2015
- Subjects: Sewage - Purification - Heavy metals removal , Heavy metals - Absorption and adsorption , Hydrazine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/56204 , uj:16342
- Description: Abstract: The removal of heavy metals from acidic mineral effluents (pH<3) is among the most important issues for many industrialized countries. Removal of Fe3+, Al3+ and Mn2+ from acidic mineral effluents was studied using reductive precipitation as an alternative method. A comparative study of using different reducing agents (hydrazine, dimethylamine borane (DMAB) and glyoxylic acid) and different seeding materials (Nickel powder, Fe powder, Granulated Blast Furnace Slag (GBFS) and Basic Oxygen Furnace Slag (BOFS) respectively) was done. Reductive precipitation batch experiments were conducted where metal ions solution, seeding material and a reducing agent were added to a batch reactor. The volume of acidic mineral effluents was 500 ml and 30g of the seeding materials and stoichiometric amounts of the different reducing agents. The obtained BOFS before and after reductive precipitation was characterized for particle size distribution using MPAM, surface morphology and surface functional groups were done using SEM and FTIR respectively. Identification of phases was done using XRD while elemental composition was performed using XRF. using SEM and surface functional groups using FTIR, identification of phases using XRD, elemental composition using XRF. BOFS was the only seeding material characterized since it was found to be more effective and efficient than other seeding materials... , M.Tech. (Chemical Engineering)
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Recovery of base metals from nitric and sulphiric solutions using carbon nanotubes
- Authors: Mgwetyana, Unathi
- Date: 2014-01-27
- Subjects: Nanotubes , Extraction (Chemistry) , Heavy metals - Absorption and adsorption , Water - Purification - Adsorption
- Type: Thesis
- Identifier: uj:7961 , http://hdl.handle.net/10210/8861
- Description: M.Tech. (Extraction Metallurgy) , For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...
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- Authors: Mgwetyana, Unathi
- Date: 2014-01-27
- Subjects: Nanotubes , Extraction (Chemistry) , Heavy metals - Absorption and adsorption , Water - Purification - Adsorption
- Type: Thesis
- Identifier: uj:7961 , http://hdl.handle.net/10210/8861
- Description: M.Tech. (Extraction Metallurgy) , For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...
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Polymer-zeolite nanocomposites : preparation, characterization and application in heavy-metal removal
- Authors: Mthombo, Sydney Thabo
- Date: 2013-09-11
- Subjects: Nanocomposites (Materials) , Polymers , Zeolites , Heavy metals - Absorption and adsorption , Water - Purification
- Type: Thesis
- Identifier: uj:7734 , http://hdl.handle.net/10210/8603
- Description: M.Sc. (Chemistry) , Polymer nanocomposites are a new class of composites in which at least one dimension of the particles dispersed in the polymer matrix is in the nanometer range. Recently, different types of zeolite minerals, either natural (Clinoptilolite, chabazite, modernite) or synthetic (A-type, X-type, Y-type) are being employed as particulate fillers into the polymer matrix. Owing to their unique ion exchange phenomenon, zeolites have been widely studied as heavy metal adsorbents, but very few researchers have focused on the sorption of heavy metal ions on zeolite-filled polymer nanocomposites...
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- Authors: Mthombo, Sydney Thabo
- Date: 2013-09-11
- Subjects: Nanocomposites (Materials) , Polymers , Zeolites , Heavy metals - Absorption and adsorption , Water - Purification
- Type: Thesis
- Identifier: uj:7734 , http://hdl.handle.net/10210/8603
- Description: M.Sc. (Chemistry) , Polymer nanocomposites are a new class of composites in which at least one dimension of the particles dispersed in the polymer matrix is in the nanometer range. Recently, different types of zeolite minerals, either natural (Clinoptilolite, chabazite, modernite) or synthetic (A-type, X-type, Y-type) are being employed as particulate fillers into the polymer matrix. Owing to their unique ion exchange phenomenon, zeolites have been widely studied as heavy metal adsorbents, but very few researchers have focused on the sorption of heavy metal ions on zeolite-filled polymer nanocomposites...
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Biodegradable polymer composites : synthesis, properties and application in water purification
- Authors: Vilakati, Gcina Doctor
- Date: 2012-05-02
- Subjects: Polymer biodegradation , Water purification , Biodegradation , Composite materials , Polymer deterioration , Heavy metals - Absorption and adsorption
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/371689 , uj:2232 , http://hdl.handle.net/10210/4672
- Description: M.Sc. , The addition of lignocellulosic fibres to thermoplastic polymers is known to increase the toughness of the polymers but it compromises the tensile strength. On the other hand, inorganic fillers like TiO2 are known to improve the tensile strength of polymers. These plant fibres have been used as adsorbents of metal pollutants in water. Best results were obtained when such materials were ground to fine powder but due to low density, the fibres float and form aggregates in water. Being highly biodegradable in nature makes plant fibres unsuitable for water treatment over lengthy periods of time. They cannot be used as standalone materials. Mixing these adsorbents with polymers, which cannot only act as support for the adsorbents but also disperse the fibres within it thus preventing leaching, is a cause for concern. This study was aimed at fabricating plant fibre-polymer composites that will have improved mechanical and thermal properties. These composites were to be tested for their ability to be used as metal ion adsorbents. The composites were fabricated using a melt-mix compounding method. Two thermoplastic polymers, EVA and PCL were each mixed with either lignin or SCB and TiO2 in different ratios. A rheomex mixer coupled with a single screw extruder which was attached to a sheet die was used to synthesise the composites. TGA and DSC were used for thermal propagation while the mechanical properties were investigated using an instron. Metal ion adsorption measurements were analysed using an atomic absorption spectrometer (AAS). These adsorbents were used to remove Cr(VI), Cr(III) and Pb(II), varying different environmental parameters like pH, concentration, time and adsorbent at constant temperature. The reinforcing effect of both lignin and SCB resulted to poor thermal and mechanical properties. This was shown by a decrease in onset degradation temperature and the tensile and toughness of the composites compared to the neat polymers. The incorporation of TiO2 on SCB-EVA composites, however, improved the mechanical strength and resulted in a thermally stable composite compared to counterpart composites without TiO2. This observation was surpassed at high filler loading as the addition of TiO2 resulted in a decrease of the properties. For the tensile strength, neat EVA recorded 11.35 MPa while 2% TiO2-EVA registered 12.49 MPa for example. For the same composite, the onset degradation temperature for EVA was 353 oC but shifted to 368 oC after the addition of TiO2. At higher filler loading, no effect was observed when adding TiO2.
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- Authors: Vilakati, Gcina Doctor
- Date: 2012-05-02
- Subjects: Polymer biodegradation , Water purification , Biodegradation , Composite materials , Polymer deterioration , Heavy metals - Absorption and adsorption
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/371689 , uj:2232 , http://hdl.handle.net/10210/4672
- Description: M.Sc. , The addition of lignocellulosic fibres to thermoplastic polymers is known to increase the toughness of the polymers but it compromises the tensile strength. On the other hand, inorganic fillers like TiO2 are known to improve the tensile strength of polymers. These plant fibres have been used as adsorbents of metal pollutants in water. Best results were obtained when such materials were ground to fine powder but due to low density, the fibres float and form aggregates in water. Being highly biodegradable in nature makes plant fibres unsuitable for water treatment over lengthy periods of time. They cannot be used as standalone materials. Mixing these adsorbents with polymers, which cannot only act as support for the adsorbents but also disperse the fibres within it thus preventing leaching, is a cause for concern. This study was aimed at fabricating plant fibre-polymer composites that will have improved mechanical and thermal properties. These composites were to be tested for their ability to be used as metal ion adsorbents. The composites were fabricated using a melt-mix compounding method. Two thermoplastic polymers, EVA and PCL were each mixed with either lignin or SCB and TiO2 in different ratios. A rheomex mixer coupled with a single screw extruder which was attached to a sheet die was used to synthesise the composites. TGA and DSC were used for thermal propagation while the mechanical properties were investigated using an instron. Metal ion adsorption measurements were analysed using an atomic absorption spectrometer (AAS). These adsorbents were used to remove Cr(VI), Cr(III) and Pb(II), varying different environmental parameters like pH, concentration, time and adsorbent at constant temperature. The reinforcing effect of both lignin and SCB resulted to poor thermal and mechanical properties. This was shown by a decrease in onset degradation temperature and the tensile and toughness of the composites compared to the neat polymers. The incorporation of TiO2 on SCB-EVA composites, however, improved the mechanical strength and resulted in a thermally stable composite compared to counterpart composites without TiO2. This observation was surpassed at high filler loading as the addition of TiO2 resulted in a decrease of the properties. For the tensile strength, neat EVA recorded 11.35 MPa while 2% TiO2-EVA registered 12.49 MPa for example. For the same composite, the onset degradation temperature for EVA was 353 oC but shifted to 368 oC after the addition of TiO2. At higher filler loading, no effect was observed when adding TiO2.
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