Modification of polyethersulfone by grafting acrylic-acid based monomers for improved hydrophilicity and pH-responsive properties of membranes
- Authors: Kgatle, Masaku
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Membrane filters , Nanofiltration , Graft copolymers , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124976 , uj:20981
- Description: Abstract: The quality of drinking water is continuously deteriorating due to pollutants that end up in water arising from a variety of industries. These pollutants reduce the value of water thereby posing risks to people’s health and the environment. Thus, there is a need to develop techniques that will be effective in wastewater treatment to obtain potable water. Membrane technology has increasingly become the most reliable, applicable and cost-effective technique for drinking water treatment solution. However, membrane fouling has been identified as the major obstacle to the applicability of this technique. In order to alleviate this issue, many studies have proved that improving the hydrophilicity of a membrane surface is significant. In this study, acrylic acid (AA)-based monomers (acrylic acid (AA), methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA)) were graft-polymerized onto hydrophobic polyethersulfone (PES) using benzoyl peroxide (BPO) as the chemical initiator for the development of membranes with pH-responsive and antifouling properties. The confirmation of successful grafting was done using nuclear magnetic resonance (NMR) and fourier transform infrared (FTIR) spectroscopies. Flat-sheet pristine and grafted PES membranes were prepared by phase inversion via immersion precipitation technique. The morphology of the membranes was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, membrane hydrophilicity and performance were investigated using contact angle measurements and dead-end filtration (pure water flux, bovine serum albumin (BSA) rejection and fouling analysis). The SEM analysis showed an increase in the pore size of the PES-g-PAA, PES-g-PMAA and PES-g-PEGDMA membranes in comparison with the pristine PES membrane. The contact angle measurements indicated significant increases in the hydrophilicities with chemical grafting of the AA-based monomers onto PES. The pH-responsive tests proved that the grafted PES membranes all... , M.Sc. (Chemistry)
- Full Text:
- Authors: Kgatle, Masaku
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Membrane filters , Nanofiltration , Graft copolymers , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124976 , uj:20981
- Description: Abstract: The quality of drinking water is continuously deteriorating due to pollutants that end up in water arising from a variety of industries. These pollutants reduce the value of water thereby posing risks to people’s health and the environment. Thus, there is a need to develop techniques that will be effective in wastewater treatment to obtain potable water. Membrane technology has increasingly become the most reliable, applicable and cost-effective technique for drinking water treatment solution. However, membrane fouling has been identified as the major obstacle to the applicability of this technique. In order to alleviate this issue, many studies have proved that improving the hydrophilicity of a membrane surface is significant. In this study, acrylic acid (AA)-based monomers (acrylic acid (AA), methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA)) were graft-polymerized onto hydrophobic polyethersulfone (PES) using benzoyl peroxide (BPO) as the chemical initiator for the development of membranes with pH-responsive and antifouling properties. The confirmation of successful grafting was done using nuclear magnetic resonance (NMR) and fourier transform infrared (FTIR) spectroscopies. Flat-sheet pristine and grafted PES membranes were prepared by phase inversion via immersion precipitation technique. The morphology of the membranes was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, membrane hydrophilicity and performance were investigated using contact angle measurements and dead-end filtration (pure water flux, bovine serum albumin (BSA) rejection and fouling analysis). The SEM analysis showed an increase in the pore size of the PES-g-PAA, PES-g-PMAA and PES-g-PEGDMA membranes in comparison with the pristine PES membrane. The contact angle measurements indicated significant increases in the hydrophilicities with chemical grafting of the AA-based monomers onto PES. The pH-responsive tests proved that the grafted PES membranes all... , M.Sc. (Chemistry)
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Fouling of nanofiltration membranes : mechanisms and implications for trace organic rejection
- Authors: Mahlangu, Oranso Themba
- Date: 2015
- Subjects: Fouling , Membrane filters , Membrane separation , Water - Purification - Membrane filtration , Water - Purification - Organic compounds removal
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/58774 , uj:16489
- Description: Abstract: Please refer to full text to view abstract , Ph.D. (Chemistry)
- Full Text:
- Authors: Mahlangu, Oranso Themba
- Date: 2015
- Subjects: Fouling , Membrane filters , Membrane separation , Water - Purification - Membrane filtration , Water - Purification - Organic compounds removal
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/58774 , uj:16489
- Description: Abstract: Please refer to full text to view abstract , Ph.D. (Chemistry)
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Nanozeolite-functionalized poly(lactic acid) ultrafiltration membranes for water treatment
- Authors: Matseke, Mphoma Sophy
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Membrane filters , Ultrafiltration , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84691 , uj:19252
- Description: Abstract: Water is a scarce resource. This resource deteriorates everyday due to industrial and agricultural activities and other detrimental human activities. Many techniques are already in place for the treatment of drinking water. Membrane technologies have become popular in water treatment in recent times. However, conventional membrane techniques have several drawbacks such as hydrophobicity, low mechanical strength, low chemical reactivity and high propensity of fouling. Ultrafiltration (UF) membranes, in particular, have gained considerable attention in water treatment applications due to their low costs and easy maintenance compared to their counterparts. These membranes utilize known polymer backbones such as polyethersulfone (PES), polysulfone (PSf), and polyvinylfluoride (PVDF). However, the permeabilities for these membranes reduce drastically during water treatment processes. This is due to fouling that occurs on the membrane surface. Membrane fouling is generally caused by adsorption of solutes on the membrane surface and/or the blocking of the membrane pores. Further, UF membranes made from these polymers have low mechanical strength and therefore easily break up when subjected to high pressure systems. This subsequently results in an increase in operating costs and a decrease in overall performance and life-span of the membrane... , M.Sc.
- Full Text:
- Authors: Matseke, Mphoma Sophy
- Date: 2016
- Subjects: Water - Purification - Membrane filtration , Membrane filters , Ultrafiltration , Polymeric composites
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84691 , uj:19252
- Description: Abstract: Water is a scarce resource. This resource deteriorates everyday due to industrial and agricultural activities and other detrimental human activities. Many techniques are already in place for the treatment of drinking water. Membrane technologies have become popular in water treatment in recent times. However, conventional membrane techniques have several drawbacks such as hydrophobicity, low mechanical strength, low chemical reactivity and high propensity of fouling. Ultrafiltration (UF) membranes, in particular, have gained considerable attention in water treatment applications due to their low costs and easy maintenance compared to their counterparts. These membranes utilize known polymer backbones such as polyethersulfone (PES), polysulfone (PSf), and polyvinylfluoride (PVDF). However, the permeabilities for these membranes reduce drastically during water treatment processes. This is due to fouling that occurs on the membrane surface. Membrane fouling is generally caused by adsorption of solutes on the membrane surface and/or the blocking of the membrane pores. Further, UF membranes made from these polymers have low mechanical strength and therefore easily break up when subjected to high pressure systems. This subsequently results in an increase in operating costs and a decrease in overall performance and life-span of the membrane... , M.Sc.
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Incorporation of zwitterion modified graphene oxide onto thin-film composite layer to enhance flix and solute rejection
- Authors: Xabela, Sinethemba Snezz
- Date: 2019
- Subjects: Nanostructured materials , Membrane separation , Graft copolymers , Nanofiltration , Membrane filters
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401694 , uj:33583
- Description: Abstract : In this work, surface Zwitterion functionalization of graphene oxide (GO) was carried out by grafting poly(sulfobetaine methacrylate) (PSBMA) onto the GO surface by means of reverse atom transfer radical polymerization (RATRP) approach to generate GO-PSBMA nanoplates. GO-PSBMA was characterized by Fourier transforms infrared spectra (FT-IR), thermal gravimetric analysis (TGA), X-Ray Diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM) techniques. The influence of GO-PSBMA was investigated on different membrane polymers by incorporating different amounts of this additive into cellulose acetate (CA) and polyphenylsulfone (PPSU) casting solutions through phase inversion method, initially for the removal of both organic dyes and salts in water. Furthermore, GO-PSBMA was incorporated into the polyamide (PA) selective layer to develop a novel thin-film composite (TFC) membrane for desalination application. The effect of GO-PSBMA on the morphology and surface property of the CA, PPSU and TFC membranes was examined using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and ATR-FTIR. The contact angle (CA), pure water flux (PWF) and antifouling properties of modified membranes were also used to investigate the membranes performance. On cellulose acetate hybrid membranes, it was found that the water flux of the hybrid membrane was greatly enhanced from 100.71 L.m-2.h-1 to 258.39 L.m-2.h-1 when the GO-PSBMA content increased from 0 to 0.5 wt.%. The antifouling tests revealed that the GO-PSBMA embedded membranes had an excellent antifouling performance: a high flux recovery ratio (FRR) (93%) and a low total flux decline ratio (0.01%). Additionally, the hybrid membranes exhibited a distinct advance in the mechanical strength due to the addition of highly rigid GO. Notably, compared with unmodified CA membranes, the hybrid membranes had a higher retention of CR dye (99.01%), MO dye (84%) and MB dye (95%), and a lower rejection of salts at an operational pressure of 900 kPa, rendering the membranes... , M.Sc. (Chemistry)
- Full Text:
- Authors: Xabela, Sinethemba Snezz
- Date: 2019
- Subjects: Nanostructured materials , Membrane separation , Graft copolymers , Nanofiltration , Membrane filters
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401694 , uj:33583
- Description: Abstract : In this work, surface Zwitterion functionalization of graphene oxide (GO) was carried out by grafting poly(sulfobetaine methacrylate) (PSBMA) onto the GO surface by means of reverse atom transfer radical polymerization (RATRP) approach to generate GO-PSBMA nanoplates. GO-PSBMA was characterized by Fourier transforms infrared spectra (FT-IR), thermal gravimetric analysis (TGA), X-Ray Diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM) techniques. The influence of GO-PSBMA was investigated on different membrane polymers by incorporating different amounts of this additive into cellulose acetate (CA) and polyphenylsulfone (PPSU) casting solutions through phase inversion method, initially for the removal of both organic dyes and salts in water. Furthermore, GO-PSBMA was incorporated into the polyamide (PA) selective layer to develop a novel thin-film composite (TFC) membrane for desalination application. The effect of GO-PSBMA on the morphology and surface property of the CA, PPSU and TFC membranes was examined using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and ATR-FTIR. The contact angle (CA), pure water flux (PWF) and antifouling properties of modified membranes were also used to investigate the membranes performance. On cellulose acetate hybrid membranes, it was found that the water flux of the hybrid membrane was greatly enhanced from 100.71 L.m-2.h-1 to 258.39 L.m-2.h-1 when the GO-PSBMA content increased from 0 to 0.5 wt.%. The antifouling tests revealed that the GO-PSBMA embedded membranes had an excellent antifouling performance: a high flux recovery ratio (FRR) (93%) and a low total flux decline ratio (0.01%). Additionally, the hybrid membranes exhibited a distinct advance in the mechanical strength due to the addition of highly rigid GO. Notably, compared with unmodified CA membranes, the hybrid membranes had a higher retention of CR dye (99.01%), MO dye (84%) and MB dye (95%), and a lower rejection of salts at an operational pressure of 900 kPa, rendering the membranes... , M.Sc. (Chemistry)
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Fabrication of positively charged membranes with high antifouling characteristics via graphene oxide incorporated pes/pei/agno3 for the removal of heavy metals and dyes from wastewater
- Authors: Nonso, Chukwuati C
- Date: 2019
- Subjects: Membrane filters , Water - Purification - Membrane filtration , Sewage - Purification
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/400955 , uj:33487
- Description: Abstract : A series of ultrafiltration (UF) membranes based on the hydrophobic polyvinylidene fluoride (PVDF) and hydrophilic polyethersulfone (PES) containing new nanofillers based on graphene oxide (GO) were fabricated and their performance assessed against both organic dye and metal ion rejection. The incorporated nanofillers were GO nanosheets coated with hyperbranched polyethyleneimine (HPEI, HPEI@GO) in the first instance and its composite with silver nanoparticles (AgNPs, AgNPs/HPEI@GO). Different weight concentrations (wt%) of these modifiers were incorporated into PES or PVDF polymers matrix followed by fabrication of composite membranes through phase inversion method. The prepared materials, i.e. GO nanosheets, the various GO composite and the fabricated membranes were characterised using various physicochemical techniques such as Fourier Transform Infrared (FTIR), Transmission Electron Microscope (TEM), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) Thermal Gravimetric Analysis (TGA), Braunuer Emmet Teller (BET), X-ray diffraction (XRD), Raman, Atomic Force Microscopy (AFM), water uptake, contact angle (CA) as well as membranes performance through pure water flux, flux recovery and rejection capacities. Raman spectroscopy was primarily used to confirm the nature of GO while FTIR was utilised to confirm the presence of the HPEI polymer deposited on GO nanosheets. For instance, the coating of the HPEI on the surface of GO nanosheets via grafting of HPEI on the surface of GO nanosheets was confirmed by the presence of the CN groups and cationic NH groups on the vibration pattern of HPEI@GO composite. On the other hand, the SEM-EDs analyses revealed the elemental composition of the synthesised GO nanosheets and GO composite to be Carbon, Oxygen, Nitrogen, and Silver affirming the FTIR results. The pure water flux of the unmodified PES membranes was improved from 35±0.52 L/m2h to the range of 77±0.92 to120±1.44 L/m2h (which is 114% to 243%) for the series of GO@PES membranes compared to the baseline membranes. Thus, in the series of HPEI/GO@PES containing membranes, the flux improved to the range of 55±0.82 to vi 89±1.33 L/m2h (which is 57% to 171% increase) and the series of AgNPs/HPEI/GO@PES membranes were improved to the range of 40±0.60 to 50±0.75 L/m2h (which is 14% to 66% increase). This observed improve could be attributed to the incorporated charge and oxygen functionalities. The Flux recovery ratio (FRR) of the synthesised membranes were also improved from 45% for the unmodified PES membranes to the range of 80% to 93% for the series of GO@PES membranes, 74% to 78% for the series of HPEI/GO@PES and 74% to 75% for the series of AgNPs/HPEI/GO@PES membranes due to less attachment of the bovine serum albumin (BSA) solution on the membranes surface and pores. The fouling propensity of PES membranes was further evaluated using organic pollutants such as MO, MB, AR, CR, and BPA after a prolong filtration and washing. The FRR of the unmodified PES membranes was 42%. This was improved to the range of 80% to 92% for the series of GO@PES membranes, 76% to 78% for the series of HPEI/GO@PES membranes and 71% to 73% for the series of AgNPs/HPEI/GO@PES membranes due to less attachment of dye molecules on the membranes surface and pores, indicating that the modified PES membranes had improved antifouling properties. The cleaned membranes were further subjected to SEM-EDS surface morphology and elemental composition analysis to ascertain the degree of foulants attachment on the membrane’s surfaces i.e. a post-mortem of the membranes was undertaken. This confirmed that the unmodified PES membranes were more fouled. The observed improvement in the antifouling properties of the modified membranes could be attributed to the presence of hydrophilic functionalities from the incorporated nanofillers. The series of the positively charged HPEI/GO@PES membranes at pH 6.8 and 8.0 showed a progressive increase in rejection capacity with increase in weight concentration of the GO composite in the PES matrix. At pH 6.8, the rejection capacity was enhanced from 90% to 95% for Pb2+, 77% to 85% of Cr6+ and 69% to 81% of Cd2+ which were higher compared to the rejection capacity of the unmodified PES membranes. Similar trend in rejection pattern was observed at pH 8.0 for the same series of membranes. For the series of GO@PES, and AgNPs/HPEI/GO@PES membranes, the ability of these membranes to reject these metal ions at pH 6.0, 6.8, vii and 8.0 declines as the weight concentration of the GO nanosheets and GO composite increased in the PES matrix. This could be due to increased membranes micropores and macro-voids (SEM images). The positively charged PES membranes displayed high removal capacity of above 90% for small positively charged methylene blue dye and less rejection capacity of 73% and less for a bigger negatively charged amaranth dye. The difference in the rejection capacity of the synthesised membranes could be attributed to the chemical nature of the membranes surface in contact with the pollutants, molecular weight cut off of the membranes films as well as the surface charge of the pollutants to be rejected. As a result to which the positively charged membranes had high removal efficiency for the methylene blue dye. A similarly improve in rejection pattern of pollutants were also observed for the graphene-based nanomaterials modified PVDF membranes. The observed significant improvement in the modified membranes can be attributed to the presence of oxygenated and charged functionalities on the surfaces of the synthesised graphenebased nanofillers compared to unmodified membranes... , M.Sc. (Chemistry)
- Full Text:
- Authors: Nonso, Chukwuati C
- Date: 2019
- Subjects: Membrane filters , Water - Purification - Membrane filtration , Sewage - Purification
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/400955 , uj:33487
- Description: Abstract : A series of ultrafiltration (UF) membranes based on the hydrophobic polyvinylidene fluoride (PVDF) and hydrophilic polyethersulfone (PES) containing new nanofillers based on graphene oxide (GO) were fabricated and their performance assessed against both organic dye and metal ion rejection. The incorporated nanofillers were GO nanosheets coated with hyperbranched polyethyleneimine (HPEI, HPEI@GO) in the first instance and its composite with silver nanoparticles (AgNPs, AgNPs/HPEI@GO). Different weight concentrations (wt%) of these modifiers were incorporated into PES or PVDF polymers matrix followed by fabrication of composite membranes through phase inversion method. The prepared materials, i.e. GO nanosheets, the various GO composite and the fabricated membranes were characterised using various physicochemical techniques such as Fourier Transform Infrared (FTIR), Transmission Electron Microscope (TEM), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) Thermal Gravimetric Analysis (TGA), Braunuer Emmet Teller (BET), X-ray diffraction (XRD), Raman, Atomic Force Microscopy (AFM), water uptake, contact angle (CA) as well as membranes performance through pure water flux, flux recovery and rejection capacities. Raman spectroscopy was primarily used to confirm the nature of GO while FTIR was utilised to confirm the presence of the HPEI polymer deposited on GO nanosheets. For instance, the coating of the HPEI on the surface of GO nanosheets via grafting of HPEI on the surface of GO nanosheets was confirmed by the presence of the CN groups and cationic NH groups on the vibration pattern of HPEI@GO composite. On the other hand, the SEM-EDs analyses revealed the elemental composition of the synthesised GO nanosheets and GO composite to be Carbon, Oxygen, Nitrogen, and Silver affirming the FTIR results. The pure water flux of the unmodified PES membranes was improved from 35±0.52 L/m2h to the range of 77±0.92 to120±1.44 L/m2h (which is 114% to 243%) for the series of GO@PES membranes compared to the baseline membranes. Thus, in the series of HPEI/GO@PES containing membranes, the flux improved to the range of 55±0.82 to vi 89±1.33 L/m2h (which is 57% to 171% increase) and the series of AgNPs/HPEI/GO@PES membranes were improved to the range of 40±0.60 to 50±0.75 L/m2h (which is 14% to 66% increase). This observed improve could be attributed to the incorporated charge and oxygen functionalities. The Flux recovery ratio (FRR) of the synthesised membranes were also improved from 45% for the unmodified PES membranes to the range of 80% to 93% for the series of GO@PES membranes, 74% to 78% for the series of HPEI/GO@PES and 74% to 75% for the series of AgNPs/HPEI/GO@PES membranes due to less attachment of the bovine serum albumin (BSA) solution on the membranes surface and pores. The fouling propensity of PES membranes was further evaluated using organic pollutants such as MO, MB, AR, CR, and BPA after a prolong filtration and washing. The FRR of the unmodified PES membranes was 42%. This was improved to the range of 80% to 92% for the series of GO@PES membranes, 76% to 78% for the series of HPEI/GO@PES membranes and 71% to 73% for the series of AgNPs/HPEI/GO@PES membranes due to less attachment of dye molecules on the membranes surface and pores, indicating that the modified PES membranes had improved antifouling properties. The cleaned membranes were further subjected to SEM-EDS surface morphology and elemental composition analysis to ascertain the degree of foulants attachment on the membrane’s surfaces i.e. a post-mortem of the membranes was undertaken. This confirmed that the unmodified PES membranes were more fouled. The observed improvement in the antifouling properties of the modified membranes could be attributed to the presence of hydrophilic functionalities from the incorporated nanofillers. The series of the positively charged HPEI/GO@PES membranes at pH 6.8 and 8.0 showed a progressive increase in rejection capacity with increase in weight concentration of the GO composite in the PES matrix. At pH 6.8, the rejection capacity was enhanced from 90% to 95% for Pb2+, 77% to 85% of Cr6+ and 69% to 81% of Cd2+ which were higher compared to the rejection capacity of the unmodified PES membranes. Similar trend in rejection pattern was observed at pH 8.0 for the same series of membranes. For the series of GO@PES, and AgNPs/HPEI/GO@PES membranes, the ability of these membranes to reject these metal ions at pH 6.0, 6.8, vii and 8.0 declines as the weight concentration of the GO nanosheets and GO composite increased in the PES matrix. This could be due to increased membranes micropores and macro-voids (SEM images). The positively charged PES membranes displayed high removal capacity of above 90% for small positively charged methylene blue dye and less rejection capacity of 73% and less for a bigger negatively charged amaranth dye. The difference in the rejection capacity of the synthesised membranes could be attributed to the chemical nature of the membranes surface in contact with the pollutants, molecular weight cut off of the membranes films as well as the surface charge of the pollutants to be rejected. As a result to which the positively charged membranes had high removal efficiency for the methylene blue dye. A similarly improve in rejection pattern of pollutants were also observed for the graphene-based nanomaterials modified PVDF membranes. The observed significant improvement in the modified membranes can be attributed to the presence of oxygenated and charged functionalities on the surfaces of the synthesised graphenebased nanofillers compared to unmodified membranes... , M.Sc. (Chemistry)
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