Fabrication of Poly(Vinylidene Fluoride) (PVDF) Membranes

In water filtration processes, the employment of polymeric membranes has become increasingly popular over the past few decades. However, the application of membrane processes is often limited due to the low fluxes and membrane failures caused by fouling and low membrane durability, which eventually leads to high operating costs in comparison with conventional processes. These limitations could be overcome by the development of high performance membranes with enhanced properties through a cost effective method. This thesis explores the preparation of high performance poly(vinylidene fluoride) (PVDF) membranes with the use of inorganic silica particles via a conventional immersion precipitation method and from an amphiphilic graft copolymer. A technique to improve the performance of PVDF membranes fabricated via immersion precipitation has been developed, which involves using inorganic silica (SiO2) particles during the preparation of the dope solution, followed by subsequent acid or alkaline treatments of the resultant membranes. By removing the SiO2 particles from the membrane substrates using either an acid or alkaline treatment, the resultant membranes exhibit an interconnected porous structure accompanied by a significant improvement in the water permeability. Due to the poor mechanical strength demonstrated by the NaOH treated membranes, detailed investigations of the stability of PVDF membranes in NaOH solutions are carried out on hollow fibre membranes prepared from different raw materials. Hollow fibre membranes exhibit different degrees of chemical degradation upon exposure to a sodium hydroxide solution under various conditions. Also, a simplified method has been developed as a cost effective way for the preparation of PVDF membranes with improved hydrophilicity, fouling resistance and water permeability from the amphiphilic graft copolymer, PVDF-g-PEGMA, which has a PVDF backbone and poly(ethylene glycol) methyl ether methacrylate (PEGMA) side chains. By eliminating three common steps involved during the conventional preparation method, the use of chemicals and energy can be substantially reduced

Immobilization of bovine serum albumin on the chitosan/PVA film

Chitosan/polyvinyl alcohol (Chitosan/PVA) blended film was prepared by direct blend process and solution casting methods. In order to reduce the swelling ratio and enhance the chemical and mechanical stability, Chitosan/PVA film was cross-linked with glutaraldehyde in order to produce Chitosan-g-PVA. Bovine serum albumin (BSA) was used as a model protein to incorporate into the Chitosan-g-PVA. The chemical structure and morphological characteristics of films were studied by FT-IR and scanning electron microscopy (SEM). Mechanical and physical properties of blended films such as tensile properties in the dry and wet states, water uptake and water contact angle measurement were characterized. Blending PVA and chitosan improved strength and flexibility of the films. Crosslinking with glutaraldehyde further improves the tensile strength and decrease the hydrophilicity of films. BSA immobilized on the Chitosan-g-PVA film was calculated as BSA encapsulation efficiency

Diamine modified polymeric membranes for hydrogen/carbon dioxide separation

The separation of H2/CO2 is technologically crucial to produce clean and renewable H2-based energy. There are several established methods used to separate H2 from CO2, but membrane based separation is becoming more prominent due to high energy efficiency and cost effectiveness. However, separation efficiency of existing polymeric membranes is limited due to unfavourable diffusivity and selectivity between H2 and CO2. As such, research objective for this work is to investigate the effectiveness of diamine modification towards two different polymeric membrane materials, PSf and P-84, on their performance in H2/CO2 separation. The effects of different operating pressures and modification time on the permeance and selectivity are also studied. Comparison of pure and modified membranes will be further interpreted. The fabrication of membranes is done by using controlled evaporation method. Then, the prepared membranes will undergo diamine modification using BuDA for 10 and 30 minutes reaction times. All samples were analyzed by gas permeation test for separation performance and SEM and FTIR for membranes characterization. From SEM analysis, the images show that both polymers have defectfree surfaces and porous cross-section structures. FTIR spectra validate the cross-linking reaction by observing the existence of adsorption peak at 1529 cm-1. This specific characteristic peak implies the occurrence of C-N stretch within the membranes. The gas permeation test shows the respective modification towards P-84 and PSf for 10 and 30 minutes reaction times causes H2 permeability to increase drastically. Based on the experimental result, P-84 membrane with 10 minutes BuDA-modification reaction time and 5 bar operating pressure gives the best H2 permeability performance. By increasing the time to 30 minutes, the H2/CO2 selectivity of both polymers were increased to 4.97 and 6.09, respectively compared to its neat membranes

Fabrication of poly(vinylidene fluoride) (PVDF) membranes

In water filtration processes, the employment of polymeric membranes has become increasingly popular over the past few decades. However, the application of membrane processes is often limited due to the low fluxes and membrane failures caused by fouling and low membrane durability, which eventually leads to high operating costs in comparison with conventional processes. These limitations could be overcome by the development of high performance membranes with enhanced properties through a cost effective method. This thesis explores the preparation of high performance poly(vinylidene fluoride) (PVDF) membranes with the use of inorganic silica particles via a conventional immersion precipitation method and from an amphiphilic graft copolymer. A technique to improve the performance of PVDF membranes fabricated via immersion precipitation has been developed, which involves using inorganic silica (SiO2) particles during the preparation of the dope solution, followed by subsequent acid or alkaline treatments of the resultant membranes. By removing the SiO2 particles from the membrane substrates using either an acid or alkaline treatment, the resultant membranes exhibit an interconnected porous structure accompanied by a significant improvement in the water permeability. Due to the poor mechanical strength demonstrated by the NaOH treated membranes, detailed investigations of the stability of PVDF membranes in NaOH solutions are carried out on hollow fibre membranes prepared from different raw materials. Hollow fibre membranes exhibit different degrees of chemical degradation upon exposure to a sodium hydroxide solution under various conditions. Also, a simplified method has been developed as a cost effective way for the preparation of PVDF membranes with improved hydrophilicity, fouling resistance and water permeability from the amphiphilic graft copolymer, PVDF-g-PEGMA, which has a PVDF backbone and poly(ethylene glycol) methyl ether methacrylate (PEGMA) side chains. By eliminating three common steps involved during the conventional preparation method, the use of chemicals and energy can be substantially reduced.EThOS - Electronic Theses Online ServiceThe University of Malaya and the Ministry of Higher Education MalaysiaGBUnited Kingdo

Prediction of CO2/O2 absorption selectivity using supported ionic liquid membranes (SILMs) for gas–liquid membrane contactor

Given their unique and tunable properties as solvents, ionic liquids (ILs) have become a favorable solvent option in separation processes, particularly for capturing carbon dioxide (CO2). In this work, a simple method that can be used to screen the suitable IL candidates was implemented in our modified gas–liquid membrane contactor system. Solubilities, selectivities of CO2, nitrogen (N2), and oxygen (O2) gases in imidazolium-based ILs and its activity coefficients in water and monoethanolamine (MEA) were predicted using conductor-like screening model for real solvent (COSMO-RS) method over a wide range of temperature (298.15–348.15 K). Results from the analysis revealed that [emim] [NTf2] IL is a good candidate for further absorption process attributed to its good hydrophobicity and CO2/O2 selectivity characteristics. While their miscibility with pure MEA was somehow higher, utilizing the aqueous phase of MEA would be beneficial in this stage. Data on absorption performances and selectivity of CO2/O2 are scarce especially in gas–liquid membrane contactor system. Therefore, considering [emim] [NTf2] IL as a supporting material in supported ionic liquid membranes (SILMs), using aqueous phase of MEA as an absorbent would result in a great membrane-solvent combination system in furthering our gas–liquid membrane contactor process. In conclusion, COSMO-RS is a potentially great predictive utility to screen ILs for specified separation applications. In addition, this work provides useful results for the [emim] [NTf2]-SILMs to be extensively applied in the field of CO2 capture and selective O2 removal

A Review on Methanol as a Clean Energy Carrier: Roles of Zeolite in Improving Production Efficiency

Clean methanol can play an important role in achieving net zero emission targets by decarbonizing the energy and chemical sectors. Conventionally, methanol is produced by using fossil fuel as raw material, which releases a significant amount of greenhouse gases (GHGs) into the environment. Clean methanol, which is produced by hydrogen (H2) from renewable sources (green H2) and captured carbon dioxide (CO2), is totally free from the influence of fossil fuel. Due to its vast applications, clean methanol has potential to substitute for fossil fuels while preventing further GHGs emissions. This review addresses the feasibility of producing clean methanol from renewable resources, i.e., green H2 and captured CO2. Availability of these raw materials is the main factor involved in establishing the circular economy of methanol, therefore, their potential sources and the possible pathways to access these sources are also summarized. Renewable energy sources such as solar, wind and biomass should be utilized for producing green H2, while CO2 captured from air, and more likely from point emission sources, can be recycled to produce clean methanol. After producing methanol from CO2 and H2, the removal of by-product water by distillation is a big challenge due its high energy consumption. An alternative approach for this methanol-water separation is membrane technology, which is an energy saving option. Water-selective zeolite membranes can separate water post-synthesis, as well as during the synthesis. Production efficiency of methanol can be enhanced by utilizing zeolite membranes inside the methanol synthesis reactor. Furthermore, CO2 conversion as well as methanol selectivity, purity and yield can also be increased significantly by selectively removing by-product water using a zeolite membrane reactor

Preparation and Characterization of Poly(lactic Acid)-based Composite Reinforced with Oil Palm Empty Fruit Bunch Fiber and Nanosilica

The properties of poly(lactic acid) (PLA) bio-composite films reinforced with oil palm empty fruit bunch (OPEFB) fiber and nanosilica were studied in this work. The composite films were prepared via the solvent casting method. The composites were characterized via Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, field-emission scanning electron microscopy (FESEM), tensile testing, and X-ray diffraction (XRD). Ultraviolet visible spectroscopy results revealed that the PLA-based composites and neat PLA had similar light transmittances of approximately 89%. The FTIR and FESEM results showed that OPEFB fibers and nanosilica were embedded into the PLA matrix. The tensile strength of the composites with addition of nanosilica increased with an increasing fiber load content. The XRD analysis showed that the addition of organic or inorganic silica reduced the crystallinity of the composites. The water vapor permeability test results indicated that the inorganic silica decreased the diffusion rate of water molecules through the polymer film. The OPEFB-reinforced PLA blend with additional organic silica exhibited a higher thermal stability than the composites reinforced with inorganic silica

Mechanism of bacterial adhesion on ultrafiltration membrane modified by natural antimicrobial polymers (chitosan) and combination with activated carbon (PAC)

Bacterial adhesion to surfaces is related to several factors, such as surface charge, surface energy, and substrate characteristics (leading to the formation of biofilms). Organisms are dominant in most environmental, industrial, and medical problems and processes that are of interest to microbiologists. Biofilm cells are at least 500 times more resistant to antibacterial agents compared to planktonic cells. The usage of ultrafiltration membranes is fast becoming popular for water treatment. Membrane lifetime and permeate flux are primarily affected by the phenomena of microbial accumulation and fouling at the membrane's surface. This review intends to understand the mechanism of membrane fouling by bacterial attachment on polymeric ultrafiltration membrane modified by natural antimicrobial polymers (chitosan) combined with powder activated carbon. Also, to guide future research on membrane water treatment processes, adhesion prediction using the extended Derjaguin-Landau-Verwey-Overbeek theory is discussed

Fabrication and characterization of mullite ceramic hollow fiber membrane from natural occurring ball clay

This work aims to study the physico-chemical and permeation properties of ceramic hollow fiber microfiltration (MF)membranes. Ball clay from Perak, Malaysia was used as an alternative starting material for membrane preparation. The membranes were prepared at various solid loadings (37.5 to 50 wt%)and sintering temperatures (1150 to 1300 °C)via phase inversion-based extrusion/sintering method. Prior to membrane fabrication, the as-received ball clay underwent pre-treatment and was characterized using thermal gravimetric analysis (TGA), laser diffraction particle size analyzer (Metasizer 3000), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD)and Fourier-transform infrared spectroscopy (FTIR). Sintered hollow fiber membranes were characterized in terms of crystalline phase using thin-film XRD, surface morphology via scanning electron microscope (SEM), mechanical property using 3-point (3p)method, wall thickness, porosity, pore size distribution and permeation property. XRD patterns show that the ball clay contains 85.9% kaolinite, 9.5% illite, 3.6% quartz and 1% maghemite. After sintering, the major phase of the hollow fiber membranes transformed into mullite (91 to 94%)with minor traces of quartz. The membranes' properties strongly depend on both solid loading and sintering temperature. Moreover, when the hollow fiber membrane with solid loading of 47.5 wt% was sintered at 1250 °C, its mechanical strength (55.8 ± 5.8 MPa)was comparable to that of purity-based ceramic hollow fiber membranes. The membrane has an average porosity and pore size of about 50.5 ± 2.1% and 0.61 Μm, respectively, which are within microfiltration range, and has an average pure water flux of 1286 ± 181 L/m2.hr. Compared with its high purity metal oxide ceramic counterparts, this alternative ball clay-based hollow fiber membrane can be sintered at lower sintering temperature while exhibiting comparable mechanical strength and water flux

PVDF-co-HFP/superhydrophobic acetylene-based nanocarbon hybrid membrane for seawater desalination via DCMD

Surface hydrophobicity is the most desirable characteristic for high DCMD performance. Superhydrophobic carbon nanomaterials/powder activated carbon (CNMs/PAC) has unique properties and believed to be the proper candidate to increase the membrane hydrophobicity with maintaining good mechanical properties and high porosity at the same time. In this work, we introduce a phase inversion process based on central composite design, aimed at minimizing the number of experiments required for membrane fabrication. The hydrophobic membrane fabrication conditions are modeled as independent parameters, with the flux provided as the model response. The analyses performed on the membrane structure and surface, as well as its mechanical properties revealed that the superhydrophobic CNMs/PAC significantly enhances the hydrophobicity of the composite membrane surface. The accuracy measurements obtained by analysis of variance showed that the model developed and all the proposed parameters have significant effects on the flux. However, the CNMs/PAC emerged as the most significant influential factor and interacted with polymer concentration and casting knife thickness to exert effects on the permeate flux. The optimum preparation parameters were 775.21 mg carbon loading, PVDF-HFP concentration of 21.86 g and casting knife thickness of 118.93 μm, as these values yield the highest flux of about 102 kg/m2h