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Oxygen enriched air (OEA) is widely applied in various areas such as chemical and medical applications. Currently, cryogenic distillation and pressure swing adsorption are the two common technologies that being commercially used for i the production of OEA. However, these two techniques are not economically favorable due to required intensive energy and large built-up area. With the advancement of membrane technology in separation process, it garners the interest from both industrial and academic to explore the feasibility of membrane in gas separation. In this study, polysulfone (PSF) hollow fiber membranes with poly(ether block amide) (PEBAX) coating were used for the separation of O2/N2 gas. The hollow fiber membranes used in this work were fabricated by phase inversion spinning process using PSF pellet, along with N,N-dimetyhlacetamide (DMAc) and ethanol (EtOH) as solvent and co-solvent, whereas tetrahydrofuran (THF) as additive. The fabricated membrane exhibited dense structure in the inner layer whereas finger like layer at the outer surface. The formation of this structure was attributed by rapid phase inversion of the solution arose from strong solvent used. The EDX surface mapping analysis confirmed the formation of PEBAX coating on the membrane surface. Gas permeation study in this work illustrated that the pristine PSF membrane exhibited better gas separation performance relative to the PEBAX coated membrane with 20% higher in terms of permeance. The results obtained from this work suggested that the PEBAX coating enhanced the membrane surface but not certain to improve the gas separation performance. Further study on the PEBAX materials for the membrane coating is essential to polish its potential in gas separation.

In oily wastewater treatment using membrane technology, surface fouling is the major issue that could deteriorate membrane flux and shorten its lifespan. Therefore, nanocomposite membranes were developed in this study by incorporating titanium dioxide (TiO2) and hydrous manganese oxide (HMO) nanoparticles into polymeric membrane matrix. Three different types of membranes were fabricated. They were pristine PES and membrane incorporated with TiO2 or HMO. With respect to pure water flux, TiO2- and HMO-incorporated membranes showed value of 57 and 40 L/m2.h, respectively. These values were 33-90% higher than that of control PES membrane. In treating 500 ppm oily solution, TiO2 membrane exhibited the highest water flux. However, the membrane’s oil removal rate was slightly compromised. When tested with higher concentration of oily solution (5,000 or 10,000 ppm), TiO2- and HMO-incorporated membranes still showed promising water flux with 94.5-99.6% oil removal rate. This proved that ultrafiltration membrane incorporated with suitable nanomaterials could improve the water flux of pristine PES membrane and is of more practical for industrial applications.

In this work, the efficiency of crude palm oil (CPO) deacidification using solvent extraction integrated with membrane technology is studied. Different solvents including ethanol, hexane and methanol were selected to extract the palmitic acid from model fatty system in the model fatty system to solvent ratio of 1:2. Experimental results showed that ethanol was the best solvent to extract palmitic acid from the model fatty system, recording about 65.5% fatty acid reduction in the model fatty system. Three commercial solvent resistant nanofiltration (SRNF) membranes (SolSep NF010206, NF030306, and NF030705) were then selected to examine their respective performance in recovering ethanol from palmitic acid-rich ethanol solvent. The results revealed that the combination of solvent extraction and membrane technology is remarkable simple and waste-free approach to overcome major drawbacks of conventional refinery operation.

The membrane technology is still considered a costly method to produce potable water. In view of this, RO membrane with enhanced water permeability without trade-off in salt rejection is desirable as it could further reduce the cost for water desalination. In this study, thin film nanocomposite (TFN) membranes containing 0.05 or 0.10 w/v% hydrophilic nanofillers in polyamide layer were synthesized via interfacial polymerization of piperazine and trimesoyl chloride monomers. The resultant TFN membranes were characterized and compared with a control thin film composite (TFC) membrane. Results from the filtration experiments showed that TFN membranes exhibited higher water permeability, salt rejection and fouling resistance compared to that of the TFC membrane. Excessive amount of nanofillers incorporated in the membrane PA layer however negatively affected the cross-linking in the polymer matrix, thus deteriorating the membrane salt rejection. TFN membrane containing 0.05 w/v% of nanofillers showed better performances than the TFC membrane, recording a pure water flux of 11.2 L/m2∙h, and salt rejection of 95.4%, 97.3% and 97.5% against NaCl, Na2SO4 and MgSO4, respectively.

The introduction of inorganic nanoparticles in polymeric dope solution for the fabrication process of membrane can potentially enhance the separation performances of membrane without negatively affecting its permeability. In this study, hollow fiber mixed matrix membranes were prepared by incorporating polyethersulfone (PES) membranes with silicon dioxide (SiO2) nanoparticles at different concentration. Prior to separation tests, the prepared membranes were characterized by SEM, EDX, DSC, water contact angle, and FTIR-ATR in order to study the impact of silica nanoparticles on the properties of the membranes. Bisphenol A (BPA) was selected as the subject compound of this study because it is one of the emerging pollutants that have been frequently detected in the water treatment plant (WTP). BPA was spike into the pre-treated water sample taken from the WTP and was used as the feed solution to evaluate the membrane performance in terms of water flux and removal rate. The addition of SiO2 was reported to improve the hydrophilicity of membrane and induce greater micro-voids formation in the membrane structures, leading to increased water flux during BPA filtration process. The presence of more silanol (Si-OH) and siloxane (Si-O-Si) bonding groups resulted from increased SiO2 contents in membrane has improved membrane adsorption rate and further increased BPA removal.

Sulfonated poly (ether ether ketone) (SPEEK)/Cloisite 15A® nanocomposite membranes were prepared via solution intercalation method. For better dispersion of nanoclay in the polymer matrix, the solution intercalation method was modified and a compatibilizer was introduced. The state of nanoclay dispersion was determined by FESEM. The effect of the solution formulation preparation method and compatibilizer on the performance properties such as proton conductivity and methanol permeability of all membranes was studied. FESEM analysis confirmed that SPEEK/Cloisite 15A® nanocomposite membrane prepared via modified solution intercalation method and in the presence of compatibilizer was the best membrane in terms of its morphological structure. Due to its well nanoclay distribution in polymer matrix, this kind of membrane exhibited the highest selectivity owing to its high proton conductivity and low methanol permeability. SPEEK/Cloisite 15A® with compatibilizer prepared via modified solution intercalation method was found to be the best membrane.

In this study, polyphenylsulfone (PPSU) which is a third member of the polysulfone (PSF) family, with even better properties than PSF and polyethersulfone (PES) was used to prepare flat sheet solvent resistant nanofiltration (SRNF) membranes. The SRNF membranes were prepared from different PPSU concentrations (i.e. 17, 21 and 25 wt%) via phase inversion method. The performance of membranes was then evaluated by measuring the methanol flux and rejection against dyes of different molecular weight (MW) dissolved in methanol. The study revealed that the membrane with the lowest polymer concentration produced the highest pure methanol flux and required the longest time to achieve steady-state owing to its porous structure. Results also showed that the flux of the membranes tended to decrease with filtration time due to the membrane compaction. With respect to the membrane separation performance, it was found that the membrane dye rejection increased while permeate flux decreased with increasing the MW of dye components from 269 to 1470 g/mol, irrespective of the polymer concentration. Furthermore, the membrane MWCO was found to change with polymer concentration in which an increase in polymer concentration led to a lower membrane MWCO.

Membrane distillation (MD) is one of the recent rising membrane separation techniques adopted in the desalination and wastewater treatment. Unlike other pressure-driven separation processes such as reverse osmosis and nanofiltration, MD is a thermal-driven process which involves vapor pressure difference across the feed and permeates solutions. As such, MD requires low energy consumption. Hydrophobic polymeric materials such as polyvinylidene fluoride (PVDF) are frequently used in direct contact membrane distillation (DCMD) due to low surface energy and promising thermal resistance. In this study, the DCMD hollow fiber membranes were separately prepared with PVDF and PVDF blended with lithium chloride (LiCl) through dry/wet phase inversion method. Subsequently, the membranes were used in a DCMD process to remove sodium chloride (NaCl) under different feed inlet temperatures to examine the effect of LiCl additives on the neat membrane. The result showed that by adding LiCl into the neat membrane solution, the finger-like structure was change to a sponge-like structure with microvoids. Furthermore, the performance of the LiCl additive membrane in term of permeate flux was found to be 20% higher compared to that of the neat membrane. Other results of the membrane characteristics were also discussed.

Polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration (UF) membranes consisted of TiO2 and different molecular weight (Mw) of polyvinylpyrrolidone (PVP) (i.e. 10, 24, 40 and 360 kDa) were prepared to treat synthesized oily wastewater. The membrane performances were characterized in terms of pure water flux, permeate flux and oil rejection while the membrane morphological properties were studied using SEM and AFM. PVDF-TiO2 composite membrane prepared from PVP40k was found as the optimum membrane due to its high flux and high rejection during filtration process, recording 45 L/m2.h and 80% respectively, when tested using 250 ppm oily solution under submerged condition. The experimental results demonstrated that with increasing Mw of PVP, PVDF-TiO2 membrane had higher protein rejection, smaller porosity and smoother surface layer. With increasing oil concentration from 250 to 1000 ppm, the permeate flux of the PVDF-PVP40k was obviously decreased while the oil rejection was gradually increased due to the additional selective layer formed on the membrane surface. Based on the findings, the PVDF-TiO2 membrane with PVP40k can be considered as a potential membrane for oily wastewater industry due to the high permeate flux and oil rejection.

The objectives of this study are to study the effect of hydrophobicity degree of polyvinylidene fluoride (PVDF) hollow fiber membranes blended with different types of additives i.e. ethylene glycol (EG) and polyvinylpyrrolidone (PVP) on textile wastewater application. The degree of hydrophobicity of each membrane was analyzed using contact angle goniometer. The membrane morphology and gas permeability were characterized prior to filtration experiment. Both membranes were tested using direct contact membrane distillation (DCMD) system and their performances were evaluated with respect to water flux and dye removal. This study revealed that the membrane with higher contact angle has greater stability in terms of flux and dye rejection compared to the membrane with low hydrophobic property. This is mainly due to the low surface energy obtained by the highly hydrophobic membrane that prevented the liquids from both sides to penetrate through membrane pores.

Palm oil mill effluent (POME) is the largest pollutant discharged into the rivers of Malaysia. An efficient treatment system is highly desirable in palm oil mills in order to control the effluent discharged to any water bodies. In this study, composite ultrafiltration (UF) membranes were successufully prepared by incorporating polysulfone (PSF)/polyphenylsulfone (PPSU) blend membranes with inorganic TiO2 nanoparticles in the range of 0–4 wt%. Prior to POME treatment process, the properties of the resulting membranes were first characterized with respect to pure water flux, BSA rejection, hydrophilicity and structural morphologies. Of the membranes tested, it is found that membrane without TiO2 incorporation demonstrated the highest pure water flux, i.e. 82.81 L/m2h with BSA rejection of 98% when tested at 2 bar. The decreasing water flux with increasing TiO2 loading in the membrane is mainly due to the high viscosity of the dope solution which delayed the phase inversion process and resulted in reduced surface pore size. For the POME treatment process, the results showed that UF membrane could effectively treat the wastewater by removing up to 87% BOD3, 90% COD and almost complete elimination of turbidity.

One of the big challenges in developing a good asymmetric membrane is macrovoid formation that leads to reduction of rejection value. The most common method to reduce or suppress macrovoid formation is by addition of controlled solvent to the coagulation bath. Therefore, the effect of difference coagulants based on dissolved KCl (monovalent) and dissolved Na2SO4(divalent) with different concentration onto asymmetric Polysulfone (PSf) ultrafiltration membrane was investigated in this work. The PSf ultrafiltration membranes were prepared by using phase inversion method using these two immerse aqueous solutions. The performances of membranes were evaluated via pure water flux (distilled water) and solute rejection (humic acid). Results on the cross section revealed that the structure of membrane show a straight pattern of bigger finger-like pore structure from top to bottom layer tend to reduce with at the same time the diameter of finger-like pore structure also increased, as salt medium of coagulant increases. These obviously shown by permeation values for both salt mediums were higher compared to without salt coagulant. This reduction of finger-like structure at bottom layer occurred along together with the formation of sponge shape structure. The growth of thick sponge shape is strongly influence by kinetic phase inversion of salt coagulant that also creates resistance to permeation mechanism. However the intense salt coagulant medium can cause the bigger sponge structure that will slightly reduce rejection and increase the permeation. This was proved by the rejection of KCl medium started to increase at 1-3% but slightly reduced at 4%. Based on the result analysis demonstrated that the ideal membrane with highest rejection and good permeation values was membrane immersed into 1% Na2SO4 coagulation medium.

The present study focuses on the effect of poly (acrylonitrile) (PAN)-g-poly (vinyl alcohol) (PVA) amphiphilic copolymer as an additive on fabrication of PAN-based UF hollow fiber membrane. The PAN-based hollow fiber membranes with different copolymer composition in dope solution were prepared via dry-wet phase inversion process. Compared to PAN-based membrane, membranes incorporated with PAN-g-PVA copolymer displayed good morphology and better hydrophilicity. It is found that pure water flux of the membrane incorporated with amphiphilic copolymer was 5 times higher than that of control membrane, recording 244.97 L/m2.hr when tested at 1 bar. Results also showed that the UF membranes incorporated with amphiphilic copolymer were able to retain efficiently bovine serum albumin (BSA) (66 kDa) and possessed better anti-fouling performance.