Zirconium-based metal–organic framework (Zr-based MOF) often appears as a highly stable material in terms of thermal and chemical aspects. However, intrinsic defects that occur in its framework lead to poor membrane performance, which hinders its amazing properties. Therefore, a new approach in preparing UiO-66-NDC (UiO: University of Oslo, NDC: naphthalenedicarboxylic acid) membrane supported on ceramic hollow fibre was designed to tackle such problems. Polymerising the MOF active layer using ultraviolet curable resin (UCR) improved the original UiO-66-NDC framework, resulting in perfect octahedron crystal morphology and smoother and densely packed integrated layers, as shown through FESEM and AFM. XPS results reveal that the photopolymerisation process lengthened the UiO-66-NDC chain during the reaction, which then supplied additional atoms from UCR to the missing linker position inside UiO-66-NDC framework. The negative water flux turned to positive water flux (from −718.820 to 16.189 L/m²∙h), with a sharp decrement in reverse solute flux (from 34.194 to 0.007 kg/m²∙h) in the forward osmosis (FO) test.

This work discusses the preparation, characterization, and feasibility test of composite zeolite hollow fiber membranes, with UV-curable resin as a secondary coating material, in removing Ni (II) using FO process. The preparation of the membrane started by depositing zeolite membrane onto alumina hollow fiber, followed by photopolymerization process once the outer layer was fully covered. Various characterization techniques were used on the composite membrane, namely field emission-scanning electron microscopy (FESEM), X-ray diffraction analysis, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, contact angle measurement, and performance tests using FO. The results show that the membranes enabled a reduction of reverse solute once incorporated with UV-curable resin. The lowest reverse solute flux obtained was 0.008 kg m⁻² h⁻¹, when pure water was flowed in the outer surface and 100,000 mg L⁻¹ sodium chloride (NaCl) was used in the lumen. The UV-curable resin was unstable in the presence of Ni (II), which later formed complex ions. Adsorption of Ni (II) ions caused agglomeration of zeolite particles, causing membrane defects.

This work describes the development of ZIF-8 membranes supported on alumina hollow fiber via electroless deposition (ELD) of ZnO followed by solvothermal synthesis for water desalination. The relatively low operating temperature of ELD of ZnO provided an alternative method to fabricate pure-phase ZIF-8 membrane. As-prepared ZnO and ZIF-8 samples were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), water contact angle, and Fourier transform infrared spectroscopy (FTIR). The performance of ZIF-8 membrane was evaluated using forward osmosis (FO) using active layer facing feed solution. The well-intergrown membrane provided high water flux up to 12.25 L/m²h with reverse solute flux as low as 0.029 kg/m²h when using 100,000 ppm NaCl solution and water as the draw and feed solutions, respectively. Furthermore, the membrane showed high KCl (87.8%) and NaCl (88%) rejection and excellent CaCl₂ (95%) and MgCl₂ (98%) salt rejection in FO using 1.0 M dextrose solution as the draw solution. Interestingly, the rejection of AlCl₃ salt was only as high as 46% due to the instability of ZIF-8 in the AlCl₃ solution causing the loss of its crystallinity. The ZIF-8 material showed no degradation in various saline solutions (e.g., KCl, NaCl, CaCl₂, and MgCl₂) except for AlCl₃ solution even at a high concentration of 40,000 ppm for 720 h. The findings suggest that the prepared ZIF-8 membrane is a potential membrane for desalination application due to its excellent separation performance toward certain salts.

Water pollutant such as dyes had danger the water quality. Todays, porous materials are great potential for dye adsorption from water bodies. In this study, the iron-based metal–organic framework (MOF-Fe) of MIL-101 is synthesized through a facile solvothermal method. The amine-functionalization effect of the MOF-Fe (amine-MOF-Fe) is evaluated for the adsorptive removal of methylene blue (MB) from aqueous solution. The adsorption behaviour had shown a rapid MB adsorption within the first hour of the process due to the pore-filling mechanism of the porous MOF-Fe structure. The electrostatic interaction between the amino group of amine-MOF-Fe and MB had contributed to the high adsorption capacity. The amine-functionalization effect also found the amine-MOF-Fe is having two times higher adsorption capacity when used with the loading two times lower than non-functionalized MOF-Fe. The maximum equilibrium adsorption capacities were measured at 149.25 and 312.5 mg/g with optimum MOFs loading of 0.8 and 0.4 g/L for MOF-Fe and amine-MOF-Fe, respectively. The adsorption mechanism proposed includes the electrostatic interaction, pore filling, hydrogen bonding, and π–π stacking. The regeneration study showed the MOFs could be recycled without interfering with the removal efficiency. Hence, the results indicate that the MOFs had desirable reusability for the practical adsorption of cationic dyes with its features of fast adsorption and high capacity.

This work describes the fabrication and evaluation of fluoropolymer surface coating on polymer fibre core prepared from polymethyl methacrylate (PMMA) using ultraviolet (UV) photopolymerisation curing method. The curing condition has a significant influence on the coating adhesion on the core. The focus of this study was to evaluate an effective and simple process for polymer optical fabrication using UV curing with dip-coating method. The coating performance was evaluated through surface morphology analysis and physical properties. FESEM–EDX images indicate that the fluoropolymer coating formed a compact structure with a cladding thickness of 67.63 μm for the highest UV irradiation strength. FTIR analysis revealed the presence of fluorine elements on coated fibre with EDX surface mapping of fluorine dispersion. The performance of the fibre was studied and compared with commercially available polymer optical fibre in terms of fibre spectral fluorescence properties and light attenuation. The dip-coating photopolymerisation method was effective in forming the cladding for step-index polymer fibre with similar spectral excitation wavelength recorded at 620 to 630 nm with the lowest power loss at −13.40 dBm.

This work investigated the effects of reactant concentrations and synthesis periods on in situ deposition of zeolite membranes on glass hollow fibers. The separation performances of the zeolite membranes in forward osmosis applications were studied based on pure water fluxes and reverse solutes. The reactant concentration of 0.66 M enabled zeolite membrane deposited onto glass hollow fiber to give a water flux of 4.50 L m⁻² hr⁻¹ with reverse solute of 0.05 kg m⁻² hr⁻¹. When the deposition time was reduced to 12 h and 18 h, water fluxes increased to 62.25 and 71.92 L m⁻² hr⁻¹, respectively.

A-type zeolite membranes were synthesized on porous glass hollow fibers that prepared using the in-situ hydrothermal process. The porous glass hollow fibers were prepared using the phase inversion and sintering technique with the addition of yttria stabilized zirconia (YSZ) to improve their porosity. The glass hollow fibers were characterized using the scanning electron microscope (SEM), Fourier transform infrared (FTIR), mechanical properties and water permeability. The porosities of pure glass hollow fiber were improved by the addition of YSZ particles, which lead to an increase in the pure water permeability. The water permeability shows that the glass hollow fiber prepared form spinning suspension E, which has 30 wt% zeolite particles and 20 wt% YSZ particles, has the highest permeability of 155.65 L m⁻² hr⁻¹ bar⁻¹ compared to the previous work, which was only 4.0 L m⁻² hr⁻¹ bar⁻¹. This glass hollow fiber was later used as the support for the incorporation of zeolite membrane for the desalination application. The performance of membranes is separating sodium chloride (NaCl) salt solution were tested using two different setups, namely pressure driven reverse osmosis (RO) and sweeping liquid assisted reverse osmosis (SLRO). The solute flux for 5,000 and 10,000 ppm NaCl salt solutions were 24.45 and 17.86 L m⁻² hr⁻¹, respectively. Both operations enabled the solute rejection up to 98%.

Membranes for desalination using forward osmosis (FO) should be stable and ordered, with high water flux and low reverse solute flux performances. In this study, metal-organic framework (MOF) was embedded on a ceramic membrane surface in order to make it feasible to be used in FO process. Two-stage preparation steps were taken involving sol-gel Pechini’s method for membrane surface modification, followed by solvothermal synthesis to finally deposit the MIL-140B (MOF) on the membrane’s surface. 1D structure of our MOF (MIL-140B) was observed using field-emission scanning electron microscopy (FE-SEM) and its unaffected crystallinity was proved using X-ray diffraction (XRD) regardless of changes in the study parameters (reactant concentration and time of synthesis). Brunauer-Emmett-Teller (BET) conducted in this study displayed type IV isotherm pattern with hysteresis loop which signify MIL-140B as a mesoporous particle. The final performance results concluded that 0.3 M reactant concentration under 16 h synthesis time was the best preparation condition since sample D gave excellent water flux (12.023 L/m² h) and showed remarkable drop in the reverse solute flux (0.094 L/m² h) performances. These results indicate a potential of high FO membrane efficiency as comparable to the best in the literature.

This work describes the fabrication and evaluation of small core diameter Polymeric Optical fibres (POF) prepared from Poly(Methyl Methacrylate) (PMMA). Based on prior study, POF  has a very interesting property in terms of short-reach local area networks due to the simpler manufacturing process and inherent immunity to electromagnetic interference and radiation. It can overcome the limiting factors of conventional glass-based optical fibre in terms of cost-effective, flexibility and easy installation. This study focused on introducing effective fabrication method to produce small diameter PMMA POF core using extrusion process. Prior to extrusion, we managed to produce PMMA cores with diameters of 650 μm, 750 μm and 850 μm. Based on the outcome of this study, the drawing tension and extrusion temperature have been identified as major influences on core diameter. The SEM images indicated that dense structure and clean surface whereas DSC and TGA  analyses revealed that almost similar glass transition temperature and degradation weight loss in between fabricated PMMA core and industrial polymer optical fibre.

This work investigated the feasibility of a metal–organic framework (MOF), Christian-Albrechts-University (CAU-1), deposited on alumina hollow fiber for desalination applications. CAU-1 membranes, synthesized using the solvothermal approach, were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and contact angle measurement. The performances of the CAU-1 membranes were tested using forward osmosis (FO). Using a configuration of active layer facing feed, the CAU-1 membrane (M6) had the highest flux of 18 L m⁻² h⁻¹ with a reverse solute value of 0.079 kg m⁻² h⁻¹. The M6 membrane was further tested using a configuration of active layer facing draw. Surprisingly, the flux moved from the high salt concentration to low salt concentration, obeying the reverse osmosis phenomenon under low pressure. At 10,000 ppm of salt concentration, M6 membrane showed solute fluxes of 4.07 and 3.07 L m⁻² h⁻¹ for NaCl and MgSO₄ with rejections of 75% and 65%, respectively. Guest molecules and an amine group in CAU-1 were responsible in affecting the performance of the membrane for desalination application.

This work describes the development of photocatalytic mesoporous aluminum oxide (alumina) membranes for oil emulsion separation. The mesoporous alumina membrane was deposited on alumina hollow fiber using hydrothermal synthesis. Aluminum nitrate nonahydrate, Al(NO₃)₃.9H₂O, cetyltrimethylammonium bromide (CTAB), and urea were used in the preparation of the mesoporous alumina membranes. The successfully prepared mesoporous alumina membranes on ceramic support were then deposited with copper-doped ceria, which acted as photocatalyts, using the sol-gel Pechini method. The results showed that the membranes had an excellent separation performance in separating 1000 ppm polyethylene glycol and 1000 ppm bovine serum albumin when the samples were calcined at 800 °C. Under UV irradiation, there was a remarkable increase in the permeability of water through the membrane. The photocatalytic mesoporous alumina membrane showed a permeability of 1422 L/h m² bar with 92% oil emulsion rejection. An excellent increase in the performance can be associated with the production of superoxide radical and hydroxyl radicals by the photocatalytic membrane once exposed to UV light.

Removal by absorptive ceramic membranes can simultaneously absorb and separate metal ions from water. Alumina/yttria‐stabilized zirconia (Al₂O₃/YSZ) hollow‐fiber membranes, fabricated using phase inversion and sintering process, were deposited with iron oxide by an in‐situ hydrothermal process. The results showed that α‐Fe₂O₃ was produced and incorporated across the membranes. A reduction in flux was recorded with the deposition of α‐Fe₂O_3. However, it improved the adsorption capacity for heavy metal adsorption. The adsorption‐separation test demonstrated that the optimized membrane is able to completely remove Pb(II) ions after two hours.

This work describes the development of zeolitic imidazolate framework-8 (ZIF-8) membranes on modified alumina hollow fiber for desalination by forward osmosis. Effects of different seeds (ZnO, NiO and PDA) and sodium formate on in-situ deposition of ZIF-8 were studied in relation to the membrane’s morphology and performance. XRD result shows that ZIF-8 was successfully synthesized in the presence of sodium formate. FESEM images showed PDA modified support was unsuccessful in producing well defined and dense ZIF-8 membrane layer even after another ZIF-8 re-deposition due to its minimal amount. The NiO modified support was also found unsuccessful, as ZIF-8 crystals were formed in clusters. On the contrary, dense ZIF-8 membrane was successfully prepared on ZnO modified support with SF-1 synthesis solution producing bigger ZIF-8 crystal and thinner ZIF-8 membrane than as of SF-2. Water flux performance in forward osmosis showed that NiO/ZIF-8, PDA/ZIF-8 and PDA/ZIF-8 (re-deposition) membranes gave negative water fluxes of -50 kg/m²·h, -5.2 kg/m²·h and -1.7 kg/m²·h with reverse solutes of 42.66 mol/m²·h, 27.42mol/m²·h and 3.22 mol/m²·h, respectively, indicating the solute from draw solution diffused into the feed solution. However, ZIF-8 membrane prepared using SF with molar ratio of 1, on the ZnO modified support had a water flux of 13.3 kg/m²·h, reverse solute of 0.95 kg/m²·h and salt rejection of 52.1%. When the SF ratio was increased to 2, the ZIF-8 membranes showed a water flux of 12.5 kg/m²·h, reverse solute of 1.64 kg/m²·h and salt rejection of 54.9%. The moderate salt rejection could be associated with defects in the ZIF-8 membranes due to poor grain boundaries.

This work describes the development of supported zeolite-Y membranes, prepared using the hydrothermal method, for the removal of nickel from an aqueous solution. Alumina hollow fibers prepared using the phase inversion and sintering technique were used as an inert support. The supported zeolite-Y membranes were characterized using the field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and the water permeation and rejection test. The performance of the supported zeolite-Y membranes for heavy metal removal using batch adsorption and filtration test was studied using the atomic absorption spectroscopy (AAS). The adsorption study shows that the removal of nickel was pH-dependent but affected by the presence of α-alumina. The seeded zeolite-Y membrane gave the highest adsorption capacity which was 126.2 mg g^-1. This enabled the membrane to remove 63% of nickel ions from the aqueous solution within 180 min of contact time. The adsorption mechanism of nickel onto the zeolite-Y membrane was best fitted to the Freundlich isotherm. The kinetic study concluded that the adsorption was best fitted to pseudo-second-order model with higher correlation coefficient (R² = 0.9996). The filtration study proved that the zeolite-Y membrane enabled to reduce the concentration of heavy metal at parts per billion level.

This work discusses the preparation and characterizations of glass hollow fiber membranes prepared using zeolite-5A as a starting material. Zeolite was formed into a hollow fiber configuration using the phase inversion technique. It was later sintered at high temperatures to burn off organic materials and change the zeolite into glass membrane. A preliminary study, that used thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), confirmed that zeolite used in this study changed to glass at temperatures above 1000 °C. The glass hollow fiber membranes prepared using the phase inversion technique has three different microstructures, namely (i) sandwich-like structure that originates from inner layer, (ii) sandwich-like that originates from outer layer, and (iii) symmetric sponge like. These variations were influenced by zeolite weight loading and the flow rate of water used to form the lumen. The separation performances of the glass hollow fiber membrane were studied using the pure water permeability and the rejection test of bovine serum albumin (BSA). The glass hollow fiber membrane prepared from using 48 wt% zeolite loading and bore fluid with 9 mL min⁻¹ flow rate has the highest BSA rejection of 85% with the water permeability of 0.7 L m⁻² h⁻¹ bar⁻¹. The results showed that the separation performance of glass hollow fiber membranes was in the ultrafiltration range, enabled the retention of solutes with molecular sizes larger than 67 kDa such as milk proteins, endotoxin pyrogen, virus, and colloidal silica.

This paper reports the preparation of the dual layer ceramic hollow fiber membrane that made of alumina and a mixed ion electron conducting (MIEC) material for simultaneous reaction and separation applications. Alumina hollow fiber membrane was prepared using the phase inversion process followed by a sintering technique at elevated temperature. The alumina hollow fiber membrane was used as membrane support onto which a thin and dense layer of lanthanum strontium cobalt ferrite (LSCF) was deposited. The main objective of this study was to investigate the LSCF coating formulations used in the deposition of LSCF layer onto alumina substrate membrane. The sintering temperature of thin LSCF layer was varied to investigate gas-tightness properties of LSCF membrane. A series of characterizations were conducted for both the support and the LSCF membrane. The result showed that the thin layer membranes with thicknesses ranging from 3 to 20 μm were successfully deposited on the surface of alumina hollow fiber support. The sintering process improved the gas-tightness properties but the sintering temperature above 1150oC caused defects on the surface of LSCF membrane.

Asymmetric alumina hollow fiber membranes were prepared using the phase inversion technique followed by the sintering process at high temperatures. The ceramic suspensions were formulated by mixing alumina powder with polyethersulfone (PESf), polyethylene glycol-30-dipolyhydroxystearate and N-methyl-2-pyrrolidone (NMP) as the polymer binder, dispersant and solvent, respectively. The objectives of this study were (i) to investigate the effects of spinning parameters, namely, ceramic loading, ceramic to polymer binder ratio, different internal coagulant temperatures and air gap variation on asymmetric structure formation and (ii) to study the self-cleaning properties of alumina hollow fiber membranes. The ceramic hollow fiber membrane was characterized in terms of its viscosity, structural morphology and mechanical strength using a scanning electron microscope (SEM). The results showed that the finger-like structures in alumina hollow fiber membranes could be formed but their patterns were influenced by the ceramic suspension and spinning parameters. Variations in their morphology resulted in significant effects on the mechanical properties and permeability of ceramic hollow fiber membranes. A CuO/CeO₂ catalyst was deposited onto the alumina membrane support with the catalyst distribution determined by SEM/EDX. Self-cleaning properties were examined by comparing normal cleaning and self-cleaning properties with irradiation of UV for protein rejection. The result of self-cleaning by UV showed higher bovine serum albumin (BSA) permeation due to super-hydrophilicity of the CuO/CeO₂ catalyst.

This work describes the preparation of yttria-stabilized zirconia (YSZ) hollow fibre membranes using the phase inversion and sintering process. The study aims to provide generic information on the effects of membrane preparation on the morphology and mechanical properties of YSZ hollow fibre membranes. In this work, ceramic suspensions were prepared by mixing YSZ particles, dispersant, polymer binder and organic solvent using a planetary ball milling machine. This process was followed by extrusion into a coagulation bath via an air gap, drying and sintering process at temperatures ranging from 1250 °C to 1400 °C. The results show that by varying the YSZ loading and YSZ/PESf ratio, different morphologies of ceramic hollow fiber membranes can be obtained due to variations in the viscosities of ceramic suspensions. Similarly, air-gap length between the spinneret and coagulant surface was found to affect the growth of the finger-like structures and sponge-like regions. Varying these parameters also gave significant effects on the mechanical strength of the ceramic membrane due to the change in membrane thickness and compactness. The sintering process had insignificant effects on the membrane morphology but the process can be used to enhance the mechanical strength of ceramic hollow fiber membranes. The optimum temperature of the sintering process was identified. It was found that increasing the sintering temperature further caused a reduction in the mechanical strength due to crack formation in the ceramic hollow fiber membrane. The preliminary performance tests showed that the ceramic hollow fiber membrane sintered at 1300 °C has a pure water flux of 118.4 L/m² h. It also has a high PEG rejection with molecular weight cut off (MWCO) of 60 kDa.

This article describes the preparation of titanium dioxide (TiO₂) hollow fiber membrane using phase inversion and sintering technique. In this study, nano-sized TiO₂ powders with different particle sizes were used to prepare ceramic hollow fiber membranes. In a series of preparation steps, a dispersant was dissolved in organic solvent before the addition of ceramic powders. These steps were followed by the addition of polymer binder. The membrane precursor was obtained by extruding the ceramic suspension into a coagulation bath, which enabled the precipitation of the precursor of ceramic hollow fiber membrane. The dried precursor was later sintered at temperatures ranging from 1200 to 1300^oC to obtain TiO₂ hollow fiber membrane. Scanning electron microscopy (SEM) was used to study the morphology of TiO₂ hollow fiber membrane. The SEM images show the membrane can be shaped into asymmetric structure and symmetric structure based on the ceramic suspension compositions. The highest mechanical strength obtained was 223 MPa when the membrane prepared using 20 wt. % ceramic loading of single nano-sized powder and sintered at 1300^oC. TiO₂ hollow fiber membrane prepared using similar ceramic loading showed high permeation rate of inert gas. High pure water fluxes were obtained when permeability tests was carried out using TiO₂ hollow fiber membrane, prepared using mixture of nano-sized particles, even though its cross-section have a sponge-like structure.