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No abstract is provided for this article.
Membrane distillation (MD) is a thermally driven membranous process and in the recent years, it has received increasing attention in desalination. Generally, polymeric membranes have dominated the MD studies due to their intrinsic hydrophobic properties and high availability. On the other hand, the development of ceramic membranes for MD desalination is developing, gradually replacing their polymeric counterparts due to superior properties in terms of thermal, chemical and mechanical stabilities, as well as potentially longer service terms. This review describes and evaluates the fabrication methods of ceramic membranes as well as discusses the latest discoveries of ceramic membranes for MD desalination. Despite outstanding properties, the efforts in developing ceramic membranes as a replacement for polymeric membranes in MD desalination are meeting challenges and obstacles; hence, in the last part of this article, the current challenges and future research opportunities of ceramic membrane development will also be addressed.
Photocatalytic membrane has received overwhelming attention in recent years and has been considered as one of the most promising advanced oxidation processes. In such system, the photocatalytic membranes are constantly exposed to UV irradiation and the effects of UV irradiation on the structure and long-term stability of polymer membranes are still questionable, and therefore, it deserves to be investigated. This study focuses on the stability of the TiO2/PVDF dual layer hollow fiber (DLHF) membranes against photocatalytic reactions for photocatalytic-membrane process. 3wt% of TiO2 nanoparticles loading in DLHF membranes was evaluated under 8W UVA in 30 days. The membrane stability was characterized by observing the changes in Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscope (SEM) and tensile strength analysis. The results revealed that some differences in FTIR peaks between new membranes and used membranes were found, suggesting that UV irradiation has some effect on the stability of the TiO2/PVDF membrane for 30 days exposure. The tensile strength of used membrane showed a moderate decrease with increasing UV exposure time, resulting in negative impacts on the membrane overall stability. This work is particularly importance to evaluate the sustainability of polymeric membrane, which has considered as heart of photocatalytic membrane reactor for wastewater treatment process.
Omniphobic silica sand ceramic hollow fiber membrane (SCHFM) was successfully fabricated for the reduction of the wetting and fouling in direct contact membrane distillation (DCMD). Surface functionalization of the laboratory spun SCHFM was performed following a series of steps 1) deposition of spherical silica nanoparticles (SiNPs), 2) fluorination by 1H,1H,2H,2H perfluorodecyltriethoxysilane (FAS17) and 3) poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) coating to glue SiNPs to the SCHFM surface. Initially, the pristine SCHFM was hydrophilic, but when the surface modification was fully applied the hollow fiber became omniphobic, exhibiting high contact angles for all tested liquids of different surface tensions, such as distilled water, red palm oil and ethanol. For example, one of the surface modified hollow fibers, called SiNPs-FAS-PVDF/FAS, was superomniphobic toward water (167°) and red palm oil (157°), and near superomniphobic toward ethanol (146.1°). As for the DCMD experiments with the feed solution containing 35 g/L NaCl and 10 mg/L humic acid, two of the surface modified hollow fibers, called SiNPs-PVDF/FAS and SiNPs-FAS-PVDF/FAS, showed high anti-fouling and anti-wetting resistance during the entire DCMD operation period of 400 min with little flux reduction and no observable increase in the conductivity of the permeate stream. The anti-fouling resistance of these hollow fibers was further evidenced by the cleanness of the surface in the micrographic picture taken after the DCMD run. The omniphobicity of these hollow fibers is ascribed to the combined effects of surface tension decrease by the FAS17 fluorination and the formation of the re-entrant structure by the densely packed SiNPs. With reasonably high fluxes of 35.1 kg/m2∙h and 43.6 kg/m2∙h, for SiNPs-PVDF/FAS and SiNPs-FAS-PVDF/FAS, respectively, and 100% of salt rejection, these hollow fibers have potential for seawater desalination by DCMD.
Recently, ceramic membrane gradually acquired attention from researchers due to the advantages of ceramic’s behavior, which allows the ceramic to overcome the limitations of using polymeric membrane. This work focused on the fabrication of ceramic hollow fibre membrane from a ceramic suspension solution containing yttria-stabilized zirconia (YSZ), polyethersulfone (PESf), N-methylpyrrolidone (NMP) and dispersants using combined phase inversion sintering technique. In this study, ceramic hollow membrane precursors were sintered at different sintering temperature ranging between 1250°C and 1400°C. The influences of sintering temperature on the microstructure, porosity and pore size distribution, mechanical strength and pure water flux of ceramic hollow fibre membrane were investigated in detail. The results show an asymmetric structure of YSZ hollow fibre membrane containing finger-like structure and sponge-like structure. The sponge-like structure can serve as a separation layer, while finger-like-structure performs as a supported layer. It is observed that sintering process caused a significant densification of sponge-like structure (microstructure). Sintering at temperature 1400°C shows the formation of non- interconnected voids. Sintering at 1300°C is sufficient enough having a mechanical strength of 227.55MPa with an apparent porosity of 45.09% and PWF of 118.39L.m¯².hr¯¹.
Flexible hollow fiber polymeric membrane based thin film substrate sputtered with thin layer photocatalyst is a novel configuration for photocatalytic applications. This article focuses on the fabrication of copper oxide/polyvinylidene fluoride thin film hollow fiber membrane (CuxO/PVDF TF HFM) by using radio frequency (RF) magnetron sputtering of CuxO over PVDF hollow fiber membrane (HFM). Different phase of copper oxide (CuxO) detected on the layer of PVDF HFM by X-ray diffraction (XRD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), depending on oxygen flow rate. 10-20 mL/min O2 flow rate produces Cu2O phase while 25 and 30 mL/min produces CuO phase. Sputtered CuxO/PVDF TF HFM at 20 mL/min O2 shows bigger grain size of 2.1 nm with 0.35 nm of dislocation density and 0.019 nm of lattice strain. The higher the O2 flow rate, the thicker and the more uniform the sputtered CuxO/PVDF TF HFM was produced as indicated by field emission scanning electron microscopy (FESEM). The atomic force microscopy (AFM) analysis showed the increasing surface roughness of the sputtered 10 mL/min CuxO/PVDF TF HFM at 8.26 nm, as compared to the neat PVDF HFM at 6.15 nm. About 70% of 2 mg/L bisphenol A (BPA) in synthetic wastewater was successfully photodegraded while outstanding 88.89% degradation of BPA in real treated sewage wastewater achieved using 20 mL/min CuxO/PVDF TF HFM after 360 min light irradiation. About 71.33% of regeneration efficiency was achieved after 3 consecutive cycles that this technique promises the good reusability with strong adhesion capability.
The world is facing a water crisis, and Australia is no exception. New regimes for the supply, use, and delivery of water are needed to ensure a sustainable water future. Black water reuse through ‘sewer mining’ or onsite treatment, proposes to be one initiative that may possibly offer a viable and sustainable alternative approach to water provision in many contexts. However, despite the potential benefits of black water reuse, its feasibility is not yet fully understood. In particular, there is much uncertainty surrounding the following issues: (1) community acceptance, (2) policy complexities, (3) performance impacts of these localised systems, and (4) environmental balance over the full life cycle. This paper outlines research needs surrounding black water reuse with a focus on these four major issues. The paper presents a research agenda to address these important issues. This research agenda involves two Australian commercial case studies: the Council House 2 building in Melbourne, and the Bendigo Bank building in Bendigo.
No abstract is provided for this article.
For plastic spintronics, it has thus far been a challenge to develop a (magnetic nanostructures)/polymer heterostructure at low temperature due to the thermal sensitivity of polymers. In this context, half-metallic magnetite (Fe3O4) films of different thicknesses were coated on flexible polymethyl methacrylate (PMMA) substrates by reactive sputtering at 300 K. Grain size and thickness increased from ~10 nm to ~34 nm and 50 nm to 400 nm with an increase in the deposition time from 165 to 1335 s, respectively. Moreover, a sharp rise in grain size was observed when the thickness of the film reached 200 nm, and finally, saturation took place at 400 nm. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) studies confirmed the absence of the γ-Fe2O3 phase and thus the successful deposition of Fe3O4 thin films on the PMMA substrate. Parameters as such as Verwey transition (T v ) (~125 K), saturation magnetization (M s ) (~354 emu/cm3) and magnetoresistance (MR) (−8.6% under 60 KOe at 300 K) under H ∥ Film plane were obtained for Fe3O4/PMMA heterostructures with a film thickness of 200 nm. The resistivity (ρ), T v , M s and MR were hardly affected on several bending tests, proving that Fe3O4/PMMA heterostructures are exciting materials for future flexible spintronics.
The selection of a suitable cladding material for a fibre optic is crucial, and the application of polymeric material in high temperature conditions is garnering much attention from many researchers. However, polymer suffers from a weak thermal resistance, limiting its use in high temperature conditions. Therefore, this study aims to develop a new potential cladding material that has a good balance between optical and thermal properties. Two sets of cladding materials are proposed, namely the blend of polycarbonate/polymethyl methacrylate (PC/PMMA) and polymethylpentene (PMP). The cladding materials were dissolved in different solvents, followed by the casting on a glass plate to form a flat sheet cladding layer. PC/PMMA blend showed a miscible blending with a single Tg value and physical blending. Both PC/PMMA blend and PMP claddings demonstrated more than 90% of luminous transparency. The materials also showed high thermal stability with the onset degradation temperature of ∼ 300 °C. The optimum ratio for PC/PMMA was 80/20. Next, the cladding layer was fabricated by coating the core in 80/20 PC/PMMA and PMP. The scanning electron microscopy (SEM) image reveals that core–clad ratio for the PC fibre is 1.02 for both materials. The maximum tensile strength for the PC with PMP cladding was higher than that of the PC with PC/PMMA cladding. PMP-clad fibre has higher power output, which was a 60% increment from bare PC fibre output compared to PC/PMMA-clad fibre, with only 28.8% power output increment. Though both materials have huge potential to be used as the cladding for PC core, PMP cladding showed superior performance compared to PC/PMMA cladding.
Low-cost green ceramic hollow fiber membranes (CHFM) were successfully designed and fabricated from the industrial waste ash, palm oil fuel ash (POFA) via phase inversion-based extrusion/sintering techniques for water filter application. The extrusion process parameters such as suspension viscosity, air gap distance, and bore fluid flow rate were systematically explored to produce the membrane with the desired morphology. A high suspension viscosity would result in a small macro-voids structure. Moreover, a high air gap distance would induce fiber with long macro-voids structure, while a low bore fluid flow rate would lead to the formation of distorted lumen structure. The effect of sintering temperature towards CHFM was also studied in detail. An increase in sintering temperature improved the membrane bending strength, but also adversely affected the pure water flux due to lower porosity and higher tortuosity. The developed membranes achieved excellent bending strengths of > 75 MPa at relatively low sintering temperatures than the alternative ceramic counterparts, due to its high potassium oxide, K 2 O content, which acted as the low melting point sintering aid. The relatively low sintering temperature of POFA-derived CHFMs could reduce the energy consumption and sintering duration, which could be more economically attractive, as compared to their ceramic counterparts, thus benefiting industrial users.
Palm oil fuel ash (POFA) is one of the most abundant industrial wastes in palm oil producing countries like Indonesia and Malaysia. Due to its unique characteristics such as high silica and hydroxyl group contents, it has high potential to be used as the main material for the fabrication of low cost and green ceramic hollow fiber membrane. This work investigated the effect of pre-treatment temperature of POFA towards the properties of the derived ceramic hollow fiber membranes. The properties of POFA such as morphology, mineralogical and chemical composition, thermal behavior, surface and pore properties were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray fluorescence (XRF), carbon element analysis, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and nitrogen (N2) sorption technique. Effect of POFA pre-treatment temperature on the membrane properties were evaluated and characterized in terms of morphology, bending strength, pore size distribution, porosity and pure water flux (PWF). Finally, the separation performance of the membranes was also investigated using oil/water emulsion filtration tests. The results showed that the membrane properties were significantly improved for the membranes derived from pre-treated POFA compared to the untreated one. The highest bending strength of ∼60 MPa was achieved for TP700 membrane which was pre-treated at 700 °C. However, the PWF decreased from 219.2 to 28.4 L/m2 h for untreated POFA (UP) derived and TP700 membranes, respectively. Besides, an enhanced oil/water separation performance was obtained for membranes fabricated from pre-treated POFA with the highest oil rejection of 88.9%. These results showed that POFA derived ceramic hollow fiber membrane could provide the basis for the development of low cost and green ceramic hollow fiber membranes from waste ash for separation applications.
Micro-tubular solid oxide fuel cell (MT-SOFC) has recently attracted much attention due to their greater tolerance to thermal cycling, quicker start-up capability, higher output density and better portable characteristics as compared with planar and tubular SOFCs. MT-SOFC requires one of the cell components to act as a support for deposition of remaining cell layers. In fact, the support fabrication step is the most important part as the quality of the support greatly affects performances of the MT-SOFCs. However, there is limited information regarding the fabrication processes especially extrusion of the support for the MT-SOFCs. The aim of this paper is to review on conventional and recent introduced phase inversion-based extrusion techniques, their characteristics and performances. A brief discussion on future direction of a more advanced phase inversion-based extrusion in the MT-SOFCs fabrication, including co-extrusion technique is also included.
