The usage of ceramic membranes is gaining enormous attention due to their higher selectivity, permeation rate, and chemical and thermal stability as compared to the polymeric membrane. Owing to the fact of these superior properties, the search of a low-cost ceramic membrane is still in demand. To date, the fabrication of ceramic membrane using natural zeolite as the membrane ceramic loading has yet to be explored. Thus, this study aims to develop natural zeolite (Clinoptilolite) as the ceramic source in the fabrication of low-cost hollow fibre ceramic membrane (HFCM) via phase inversion and sintering techniques. Several fabrication parameters were also studied namely air gap distance, bore fluid flow rate and sintering temperature throughout this research. The best ceramic membrane was fabricated using 5 cm air-gap distance, 13 mL min-1 of bore fluid flow rate and 1000 °C of sintering temperature. The acceptable strength and morphological behaviour of finger-like and sponge-like voids were found to be an advantageous characteristic of the fabricated membrane. The cheap and yet abundant raw ceramic material as well as low sintering temperature are eventually reduced the cost of membrane production.
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Micro-tubular solid oxide fuel cells (MT-SOFCs) have attracted much attention due to; higher volumetric output density, greater tolerance to cycling, quicker start-up capability and better mobility. Fabrication process of MT-SOFCs is one of the critical factor that ensures the success of a cell. There are three main components (i.e. anode, electrolyte and cathode) in the development of MT-SOFCs which are generally fabricated through separated and multiple laborious steps. This study aims to produce a novel anode/electrolyte/cathode (NiO-CGO/CGO/LSCF-CGO) triple-layer hollow fiber (TLHF) in a single-step using phase inversion based co-extrusion combined with co-sintering technique. The challenge lies within the diverse sintering behaviors among the anode, electrolyte and cathode layers at some point of the cell fabrication. In this study, the TLHF was found being able to survive the co-sintering at 1450 °C resulting a defect free precursor producing 0.48 Wcm−2 maximum power densities at 525 °C, which is comparable with the cell fabricated using conventional multiple-step process.
This study focuses on the design and performance of a hybrid system consisting of a photocatalytic reactor and a membrane permeation cell. Initially, an ultraviolet lamp was installed in the photocatalytic reactor to decompose the organic pollutants in the presence of 200ppm titanium-dioxide (TiO2). Individual hydrocarbon pollutants were identified by gas chromatography–mass spectrometry (GC–MS) analysis of wastewater samples. Polyvinylidene fluoride (PVDF)/multi-walled carbon nanotube (MWCNT) nanocomposite membranes were fabricated to enhance the rejection, flux and fouling resistance for full filtration of pollutants from photocatalytic reactor such as decomposed refinery wastewater and TiO2 photocatalyst. The nanocomposite membranes were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TiO2 cross-over during permeation was detected by using an atomic adsorption spectrometer, which proved that TiO2 rejection was more than 99% for oxidized MWCNT nanocomposite membranes. Furthermore, GC–MS analysis was concluded over 90% decomposition which occurred by photocatalytic reaction and practically all pollutants were removed by ultrafiltration permeation cell. The nanocomposite membrane with 1.0wt.% of oxidized MWCNTs incorporated in PVDF matrix was found to be the best nanocomposite membrane among all of the fabricated membranes for the filtration purposes, due to the over 99% rejection and excellent anti-fouling property.
A new micron-sized leaf- two-dimensional (2D) structured zeolitic imidazolate framework (ZIF-L) and nano-sized ZIF-8 were successfully synthesised in aqueous basic solution at room temperature with the same molar ratio of reagents (Zn+2/Hmim=8). Both ZIFs have attracted tremendous research interest due to their wide applications including absorption, separation, and catalysis. This phase and morphology change could be tailored by changing the concentration of base-type additive triethylamine (TEA). Also, this morphology change from 2D (ZIF-L) to three-dimensional (3D) (ZIF-8) was observed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), attenuated total reflectance infrared (ATR-IR) spectroscopy analysis, and surface area and pore textural properties using micromeritics gas adsorption analyser. The total amount of basic sites and carbon dioxide (CO2) desorption capacity were also calculated using CO2 temperature-programmed desorption (CO2-TPD) technique. Furthermore, TEA/total mole ratio of 0.0006 was proved as transition loading between two phases. Also, the particle and crystal size of samples decreased with increasing TEA/total mole ratio. The smallest ZIF-L and ZIF-8 particles obtained were 1.6μm and 177nm, respectively that showed excellent thermal stability. The basicity and uptakes of CO2 improved proportionally with TEA and followed this order: ZIF-8>ZIF-L. This study provides some new insights into zeolitic imidazolate framework by controlling crystal growth and morphology.
This present study aims to develop a visible-light driven photocatalytic dual layer hollow fiber (DLHF) membrane for photodegradation activity. Nitrogen-doped TiO2 DLHF membranes with different loadings of N-doped TiO2 were successfully fabricated via a single step co-extrusion method. The fabricated membranes were characterized for their morphology and properties. The incorporation of N-doped TiO2 into membrane matrix has shifted the absorption capability into visible light region with lowest band gap energy obtained was 2.63eV. The photocatalytic performance evaluations of the N-doped TiO2 DLHF reported 75% and 100% of Reactive Black 5 (RB5) removal were achieved after 360 min of visible and UV light illumination respectively. Altogether, N-doped TiO2 DLHF exhibits excellent photocatalytic degradation activity under visible and UV light irradiation, hence have a promising potential in removing RB5 and other organic contaminants for water treatment.
Palm oil fuel ash (POFA) is a waste material generated in large quantities by palm oil industry worldwide. To avoid the rising disposal costs and environmental issues, its positive and cost-effective utilization is the urgent requirement. An economical, single-step, and green chemical method has been adopted in this study to convert as received waste byproduct, POFA, from oil palm mills to produce precious "POFA derived graphene (PDG) nanosheets." The results analyses from different latest instrumental techniques like Raman, High-resolution transmission electron microscopy (HRTEM) and Atomic force microscopy (AFM) confirmed the successful synthesis of 1–8 layer PDG nanosheets with high yield (> 25 wt%). Parameters like temperature, the ratio of KOH: POFA, and reaction time were optimized to get the maximum yield and removal of all inorganic impurities up to < 0.5 wt.% in the final sample. Clean and smooth edges of PDG with hexagonal rings were also observed using HRTEM. In addition, the surface area of PDG was improved up to 1506.60 m2/g along with a high degree of porosity. Waste POFA ash as the cheapest carbon precursor used for the first time to synthesize economical graphene using a single-step, single chemical method. As a low cost carbon source, POFA, proves to be economical for scalable and sustainable production of PDG and presents an environment-friendly approach towards a green environment, besides promoting the circular economy concept.
In this work, a cerium-gadolinium oxide (CGO)/nickel (Ni)-CGO hollow fibre (HF) for micro-tubular solid oxide fuel cells (SOFCs), which consists of a fully gas-tight outer electrolyte layer supported on a porous inner composite anode layer, has been developed via a novel single-step co-extrusion/co-sintering technique, followed by an easy reduction process. After depositing a multi-layers cathode layer and applying current collectors on both anode and cathode, a micro-tubular SOFC is developed with the maximum power densities of 440–1000Wm−2 at 450–580°C. Efforts have been made in enhancing the performance of the cell by reducing the co-sintering temperature and improving the cathode layer and current collection from inner (anode) wall. The improved cell produces maximum power densities of 3400–6800Wm−2 at 550–600°C, almost fivefold higher than the previous cell. Further improvement has been carried out by reducing thickness of the electrolyte layer. Uniform and defect-free outer electrolyte layer as thin as 10μm can be achieved when the extrusion rate of the outer layer is controlled. The highest power output of 11,100Wm−2 is obtained for the cell of 10μm electrolyte layer at 600°C. This result further highlights the potential of co-extrusion technique in producing high quality dual-layer HF support for micro-tubular SOFC.
