Due to the rapid growth of modern life nowadays, water resources become the most important needs toward ecosystem. Access to the safe and clean water has become the major obstacles in the society. The urban rapid development of buildings, industries and agriculture has caused water pollution by various contaminants that are incompletely treat and removed before discharging it into the water streams. Efficient wastewater treatment system is really important for removing various pollutants in order to maintain a healthy and safe environment. Wastewater treatment has also become an important goal for the protection of human and animals’ health. In this study, wastewater treatment method specifically the use of membrane technology through modification of polyvinylidene fluoride (PVDF) membrane in removal of various contaminants is reviewed. The use of outstanding modified PVDF membrane in removal of heavy metal, dyes, contaminants of emerging concern and oil emulsion has been discussed in many previous studies. Finally, the use of membrane as the key technology in wastewater treatment provides potential and beneficial solution for water industries in purification of water in the future.
Membrane distillation (MD) is a hybrid of thermal and membrane processes that utilizes a hydrophobic membrane to separate volatile solutes from feed solution at fairly high temperatures. This process is known to be capable of achieving excellent separation efficiency at low pressure. However, the commercialization of MD has been hampered by low flux performance. To date, different membrane designs have been introduced to ameliorate the flux performance of MD membranes. This article aims to review four key membrane innovations that could enhance the flux performance of MD including the phase inversion-based asymmetric membrane structures, hydrophobic/hydrophilic membrane structures, electrospun nanofibrous membranes (ENMs), and the incorporation of carbon materials. The state-of-the-art of these developments and their recent research trends have been extensively discussed. An update-to-date review of high-flux MD membrane innovations have also been provided. The economic potential of MD membranes is addressed in the final part of this article.
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.
In this study, Ni–CGO anodes hollow fibre with controlled asymmetric structures, i.e. adjustable ratios between thickness of the outer sponge-like and the inner finger-like layers, have been developed for intermediate temperature micro-tubular solid oxide fuel cells (SOFCs), using a combined phase inversion/sintering technique followed by a post-reduction process. The control over the asymmetric structure is achieved by employing ethanol as a non-solvent to adjust the initial properties of the spinning suspensions, which affects the phase inversion process and results in a series of asymmetric structures from very thin sponge-like layer supported on considerably thicker finger-like layer (0wt.% ethanol), to the one consisting of nearly a full sponge-like structure (35wt.% ethanol). The characteristic of the anode hollow fibre is found significantly affected by such changes in asymmetric structures. For example, the experimental results show that the mechanical strength and electrical conductivity increase up to 241MPa and 11,246Scm−1, respectively, but with high resistance for the fuel transport for a full sponge-like structure of the fibres prepared with 35wt.% of ethanol.
Fabrication of polycarbonate polymer optical fibre core using various extrusion temperatures and drawing speeds was experimentally demonstrated. Extrusion temperature had a significant effect on fibre performance. The optimum temperature in which fibre exhibited the best thermal and optical properties was 290 °C, however, at higher temperature due to degradation of the polymer the fibre lost its quality for light propagating. The mechanical properties of the fibre were influenced by its diameter. Increasing the drawing speed to 20 rpm reduced the diameter of the fibre to ~341 μm and Young’s modulus and tensile strength increased to 2.12 and 119.06 MPa, respectively. Our comprehensive investigation of polycarbonate polymer core features may propose a novel method for precise fabrication of polymer optical fibre suitable in optical industries.
This study describes the preparation of green ceramic hollow fibre membranes derived from metakaolin (MK) and corn cob ash waste (CCA) as membrane support for water filtration and oil-water separation using phase inversion and sintering techniques. Pristine MK membrane is closely associated with its brittleness property and possesses low strength. In this study, a proportion of MK was substituted with corn cob ash (CCA), an agricultural waste by-product as pore forming agent material and sintering aid in preparing MK–corn cob ash hollow fibre membrane (h-MCa) for enhanced permeation and strength properties. MK:CCA ratio loadings at 35 wt % of powder were adjusted for fibres A-100:0, B-75:25, C-50:50, D-25:75, and E−0:100. The SEM image supported by EDSA revealed the high agglomeration of CCA–SiO2 particles coated with KCl, as the XRD analysis displayed mainly the crystal phases of KCl. The high content of CCA–KCl revealed its significant effect as body shaping and body forming in preform controlling the h-MCa suspension matrix structure. The viscosity of the suspension correlated with the dissolution of KCl in NMP suspension and MK–CCA fraction ratio to effectively function as a green enhancer and porogen towards the particle arrangement in the ceramic membrane matrix. The feasibility study showed that fibre B exhibited higher permeability (1359.93 L/m2h), oil/water removal efficiency (74.73%), and CCA maintained superior mechanical strength (41.61 MPa) at a significant low sintering temperature of 1200 °C, as the CCA possessed a great fluxing agent in the sintered membrane. Therefore, this study proved that green MK–CCA was effective, sustainable, and ecologically environmentally friendly for ceramic membrane support applications.
The DMFC commercialization and practical operations are still confronts several major challenges particularly in high cost, maintaining long-term stability and durability, deteriorating of anode electrocatalyst performance as well as the sluggish methanol oxidation kinetic reaction occurred at the anode due to the poisoning effect of the platinum (Pt) electrocatalyst. The selection of the appropriate anode electrocatalysts for methanol oxidation reaction (MOR) is quite limited, only the anode electrocatalysts that can enhance the MOR activity and minimize the poisoning effect by the carbonaceous intermediate species-like carbon monoxide (CO) can be considered to improve the DMFC performance. The strategy of coupling or alloying Pt with other noble or non-noble metals can prevent such mentioned problems above and able to upgrade the ability of anti-CO poisoning through the modification of the CO adsorption site. In general, the highly accessible of electrocatalytic active sites and dispersed are very important for the superior Pt-based alloy electrocatalyst performance through the utilization of the electrocatalyst support with the large specific surface areas. However, the commonly used carbon supporting materials for monometallic Pt and bimetallic Pt-based alloy electrocatalysts suffer from severe corrosion due to the electrooxidation on the surface under acidic condition at high operating voltages for prolonged times which resulting the dissolution, aggregation, migration and detachment of Pt NPs leading to a serious problem of stability. The most efficient strategy to overcome the limitations described above is through the embedding the monometallic Pt and bimetallic Pt-based alloy electrocatalyst on the metal oxides. This proposed strategy provides a medium to anchor the Pt-based alloy electrocatalyst securely onto the carbonaceous support materials and the electrocatalytic performance of the electrocatalyst also have been proven to be significantly improved in oxidizing the methanol in DMFC. Nevertheless, studies on the possible combination of both supported Pt-based alloy electrocatalyst embedding metal oxides as the potential anode nanocomposite electrocatalyst with careful design still lacking and remains important challenge.
No abstract is provided for this article.
