Two types of micro‐tubular hollow fiber SOFCs (MT‐HF‐SOFCs) were prepared using phase inversion and sintering; electrolyte‐supported, based on highly asymmetric Ce 0.9 Gd 0.1 O 1.95 (CGO) HFs and anode‐supported based on co‐extruded NiO‐CGO(CGO)/CGO HFs. Electroless plating was used to deposit Ni onto the inner surfaces of the electrolyte‐supported MT‐HF‐SOFCs to form Ni‐CGO anodes. LSCF‐CGO cathodes were deposited on the outer surface of both these MT‐HF‐SOFCs before their electrochemical performances were compared at similar operating conditions. The performance of the anode‐supported MT‐HF‐SOFCs which delivered ca. 480 mW cm –2 at 600 °C was superior to the electrolyte‐supported MT‐HF‐SOFCs which delivered ca. six times lower power. The contribution of ohmic and electrode polarization losses of both FCs was investigated using electrochemical impedance spectroscopy. The electrolyte‐supported MT‐HF‐SOFCs had significantly higher ohmic and electrode polarization ASR values; this has been attributed to the thicker electrolyte and the difficulties associated with forming quality anodes inside the small (<1 mm) lumen of the electrolyte tubes. Further development on co‐extruded anode‐supported MT‐HF‐SOFCs led to the fabrication of a thinner electrolyte layer and improved electrode microstructures which delivered a world leading 2,400 mW cm –2 . The newly made cell was investigated at different H 2 flow rates and the effect of fuel utilization on current densities was analyzed.
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An elevator is a machine that vertically transports people between different levels of a building. It is a typical confined space for contracting airborne diseases, such as coronavirus disease 2019 (COVID-19). The purpose of this study is to examine the dispersion of sneeze particles on the infection risk among passengers in a public elevator. A computational fluid dynamics (CFD) model representing an elevator was constructed. A CFD model was verified and validated based on the onsite measurement data. Renormalization Group (RNG) k-ε turbulence model developed based on the Eulerian tracking approach was used to simulate the airflow, while the discrete phase model (DPM) developed based on the Lagrangian tracking approach was used to simulate the particle dispersion during sneezing process. Simulation results show that particle concentration increased by 10 % and 2 % in case 2 (ceiling-mounted air supply diffuser and one low-level exhaust outlet) and case 3 (ceiling-mounted air supply diffuser and exhaust outlet), respectively. In contrast, case 4 shows that integration of the ceiling-mounted air supply diffuser with two-sided low-level exhaust outlet) minimized the particle adherence by 34 % on the manikin, from the time of 0 s – 5 s. Thus, ventilation strategy demonstrated in case 4 is sufficient to minimize particle dispersion and has a particle reduction rate of 0.006 kg/m3 ∙ s. Although case 1 (ceiling-mounted air supply diffuser and ceiling-mounted exhaust outlet) could prevent the particles trapped on the manikin from 0 s to 5 s, it does not perform well from the time of 5 s – 10 s.
A low-cost hydrophobic mullite hollow fibre membrane (Hy-MHFM) fabricated via phase inversion/sintering technique followed by fluoroalkyl silane (FAS) grafting is presented in this study. The prepared CHFMs were characterized before and after the grafting step using different characterization techniques. The pore size of the CHFM surface was also determined using ImageJ software. The desalination performance of the grafted membrane was evaluated in direct contact membrane distillation (DCMD) using synthetic seawater of varying salt concentrations for 2 h at various feedwater temperatures. The outcome of the evaluations showed declines in the permeate flux of the membrane at increasing feed concentration, as well as increased flux with increased feed temperature. The long-term stability of the membrane was achieved at time 20 h, feed temperature 60 °C, and permeate temperature 10 °C, the membrane achieved a salt rejection performance of about 99.99 % and a water flux value of 22.51 kg/ m2 h.
Siliconizing is one of the surface hardening treatments where silica diffuses into a metal substrate forming a thin layer coating material. This paper discussed on appropriate Design of Experiment (DOE) involved in performing siliconizing process onto mild steel substrate using Tronoh Silica Sand (TSS). Available knowledge on the siliconizing related parameters, material selection issue, temperature-time dependence and effects on the interface, structure and properties of siliconized substrate were critically reviewed. Critical parameters for the siliconizing process on mild steel substrate by using TSS were established. In order to enhance formation of the thin film coating, simultaneous TSS powder pack for siliconizing process was designed. Associated siliconizing mechanism in producing the thin film coating will be discussed and established.
In parallel to the rapid growth in economic and social activities, there has been an undesirable increase in environmental degradation due to the massively produced and disposed waste. The need to manage waste in a more innovative manner has become an urgent matter. In response to the call for circular economy, some solid wastes can offer plenty of opportunities to be reutilized as raw materials for the fabrication of functional, high-value products. In the context of solid waste-derived polymeric membrane development, this strategy can pave a way to reduce the consumption of conventional feedstock for the production of synthetic polymers and simultaneously to dampen the negative environmental impacts resulting from the improper management of these solid wastes. The review aims to offer a platform for overviewing the potentials of reutilizing solid waste in liquid separation membrane fabrication by covering the important aspects, including waste pretreatment and raw material extraction, membrane fabrication and characterizations, as well as the separation performance evaluation of the resultant membranes. Three major types of waste-derived polymeric raw materials, namely keratin, cellulose, and plastics, are discussed based on the waste origins, limitations in the waste processing, and their conversion into polymeric membranes. With the promising material properties and viability of processing facilities, recycling and reutilization of waste resources for membrane fabrication are deemed to be a promising strategy that can bring about huge benefits in multiple ways, especially to make a step closer to sustainable and green membrane production.
The main problem usually faced by commercial ceramic membranes in the treatment of produced water (PW) is low water flux even though ceramic membrane was well-known with their excellent mechanical, thermal, and chemical properties. In the process of minimizing the problem faced by commercial ceramic membranes, titanium dioxide (TiO2) nanocomposites, which synthesized via a sol-gel method, were deposited on the active layer of the hydrolysed bentonite membrane. This paper studied the influence of grafting time of TiO2 nanocomposite on the properties and performance of the coated bentonite membranes. Several characterizations, which are Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray Spectroscopy (EDX), contact angle, porosity, and average pore size, were applied to both pristine and coated bentonite membranes to compare the properties of the membranes. The deposition of TiO2 nanoparticles on the surface of the coated bentonite membranes was successfully confirmed by the characterization results. The pure water flux performance showed an increment from 262.29 L h−1 m−² bar−1 (pristine bentonite membrane) to 337.05 L h−1 m−² bar−1 (Ti-Ben 30) and 438.33 L h−1 m−² bar−1 (Ti-Ben 60) as the grafting time increase but when the grafting time reached 90 min (Ti-Ben 90), the pure water flux was decreased to 214.22 L h−1 m−² bar−1 which is lower than the pristine membrane. The oil rejection performance also revealed an increase in the oil rejection performance from 95 to 99%. These findings can be a good example to further studies and exploit the advantages of modified ceramic membranes in PW treatment.
The performance of ceramic, polymeric, and carbon membranes is commonly associated with the membrane surface and cross-sectional morphology. Thus, a proper characterization on the membrane structures is crucial for the development of commercial membranes. Therefore, in this chapter, three important morphological characterization techniques, which are scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX) spectroscopy will be discussed in detail. At the beginning part of the chapter, the operation principle of SEM, FESEM, and EDX will be established. Qualitative and quantitative findings that can be obtained from SEM, FESEM, and EDX will be addressed by giving several structure types that are normally found in ceramic, polymeric, and carbon membranes as examples. The chapter concludes by discussing the advantages and disadvantages of using SEM, FESEM, and EDX as main membrane analyses.
Membrane distillation (MD) has proved worthwhile in treatment of hypersaline feeds demonstrating near complete rejection of dissolved solutes without any effect on the process conditions. This makes it potential treatment option for hypersaline oilfield produced water (PW) with salinity level far greater than that of seawater. Polymeric membranes have recently garnered more attention than their ceramic counterparts in oily wastewater treatment owing to ease of synthesis and relative cost advantage. However, lower mechanical durability and the propensity for fouling of these membranes due to presence of low surface energy organics in PW ultimately affects MD performance in its treatment. Studies elucidating the mechanism of fouling between PW feed and membranes in MD is scarcely reported in the literature. Various fouling mitigation approaches have shown promise towards the realization of MD as a viable option for PW treatment. Hybridization of MD, use of (super)hydrophobic MD membranes with feed pre-treatment using other technologies and/or membrane post-cleaning, integrated MD systems and recently omniphobic and Janus modifications of MD membranes have all been reported for treatment of PW showing more promise towards achieving ultrapure-distillate treatment. In this article, the performance of these polymeric MD membranes used in PW treatment in comparison to the other conventional treatment options as well as advances in MD as a cost-effective alternative for beneficial re-use of PW is reviewed, highlighting the areas requiring further study for this line of research. Because MD is still largely energy inefficient, several efforts to realize it as an all-round competitive technology focusing on long-term stability, brine handling capacity and potentials for cost savings with alternative and rather sustainable energy source are also discussed.
This work presented the adsorptive hollow fibre ceramic membrane (HFCM) derived from clinoptilolite for effective removal of ammonia from water. The effect of different sintering temperature of HFCM (900–1150 °C) and pH of ammonia feed solution (pH 2 – pH 11) were examined. The membranes were fully characterized by the scanning electron microscopy (SEM), mechanical strength, water permeability, X-ray diffraction (XRD), X-ray fluorescence (XRF) and zeta potential to get the better understand of its physicochemical properties and ammonia adsorption mechanism relationship. The best fabricated HFCM was produced when sintered at 1050 °C with 54.20 MPa and 228.25 L/m2·h of mechanical strength and water permeability, respectively. The adsorption kinetics behavior showed that the adsorption process was best fitted to pseudo-second order kinetic model with 12.468 mg/g adsorption capacity. The morphology and negatively charged surface of the HFCM have significantly contributed to the high adsorption of the ammonia (96.67 %) from the feed solution. The maximum adsorption activities were achieved at pH 7 with 0.4 g/L HFCM within 120 min of residence time. The results indicated that the adsorptive HFCM have significant potential to be developed as simple, economical and effective remover for the ammoniacal wastewater treatment.
Discharging improperly treated oily-produced water (OPW) into the environment can have significant negative impacts on environmental sustainability. It can lead to pollution of water sources, damage to aquatic ecosystems and potential health hazards for individuals living in the affected areas. Ceramic hollow fiber membrane (CHFM) technology is one of the most effective OPW treatment methods for achieving high oil removal efficiency while maintaining membrane water permeability. In this study, low-cost calcium bentonite hollow fiber membranes (CaB-HFMs) were prepared from high-alumina calcium bentonite clay with various preparation parameters, including calcium bentonite content, sintering temperature, air gap distance and bore fluid rate. The prepared CaB-HFMs were then subjected to characterization using scanning electron microscopy (SEM), a three-point bending test, porosity, average pore size, hydraulic resistance and flux recovery ratio (FRR) analysis. Statistical analysis employing central composite design (CCD) assessed the interaction between the parameters and their effect on CaB-HFM water permeability and oil removal efficiency. Higher ceramic content and sintering temperature led to reduced porosity, smaller pore size and higher mechanical strength. In contrast, increasing the air gap distance and bore fluid rate exhibit different trends, resulting in higher porosity and pore size, along with weaker mechanical strength. Other than that, all of the CaB-HFMs displayed low hydraulic resistance (<0.01 m2 h.bar/L) and high FRR value (up to 95.2%). Based on CCD, optimal conditions for CaB-HFM were determined as follows: a calcium bentonite content of 50 wt.%, a sintering temperature of 1096 °C, an air gap distance of 5 cm and a bore fluid rate of 10 mL/min, with the desirability value of 0.937. Notably, the optimized CaB-HFMs demonstrated high oil removal efficiency of up to 99.7% with exceptional water permeability up to 535.2 L/m2.h.bar. The long-term permeation study also revealed it was capable of achieving a high average water permeation and a stable oil rejection performance of 522.15 L/m2.h.bar and 99.8%, respectively, due to their inherent hydrophilic and antifouling characteristics, making it practical for OPW treatment application.
