This study aims to investigate the fabrication of anode/electrolyte dual-layer hollow fiber (DLHF) with improved electrolyte properties and reduced sintering temperature for intermediate temperature solid oxide fuel cells (IT-SOFCs) via a single-step phase inversion-based co-extrusion/co-sintering technique. The sintering properties of cerium gadolinium oxide (CGO) electrolyte were studied by comparing two approaches: i) using mixed particle size electrolyte; and (ii) adding lithium oxide as sintering additive in electrolyte. When comparing the maximum power density of MT-SOFC namely nickel (Ni)-CGO/CGO (unmodified), Ni-CGO/30%nano-70%micron CGO (first approach) and Ni-CGO/lithium (Li)-CGO (second approach); it was found that the Ni-CGO/30%nano-70%micron CGO cell performed the best. At 500 °C, the cell produced the highest maximum power density, which was 27.5 mWcm−2 as compared to Ni-CGO/Li-CGO cell (6 mWcm−2) and Ni-CGO/CGO cell (20 mWcm−2). The high maximum power density was attributed to the porous anode in Ni-CGO/30%nano-70%mic CGO dual layer hollow fiber which provided higher number of active reaction sites. Meanwhile, the dense electrolyte layer possessed pore filling caused by the introduction of 30% nano size CGO particles which reduced the direct flow of gases between the electrodes. The results have proven that incorporating nano size CGO and sintering additives accelerated the densification of ceria electrolyte, as well as presented an advanced electrolyte material for MT-SOFC.
Hollow fiber membrane (HFM) technology has received significant attention due to its broad range separation and purification applications in the industry. In the current study, we applied bibliometric analysis to evaluate the global research trends on key applications of HFMs by evaluating the global publication outputs. Results obtained from 5626 published articles (1970–2020) from the Scopus database were further manipulated using VOSviewer software through cartography analysis. The study emphasizes the performance of most influential annual publications covering mainstream journals, leading countries, institutions, leading authors and author’s keywords, as well as future research trends. The study found that 62% of the global HFM publications were contributed by China, USA, Singapore, Japan and Malaysia, followed by 77 other countries. This study will stimulate the researchers by showing the future-minded research directions when they select new research areas, particularly in those related to water treatment, biomedical and gas separation applications of HFM.
This study introduces an integrated system of direct contact membrane distillation (DCMD) and microalgae bioremediation for green removal of arsenic from the polluted river water. An inexpensive hydrophobic kaolin hollow fiber membrane (h-KHFM) was fabricated and used in the DCMD process for arsenic treatment on the polluted river water. The membrane demonstrates an excellent arsenic rejection of 100 % and a stable flux of 23.3 kg/m2h throughout the prolonged operation of 70 h. The performance of this membrane was compared with those of NF and RO; the results indicate superior performance of h-KHFM over the latter two processes in terms of permeate flux, arsenic rejection, as well as the performance flexibility and consistency at various pH conditions. The arsenic-rich retentate of the DCMD process is then bioremediated using Botryococcus sp. with an initial cell concentration of 1 × 106 cells/mL at the outdoor conditions. The findings show that Botryococcus sp. successfully grow in the retentate with a common microalgae growth pattern during the 20 days test period, which indicates the potential and feasibility of this integrated system for the arsenic retentate management. This study is pioneer and could provide an insight for the development of wastewater treatment technologies with zero waste discharge.
The addition of antibacterial material to hollow fiber membranes improves the membrane anti-biofouling characteristics. Antibacterial membranes were fabricated in this study to improve membrane function while also extending membrane lifetime. Neat polyvinylidene difluoride (PVDF) and PVDF hollow fiber membrane with the incorporation of antibacterial agent zinc oxide (ZnO) nanoparticles with various loading (2.5–7.5 wt.%) were fabricated by using dry/wet spinning method. The membrane structure, particle distribution, functional group, hydrophilicity, and pore size of each membrane were all assessed. The result shows that all ZnO/PVDF hollow fiber membranes have the asymmetric structure with even dispersion of ZnO nanoparticles throughout the membranes. The results showed that increased ZnO loadings considerably improved membrane hydrophilicity, and average pore size, in addition to good performance of pure water flux. Antibacterial testing shows that ZnO incorporated in the membrane matrix and membrane surfaces prevents bacteria that cause biofouling from adhering to the membrane. ZnO/PVDF membrane recorded excellent bovine serum albumin (BSA) rejection at 93.4% ± 0.4 with flux recovery rate at 70.9% ± 2.1. These results suggest that antibacterial ZnO/PVDF hollow fiber membranes are promising in relation to reducing biofouling for various water and wastewater treatment.
Incorporation of zinc oxide (ZnO) nanoparticles has played an important role on the improvement of unique membrane characterization and performance, most notably the hydrophilic modification of the membrane for higher pure water permeability. Additionally, the permeability of the membrane can be improved via introduction of braid support by reducing the thickness of the membrane separation layer. Moreover, the braided hollow fiber membrane (BHFM) is able to perform under higher pressure conditions compared to hollow fiber membranes. In this paper, hybrid polysulfone (PSf)/ZnO BHFMs were fabricated via phase inversion method. Hydrophilic 10 ± 1.8 nm polycrystalline ZnO nanoparticles synthesized via sol-gel method were incorporated on BHFM to improve the hydrophilicity and increase flux with constant rejection under high pressure and the effect of the ZnO loading on the membrane properties and performance were thoroughly studied. The fabricated BHFMs with 0.0, 0.5, 1.0 and 1.5 wt% of ZnO nanoparticles concentration were defined as BHFM1, BHFM2, BHFM3 and BHFM4 respectively. Scanning electron microscopy (SEM), contact angle, mechanical strength, flux performance, rejection with bovine serum albumin (BSA) and fouling of best performed membrane were conducted to achieve the target of this paper. The performance of these hybrid ZnO/PSf BHFMs were compared with neat PSf hollow fiber membrane (HFM) and previous studies. The findings from this research work shows that BHFM4 has the most desired properties for wastewater treatment application. The ZnO nanoparticles in BHFM4 have improved hydrophilicity from 108.79° to 71.02°, and thus BHFM4 has increased flux performance from 36.20 to 919.12 L/m2 h at 1.0 bar pressure and 193.48 to 1909.11 L/m2h at 4.0 bar pressure when compared with BHFM1. Constant BSA rejection rates (> 90%) were observed in all BHFMs. The improved hydrophilicity and pure flux performance with constant rejection rate in high pressure conditions illustrates the suitability of fabricated ZnO/PSf BHFMs in wastewater treatment applications.
The availability of clean and safe water for drinking is essential for human life and existence, which ideally should be suitable for consumption and not contain pathogenic microorganisms, or any contamination leading to pollution. Water treatment systems are integral to modern water purification processes, yet they are frequently challenged by biofouling. Biofouling continues to be a major obstacle in water treatment systems, resulting in decreased efficiency, higher energy usage, and increased operational expenses. Therefore, this study aimed to determine the bacteriological characteristics of drinking water by isolating and identifying bacterial strains from water samples contributing to biofouling. Samples were obtained from water treatment systems (WTS) at different locations in Malaysia. Selected isolates of unique bacterial strains were identified and assigned their accession numbers. Phylogenetic analysis revealed that these isolates were related to Bacillus cereus, Stenotrophomonas maltophilia , and Stenotrophomonas pavanii species, suggesting that deterioration in water quality from the source, human error, and technical failure may cause decline even if the most desirable treatment systems and disinfection procedures applied.
No abstract is provided for this article.
A two-dimensional zeolitic imidazolate framework with a leaf-like structure (ZIF-L) was synthesized in aqueous solution at room temperature with a molar ratio of Zn+2/Hmim (1: 8). Various triethylamine (TEA) concentrations were also used for the rapid production of ZIF-L. Different characterization techniques like X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) were performed to investigate the effect of base type additive triethylamine (TEA) on the crystal morphology, crystallinity, particle size and thermal stability of ZIF-L particles. From the experimental results, it was found that ZIF-L with a particle size of 5.3 μm was formed at TEA/total mole ratio of 0, but particle size was decreased when TEA/total mole ratio was increased up to 0.0003. The smallest ZIF-L particles obtained were 3 μm that showed excellent thermal stability. It can be concluded that this promising synthesis method with base-type additive would provide the new insights in the development of ZIFs materials in economical ways. © 2018, Malaysian Society of Analytical Sciences.
This chapter presents the development of membranes and membrane processes. The first part of this chapter addresses the fundamental principle of the membrane, including the definition of a membrane and its performance parameters, i.e., flux and selectivity. The membrane processes are influenced by their classifications, i.e., membrane's material type, separation regime, and membrane geometry. The examples of membrane processes according to a driving force such as transmembrane pressure (microfiltration, ultrafiltration, nanofiltration, reverse osmosis), concentration gradient (forward osmosis), and vapor partial pressure gradient (gas separation, membrane distillation) are included. The chapter ends with a discussion on the fouling issues in membrane applications.
