Publications

Surface Modification of Uio-66 on Hollow Fibre Membrane for Membrane Distillation

The hydrophobicity of metal–organic frameworks (MOFs) is critical in enhancing the separation process in membrane distillation. Herein, a new superhydrophobic University of Oslo 66 (UiO-66) MOFs was successfully constructed on the top of alumina hollow fibre (AHF) membrane for desalination purposes. The fabrication methodology of the membrane involved in situ growth of pure crystalline UiO-66 on top of AHF and post-synthetic modification by fluorosilane grafting. The resultant membrane was characterised to study the physicochemical properties of the pristine and modified membrane. A superhydrophobic UiO-66 with a contact angle of 154° and high liquid entry pressure was obtained by introducing a highly branched fluorocarbon chain while maintaining its crystallinity. As a result, the modified membrane achieved 14.95 L/m2∙h water flux and 99.9% NaCl rejection with low energy consumption in the direct contact membrane distillation process. Furthermore, the high surface energy contributed by UiO-66 is maximised to produce the maximum number of accessible sites for the grafting process. The synergistic effect of surface hydrophobicity and porous UiO-66 membrane in trapping water vapour shows great potential for desalination application.

Challenges and outlooks of photocatalytic membrane: System scaling up to pilot-scale

As a new field of materials development, photocatalytic membranes have been making progress by moving out from laboratory into real applications in water treatment and/or energy storage, making its presence influential in the body of literature. This chapter reviews the progress in semiconductor materials and their applications in water treatment and energy storage to mitigate their impacts on the environment. To bridge the existing research gaps in the body of literature, this chapter critically evaluates challenges in pilot studies of photocatalytic membrane. Challenges and perspectives of photocatalytic membrane are elaborated. It is anticipated that this would contribute to new understanding in the photocatalytic membrane on the relationship between materials’ structures and photoreaction performance that paves the way for a new direction of photocatalysis technology in pilot scales. Subsequently, the development of its next generation allows an efficient collection of the sunlight to catalyze chemical reactions, promoting solar energy utilization.

Cross-flow filtration of soluble minerals from organic acid using a supported polyvinyl alcohol (PVA) membrane

Phenol removal and hydrogen production from water: Silver nanoparticles decorated on polyaniline wrapped zinc oxide nanorods

The toxic and carcinogenic organic compounds discharge from industries, contaminate the natural reservoirs of water and air which eventually pose a global threat not only to the aquatic life but also to the humanity. Herein, ternary nanocomposites of silver-nanoparticle (AgNPs)-decorated on polyaniline (Pani)-wrapped zinc oxide nanorods (AgNPs@Pani/ZnO) were prepared via a facile approach. The nanocomposite degraded 97.91% phenol with an optimized dosage and concentration of H2O2. Moreover, the apparent rate constant for phenol degradation was 3.69 times higher than for pure ZnO nanorods. The hydrogen production from AgNPs@Pani/ZnO was 1.58 and 2.74 times higher than Pani/ZnO and ZnO, respectively. The enhanced phenol degradation and hydrogen production is attributed to the transfer of holes to the Pani, from which the electrons were transferred to the conduction band of ZnO and eventually to the conduction band of the AgNPs, where they accelerated the redox reactions for rapid photolysis of water and phenol. The concentration of the catalyst dosage affected the rate of phenol degradation. Further, response surface methodology was also applied in order to design 13 sets of random experiments in which the catalyst dosage and degradation time were varied to predict the phenol degradation.

WITHDRAWN: Synthesis and characterization of nano-zinc oxide: adsorption of acid blue 92 dye, isotherms, thermodynamics and kinetics

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

Effect of bisphenol a on the intestinal barrier: evidences from animal studies

Objective: Bisphenol A (BPA), a xenoestrogen chemical compound has wide range of harmful effects in the body. It is not clear whether BPA induced harmful effects in the body occurs through disrupting the intestinal barrier (IB). Objective of this review is to provide an up to date information about the effect of BPA on the IB. Materials and Methods: Literatures were searched in PubMed, Scopus and Google Scholar using the key words 'BPA' paired with 'intestinal barrier', 'intestinal barrier function', 'gut barrier function', 'gut' and 'intestinal permeability' from the year 1980 till early March 2018. Results: Only six animal studies were found. BPA was found to increase intestinal permeability, an indicator of compromised IB in one study. But it dose-dependently decreased intestinal permeability in ovariectomized animals. BPA has been reported to alter gut microbiota in five studies. Altered gut microbiota is proposed to be an important factor contributing to compromised IB. Conclusion: The effect of BPA on the IB varies on the species, gender, presence or absence of endogenous estrogen and maturity of the gut. However, five out of six studies are in agreement that BPA altered intestinal microbial flora.

Modeling, simulation, and theory of the mass transfer mechanism of photocatalytic membrane reactor

Advanced oxidation processes with photocatalysis can effectively destroy the organic pollutants in wastewater such as phenols, pesticides, pharmaceuticals, and dyes that have serious impacts on human health and aquatic life. Hence, many attempts have been made to construct photocatalytic reactors and test their performance, especially using titanium dioxide (TiO2), a semiconductor, as the photocatalyst. Among others, the photocatalytic membrane reactor (PMR) demonstrated its high efficiency due to its synergistic combination of the photocatalytic reaction and membrane separation. Thus, PMRs of many different configurations have been constructed and their performances were tested experimentally in the laboratory. Nevertheless, a detailed reactor simulation rarely can be found, despite PMR’s special feature of light intensity attenuation where the light keeps traveling in the reactor. To fill this knowledge gap, an attempt is made in this work to simulate the performance of phenol removal from aqueous solution using different types of photocatalytic reactors and using only separation by a nanofiltration membrane. The process simulation is made for the following three cases: 1. Batch slurry-type photochemical reactor with TiO2 nanoparticles and ultraviolet (UV) irradiation; 2. Semibatch PMR system with TiO2 nanoparticles and with UV irradiation; 3. Semibatch system without TiO2 nanoparticles and without UV irradiation; 4. The comparison of the above three cases is highlighted in the end.

Antifouling properties of hollow fibre alumina membrane incorporated with graphene oxide frameworks

Membrane fouling takes place due to foulant adsorption on the membrane surface, which leads to the reduction of membrane performance and its durability in application. Hollow fibre alumina membrane incorporated with graphene oxide frameworks (GOFs) could avoid this phenomenon by forming GOFs/alumina composite membranes. Field emission scanning electron microscope (FESEM) structure shows that these composite membranes successfully developed GO and GOFs films with a thickness in the range of ∼234 to ∼635 nm. Meanwhile, the atomic force microscope (AFM) images show that their average roughness (Ra) becomes smoother, in the range of 30–46 nm, which would enhance antifouling properties. GOF(BDA)/alumina had highest proteins separation for all proteins, which are 98.40, 98.32, 95.82 and 95.65 % for bovine serum albumin (BSA), egg albumin (EA), trypsin (TR) and lysozyme (LSZ), respectively. Furthermore, this composite membrane had high flux recovery rate (FRR) of 94.86 % and 95.21 % at low total fouling ratio (Rt) of 21.70 % and 30.22 % for long-term filtration of LSZ protein and humic acid (HA) solute, respectively. Thus, this composite membrane showed better antifouling properties in proteins separation and HA removal application due to formation GOFs film.

Treatment of oily wastewater using photocatalytic membrane reactors: A critical review

Oily wastewater is generated from various sources such as oil/gas exploration (produced water), oil refining, pharmaceutical, food industries, and household waste. Toxins in oily wastewater often percolate into drinking water, seawater, and groundwater. This becomes a source of environmental and public health concern. Due to its hazardous nature, the discharge of oily wastewater into the environment is strictly regulated. This work critically reviews progress in photocatalytic membrane reactor (PMR) for oily wastewater treatment, regulations on allowable oil discharge, various factors that affect PMR performance, and its self-cleaning and anti-fouling properties in oily wastewater treatment. Their removal performance for stabilized oil emulsion and trace oil contaminants is highlighted. This work also evaluates trends of integrated techniques, utilization of functional materials, PMR scale-up and the outlook of PMR. It was evident from 226 published articles (1976–2022) that oily waste water contamination has been a source of concern and PMR which integrates both membrane filtration and photodegradation processes, has emerged as a promising technology for oily wastewater treament, simultaneously degrading oil emulsion and undertaking separation. The PMRs attained over 96% oil rejection. Both the UV and visible light aided the degradation of oil using the PMR. High membrane surface area, provides additional sites for the photocatalyst to occupy, contributing to an efficient degradation. Concludingly, PMRs can exhibit a high flux of recovery ratio after several filtration cycles under UV/Vis irradiation, and with proper design and fabrication methods, the membranes can do self-cleaning and be re-used for several cycles of filtration with high efficiency.

Fabrication of low-cost ceramic hollow fiber membranes from aluminium dross waste for water purification

In this study, alumina-spinel composite hollow fibre membranes were fabricated from abundantly available aluminium dross waste, which can be commonly obtained from aluminium-producing factory. The hollow fibre membranes were successfully fabricated by using a combine phase inversion method and sintering technique. The effects of sintering temperatures on morphology, mechanical strength, and permeability of the hollow fibre membranes were systematically investigated. X-ray fluorescence (XRF) was used to analyze the composition of the aluminium dross waste, while x-ray diffraction analysis (XRD) were further studied to characterize the major crystalline phase of the sintered hollow fibre membranes. An increase in sintering temperatures resulted in densification of hollow fibre membrane, consequently induced the flux reduction. The presence of spinel in microstructural of hollow fibre assisted in decreasing the sintering temperature. As comparison to pure alumina membrane counterparts, this alternative ceramic hollow fibre membrane exhibited a comparable mechanical strength of 78.3-155.1 MPa with lower sintering temperatures ranging from 1350 ˚C to 1400 ˚C at ceramic loading of 40%.

Recent progress, bottlenecks, improvement strategies and the way forward of membrane distillation technology for arsenic removal from water: A review

Arsenic (As) is a common aquatic pollutant that enters the environment from anthropogenic sources and causes serious public health issues. Various conventional techniques have been applied for As removal from drinking water. However, those conventional techniques could not meet the requirement of the As discharge standard of <10 mg/L in drinking water set by the World Health Organization (WHO). To deal with this bottleneck, membrane distillation (MD) offers a complete As removal from an aqueous solution due to its higher rejection rate with less energy consumption than thermal techniques that require high thermal energy. This article reviews the recent progress of MD configurations, membrane modules, and membrane materials employed for As removal. This work also uncovers the technological solutions of MD in tackling a variety of bottlenecks in removing As from aqueous solutions. This includes integrating MD with alternative energy sources and/or forward osmosis (FO) to incorporate its hybrid systems with less energy consumption or a high separation rate. Limitations, challenges, and opportunities of MD systems for As removal were highlighted with a technological solution to these bottlenecks. The MD systems can effectively remove As (III) and As (V) with 100 % As rejection using hydrophobic ceramic and polymeric membranes. Overall, MD could play a role in helping the water industry meet the United Nations' Sustainable Development Goals (SDGs), such as clean water, affordable energy, and climate change mitigation.

Metal Organic Framework in Membrane Separation for Wastewater Treatment: Potential and Way Forward

No abstract is provided for this article.

Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes

Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm−2 h−1 to 95.36Lm−2 h−1 upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application.

Effect of sintering temperature on functional properties of mullite-kaolinite and stainless steel composed hollow fibre membrane for oil-in-water emulsion separation

Background The commercialization of mullite-kaolinite hollow fibre HFMs is still obstructed due to the weakness of their mechanical strength. Methods This study investigates the effect of different sintering temperatures (i.e., 1350, 1400, 1450 and 1500 °C) on the mechanical strength and other functional properties of ceramic HFMs composed of mullite-kaolinite and stainless steel (SS). The membranes were tested and evaluated through an oil-in-water separation process using three oily emulsions (i.e. 1000, 1500, and 2000 ppm) in a filtration system for 120 min. Significant findings The results showed a successful preparation for mullite-SS HFMs with asymmetrical and sponge-like structures. Increased sintering temperatures from 1350 to 1500 °C significantly integrated mullite and SS particles, and forming robust bonds improved the mechanical strength. Amongst all mullite-SS HFMs, the membrane sintered at 1450 °C was the most suitable for oil-in-water separation due to its optimum properties compared to other mullite-SS HFMs. As compared to mullite HFMs counterparts, the mullite-SS HFM at 1450 °C exhibited higher mechanical strength, oil rejection rate and permeate flux of 106.4 MPa, 99.05% and 345 L/m2.h, respectively. In addition, it showed higher mechanical stability and separation performance for a longer filtration time of 120 min than other CHFMs prepared from different low-cost materials reported in previous works. This membrane offers an advantage in mechanical strength, water flux, and rejection performance, making it suitable for various water treatment applications.

Co-extruded dual-layer hollow fiber with different electrolyte structure for a high temperature micro-tubular solid oxide fuel cell

In this study, the phase inversion-based co-extrusion method was employed to fabricate a structural-improved electrolyte/anode dual-layer hollow fiber (HF) precursor, which was then co-sintered at 1450 °C. The electrolyte structures were thoroughly investigated by varying the loading of electrolyte material (i.e. Yttria-stabilized zirconia, YSZ) with differing particle sizes (i.e. micron, sub-micron, and nano-sized) during suspension preparation. The results showed that the most promising electrolyte layer with thin, dense, gas-tight, and defect-free properties was obtained by mixing 70% submicron-YSZ and 30% nano-YSZ in electrolyte suspension (E-0.7sub0.3nano). This electrolyte formulation co-extruded with a thick nickel-oxide-YSZ (NiO-YSZ) anode layer yielded the highest bending strength of 85 MPa, providing major mechanical strength to the HF. Besides that, the nitrogen permeability value at 2.87 × 10−6 mol m−2 s−1 Pa−1 suggested that the electrolyte was gas-tight, preventing fuel and oxidant transport. The fiber was then reduced to nickel (Ni)-cermet anode. It was developed to be a complete micro-tubular solid oxide fuel cell (MT-SOFC) by depositing the lanthanum strontium cobalt ferrite (LSCF)/YSZ cathode via brush painting on the dual-layer HF. The cell was fed with hydrogen gas and yielded an open-circuit voltage (OCV) as high as 1.06 V with maximum power density of 0.243 W cm−2, at 875 °C. Based on this test, it was found that the electrolyte structural-modified dual-layer hollow fiber-based MT-SOFC using mixed particle sizes may result in a promising OCV. However, the relatively low value for power density may be due to a less porous anode; thus, improvements in the anode's structure are required in future research.

Synthesis of polyethersulfone membranes with the addition of silver nitrate for water filter applications

Clean water is a fundamental need in human life. Clean water is becoming limited due to increasing population growth and pollution. On the other hand, environmental damage due to domestic and factory liquid waste disposal is also a factor that makes the scarcity of clean water sources. Water purification is essential to maintain the sustainability of human life. Polyethersulfone (PES) polymer-based membrane technology is one of the approaches used to overcome this problem. To be effective as a water filtration membrane, PES is added with Silver Nitrate (AgNO3) for antibacterial purposes and to reduce the fouling effect. This study looks at different concentrations of silver nitrate in increasing the flux of PES-based membranes. The method used was electric field treatment to modify the membrane surface. SEM results show that PES/AgN03 membranes PA1, PA2, and PA3 produce porous, smooth, thin, densely arranged structures with typical finger-like pore sub-structures that correspond to PES characteristics. While testing mechanical properties resulted in the membrane PA1 having a strength of 5.74206 MPa, PA2 with a tensile strength of 3.81310 MPa, and PA3 having a tensile strength of 3.07480 MPa showing that the increasing AgNo3 decreased the tensile strength of the membrane. The wettability of membranes ranging between 135.2°, 137.6°, and 140.4° implies that due to their hydrophilicity, PES/AgNo3 membranes absorb more contaminants and impurity particles. CWP testing showed that the membrane flux ranged from 3.88797 L.m-2.h-1.bar-1, 3.69523 L.m-2.h-1.bar-1, and 3.01345 L.m-2.h-1.bar-1. Based on the test results, PES membrane added with silver nitrate with accurate composition has potential in water filtration applications

Efficient removal of partially hydrolysed polyacrylamide in polymer-flooding produced water using photocatalytic graphitic carbon nitride nanofibres

In this work, graphitic carbon nitride (GCN) photocatalyst-incorporated polyacrylonitrile (PAN) nanofibres (GCN/PAN nanofibres) were successfully prepared using electrospinning technique. The physicochemical properties of the fabricated GCN/PAN nanofibres were analysed using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), elemental analyser, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV–vis–NIR spectroscopy. The photocatalytic degradation by GCN/PAN nanofibres exhibited 90.2% photodegradation of partially hydrolysed polyacrylonitrile (HPAM) after 180 min under UV light irradiation in a suspension photocatalytic reactor. The results suggest that the photodegradation of HPAM contaminant by GCN/PAN nanofibres was due to the synergetic effects of HPAM adsorption by the PAN nanofibres and HPAM photodegradation by the GCN. This study provides an insight into the removal of HPAM from polymer-flooding produced water (PFPW) through photocatalytic degradation of liquid-permeable self-supporting nanofibre mats as a potentially promising material to be used in industrial applications.

Development of Free-Standing Titanium Dioxide Hollow Nanofibers Photocatalyst with Enhanced Recyclability

Titanium dioxide hollow nanofibers (THN) are excellent photocatalysts for the photodegradation of Bisphenol A (BPA) due to their extensive surface area and good optical properties. A template synthesis technique is typically employed to produce titanium dioxide hollow nanofibers. This process, however, involves a calcination procedure at high temperatures that yields powder-form photocatalysts that require post-recovery treatment before recycling. Meanwhile, the immobilization of photocatalysts on/into a membrane has been reported to reduce the active surface area. Novel free-standing TiO