Publications

Incorporation of N-doped TiO2 into dual layer hollow fiber (DLHF) membrane for visible light-driven photocatalytic removal of reactive black 5

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.

Performance Analysis of Blended Membranes of Cellulose Acetate with Variable Degree of Acetylation for CO2/CH4 Separation

The separation and capture of CO2 have become an urgent and important agenda because of the CO2-induced global warming and the requirement of industrial products. Membrane-based technologies have proven to be a promising alternative for CO2 separations. To make the gas-separation membrane process more competitive, productive membrane with high gas permeability and high selectivity is crucial. Herein, we developed new cellulose triacetate (CTA) and cellulose diacetate (CDA) blended membranes for CO2 separations. The CTA and CDA blends were chosen because they have similar chemical structures, good separation performance, and its economical and green nature. The best position in Robeson’s upper bound curve at 5 bar was obtained with the membrane containing 80 wt.% CTA and 20 wt.% CDA, which shows the CO2 permeability of 17.32 barrer and CO2/CH4 selectivity of 18.55. The membrane exhibits 98% enhancement in CO2/CH4 selectivity compared to neat membrane with only a slight reduction in CO2 permeability. The optimal membrane displays a plasticization pressure of 10.48 bar. The newly developed blended membranes show great potential for CO2 separations in the natural gas industry.

Research and Development Journey and Future Trends of Hollow Fiber Membranes for Purification Applications (1970–2020): A Bibliometric Analysis

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.

Antifouling polysulfone membranes blended with green SiO2 from rice husk ash (RHA) for humic acid separation

This study investigated the effects of silica prepared from rice husk (RHA) as an antifouling additive in the polysulfone (PSf) membrane. The ultrafiltration mixed matrix PSf/rice husk silica (RHS) flat-sheet membrane was prepared via phase inversion technique at different percentages of silica concentration. The characterization and performance test were conducted on the prepared membrane. The thermal stability of the membrane was observed by using thermogravimetric analysis (TGA). The cross section area and particles distribution of additive were carried out by using the scanning electron microscope (SEM) while the surface morphology was investigated via field emission scanning electron microscope (FESEM). The surface roughness and hydrophilicity were also determined by using atomic force microscopy (AFM) and contact angle measurement respectively. The performance of the membrane was evaluated in terms of pure water flux (PWF), humic acid rejection and antifouling properties. The results of SEM, FESEM and AFM revealed that the incorporating of RHS improved the microstructure of the membrane especially at top layer and sub layer. The results also demonstrated that the mean pore size decreased and the hyrophilicity increased with an increase of RHS particles in PSf membrane. The performance result was found that the addition of RHS in the PSf membrane significantly improved the PWF, rejection and antifouling properties. The results indicated that the addition of 4g RHS give the highest flux at 300.50L/m2 h (LMH) and excellent mitigating fouling. The highest rejection was found at 3g of RHS with a value of 98% for ultraviolet light (UV254) and 96% for Dissolved Organic Carbon (DOC).

Design and performance study of hybrid photocatalytic reactor-PVDF/MWCNT nanocomposite membrane system for treatment of petroleum refinery wastewater

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.

TREATMENT OF HYPERBILIRUBINEMIA: VARIOUS TECHNOLOGIES AND CHALLENGES

Bilirubin removal from blood and curing patients suffering from hyperbilirubinemia by surgery, medication or interventional therapies was common, previously. Alternative bilirubin separation techniques such as plasma exchange, affinity chromatography and etc., are efficient in reducing high levels of bilirubin with fewer side effects. However, due to the various causes and complications associated with hyperbilirubinemia, different strategies are needed for the treatment. This article offers a historical overview on these strategies, challenges and also outlines the technological advantages and disadvantages associated with various bilirubin removal techniques.

Integrated green membrane distillation-microalgae bioremediation for arsenic removal from Pengorak River Kuantan, Malaysia

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.

MoS2-TiO2 coated PVDF-based hollow fiber membranes for permeate flux enhancement in membrane distillation

In this work, the surface of a PVDF-based hollow fiber membrane was modified by coating MoS2-TiO2 to improve the performance of membrane distillation (MD). The MoS2-TiO2 was first synthesized at different ratios using a one-step hydrothermal process. Then, the PVDF-based hollow fiber membrane was spun at various air gaps and PES was also added as an additive. As 5M5T (50 wt% MoS2 and 50 wt% TiO2) possessed better physicochemical properties and narrow band gap, the 5M5T was mixed with trichloro(octadecyl)silane in (OTS) at various loading to form a dip-coating solution. The PP20 membrane (PVDF + PES) spun at a 20 cm air gap was used as a support for MD due to its high porosity and low membrane thickness. It was observed that the contact angle of the MoS2-TiO2/PP20 membrane increased significantly to 136.8 ± 2.33° when the membrane was coated with 0.2% of 5M5T MoS2-TiO2. The MD performances were investigated via an in-house MD system. The results revealed that the performances of MoS2-TiO2/PP20 membranes were much higher than previously reported membranes due to their enhanced hydrophobicity and porosity properties. It was observed that a higher operating temperature could elevate the permeate flux up to 23.3 kg·m−2·h−1, but less than 0.1% changes in the rejection rate. The results obtained in this work suggest that the MoS2-TiO2 coated on the PVDF-based membrane can overcomes the typical permeability/rejection rate trade-off effect, which can play a significant role in enhancing MD performances.

Effects of TiO2 phase and nanostructures as photoanode on the performance of dye-sensitized solar cells

No abstract is provided for this article.

Evaluation of a photometric method for retardance measurement of a quarterwave phase plate

It is shown that a simple photometric method provides high accurate result for the wavelength at which the retardance of a phase plate assumes the value π/2. Result for a quartz quarterwave plate is presented and is found to be in high agreement with the result obtained by the modified Senarmont arrangement for simultaneous retardance measurement of two phase plates.

Performance of Polymer Electrolyte Membrane for Direct Methanol Fuel Cell Application: Perspective on Morphological Structure

Membrane morphology plays a great role in determining the performance of polymer electrolyte membranes (PEMs), especially for direct methanol fuel cell (DMFC) applications. Membrane morphology can be divided into two types, which are dense and porous structures. Membrane fabrication methods have different configurations, including dense, thin and thick, layered, sandwiched and pore-filling membranes. All these types of membranes possess the same densely packed structural morphology, which limits the transportation of protons, even at a low methanol crossover. This paper summarizes our work on the development of PEMs with various structures and architecture that can affect the membrane’s performance, in terms of microstructures and morphologies, for potential applications in DMFCs. An understanding of the transport behavior of protons and methanol within the pores’ limits could give some perspective in the delivery of new porous electrolyte membranes for DMFC applications.

Graphene Oxide Incorporated Psu/Spekekk for Potential Application as Proton Exchange Membranes in Fuel Cells

This study aims to develop a new PEM for fuel cell applications consisting of PSU/SPEKEKK/SGO membrane with improved physiochemical properties to surmount the low power generation of Nafion. The DFT calculations using NCI plots show that there are network interactions between PSU and SPEKEKK, established by the hydrogen bonding and vdW interactions. SGO was incorporated into the as-prepared PSU/SPEKEKK membrane. A solution casting method was employed to fabricate SGO-loaded composite membranes in the range of 0.1% to 1.5% (wt. %). Structural evidence of the SGO and composite membranes was characterized by ATR-FTIR and FESEM, respectively. Adding SGO to PSU/SPEKEKK shows a significant increase in proton conductivity due to the presence of more protonated sites (SO3H) and water-mediated interactions for proton conduction. Of all the compositions considered, PSU/SPEKEKK/SGO-0.6-1.5% loading was found to have the highest proton conductivity, 0.03Scm-1. Although adding SGO to the composite membrane has reduced water absorption, the hydrophilic oxygenated functional groups in SGO, the bound water molecules, and the increased –SO3H groups have successfully improved the proton conductivity. The findings reveal that all composite membranes showed excellent oxidative stabilities for 32 hours in Fenton’s reagent. To summarize, all composite membranes fabricated in this study showed acceptable water uptake and swelling ratio, high oxidation, excellent thermal stability, and high proton conductivity.

Source, occurrence, distribution, fate, and implications of microplastic pollutants in freshwater on environment: A critical review and way forward

The generation of microplastics (MPs) has increased recently and become an emerging issue globally. Due to their long-term durability and capability of traveling between different habitats in air, water, and soil, MPs presence in freshwater ecosystem threatens the environment with respect to its quality, biotic life, and sustainability. Although many previous works have been undertaken on the MPs pollution in the marine system recently, none of the study has covered the scope of MPs pollution in the freshwater. To consolidate scattered knowledge in the literature body into one place, this work identifies the sources, fate, occurrence, transport pathways, and distribution of MPs pollution in the aquatic system with respect to their impacts on biotic life, degradation, and detection techniques. This article also discusses the environmental implications of MPs pollution in the freshwater ecosystems. Certain techniques for identifying MPs and their limitations in applications are presented. Through a literature survey of over 276 published articles (2000–2023), this study presents an overview of solutions to the MP pollution, while identifying research gaps in the body of knowledge for further work. It is conclusive from this review that the MPs exist in the freshwater due to an improper littering of plastic waste and its degradation into smaller particles. Approximately 15–51 trillion MP particles have accumulated in the oceans with their weight ranging between 93,000 and 236,000 metric ton (Mt), while about 19–23 Mt of plastic waste was released into rivers in 2016, which was projected to increase up to 53 Mt by 2030. A subsequent degradation of MPs in the aquatic environment results in the generation of NPs with size ranging from 1 to 1000 nm. It is expected that this work facilitates stakeholders to understand the multi-aspects of MPs pollution in the freshwater and recommends policy actions to implement sustainable solutions to this environmental problem.

Self-Cleaning and Anti-Fouling Omniphobic Ceramic Surface Synthesized from Hydrothermal and Fluorination Methods

In this work, we develop omniphobic ceramic surfaces possessing flower-like re-entrant structures that can resist surface wetting against not only water but also low surface tension liquids. This can benefit a wide range of potential applications in many ceramic fields. The synergistic strategy to fabricate omniphobic ceramic surfaces relies on the construction of re-entrant structures through pre-roughening. Using TiO 2 microflowers obtained via a hydrothermal approach and post-fluorinating via surface grafting with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (C8) resulted in better metastable Cassie-Baxter state as water droplet roll-off the surface compared to non-textured ceramic surfaces where the water droplet pinned. The C8-TiO 2 -modified ceramic surface (C8/TiO 2 -CRM) can still maintain a high contact angle against palm oil (above nearly 120 o ) within 40 minutes of exposure, whereas the un-textured ceramic surface is fully wetted. In addition, the C8/TiO 2 -CRM has excellent self-cleaning, anti-fouling and “gasphilic” properties. In this work, the robustness of the composite interface from secondary re-entrant structures resulting from TiO 2 micro-flowers is further explained.

Innovative chicken eggshells-derived bio-hydroxyapatite/mullite ceramic hollow fiber adsorptive membrane for efficient cadmium removal

Novel ceramic hollow fibre membranes contactor derived from kaolin and zirconia for ammonia removal and recovery from synthetic ammonia

The adverse effects of ammonia found in wastewater streams lead to the development of advanced water treatment technology, i.e. membrane contactor (MC). In this study, single layer hollow fibre membrane (SLZK) and dual layer hollow fibre membrane (DLZK) were prepared from zirconia and kaolin and modified into hydrophobic membrane through simple grafting process via fluoroalkylsilane (FAS) agent. The properties of membranes such as morphology, surface roughness, mechanical strength, wettability and liquid entry pressure were analysed through scanning electron microscopy (SEM), atomic force microscopy (AFM), 3-point bending strength, contact angle and LEPw setup. Finally, the performance of the membranes was also investigated towards ammonia removal via membrane contactor system. Our findings showed that hydrophobicity properties significantly improved for both SLZK and DLZK membranes after grafting modification process as indicated by the increase of contact angle value from 5° and 1° to 132.7° and ~180.0° respectively. Based on the morphological analysis, the surface of DLZK showed more porous structure as compared to the SLZK. In addition, DLZK also displayed the highest mechanical strength and contact angle reading of 125 MPa and ~180° respectively. This suggests that the DLZK showed an excellent membrane contactor performance with highest value of mass transfer coefficient (3.77 x 10-5 ms-1) and almost complete removal of ammonia removal (91%). Overall, these results implied that dual layer ceramic membrane developed from kaolin and zirconia could provide the basis for the development of alternative ceramic membrane with excellent properties for membrane contactor system.

The role of solid, liquid and gaseous hydrocarbon precursors on chemical vapor deposition grown carbon nanomaterials' growth temperature

Chemical Vapor Deposition (CVD) has been hugely favored when producing high-quality carbon nanomaterials and repeatable output. Despite being hugely favored, CVD typically requires a high temperature of above 1000 °C, which becomes the downside of this method. It requires a high cost and complicated processing environment, which explains the urgent need for low-temperature processing. Molecule properties of hydrocarbon precursors are believed to have played an essential role in CVD synthesis as it can affect the growth temperature, yield, crystallinity properties and indirectly affect the morphology of the carbon nanomaterials. In this review, various solid, liquid, and gaseous hydrocarbon precursors and how they affect the growth temperature of carbon nanomaterials syntheses via CVD are discussed.

Transforming pollution into solutions: A bibliometric analysis and sustainable strategies for reducing indoor microplastics while converting to value-added products

Microplastics (MPs), as emerging indoor contaminants, have garnered attention due to their ubiquity and unresolved implications for human health. These tiny particles have permeated indoor air and water, leading to inevitable human exposure. Preliminary evidence suggests MP exposure could be linked to respiratory, gastrointestinal, and potentially other health issues, yet the full scope of their effects remains unclear. To map the overall landscape of this research field, a bibliometric analysis based on research articles retrieved from the Web of Science database was conducted. The study synthesizes the current state of knowledge and spotlights the innovative mitigation strategies proposed to curb indoor MP pollution. These strategies involve minimizing the MP emission from source, advancements in filtration technology, aimed at reducing the MP exposure. Furthermore, this research sheds light on cutting-edge methods for converting MP waste into value-added products. These innovative approaches not only promise to alleviate environmental burdens but also contribute to a more sustainable and circular economy by transforming waste into resources such as biofuels, construction materials, and batteries. Despite these strides, this study acknowledges the ongoing challenges, including the need for more efficient removal technologies and a deeper understanding of MPs' health impacts. Looking forward, the study underscores the necessity for further research to fill these knowledge gaps, particularly in the areas of long-term health outcomes and the development of standardized, reliable methodologies for MP detection and quantification in indoor settings. This comprehensive approach paves the way for future exploration and the development of robust solutions to the complex issue of microplastic pollution.