Publications

List of Contributors

The evolution of oxygen-functional groups of graphene oxide as a function of oxidation degree

Tuning the ratio of sp2/sp3 is crucial factor for obtaining high aspect ratio of graphene oxide. In this work, we reported a comprehensive study on synthesis of GO with different sp2/sp3 ratios at different oxidation reaction temperatures. The physicochemical properties of the as-prepared GO were characterized by Attenuated total reflectance infrared spectroscopy (ATR-IR), Raman spectroscopy, Solid-state nuclear magnetic resonance (SSNMR), Field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Transmission electron microscope (TEM), hydrophilicity test and zeta potential. Interestingly, GO-35 showed the smallest contact angle with carbon-to-oxygen (O/C) ratio 0.469. ATR-IR reveals the different intensity of hydroxyl (−OH), carbonyl (−CO), epoxy (C–O–C), as well as carboxyl (−COOH) moieties in the GO samples, and their intermolecular interactions significantly affected the interlayer spacing between consecutive identical planes of carbon atoms which examined using XRD. XPS confirmed that the basal species such as –OH is abundantly available in the GO-35 and unavailable in GO-50. Our results demonstrate that the properties of GO can be tuned using different oxidation reaction temperatures, which significantly influences types of oxygen-functional groups generated at different oxidation levels, thus could pave the way for various applications of graphene-based material.

Malachite Green and Leuco-Malachite Green Detection in Fish Using Modified Enzyme Biosensor

A modified enzyme-based biosensor was developed for amperometric measurement of total Malachite Green (sum of MG and LMG) in tilapia fish. The 4 UmL-1 butyrylcholinesterase enzyme (BuChE) was used and immobilized onto the surface of carbon paste electrode during the electro-polymerization of polypyrrole (PPy). It is a simple, rapid and sensitive technique used for determination of total MG using 0.1M phosphate buffer pH 8.0. In this study, butyrylthiocholine iodide (0.3 Mm BTCi) was used as a substrate which produced the thiocholine due to the enzymatic hydrolysis. Then, it was oxidized at 0.4V against silver-silver chloride electrode for 100 s. The modified enzyme biosensor provided a high sensitivity and linear concentration range from 0.25 to 10 ppb with a limit of detection (LOD) at 0.25 ppb. The results showed the linear standard curve of total MG standard solution (based on the current output in microampere) with the equation of y = - 0.9113x + 10.84, R2 = 0.9445.

Immobilizing chitosan nanoparticles in polysulfone ultrafiltration hollow fibre membranes for improving uremic toxins removal

In this study, the transport properties, and uremic toxins removal capability by polysulfone (PSF) membrane have been improved through the immobilisation of chitosan nanoparticles (CNP). Different loadings of CNP in the range of 0.1–0.5 wt% was incorporated into the polymer dope solutions to fabricate hollow fibre membranes that spun at different air-gap. The physicochemical study, pure water flux and uremic toxins analysis were employed to characterize the fabricated membranes physical and morphological characteristics. The incorporation of CNP increased PSF HFM porosity, pore size, ultrafiltration coefficient, KUF and uremic toxins clearance due to the formation of a thinner selective inner skin layer. However, the membranes spun with greater air-gap length exhibited decreased KUF and uremic toxins clearances due to increased membrane thickness and decreased porosity. The PSF membrane incorporated with 0.3 wt% CNP and spun at 50 cm air-gap demonstrated the highest KUF of 116 ml/m2.h.mmHg, BSA rejection of 91% as well as excellent uremic toxins clearances of 85%, 67% and 49% for urea, creatinine and lysozyme, respectively. These results suggested that the spinning conditions play critical roles in dictating the properties of the nanocomposite hollow fibre membrane (HFM) and the PSF/CNP HFM holds vast potential as a promising material for haemodialysis application.

Multi aspect investigation of crude oil concentration detecting via optical fiber sensor coated with ZnO/Ag nano-heterostructure

Determining the crude oil concentration changes as an essential factor in reservoir engineering, via proposed modified optical fiber sensor, offers a novel approach in oil production optimization. A highly sensitive optical fiber probe is fabricated via partially removing the cladding and coating the sensing part with zinc oxide/silver (ZnO/Ag) heterostructre layer. The ZnO outer layer has three configurations including nanoparticle, horizontally and vertically oriented nanorods. The fabricated optical fiber sensors are subjected to detect the crude oil concentration variations through detection of both wavelengths shift and intensity changes. The effect of ZnO outer layer shape, and the type of light source is used, on sensitivity of the probe is examined. Comprehensive investigation on shape dependent structural and optical properties of ZnO outer layer demonstrates that vertically oriented ZnO has larger surface area, higher average dispersion relation, better crystallinity, larger surface roughness and better adhesion (interaction) with crude oil molecules and these characteristics are responsible for its superior performance compare to other ZnO configurations. For the probe coated with vertically aligned ZnO nanorods when the infrared (IR) light source is used, the intensity and wavelength sensitivity of 0.044 dB/Δ%crude oil and 0.112 nm/Δ %crude oil are obtained respectively.

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 less than 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% arsenic 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.

Effect of coupled catalyst loading and ionomer binder on oxygen reduction reaction in high-temperature pemfc

Polybenzimidazole (PBI) was studied as an ionomer binder at varying ratios (1-7) in a 20~40 wt% Pt–Pd/C cathode-coupled catalyst layer for the oxygen reduction reaction (ORR) in a high-temperature proton exchange membrane fuel cell (HT-PEMFC). Catalytic activity was examined by CV and LSV, while the properties of the catalysts were characterized by FESEM-EDX, N2 adsorption–desorption, XRD and FTIR. The results showed that the distribution of metals on the carbon surface, carbon wall thickness and the interaction between ionomer and coupled catalysts affected the ORR performance. The fabricated membrane electrode assembly with 5:95 PBI: 30 wt% Pt–Pd/C catalyst ratio exhibited the best performance and highest durability for HT-PEMFC at 170°C, yielding a power density of 1.20 Wcm-2 with 0.02 mgPt/cm Pt loading. This result was comparable to those reported by other studies [1-4], highlighting a promising catalyst for fuel cell application.

Enhancing photocatalytic performance: studying the synthesis and characterization of AgI-tuned TiO2/ZnO hybrid ternary nanocomposites

Eliminating phenol and other contaminants from wastewater is an essential step in addressing environmental issues. Using tailored photocatalysts is essential for the effective degradation of phenol via photocatalysis. The main objective of this study is to produce TiO2/ZnO/AgI nanocomposites employing the reflux approach in order to enhance the degradation of phenol in the presence of UV radiation. The nanocomposite incorporates TiO2 and ZnO, resulting in a narrowed band gap that enhances photocatalytic activity. The addition of AgI enhances electron transport capacities, resulting in an inclusive augmentation in performance. The physicochemical properties of the nanocomposite were extensively investigated applying an array of advanced techniques including as XRD, BET, FESEM, TEM, EDX and TGA spectroscopy practices. The combined effect of TiO2, ZnO, and AgI exhibits an approximately 100 % degradation of phenol, exceeding the individual performance of each component. The outcomes indicated that the operational parameters have a substantial impact on the photocatalytic activity, and the addition of H2O2 also improves degradation. The ideal conditions require a low concentration of H2O2 and a dose of 0.3 g/350 mL of nanocomposite. The reaction rate constant was reported as 6.96 × 10−3 min−1 under optimised conditions. The ternary nanocomposite exhibited recyclability for four successive cycles, eventually displaying ∼88 % degradation. The TiO2/ZnO/AgI nanocomposite system exhibits significant photocatalytic efficiency, which has important consequences for addressing environmental concerns caused by the persistent existence of various organic contaminants in water sources.

Rapid synthesis and characterization of leaf-like zeolitic imidazolate framework Sintesis cepat dan pencirian kerangka seperti daun imidazolat zeolitik

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.

Highly Sulfonated Poly(Ether Ether Ketone) Blend with Hydrophobic Polyether Sulfone as an Alternative Electrolyte for Proton Exchange Membrane Fuel Cell

No abstract is provided for this article.

Visible-light-driven photocatalytic dual-layer hollow fibre membrane ameliorates the changes of bisphenol A exposure in gastrointestinal tract

No abstract is provided for this article.

Enhanced adsorption and biocompatibility of polysulfone hollow fibre membrane via the addition of silica/alpha-mangostin hybrid nanoparticle for uremic toxins removal

In this study, a highly biocompatible adsorptive membrane is developed for haemodialysis application. Silica/α-mangostin hybrid nanoparticle was incorporated into polysulfone (PSf) based membrane to enhance the biocompatibility and the adsorption capacity of the membrane. The PSf based membranes were fabricated via dry-wet phase inversion technique and characterised based on scanning electron microscopy and contact angle measurement. The effects of silica/α-mangostin nanoparticle incorporation into PSf membrane were evaluated in terms of permeability, p-cresol adsorption capacity, urea, and creatinine removal capabilities, bovine serum albumin rejection and p-cresol dynamic adsorption. The biocompatibility assessment was done based on platelet adhesion, antioxidant properties, and complement activation of the membrane. The incorporation of the nanoparticle into PSf based membrane helped to smoothen the surface of the membrane and enhanced its hydrophilicity of the membrane by 12.54%. The presence of silica/α-mangostin in the membrane enhanced the adsorption capacity of the membrane by 20.92% with adsorption capacity of 55.64 mg/g at 500 mg/L initial concentration. The modified PSf membrane had also successfully improved the biocompatibility of the membrane by enhancing the scavenging activity of hydrogen peroxide and nitrogen oxide by 61.8% and 36%, respectively and inhibited the formation of C5a by 27.27%. The developed biocompatible PSf based adsorptive membrane has a good potential to be used for haemodialysis application.

Single-step production of N-doped graphene powder from palm kernel shell at 500 °C

Superior photocatalytic and self-cleaning performance of PVDF-TiO₂@NH₂-MIL-125(Ti)/PVA membranes for efficient produced water treatment

This study addresses the growing need for effective water treatment technologies in response to increasing global water production. The Water Quality Index (WQI) calculations indicated poor water quality in the sample, with a value of 92.01. Membrane technology has shown potential for improving water treatment. However, issues such as fouling and selectivity often hinder its practical application. This research explores the integration of polyvinyl alcohol (PVA) and metal-organic framework TiO₂@NH₂-MIL-125(Ti) into polyvinylidene fluoride (PVDF) membranes to enhance their performance in treating produced water. The incorporation of TiO₂@NH₂-MIL-125(Ti)/PVA significantly improved the membrane's key performance indicators, including flux, rejection rates, and photocatalytic activity. The PM-04 membrane, containing 2 wt% PVA, demonstrated the highest flux rates of 143.93 L·m−2·h−1 under dark conditions and 160.66 L·m−2·h−1 under visible light. Under visible light irradiation, it achieved impressive removal efficiencies of 90.56 % for COD, 75.23 % for TDS, and 82.27 % for NH₃-N. The kinetics of COD removal followed a zero-order model, highlighting the membrane's efficient photocatalytic degradation capabilities. Additionally, the membrane's resistance to fouling was confirmed through self-cleaning and reusability tests, reducing maintenance requirements and extending its operational lifespan. With a significant processing capacity of 2,190,000 m3 per year and a competitive specific processing cost (SPC) of $0.019 per cubic meter, the PM-04 membrane offers a promising, cost-effective alternative to conventional water treatment technologies.

Fabrication of Ceramic, Hollow-Fiber Membrane: The Effect of Bauxite Content and Sintering Temperature

No abstract is provided for this article.

Immobilization techniques of a photocatalyst into and onto a polymer membrane for photocatalytic activity

This article reviews the various techniques of immobilizing a photocatalyst into and onto the polymer membrane for pollutant removal and as a problem solver in handling suspended photocatalyst issues from the previous literature. A particular focus is given to the preparation of mixed matrix membranes and deposition techniques for photocatalytic degradation in applications for wastewater treatment. Advantages and disadvantages in this application are evaluated. Various operating conditions during the process are presented. About 90 recently published studies (2008-2020) are reviewed. From the literature, it was found that TiO2 is the most favoured photocatalyst that is frequently used in photocatalytic water treatment. Dry-wet co-spinning and sputtering techniques emerged as the promising technique for immobilizing a uniformly distributed photocatalyst within the polymeric membrane, and exhibited excellence pollutant removal. In general, the technical applicability is the key factor in selecting the best photocatalyst immobilizing technique for water treatment. Finally, the scope of various techniques that have been reviewed may provide potential for future photocatalytic study.

Arsenic adsorption mechanism on palm oil fuel ash (POFA) powder suspension

The contribution of palm oil fuel ash (POFA), an agricultural waste as a low cost adsorbent for the removal of arsenite (As(III)) and arsenate (As(V)) was explored. Investigation on the adsorbency characteristics of POFA suspension revealed that the surface area, particle size, composition, and crystallinity of the SiO2 rich mullite structure were the crucial factors in ensuring a high adsorption capacity of the ions. Maximum adsorption capacities of As(III) and As(V) at 91.2 and 99.4 mg g−1, respectively, were obtained when POFA of 30 μm particle size was employed at pH 3 with the highest calcination temperature at 1150 °C. An optimum dosage of 1.0 g of dried POFA powder successfully removed 48.7% and 50.2% of As(III) and As(V), respectively. Molecular modeling using the density functional theory consequently identified the energy for the proposed reaction routes between the SiO− and As + species. The high stability of the POFA suspension in water in conjunction with good adsorption capacity of As(III) and As(V) seen in this study, thus envisages its feasibility as a potential alternative absorbent for the remediation of water polluted with heavy metals.

Fabricanon of as-spun SPEEK as a function of degree of sulfonation

The purpose of this study was 10 determine the effect of degree of sulfonation (DS) on electrospun sulfonated poly (ether ether ketone) (SPEEK) fiber. SPEEK was prepared via sulfonation process by sulfonating native poly (ether ether ketone) (PEEK) with concentrated sulfuric acid (95-97%). The prepared SPEEKs polymer was characterized for their OS via hydrogen-nuclear magnetic resonance (WNMR) spectroscopy. The electrospinning process was taking placed in developing an eleetrospun SPEEK nanofibers mat and scanning electron microscopy (SEM) was used .to observe the morphological structural of the electrospun SPEEK nanofibers. SPEEK with different DS at50%, 58%, 68% and 80% was prepared in this /study.Ir was observed that the diameter of the fiber decreased as the DS increased aithe same operating parameters (flow rate and distance from needle tip to the collector), From SEM analysis, it was found that the diameter of the SPEEK nanofiber with the DS of 50('/0, 58%, 68% and 80% was 20him, 103.8nm, 68.9nin aDd 68nrn, respectively. Eventhough the obtained as-spun nanofiber from SPEEK at DS of 500/0 showed better appearance in its nanofiber mat form but the nanofiber spun at higher DS exhibited favorable lfiber 'structure due to its smaller size in diameter.In conclusion, the higher the DS of the SPEEK the smaller the diameter of the obtained fibers was.