Siti Kartini Enche Ab Rahim
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Preferred name
Siti Kartini Enche Ab Rahim
Official Name
Siti Kartini, Enche Ab Rahim
Alternative Name
Rahim, S. K.Enche Ab
Enche Ab Rahim, S. K.
Rahim, Siti Kartini Enche Ab
Main Affiliation
Scopus Author ID
57115278300
Researcher ID
EJE-7983-2022

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Synthesis and Characterisation of Self-Cleaning TiO2/PES Mixed Matrix Membranes in the Removal of Humic Acid

2023-04-01 , Poon Y.K. , Siti Kartini Enche Ab Rahim , Ng Qi Hwa , Hoo Peng Yong , Abdullah N.Y. , Amira Mohd Nasib , Abdullah N.S.

Membrane application is widespread in water filtration to remove natural organic matter (NOM), especially humic acid. However, there is a significant concern in membrane filtration, which is fouling, which will cause a reduction in the membrane life span, a high energy requirement, and a loss in product quality. Therefore, the effect of a TiO2/PES mixed matrix membrane on different concentrations of TiO2 photocatalyst and different durations of UV irradiation was studied in removing humic acid to determine the anti-fouling and self-cleaning effects. The TiO2 photocatalyst and TiO2/PES mixed matrix membrane synthesised were characterised using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM), contact angle, and porosity. The performances of TiO2/PES membranes of 0 wt.%, 1 wt.%, 3 wt.%, and 5 wt.% were evaluated via a cross-flow filtration system regarding anti-fouling and self-cleaning effects. After that, all the membranes were irradiated under UV for either 2, 10, or 20 min. A TiO2/PES mixed matrix membrane of 3 wt.% was proved to have the best anti-fouling and self-cleaning effect with improved hydrophilicity. The optimum duration for UV irradiation of the TiO2/PES mixed matrix membrane was 20 min. Furthermore, the fouling behaviour of mixed matrix membranes was fitted to the intermediate blocking model. Adding TiO2 photocatalyst into the PES membrane enhanced the anti-fouling and self-cleaning properties.

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Parameters adjustments for facile synthesis of high magnetization iron oxide nanoparticles from natural sand

2024-02-01 , Wahfiudin A. , Pramata A.D. , Wicaksono S.T. , Ng Qi Hwa , Amira Mohd Nasib , Siti Kartini Enche Ab Rahim , Mohd Riduan Jamalludin , Hoo Peng Yong

This study explores the synthesis of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) by leveraging natural iron sand and steel wool as primary raw materials within the co-precipitation method, which reduces the cost of production compared to the commercial counterparts. The research systematically investigated the influence of the diethylamine percentage, annealing time and annealing temperature on the SPIONs’ synthesis from natural iron sand by the co-precipitation method. Fe3O4 with varying crystallite sizes, ranging from 11.5 to 14.7 nm, were confirmed. SEM highlighted the nanoparticle agglomeration, a concern addressable through surface modification techniques, as further emphasized by TEM, which confirmed the nano-scale dimensions. Magnetic saturation values were confirmed by VSM, ranging from 37 to 51 emu/g. These values established the superparamagnetic behavior, rendering the nanoparticles suitable for versatile applications. The study identifies a potential threshold effect of the diethylamine concentration on the magnetic saturation and suggests an optimum annealing temperature for energy efficiency. This research contributes valuable insights into harnessing natural iron sand for SPION synthesis, advancing cost-effective and sustainable approaches in nanomaterial development, while emphasizing the importance of parameter customization for producing high-quality SPIONs.

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Sulfonated magnetic multi-walled carbon nanotubes with enhanced bonding stability, high adsorption performance, and reusability for water remediation

2023 , Lim Chuan Chuan , Siew Hoong Shuit , Ng Qi Hwa , Siti Kartini Enche Ab Rahim , Wei Ming Yeoh , Hoo Peng Yong , Soon Wah Goh

In view of the simple and rapid conveniency of magnetic separation, magnetic nanocomposites had notably gained attention from researchers for environmental field applications. In this work, carboxylated magnetic multi-walled carbon nanotubes (c-MMWCNTs) and novel sulfonated MMWCNTs (s-MMWCNTs) were synthesized by a facile solvent-free direct doping method. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, energy dispersive X-ray, vibrating sample magnetometer, and point of zero charge analyses confirmed the successful doping of the Fe3O4 nanoparticles into the functionalized MWCNTs to form MMWCNTs. Besides, the bonding stabilities of both c-MMWCNTs and s-MMWCNTs were compared, and results showed that s-MMWCNTs possessed more substantial bonding stability than that of c-MMWCNTs with significantly less leaching amount of Fe3O4. The adsorption capacity of s-MMWCNTs was higher than that of c-MMWCNTs owing to the stronger electronegativity sulfonic group in s-MMWCNTs. Moreover, the reusability experiments proved that the adsorbent remained consistently excellent MB removal efficiency (R > 94%) even reused for twelve cycles of batch adsorption. The finding of the present work highlights the simple fabrication of novel s-MMWCNTs and its potential to be served as a promising and sustainable adsorbent for water remediation owing to its enhanced bonding stability, high adsorption performance, magnetic separability, and supreme recyclability.

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A Novel Tri-Functionality pH-Magnetic-Photocatalytic Hybrid Organic-Inorganic Polyoxometalates Augmented Microspheres for Polluted Water Treatment

2023-02-01 , Yee L.Y. , Ng Qi Hwa , Siti Kartini Enche Ab Rahim , Hoo Peng Yong , Chang P.T. , Ahmad A.L. , Low S.C. , Shuit S.H.

The severe water pollution from effluent dyes threatens human health. This study created pH-magnetic-photocatalytic polymer microspheres to conveniently separate the photocatalyst nanoparticles from the treated water by applying an external magnetic field. While fabricating magnetic nanoparticles’ (MNPs) microspheres, incorporating 0.5 wt.% iron oxide (Fe3O4) showed the best magnetophoretic separation ability, as all the MNPs microspheres were attracted toward the external magnet. Subsequently, hybrid organic–inorganic polyoxometalates (HPOM), a self-synthesized photocatalyst, were linked with the functionalized magnetic nanoparticles (f-MNPs) to prepare augmented magnetic-photocatalytic microspheres. The photodegradation dye removal efficiency of the augmented magnetic-photocatalytic microspheres (f-MNPs-HPOM) was then compared with that of the commercial titanium dioxide (TiO2) photocatalyst (f-MNPs-TiO2). Results showed that f-MNPs-HPOM microspheres with 74 ± 0.7% photocatalytic removal efficiency better degraded methylene orange (MO) than f-MNPs-TiO2 (70 ± 0.8%) at an unadjusted pH under UV-light irradiation for 90 min. The excellent performance was mainly attributed to the lower band-gap energy of HPOM (2.65 eV), which required lower energy to be photoactivated under UV light. The f-MNPs-HPOM microspheres demonstrated excellent reusability and stability in the photo-decolorization of MO, as the microspheres retained nearly the same removal percentage throughout the three continuous cycles. The degradation rate was also found to follow the pseudo-first-order kinetics. Furthermore, f-MNPs-HPOM microspheres were pH-responsive in the photodegradation of MO and methylene blue (MB) at pH 3 (acidic) and pH 9 (alkaline). Overall, it was demonstrated that using HPOM photocatalysts in the preparation of magnetic-photocatalytic microspheres resulted in better dye degradation than TiO2 photocatalysts.

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Plant-based calcium silicate from rice husk ash: A green adsorbent for free fatty acid recovery from waste frying oil

2024-02-29 , Zainor Syahira Zainal , Pengyong Hoo , Abdul Latif Ahmad , Ahmad Zuhairi Abdullah , Qihwa Ng , Siewhoong Shuit , Siti Kartini Enche Ab Rahim , Andas J.

Driven by the urgent need for a solution to tackle the surge of rice husk (RH) and waste frying oil (WFO) waste accumulation at a global scale, this report highlights the use of calcium silicates (CS) extracted from acid-pre-treated rice husk ash (RHA) for free fatty acid (FFA) removal from WFO as conventional RHA shows limited FFA adsorption performance. A novel alkaline earth silicate extraction method from acid-pre-treated RHA was outlined. The structural and behavioural attributes of the synthesised CS were identified through BET, SEM-EDS, and XRD analyses and compared to those of RHA. Notable morphology and structural modification were determined, including reducing specific surface areas, mitigating from amorphous to crystalline structure with regular geometric forms, and detecting Si–O–Ca functional groups exclusive to CS adsorbents. A comparison study showed superior lauric acid (LA) adsorption performance by CS absorbents over acid-pre-treated RHA, with a significant increase from 0.0831 ± 0.0004 mmol LA/g to 2.5808 ± 0.0011 mmol LA/g after 60 min. Recognised as the best-performing CS adsorbent, CS-1.0 was used for further investigations on the effect of dosage, LA concentration, and temperature for efficient LA adsorption, with up to 100% LA removal and 5.6712 ± 0.0016 mmol LA/g adsorption capacity. The adsorption isotherm and kinetic studies showed LA adsorption onto CS-1.0 followed Freundlich isotherm with KF = 0.0598 mmol(1-1/n) L(1/n) g−1 & Qe,cal = 3.1696 mmol g−1 and intraparticle diffusion model with kid = 0.1250 mmol g−1 min0.5 & Ci = 0.9625 mmol g−1, indicating rapid initial adsorption and involvement of carboxylate end of LA and the calcium ions on the CS-1.0 in the rate-limiting step. The high equilibrium adsorption capacity and LA adsorption rate indicated that the proposed CS-1.0 adsorbent has excellent potential to recover FFA from WFO effectively.

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Mathematical modelling of mass transport in linear, shunt and concentric microdialysis probes

2014 , Siti Kartini Enche Ab Rahim

Microdialysis is a technique for both recovering and administering substances at a target site (which may be tissues, organs, etc.), using a small equipment termed as probe. There are many types of microdialysis probes such as the linear probe, the shunt probe and the concentric probe, and the probe choices are depended on the site of implantation, whether it is for the tissue (different type of tissue for different probe design) or in the quiescent medium. Although the probe needs to be physically inserted into the site, the microdialysis probe is relatively small and is minimally-invasive (i.e., causing minimal changes or injuries to the target site). This along with many other features of microdialysis (e.g., can be performed on almost every organ and tissue, can be used on living, awake and even moving patients, etc.) make this technique very popular. Nonetheless, poor recovery, doubts related to temporal resolution, and tedious preparations plus the need of pre-runs for calibration, limits the application of this technique. These constraints are generally attributed to mass transfer limitations. In this thesis, a mathematical framework incorporating convection and diffusion equations have been proposed to represent transport phenomena in microdialysis probes. This mathematical framework is then used to analyse the possible influence of various relevant parameters on glucose (i.e., analyte) recovery. In this work, it is defined that within the probe’s membrane and probe surrounding area (PSA), the transport process is solely driven by diffusion. The model parameters and operating conditions have been obtained from literature. In the first part, a mathematical framework was constructed to represent mass transport in two primitive microdialysis probes, namely the linear and shunt probes. Using the respective mathematical frameworks, glucose recoveries under various operating conditions were compared between the two probes, which were defined to operate under similar conditions. As there is no mathematical work that has been done to evaluate these both probes, it would be interesting to see how these two microdialysis probes may perform under similar operating conditions. It is clearly seen that the frameworks were sensitive enough to show concentration changes when parameters were varied. These results were comparable to what was discussed in literature. Comparing the two probe’s performance under similar conditions, the shunt probe displayed higher glucose recoveries, which reflect better performance. The mathematical approach from the more primitive linear and shunt microdialysis probe frameworks was expanded to represent mass transport in the more complex concentric microdialysis probe. This probe is arguably the more popular and is the most commonly referred to in microdialysis literature. The framework is then used to evaluate mass transport within the probe and its surrounding area. Results on percentage recovery and overall mass transfer coefficient under various operating conditions have been discussed. Comparisons were made with the Bungay’s microdialysis framework (BMF) on mass transport performance under different design and operating parameters. The results suggested that the concentric probe framework is sensitive to parameter changes, and the concentration profiles obtained are comparable to the widely accepted BMF. This is one indication that the proposed concentric probe framework can be used to represent mass transport phenomena in such probes. The results from the numerical efforts were then compared to experimental work. It was shown that the simulated data fits well with experimental data using a 5 mm concentric probe, for membrane © This item is protected by original copyright xxvii hindrance factor, α, of 10. The comparison was done again using a similar probe, with a different length (10 mm) and fitting was also found best with α of approximately 10. It is justified that the concentric mathematical framework can be used to represent mass transport phenomena in those probes, and in one way, justifies the validity of the mathematical frameworks for the more primitive probes, beforehand.

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An insight into the adsorptive, kinetic, and mechanistic behavior of the sulfonated magnetic multi-walled carbon nanotubes adsorbent in the removal of Methylene blue

2025 , Chuan Chuan Lim , Ng Qi Hwa , Siew Hoong Shuit , Soon Wah Goh , Siti Kartini Enche Ab Rahim , Hoo Peng Yong

A simple and environmentally friendly, facile solvent-free direct doping (FSFDD) approach was employed to synthesize sulfonated magnetic multi-walled carbon nanotubes (s-MMWCNTs) which in turn employed for the eliminating of methylene blue (MB) dye from aqueous solution. While prior studies have emphasized the synthesis and innovation points of s-MMWCNTs, this work delves into the fundamental adsorption behaviors (adsorption isotherm, kinetic, thermodynamic and mechanism analysis) to provide a deeper understanding of the interactions between the adsorbent and methylene blue (MB). The developed s-MMWCNTs were characterized by zeta potential analysis, transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Moreover, the characterization of spent s-MMWCNTs by X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray (SEM-EDX) and Fourier transform infrared (FT-IR) were carried out to compare their characteristics to the freshly synthesized s-MMWCNTs. Results indicated that the Freundlich isotherm model was the best-fitted model, providing a maximum adsorption capacity of 44.64 mg g− 1. As for the adsorption kinetic studies, the MB adsorption onto s-MMWCNTs was discovered to comply with the pseudo-second-order model. Besides, the thermodynamic results suggested that the adsorption process of MB onto s-MMWCNTs occurred endothermically with spontaneity. Furthermore, the adsorption mechanisms encompassed electrostatic interaction, hydrogen bonding and π–π stacking interaction with the electrostatic interaction as the most salient attractive force in the MB adsorption onto s-MMWCNTs.

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Facile synthesis of magnetophoretic augmented adsorbent for water remediation

2024-03 , Chuan Chuan Lim , Ng Qi Hwa , Siti Kartini Enche Ab Rahim , Hoo Peng Yong , Siew Hoong Shuit , Sigit Tri Wicaksono

In this new era of globalization, magnetic adsorbents have gained vast attention from researchers in wastewater treatment applications. In this study, sulphonated magnetic multi-walled carbon nanotubes (S-MMWCNTs) were used to remove methylene blue (MB) from an aqueous solution. The S-MMWCNTs are characterized by various analytical methods to investigate their adsorbent features. Adsorption behaviours of the as-prepared composites affected by solution pH and contact time were systematically studied and discussed. The adsorption kinetic data fit the pseudo-second-order kinetic model well. Moreover, the MB removal efficiency of S-MMWCNTs only drops slightly (~6.5%) after five consecutive adsorption cycles, showing their good stability and recyclability.

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Facial synthesis of colloidal stable magnetic nanoparticles coated with high hydrophilic negative charged poly(4‐styrenesulfonic acid co‐maleic acid) sodium for water remediation

2023 , Lim Chuan Chuan , Ng Qi Hwa , Hoo Peng Yong , Siti Kartini Enche Ab Rahim , Mohd Riduan Jamalludin , Amira Mohd Nasib , Sigit Tri Wicaksono , Azzah Dyah Pramata , Siti Zullaikah

The enhancement of the colloidal stability of magnetite nanoparticles (MNPs) for environmental‐related fields has greatly attracted researchers' attention. This study used a high hydrophilic negatively charged polyelectrolyte, poly(4‐styrenesulfonic acid co‐maleic acid) sodium (PSAAS), to enhance the colloidal stability of MNPs. Coating of the naked MNPs with PSAAS polyelectrolyte is a simple and rapid method to obtain colloidally stable MNPs while sustaining the chemical reactivity of MNPs in water purification. The prepared PSAAS‐coated MNPs were characterized by scanning electron microscope, energy dispersive X‐ray, Fourier transform infrared, zeta potential analysis, transmission electron microscope and X‐ray diffraction. Moreover, the colloidal stability and adsorption performance tests of these naked MNPs and PSAAS‐coated MNPs (with different concentrations of PSAAS coated) were investigated and compared. PSAAS‐coated MNPs with 0.001 g/ml PSAAS coating possessed the best colloidal stability and the highest methylene blue (MB) dye removal efficiency (94.53 ± 0.69%). The adsorption isotherm and kinetic studies for the adsorption of MB onto PSAAS‐coated MNPs were well‐described by the Langmuir model and pseudo‐second‐order kinetic model. These magnetic adsorbents, with high separation efficiency, simple and low production cost and recyclable property, are promising as practicable adsorbents in water treatment.

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Recent advancements in smart materials for the removal of organic, inorganic and microbial pollutants in water treatment: a review

2025-02 , Soon Wah Goh , Ng Qi Hwa , Siti Kartini Enche Ab Rahim , Siew Chun Low , Hoo Peng Yong , Ryan Yow Zhong Yeo , Thiam Leng Chew , Zeinab Abbas Jawad

As the expeditious urban and industrial expansion, a substantial portion of wastewater is produced annually, posing a significant threat to environmental contamination and dwindling the availability of clean water resources. Water contaminants are generally categorized into organic, inorganic, and microbial pollutants. This escalating water pollution crisis has initiated the research community to innovate novel, effective and economical cost methods for water treatment applications. Among the approaches, adsorption has been marked by its importance in water treatment. Recent advancements in the field have focused on developing smart adsorbent materials capable of modifying their physicochemical properties in response to various external stimuli (light and magnetic field) and internal stimuli (thermal and pH fluctuation). The exploration of smart materials has captivated the interest of researchers worldwide and opened up exciting avenue for more efficient water treatment outcomes towards removing different types of pollutants. Notably, these smart materials demonstrate high pollutant uptake and release efficacy when responding to specific stimuli changes, ensuring efficient removal of contaminants and exerting self-cleaning properties. Such materials offer an environmentally benign advantage by eliminating the need for toxic organic solvents during regeneration. The review compiles and highlights the characteristics and performance of several stimuli-responsive smart materials, including thermal, light, magnetic and pH regarding organic, inorganic and microbial pollutants removal efficiencies. A particular focus is given to multi-stimuli responsive materials in environmental applications that represent the modern era and transformation of water treatment methodologies, followed by a discussion on the challenges and prospects of this particular research area.

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