Browsing by Author "Khoo, Ying Siew"

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Citation - WoS: 47
Citation - Scopus: 62
Eco-Friendly Surface Modification Approach To Develop Thin Film Nanocomposite Membrane With Improved Desalination and Antifouling Properties
(Elsevier, 2022) Khoo, Ying Siew; Lau, Woei Jye; Liang, Yong Yeow; Karaman, Mustafa; Gürsoy, Mehmet; Ismail, Ahmad Fauzi
Introduction: Nanomaterials aggregation within polyamide (PA) layer of thin film nanocomposite (TFN) membrane is found to be a common issue and can negatively affect membrane filtration performance. Thus, post-treatment on the surface of TFN membrane is one of the strategies to address the problem. Objective: In this study, an eco-friendly surface modification technique based on plasma enhanced chemical vapour deposition (PECVD) was used to deposit hydrophilic acrylic acid (AA) onto the PA surface of TFN membrane with the aims of simultaneously minimizing the PA surface defects caused by nanomaterials incorporation and improving the membrane surface hydrophilicity for reverse osmosis (RO) application. Methods: The TFN membrane was first synthesized by incorporating 0.05 wt% of functionalized titania nanotubes (TNTs) into its PA layer. It was then subjected to 15-s plasma deposition of AA monomer to establish extremely thin hydrophilic layer atop PA nanocomposite layer. PECVD is a promising surface modification method as it offers rapid and solvent-free functionalization for the membranes. Results: The findings clearly showed that the sodium chloride rejection of the plasma-modified TFN membrane was improved with salt passage reduced from 2.43% to 1.50% without significantly altering pure water flux. The AA-modified TFN membrane also exhibited a remarkable antifouling property with higher flux recovery rate (>95%, 5-h filtration using 1000 mg/L sodium alginate solution) compared to the unmodified TFN membrane (85.8%), which is mainly attributed to its enhanced hydrophilicity and smoother surface. Furthermore, the AA-modified TFN membrane also showed higher performance stability throughout 12-h filtration period. Conclusion: The deposition of hydrophilic material on the TFN membrane surface via eco-friendly method is potential to develop a defect-free TFN membrane with enhanced fouling resistance for improved desalination process. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of Cairo University.
Citation - WoS: 26
Citation - Scopus: 29
Environmentally Friendly Approach for the Fabrication of Polyamide Thin Film Nanocomposite Membrane With Enhanced Antifouling and Antibacterial Properties
(ELSEVIER, 2021) Khoo, Ying Siew; Seah, Mei Qun; Lau, Woei Jye; Liang, Yong Yeow; Karaman, Mustafa; Gürsoy, Mehmet; Ismail, Ahmad Fauzi
In this work, we employed an environmentally friendly approach based on plasma enhanced chemical vapour deposition (PECVD) to modify titania nanotubes (TNTs), aiming to obtain better dispersion of nanofillers in polyamide (PA) layer of thin film nanocomposite (TFN) reverse osmosis membrane. Owing to the hydrophilic nature of TNTs, dispersing it homogenously in organic solvent during interfacial polymerization process is difficult to achieve. Therefore, the TNTs are mildly modified by PECVD technique in order to ameliorate its stability in organic solvent. Our results showed that depositing thin layer of methyl methacrylate (MMA) on the TNTs surface could enhance its dispersion quality in organic solvent and further improve the properties of PA layer by enhancing membrane water flux by 16% without compromising NaCl rejection. More importantly, the developed TFN membrane showed excellent fouling resistance by recording flux recovery rate of 85.77% compared to 57.94% shown by the control membrane. Its antibacterial property was also obviously better than that of control membrane. Overall, the developed TFN membrane demonstrated good performance stability with respect to NaCl rejection and water permeability and the trace amount of nanofillers detected in the water sample (in the level of mu g/L) did not negatively influence the membrane filtration performance.
Citation - WoS: 46
Citation - Scopus: 49
A Green Approach To Modify Surface Properties of Polyamide Thin Film Composite Membrane for Improved Antifouling Resistance
(ELSEVIER, 2020) Khoo, Ying Siew; Lau, Woei Jye; Liang, Yong Yeow; Karaman, Mustafa; Gürsoy, Mehmet; Ismail, Ahmad Fauzi
A green approach based on plasma enhanced chemical vapour deposition (PECVD) method was adopted in this work to modify surface properties of thin film composite (TFC) membranes for improved antifouling resistance during desalination process. Two types of hydrophilic monomers, i.e., acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) was respectively deposited onto the surface of commercial TFC membranes (XLE and NF270) and the effect of plasma deposition time (15 s, 1 min and 5 min) on the membrane physiochemical properties was investigated using different analytical instruments. The deposition of AA and HEMA was able to improve the membrane hydrophilicity owing to the presence of hydroxyl and carboxyl functional groups. However, prolonged plasma polymerization period was not encouraged as it led to the formation of thicker skin layer that significantly reduced water permeability. With 15-s plasma deposition time, AA and HEMA-modified XLE and NF270 membranes could achieve higher NaCl and Na2SO4 rejections as well as demonstrate 100% flux recovery rate. The improved antifouling resistance of modified TFC membranes is mainly due to the improved surface hydrophilicity coupled with greater surface charge properties. This work demonstrated a rapid solvent-free surface modification method that can be employed to enhance TFC membrane properties for desalination process.
Citation - WoS: 30
Citation - Scopus: 34
Rapid and Eco-Friendly Technique for Surface Modification of Tfc Ro Membrane for Improved Filtration Performance
(ELSEVIER SCI LTD, 2021) Khoo, Ying Siew; Lau, Woei Jye; Liang, Yong Yeow; Karaman, Mustafa; Gürsoy, Mehmet; Lai, Gwo Sung; Ismail, Ahmad Fauzi
In this work, an environmentally friendly plasma enhanced chemical vapor deposition (PECVD) technique was employed to rapidly alter the surface properties of commercial thin film composite extra-low energy (XLE) reverse osmosis (RO) membrane to improve its fouling resistance and desalination performance. Hereafter, two different hydrophilic precursors, i.e., aniline monomer and oxygen (O-2) gas were respectively introduced to the membrane's polyamide surface at different plasma treatment duration (15 s and 60 s). At 15-s plasma treatment, our results revealed that the O2-modified membrane outperformed the polyaniline (PANI)-modified membrane and unmodified membrane, attributed to the polar functional groups presented on the polyamide surface. Compared to plasma polymerization of aniline, O-2 plasma etching can lower polyamide densification degree which potentially reduce membrane resistance. Evidently, the O-2-modified membrane exhibited higher pure water permeability (6.64 L/m(2).h.bar) compared to the PANI-modified membrane (5.57 L/m(2).h.bar). The enhanced surface hydrophilicity of O-2-modified membrane could be noticed when its water contact angle was reduced from 88.39 degrees (unmodified) to 79.46 degrees in just 15-s plasma treatment. Furthermore, this O-2-modified membrane achieved an outstanding NaCl and Na2SO4 rejection with an increment of 4.2% and 2.6%, respectively compared to the unmodified membrane. However, prolonged gas plasma treatment (60 s) should be avoided as it can damage polyamide selective layer. With respect to fouling resistance, the best O-2-modified membrane demonstrated higher flux recovery rate (96%) than that of unmodified membrane (76.5%) after being used to filter 1000-ppm sodium alginate solution. These results highlighted the versatility of O-2 plasma treatment to improve RO membrane performance.
Citation - WoS: 22
Citation - Scopus: 22
Rapid Surface Modification of Ultrafiltration Membranes for Enhanced Antifouling Properties
(MDPI, 2020) Said, Noresah; Khoo, Ying Siew; Lau, Woei Jye; Gürsoy, Mehmet; Karaman, Mustafa; Ting, Teo Ming; Ismail, Ahmad Fauzi
In this work, several ultrafiltration (UF) membranes with enhanced antifouling properties were fabricated using a rapid and green surface modification method that was based on the plasma-enhanced chemical vapor deposition (PECVD). Two types of hydrophilic monomers-acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) were, respectively, deposited on the surface of a commercial UF membrane and the effects of plasma deposition time (i.e., 15 s, 30 s, 60 s, and 90 s) on the surface properties of the membrane were investigated. The modified membranes were then subjected to filtration using 2000 mg/L pepsin and bovine serum albumin (BSA) solutions as feed. Microscopic and spectroscopic analyses confirmed the successful deposition of AA and HEMA on the membrane surface and the decrease in water contact angle with increasing plasma deposition time strongly indicated the increase in surface hydrophilicity due to the considerable enrichment of the hydrophilic segment of AA and HEMA on the membrane surface. However, a prolonged plasma deposition time (>15 s) should be avoided as it led to the formation of a thicker coating layer that significantly reduced the membrane pure water flux with no significant change in the solute rejection rate. Upon 15-s plasma deposition, the AA-modified membrane recorded the pepsin and BSA rejections of 83.9% and 97.5%, respectively, while the HEMA-modified membrane rejected at least 98.5% for both pepsin and BSA. Compared to the control membrane, the AA-modified and HEMA-modified membranes also showed a lower degree of flux decline and better flux recovery rate (>90%), suggesting that the membrane antifouling properties were improved and most of the fouling was reversible and could be removed via simple water cleaning process. We demonstrated in this work that the PECVD technique is a promising surface modification method that could be employed to rapidly improve membrane surface hydrophilicity (15 s) for the enhanced protein purification process without using any organic solvent during the plasma modification process.