Ng Qi Hwa
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Preferred name
Ng Qi Hwa
Official Name
Ng, Qi Hwa
Alternative Name
Ng, Q. H.
Qi, Hwa Ng
Ng, Qi H.
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Scopus Author ID
54413018300
Researcher ID
A-9192-2019

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  • Publication
    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.
  • Publication
    Integrating advanced Keggin-structure polyoxometalate into polymeric membrane to enhance photocatalytic self-cleaning and antifouling functionalities
    ( 2022-04-01)
    Koo D.C.H.
    ;
    Tan N.N.
    ;
    Ng Qi Hwa
    ;
    Siti Kartini Enche Ab Rahim
    ;
    Low S.C.
    ;
    Yeo R.Y.Z.
    The high photocatalytic activity of environmentally benign Keggin-type polyoxometalate (POM) was introduced into polyethersulfone (PES) membrane to promote membrane anti-fouling and self-cleaning functionality. Neat PES and POM/PES hybrid membranes were synthesized via phase inversion method. X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy proved the success of synthesizing Keggin-type POM. The traits of the membranes were evaluated using scanning electron microscopy (SEM), ATR-FTIR, contact angle measurement, porosity and porometer. The hydrophilicity of all the POM/PES hybrid membranes was enhanced and resulted in the reduction of contact angle of the membrane (52.21±0.1101°, 45.11±0.6657° and 50.30±0.1054°) for 0.025, 0.05 and 0.1 wt% POM/PES hybrid membranes, respectively, compared to that of the neat PES membrane (57.30±0.0817°). Additionally, all the POM/PES hybrid membranes showed excellent anti-fouling and self-cleaning characteristics as compared to that of the neat PES membrane. 0.05 wt% POM/PES hybrid membrane outstood all the other membranes, which marks the HA rejection at 77.12% and was able to achieve flux recovery ratio (FRR) of 111.34% with temporal superhydrophilicity effect in just merely 150 seconds at 254 nm UV irradiation.
  • Publication
    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.
  • Publication
    Photocatalytic Degradation of Methylene Blue Using Polyoxometalate as Photocatalyst
    ( 2023-06-09)
    Siti Kartini Enche Ab Rahim
    ;
    Azahri E.N.A.
    ;
    Hoo Peng Yong
    ;
    Ng Qi Hwa
    ;
    Abdullah N.S.
    Polyoxometalates (POM), Na2C6H4NO2. [PW12O40] have been synthesized under hydrothermal conditions and characterized. The SEM result indicates that morphology of photocatalyst was homogeneous. The performance of POM was then tested on photocatalytic degradation of methylene blue at different operating conditions. The degradation of methylene blue was dependent on several parameters, such as its initial concentration, HPOM loading and temperature. Langmuir–Hinshelwood model is usually used to describe the kinetics of this photocatalytic process. It was found that rate constant, kapp decreased with increasing initial concentrations of methylene blue. However, as increases in HPOM loading improved methylene blue degradation. The activation energy obtained was low due to this photocatalytic process being less dependent on temperature.
  • Publication
    Removal of methylene blue using magnetic multi-walled carbon nanotubes: process optimization study
    ( 2020-12-18)
    Lim C.C.
    ;
    Shuit S.H.
    ;
    Siti Kartini Enche Ab Rahim
    ;
    Hoo Peng Yong
    ;
    Ng Qi Hwa
    Adsorption is the most common methods used in industry for the removal of dye. In this study, magnetic multi-walled carbon nanotubes (MMWCNTs) was served as adsorbent for the removal of methylene blue (MB). Statistical optimization of the MB removal efficiency via response surface methodology coupled with central composite design was performed and reported. It was observed that all three experimental parameters: adsorption temperature (25-50 C), MB concentration (10-50 ppm) and MMWCNTs dosage (0.01-0.05 g/20mL) were significant in the removal of MB. The optimized conditions of 99.21 % MB removal efficiency can be achieved at adsorption temperature of 38 C, MB concentration of 23 ppm and MMWCNTs dosage of 0.033 g/20mL. The verification of the prediction was performed with 3 repeated experiments and the results were found to be in good agreement with the experimental data with only 0.21 % error.
  • Publication
    Glycerolysis of Lauric Acid with Strontium Enhanced 12-Tungstophosphoric Acid Incorporated SBA-15: Material Characterization and Reusability Elucidation
    ( 2022-01-01)
    Samsun N.S.
    ;
    Hoo Peng Yong
    ;
    Abdullah A.Z.
    ;
    Enche Ab Rahim S.K.
    ;
    Teoh Y.P.
    ;
    Shuit S.H.
    ;
    Ng Qi Hwa
    SBA-15 was modified with strontium before being functionalized with HPW acid to investigate its performance and stability in the glycerolysis of lauric acid. The physical and chemical characteristics of the catalyst was analyzed using Fourier Transformed Infrared (FTIR), Scanning Electron Morphology (SEM), Surface analysis (BET), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). The collective evidence and finding from material characterizations, including the successfully formed and retained SBA-15 mesopores after modification twice, SrO formation and disappearance, post SrO modification and HPW incorporation, respectively, further strengthen the claim of the strong anchoring of HPW onto the SBA-15 via the strontium-salt bridge. The reusability of the lauric acid conversion was also evaluated. The superior stability of the synthesized catalyst (HPW/SrSBA-15) was demonstrated minimal to none change in both lauric acid conversion (75.34%) and monolaurin yield (38.9%). Such result was attributed to the good interaction between HPW and SBA-15 via strontium modification and proved that the catalyst does not undergo severe deactivation and showed good catalytic activity in recycled use.
  • Publication
    Synthesis of novel magneto-hybrid polyoxometalate composite membrane with simultaneous photocatalytic self-cleaning and antifouling functionalities
    ( 2023-10-01)
    Tan N.N.
    ;
    Ng Qi Hwa
    ;
    Siti Kartini Enche Ab Rahim
    ;
    Ahmad A.L.
    ;
    Hoo Peng Yong
    ;
    Chew T.L.
    Membrane technology is ideal for removing aqueous humic acid, but humic acid deposits cause membrane fouling, a significant challenge that limits its application. Herein, this work proposed an alternative approach to the controllably magnetically induced magneto-hybrid polyoxometalate (magneto-HPOM) nanocomposite migration toward the polyethersulfone (PES) membrane surface under a magnetic field to enhance the self-cleaning and antifouling functionalities of the membrane. Before incorporating magneto-HPOM nanocomposite into the PES casting solution, functionalized magnetite nanoparticles (F-MNP) were first coated with HPOM photocatalyst to fabricate a magneto-HPOM-PES membrane. It was shown that the apparent impacts of this novel magneto-HPOM-PES membrane on the hydrophilic behavior and photocatalytic properties of the magneto-HPOM nanocomposite improve the hydrophilicity, separation performance, antifouling and self-cleaning properties of the membrane compared with neat PES membrane. Furthermore, after exposure to ultraviolet light, the magneto-HPOM-PES membrane can be recovered after three cycles with a flux recovery ratio of 107.95%, 100.06%, and 95.56%, which is attributed to the temporal super hydrophilicity effect. Meanwhile, the magneto-HPOM-PES membrane could efficiently maintain 100% humic acid rejection for the first and second cycles and 99.81% for the third cycle. This study revealed a novel approach to fabricating membranes with high antifouling and self-cleaning properties for water treatment.[Figure not available: see fulltext.]
  • Publication
    Studies on Antifouling Characteristic of the Magnetic Field Induced-PES-Fe3O4 Membrane for Water Remediation
    ( 2022-01-01)
    Tan N.N.
    ;
    Ng Qi Hwa
    ;
    Siti Kartini Enche Ab Rahim
    ;
    Heah C.W.
    ;
    Chew T.L.
    ;
    Hoo Peng Yong
    ;
    Sigit T.W.
    In this study Fe3 O4-polyethersulfone (PES) membranes were prepared in the present of a magnetic field or without a magnetic field by using the phase inversion process. A comparison of membrane properties was investigated. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used to determine the morphology and chemical composition of the prepared membranes. Furthermore, the fouling analysis of the non-magnetized and magnetized Fe3 O4-PES membranes were also conducted through the filtration study. The pure water flux of membranes increased from 158.49±11.96 L/m2·hr (neat PES) to 187.06±6.54 L/m2·hr (magnetized Fe3 O4-PES). These results showed that the magnetized Fe3 O4-PES membrane not only had the high pure water flux but also had a high HA rejection and good antifouling ability. As such, magnetized Fe3 O4-PES membrane had excellent comprehensive properties which could use for water remediation.
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