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.
Main Affiliation
Scopus Author ID
54413018300
Researcher ID
A-9192-2019

Research Output
Now showing 1 - 5 of 5
  • Publication
    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.
  • Publication
    Facial synthesis of colloidal stable magnetic nanoparticles coated with high hydrophilic negative charged poly(4‐styrenesulfonic acid co‐maleic acid) sodium for water remediation
    (Wiley, 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.
  • Publication
    Sulfonated magnetic multi-walled carbon nanotubes with enhanced bonding stability, high adsorption performance, and reusability for water remediation
    (Springer, 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.
  • Publication
    Removal of methylene blue using trifunctional magnetic polyethersulfone microcapsule: process parameters and optimization study
    ( 2025-01)
    Suh Cia Yong
    ;
    Siew Hoong Shuit
    ;
    Wei Yang Tan
    ;
    Steven Lim
    ;
    Ng Qi Hwa
    ;
    Hui San Thiam
    ;
    Shiau Foon Tee
    ;
    Kok Chung Chong
    ;
    Hoo Peng Yong
    Water pollution from dye-contaminated effluents poses a critical environmental threat. Current dye removal methods often rely on activated carbon, which is expensive and challenging to recover. This study focuses on the removal of methylene blue (MB), a cationic dye, using trifunctional polyethersulfone (PES)-encapsulated polydimethyldiallyl ammonium chloride-functionalized iron oxide (PDDA-Fe3O4) microcapsules with adsorptive, catalytic, and magnetic properties. The negatively charged PES facilitates MB adsorption through electrostatic interactions, while Fe3O4 enhances Fenton degradation and imparts magnetic responsiveness. Characterization techniques, including Fourier transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray analysis, confirmed the presence of PDDA-coated Fe3O4 and the formation of porous structures and finger-like cavities in the microcapsules. Process parameters such as microcapsule loading (10-30 g/L), MB concentration (10-50 ppm), pH (2-10), contact time (60-240 min), and H2O2 concentration (0.1-1 mol/L) were optimized using response surface methodology with a central composite design. Optimal conditions for MB removal (92.94%) were achieved with 21 g/L of microcapsules, 25 ppm of MB, pH 7, 127 minutes of contact time, and 0.45 mol/L of H2O2. These results demonstrate the efficacy of PDDA-Fe3O4@PES microcapsules for dye removal and suggest their potential for application in industries such as textiles and cosmetics, which generate high volumes of dye-contaminated wastewater.
      12  1
  • Publication
    Study on the enhancement of colloidal stable poly(sodium 4‐styrene sulfonate) coated magnetite nanoparticles and regeneration capability for rapid magnetophoretic removal of organic dye
    (Society of Chemical Industry (SCI), 2020)
    Wai Hong Chong
    ;
    Ng Qi Hwa
    ;
    Jit Kang Lim
    ;
    Swee Pin Yeap
    ;
    Siew Chun Low
    BACKGROUND: A good colloidal stability of magnetite nanoparticles (MNPs) dispersion is of utmost importance for its environmentally related applications. In the present work, a water-soluble anionic polyelectrolyte, poly(sodium 4-styrene sulfonate) (PSS), was used to stabilize dispersions of MNPs in a pH-dependent aqueous medium. RESULTS: An excellent methylene blue (MB) dye removal efficiency at equilibrium of up to 94% has been observed by the colloidally stabilized nano-magnetites. Dynamic light scattering and electrophoretic analysis showed that the PSS-coated MNPs exhibited better colloidal stability, with an almost constant hydrodynamic diameter of ~150 nm and insignificant clustering behavior throughout the measuring time scale of 5 h. Transmission electron microscopy evidenced the success coating of PSS onto MNPs. In terms of its chemical resistance, the PSS-coated MNPs were able to tolerate a wide pH range from 2 to 10. This work depicts a simple physiochemical coating method to stabilize dispersions of nano-magnetites, which promoted a better MB adsorption capacity of PSS-coated MNPs at 14.9 mg g–1 than the naked MNPs at 10.38 mg g–1. The adsorption process follows Langmuir isotherm and pseudo-second-order reaction kinetics with both correlations R2 > 0.99. PSS-coated MNPs demonstrated outstanding regeneration capacity for four batch adsorption cycles with an almost consistent MB removal efficiency higher than 85%. CONCLUSION: This in-house developed nano-sorbent has potential in economical applications with a less budgeted adsorbent replacement (at least 4 cycles of regeneration) for low-cost separation of pollutants, such as MB from polluted water.
      6  4