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

Li Ying Yee; Qi Hwa Ng; Siti Kartini Enche Ab Rahim; Peng Yong Hoo; Pei Thing Chang; Abdul Latif Ahmad; Siew Chun Low; Siew Hoong Shuit

doi:10.3390/membranes13020174

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

Membranes (Basel). 2023 Jan 31;13(2):174. doi: 10.3390/membranes13020174.

Authors

Li Ying Yee¹, Qi Hwa Ng^{1

2}, Siti Kartini Enche Ab Rahim^{1

2}, Peng Yong Hoo^{1

2}, Pei Thing Chang³, Abdul Latif Ahmad³, Siew Chun Low³, Siew Hoong Shuit^{4

5}

Affiliations

¹ Faculty of Chemical Engineering & Technology, Universiti Malaysia Perlis (UniMAP), Arau 02600, Perlis, Malaysia.
² Centre of Excellence for Frontier Materials Research (CFMR), Universiti Malaysia Perlis (UniMAP), Arau 02600, Perlis, Malaysia.
³ School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, Nibong Tebal 14300, Pulau Pinang, Malaysia.
⁴ Department of Chemical Engineering, Lee Kong Chian Faculty of Engineering & Science, Sungai Long Campus, Universiti Tunku Abdul Rahman, Jalan Sungai Long, Bandar Sungai Long, Cheras, Kajang 43000, Selangor, Malaysia.
⁵ Centre of Photonics and Advanced Materials Research, Sungai Long Campus, Universiti Tunku Abdul Rahman, Jalan Sungai Long, Bandar Sungai Long, Cheras, Kajang 43000, Selangor, Malaysia.

Abstract

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.

Keywords: augmented microspheres; hybrid polyoxometalates; magnetic responsive; pH-responsive; photocatalytic responsive.

Grants and funding

This research was funded by Ministry of Higher Education Malaysia’s (MOHE) Fundamental Research Grant Scheme (FRGS) under grant number FRGS/1/2021/TK0/UNIMAP/02/3 and the APC was funded by Universiti Malaysia Perlis (UniMAP) scientific publication fund.