Self-Assembling Of Visible-Light Responsive Nitrogen-Doped Carbon Quantum Dots/Titanium Dioxide On Poly(Acrylic Acid) Grafted Polyethersulfone Membrane For Dye Degradation And Filtration Enhancement

• Main Author: Heng, Zeng Wei
• Format: Final Year Project / Dissertation / Thesis
• Published: 2021
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.utar.edu.my/4589/1/Heng_Zeng_Wei.pdf; http://eprints.utar.edu.my/4589/

Considering the tedious post-reaction recovery of nano-sized phototcatalysts and the critical fouling problem faced in membrane separation, incorporation of photocatalyst with polymeric membrane has been developed to alleviate these issues. Due to the large band gap and the rapid recombination of electron-hole pairs of titanium dioxide (TiO2), the present work suggested the use of waste oil palm frond as an alternative precursor for nitrogen-doped carbon quantum dots (NCQDs) and proposed a straightforward in-situ hydrothermal method for the preparation of NCQDs/TiO2 nanocomposites. The nanocomposite with the optimum performance was then incorporated on PES membrane to synthesise a novel composite membrane with photocatalytic ability, high rejection, antifouling and self-cleaning properties. The photocatalytic activities of the synthesised nanocomposites and the fabricated photocatalytic membranes were evaluated through the photodegradation of methylene blue (MB) under visible-light irradiation. The photocatalytic efficiency of NCQDs/TiO2 nanocomposites (86.16%) was 2.85 times higher than its counterpart TiO2 (30.18%). The surface morphology, elemental composition, structural and optical characteristics of NCQDs/TiO2 nanocomposites have been comprehensively. The successful coupling of NCQDs/TiO2 (hereafter denoted as NTO) was confirmed by the formation of Ti–O–C bond and the electronic coupling between the π-states of NCQDs and the conduction band (CB) of TiO2. The modified membranes with varying photocatalyst concentration (0.1, 0.3 and 0.5 wt% NTO) were characterised for their surface chemistry, morphology and hydrophilicity. The photocatalytic membrane demonstrated high resistance to MB fouling and was able to revive 93.7% of original water fluxes upon 15 min of visible-light irradiation. Moreover, the modified membranes efficiently retained 90.9% of MB dye pollutant. The NTO0.5/PAA/PES membrane degraded 94.9% of MB under 1 hr of visible-light irradiation. With its twofold advantages of membrane filtration and photocatalysis, the visible-light responsive photocatalytic membrane demonstrates huge potential in waste water treatment which could minimise membrane fouling and increase the reusability of photocatalyst.