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Identifier

000454388

Title

Solar light induced photocatalytic removal of Methyl Paraben from water using g-C3N4/CeO2 photocatalyst

Alternative Title

Φωτοκαταλυτική αποδόμηση του Methyl Paraben απο το νερό με τη χρήση του φωτοκαταλύτη g-C3N4/CeO2, υπο ηλιακό φως

Author

Ζωγραφάκη, Μαρία

Thesis advisor

Αρματάς, Γεράσιμος

Reviewer

Ρεμεδιάκης, Ιωάννης
Στούμπος, Κωνσταντίνος

Abstract

Current trends in water and wastewater treatment are focused on the development of cost-effective, environmental-friendly and sustainable treatment technologies, which are consistent with the “zero” waste concept. Parabens are commonly used as antimicrobial preservatives in pharmaceutical products, cosmetics, and foodstuff. Both parabens and their halogenated products are toxic and negatively affect the anatomy and physiology of animals and humans. Solar photocatalysis, which is an advanced oxidation process, has been considered as a viable alternative for the removal of parabens and their metabolites from water due to high degradation efficiency and no demand energy. Graphitic carbon nitride (g-C3N4), a typical metal-free photocatalyst, is particularly attractive thanks to its cheapness, non-toxicity and exceptional chemical stability. Despite all the above advantages, its photocatalytic performance is still insufficient due to low visible light response and high recombination rate of the photogenerated electrons and holes. Α great number of semiconductors have been coupled with g-C3N4 to construct heterojunctions. Among them, cerium oxide (CeO2), an essential and inexpensive rare earth metal oxide, has been attracting intense attention in photocatalysis, owing to the great oxygen storage capacity (OSC) and multi-valence states of Ce4+/Ce3+, which could be beneficial to reduce the recombination rate of photoinduced charge carriers. Herein, we report for the first time an efficient photocatalytic system for methyl paraben (MP) removal, using solar (λ > 360 nm) and visible (λ > 420 nm) light-driven CeO2/g-C3N4 heterojunctions. The physicochemical properties of pure CeO2, g-C3N4, and CeO2/g-C3N4 composites were investigated using a combination of characterization techniques, such as XRD, SEM-EDS, TEM, UV-Vis, XPS and electrochemical spectroscopy. Among the catalysts with different mass ratio of CeO2, 10%CeO2/g-C3N4 showed the best photocatalytic performance. This is attributed to the enhanced charge carrier’s separation as a result of the proper band edges alignment between g-C3N4 and CeO2 components, and the strong visible light absorbance. The photocatalytic degradation of MP followed the first-order kinetics, and the 10%CeO2/g-C3N4 catalyst exhibited a 2.5- and 11.2-times higher reaction rate (k) constant than that of pure g-C3N4, investigated under solar and visible light illumination, respectively. Further, from scavenger trapping experiments it is confirmed that hydroxyl radicals (OH.) and dissolved oxygen are the predominant active species involved in MP oxidation over 10%CeO2/g-C3N4 composite catalyst.

Language

English

Subject

Carbon nitride

Cerium oxide

Μέθυλ Πάραμπεν

Οξείδιο του Δημητρίου

Φωτοκατάλυση

Issue date

2023-03-29

Collection

School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Post-graduate theses