CeO2 for Water Remediation: Comparison of Various Advanced Oxidation Processes

Abstract

Three different Advanced Oxidation Processes (AOPs) have been investigated for the degradation of the imidacloprid pesticide in water: photocatalysis, Fenton and photo-Fenton reactions. For these tests, we have compared the performance of two types of CeO2, employed as a non-conventional photocatalyst/Fenton-like material. The first one has been prepared by chemical precipitation with KOH, while the second one has been obtained by exposing the as-synthetized CeO2 to solar irradiation in H2 stream. This latter treatment led to obtain a more defective CeO2 (coded as “grey CeO2”) with the formation of Ce3+ sites on the surface of CeO2, as determined by Raman and X-ray Photoelectron Spectroscopy (XPS) characterizations. This peculiar feature has been demonstrated as beneficial for the solar photo–Fenton reaction, with the best performance exhibited by the grey CeO2. On the contrary, the bare CeO2 showed a photocatalytic activity higher with respect to the grey CeO2, due to the higher exposed surface area and the lower band-gap. The easy synthetic procedures of CeO2 reported here, allows to tune and modify the physico-chemical properties of CeO2, allowing a choice of different CeO2 samples on the basis of the specific AOPs for water remediation. Furthermore, neither of the samples have shown any critical toxicity.

Exploring the Photothermo-Catalytic Performance of Brookite TiO2-CeO2 Composites

“…The typical signal at 153 cm −1 is a fingerprint of the presence of brookite and the lack of the usual Raman bands at 516 and 448 cm −1 , typical of the anatase and rutile phases, respectively [34], which indicates that brookite is the only phase present. Bare CeO2 showed a single band at 462 cm −1 related to the cubic fluorite structure (F2g vibration) [20]. All of the TiO2-CeO2 composites exhibited the bands of pure brookite, whereas the signal of CeO2 at 462 cm −1 overlapped with the second B2g band of brookite, although it is possible to note a broadening of this band in the mixed oxide samples.…”

“…The bare CeO 2 was synthetized through the chemical precipitation with KOH (Fluka, Buchs, Switzerland) following the procedure reported in the refs. [20,78]. After digestion and filtration.…”

“…the lower band gap (2.7-2.9 eV) compared to TiO 2 (that allows the activation by solar light irradiation). the redox properties that can promote a remarkable mobility of the surface oxygen with a beneficial effect for the oxidation reactions and the formation of Ce 4+ /Ce 3+ species [19,20].…”

The Influence of Photocatalytic Reactors Design and Operating Parameters on the Wastewater Organic Pollutants Removal—A Mini-Review

“…Considering as an example, the photo-Fenton process, the oxidative species (hydroxide radicals •OH) are generated from H 2 O 2 photolysis mediated by UV reduction of Fe 3+ ions into Fe 2+ (Equations ( 1) and ( 2)). The •OH photogeneration require a maximum pH around 3, which is the precondition for Fe +3 ions to exist as Fe(OH) 2+ [26][27][28].…”

Synthesis of Novel Kaolin-Supported g-C3N4/CeO2 Composites with Enhanced Photocatalytic Removal of Ciprofloxacin

“…Ciprofloxacin (CIP), a commonly used antibiotic in all aspects of life [ 2 ], can have a serious impact on the ecological environment balance [ 3 ]. To date, several strategies, including electro-Fenton [ 4 ], biological degradation [ 5 ], adsorption [ 6 ], membrane filtration [ 7 ] and photocatalytic degradation [ 8 ], have been employed to remove contaminants. Among them, photocatalysis has attracted more attention for the degradation of antibiotics [ 9 ].…”