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The effect of dissolved chlorides on the photocatalytic degradation properties of titania in wastewater treatment

Delarmelina, Maicon ORCID:, Dlamini, Mbongiseni, Pattisson, Samuel, Davies, Philip Rosser ORCID:, Hutchings, Graham ORCID: and Catlow, Charles ORCID: 2023. The effect of dissolved chlorides on the photocatalytic degradation properties of titania in wastewater treatment. Physical Chemistry Chemical Physics 25 , pp. 4161-4176. 10.1039/D2CP03140J

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We investigate the effect of chlorides on the photocatalytic degradation of phenol by titania polymorphs (anatase and rutile). We demonstrate how solubilised chlorides can affect the hydroxyl radical formation on both polymorphs with an overall effect on their photodegradative activity. Initially, the photocatalytic activity of anatase and rutile for phenol degradation is investigated in both standard water and brines. With anatase, a significant reduction of the phenol conversion rate is observed (from a pseudo-first-order rate constant k = 5.3 x 10-3 min-1 to k = 3.5 x 10-3 min-1). In contrast, the presence of solubilised chlorides results in enhancement of rutile activity under the same reaction conditions (from 2.3 x 10-3 min-1 to 4.8 x 10-3 min-1). Periodic DFT methods are extensively employed and we show that after the generation of charge separation in the modelled titania systems, adsorbed chlorides are the preferential site for partial hole localisation, although small energy differences are computed between partially localised hole densities over adsorbed chloride or hydroxyl. Moreover, chlorides can reduce or inhibit the ability of r-TiO2 (110) and a-TiO2 (101) systems to localise polarons in the slab structure. These results indicate that both mechanisms – hole scavenging and the inhibition of hole localisation - can be the origin of the effect of chlorides on photocatalytic activity of both titania polymorphs. These results provide fundamental insight into the photocatalytic properties of titania polymorphs and elucidate the effect of adsorbed anions over radical formation and oxidative decomposition of organic pollutants.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: Royal Society of Chemistry
ISSN: 1463-9076
Funders: EPSRC
Date of First Compliant Deposit: 12 January 2023
Date of Acceptance: 23 December 2022
Last Modified: 19 Jun 2023 17:55

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