Unexpected effect of ozone on the paraben's mixture degradation using TiO2 supported nanotubes

João Gomes; João Lincho; Pawel Mazierski; Magdalena Miodyńska; Adriana Zaleska-Medynska; Rui C Martins

doi:10.1016/j.scitotenv.2020.140831

Unexpected effect of ozone on the paraben's mixture degradation using TiO₂ supported nanotubes

Sci Total Environ. 2020 Nov 15:743:140831. doi: 10.1016/j.scitotenv.2020.140831. Epub 2020 Jul 9.

Authors

João Gomes¹, João Lincho², Pawel Mazierski³, Magdalena Miodyńska³, Adriana Zaleska-Medynska³, Rui C Martins²

Affiliations

¹ University of Coimbra, CIEPQPF - Chemical Engineering Processes and Forest Products Research Center, Department of Chemical Engineering, Faculty of Sciences and Technology, Rua Sílvio Lima, Polo II, 3030-790 Coimbra, Portugal. Electronic address: jgomes@eq.uc.pt.
² University of Coimbra, CIEPQPF - Chemical Engineering Processes and Forest Products Research Center, Department of Chemical Engineering, Faculty of Sciences and Technology, Rua Sílvio Lima, Polo II, 3030-790 Coimbra, Portugal.
³ Faculty of Chemistry, Department of Environmental Technology, University of Gdansk, 80-308 Gdańsk, Poland.

PMID: 32679505
DOI: 10.1016/j.scitotenv.2020.140831

Abstract

Titanium dioxide can present advantages when coupled with ozonation. Moreover, the catalytic ozonation can be enhanced by radiation. The main disadvantage of this technology is the use of a suspended catalyst entailing a separation step. Thus, catalytic ozonation was analysed using supported TiO₂ nanotubes prepared by anodization at different voltages. The effect of different radiation sources on the catalytic ozonation of parabens was tested. The increase on voltage preparation led to plates with higher surface areas from 60 to 280 cm². However, this did not improve the parabens mixture degradation during UVA photocatalytic ozonation. The use of sunlight radiation allows a significant reduction in terms of time necessary for total parabens degradation from 15 to 10 min. However, the amount of ozone required doubles. Catalytic ozonation presents worst results than single ozonation. This means that molecular ozone is the main responsible for degradation. No dissolved ozone was detected at the experiments with supported nanotubes which could mean that it was adsorbed on the catalysts surface decreasing the degradation rates. The presence of municipal wastewaters as matrix inhibited parabens degradation for both single and catalytic ozonation, mainly due to the trapping ozone effect. In fact, for the TOD of 4.5 mg/L it was just possible to remove about 80% of parabens when MWW compared to 100% when UP was used. Even so, the presence of supported nanotubes during ozonation seems to be required to reduce the toxicity of the resultant treated effluent. In fact, the wastewater luminescence inhibition decreased (from 100 to 43%) and germination index increased (from 7 to 97%) with catalytic ozonation which may enable treated water reuse.

Keywords: Nanotubes TiO(2); Ozone; Parabens abatement; Photo-driven technologies; Toxicity reduction.