Solar photocatalytic degradation of parabens using UiO-66-NH2

https://doi.org/10.1016/j.seppur.2022.120467Get rights and content
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Highlights

  • Photocatalytic breakdown of parabens using MOFs is reported for the first time.

  • High paraben conversion in natural waters, despite variable concentrations of other organics and inorganics.

  • Stable photocatalytic performance with negligible photocatalyst detrition when using a continuous flow system.

  • The oxidation mechanism is mainly dependent on photogenerated holes and superoxide radicals.

Abstract

The photocatalytic degradation of methylparaben was investigated under simulated solar light using a synthesised metal–organic framework (UiO-66-NH2). For that purpose, the pollutant was spiked in different water matrices: distilled water, water from Lima River (Northwestern Portugal), and urban wastewater. Complete removal of the methylparaben in distilled water was achieved in 1 h reaction. In natural water matrices, the photocatalytic performance decreased to 70% removal after 3 h reaction, owing to the physical–chemical properties of the water samples. The UiO-66-NH2 photocatalyst revealed high stability under the continuous mode, reaching a steady state in 5 h, from which the removal percentage was kept constant for 25 h. The photocatalytic degradation of methylparaben gave five main reaction byproducts and four short-chain carboxylic acids, identified by LC/ESI-MS and UHPLC analyses, respectively. The mechanism of degradation was investigated by using selective scavengers. Photogenerated holes and superoxide radicals were found as the main species responsible for the degradation of methylparaben. The abatement of other parabens (as ethyl- and propylparaben) was also evaluated, being the conversion influenced by the length of the alkyl side chain. The results of this study give a comprehensive sight into the effective photocatalytic remediation of parabens using UiO-66-NH2.

Keywords

Methylparaben
UiO-66-NH2
Solar photocatalysis
WWTP effluent
Continuous flow mode
Photocatalytic mechanism

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