Solar photocatalytic degradation of parabens using UiO-66-NH2

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-NH2Authors acknowledge Spanish State Research Agency (PID2019- 106186RBI00/AEI/10.13039/501100011033). M. Peñas-Garzón is indebted to Spanish MECD (FPU16/00576 grant) and MICIU (EST19/ 00068). M.J.S. thanks to Project POCI-01-0145-FEDER-030674 (MicroPhotOGen, PTDC/NAN-MAT/30674/2017) funded by ERDF through COMPETE2020 - Programa Operacional Competitividade e Internacionalizaçao (POCI) – and by national funds through FCT - Fundaçao para a Ciência e a Tecnologia. We would like to thank the scientific collaboration financially supported by: Base-UIDB/50020/ 2020 and Programmatic-UIDP/50020/2020 Funding of Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC). Authors thank the Research Support Services of the Universidad Autónoma de Madrid (SIdI), University of Extremadura (SAIUEx), University of Málaga (SCAI) and Universidad Complutense of Madrid (CAI