Degradation studies of UV filter hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl] -benzoate (DHHB) in aqueous solution

• Type: Article in International Scientific Journal
• Date: 2021

Authors

Santos, AJM (Author) Other; Joaquim C G E Esteves da Silva (Author) FCUP

Journal

Title: Journal of Contaminant Hydrology

Vol. 236

ISSN: 0169-7722

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 1 Citation

Scopus - 1 Citation

Other information

Authenticus ID: P-00T-7KF

DOI: 10.1016/j.jconhyd.2020.103740

Abstract (EN): High performance liquid chromatography coupled with ultra-violet, diode array detection (HPLC-UV-DAD), was used to study the degradation reactions of ultraviolet (UV) filter hexyl 244-(diethylamino)-2-hydroxybenzoyl]- benzoate (DHHB). Degradation by-products were detected and identified by means of liquid chromatography coupled with diode array detection and mass spectrometry (LC-DAD-MS). Environmentally-relevant characteristics, such as water pH, chlorine levels, water temperature and dissolved organic matter (DOM) concentration, were modulated and studied in order to determine their influence on the degradation reactions. Results show that DHHB degrades quite rapidly in typical drinking water disinfection conditions, displaying a kinetic rate constant of k(obs) = 0.0060 + 0.0002 s(-1) and a half-life period of merely t(1/)(2) = 116 +/- 4 s. As far as the non-volatile disinfection by-products (DBPs) are concerned, only the mono and dichlorinated forms of DHHB were detected in the degradation reactions. Regarding influential variables on DHHB degradation, the presence or absence of DOM in solution did not alter the trends that were found (degradation of DHHB is more significant at lower pH values and higher levels of active chlorine in solution). Chlorinated DBPs have also been found to predominate under higher pH values and lower levels of chlorine, whereas they were found to be unstable and further degradable, quite likely into smaller and more volatile compounds, when in lower pH and higher chlorine concentrations. As for the photo-degradation studies, DHHB was found to be extremely photo-stable, with only about 15% degradation rate detected during artificial irradiation periods of 6 h.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9