Degradation of propranolol by UV-activated persulfate oxidation: Reaction kinetics, mechanisms, reactive sites, transformation pathways and Gaussian calculation

Tiansheng Chen; Jingshuai Ma; Qianxin Zhang; Zhijie Xie; Yongqin Zeng; Ruobai Li; Haijin Liu; Yang Liu; Wenying Lv; Guoguang Liu

doi:10.1016/j.scitotenv.2019.07.034

Degradation of propranolol by UV-activated persulfate oxidation: Reaction kinetics, mechanisms, reactive sites, transformation pathways and Gaussian calculation

Sci Total Environ. 2019 Nov 10:690:878-890. doi: 10.1016/j.scitotenv.2019.07.034. Epub 2019 Jul 6.

Authors

Tiansheng Chen¹, Jingshuai Ma¹, Qianxin Zhang¹, Zhijie Xie¹, Yongqin Zeng¹, Ruobai Li¹, Haijin Liu², Yang Liu³, Wenying Lv⁴, Guoguang Liu⁵

Affiliations

¹ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China.
² School of Environment, Henan Normal University, Key Laboratory for Yellow River and Huaihe River Water Environment and Pollution Control, Xinxiang 453007, China.
³ Faculty of Environmental & Biological Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, China.
⁴ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China. Electronic address: lvwy612@163.com.
⁵ School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China. Electronic address: liugg615@163.com.

PMID: 31302552
DOI: 10.1016/j.scitotenv.2019.07.034

Abstract

Contamination with β-blockers such as propranolol (PRO) poses a potential threat to human health and ecological system. The present study investigated the kinetics and mechanisms of PRO degradation by UV-activated persulfate (UV/PS) oxidation. Here, the experimental results showed that the degradation of PRO followed pseudo-first-order reaction kinetics, the degradation rate constant (k_obs) was increased dramatically with increasing PS dosage or decreasing initial PRO concentration. And increasing the initial solution pH could also enhance the degradation efficiency of PRO. Radical scavenging experiments demonstrated that the main radical species was sulfate radicals (SO₄^•-), with hydroxyl radicals (HO·) playing a less important role. Meanwhile, the second-order rate constants of PRO degradation with SO₄^•- and HO· were determined to be 1.94 × 10¹⁰ M^-1 s^-1 and 6.77 × 10⁹ M^-1 s^-1, respectively. In addition, the presence of natural organic matter (NOM) and nitrate anion (NO₃^-) showed inhibitory effect on PRO degradation, whereas bicarbonate anion (HCO₃^-) and chlorine anion (Cl^-) greatly enhanced the degradation of PRO. Moreover, the transformation products of PRO were identified by applying ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) technique. Molecular orbital calculations were used to estimate the reaction site of PRO with radicals, simultaneously. Hence, the transformation pathways including hydroxylation, dehydration, naphthalene ring opening, and the cleavage of aldehyde groups were proposed. This work enriches the mechanism of PRO degradation under UV/PS system on the basis of results obtained by experimental characterization and Gaussian theoretical calculation.

Keywords: Molecular orbital calculations; Propranolol; Reaction kinetics; Transformation products; UV-activation persulfate.