Efficient degradation of propranolol with electrochemically activated peracetic acid process: Mechanisms, degradation pathway, and toxicity evaluation

Abstract

Electrochemical oxidation has attracted considerable attention in advanced oxidation processes (AOPs) due to its clean and green advantages. In this work, mixed metal oxide (MMO) electrodes were applied for the first time in electrochemically activated peracetic acid (EC/PAA) to investigate the systematic degradation of propranolol (PPL). The results showed that the EC/PAA-MMO/MMO system significantly promoted the removal of PPL from water, achieving a remarkable removal rate of 87.05% within 20 min, which was better than that of electrochemically activated peroxymonosulfate (PMS) or H2O2. Hydroxyl radical (OH), organic radical (RO), singlet oxygen (1O2), and superoxide radical (O2−) were confirmed to be the primary reactive species. Apart from OH, the contribution rate of the other reactive species was up to 41.92%, which played a crucial role in the degradation of PPL. Notably, RO exhibited a specific effect on the degradation of PPL, while 1O2, and O2− were crucial in initiating the chain reaction of the reactive species. With the increasing of PAA concentration and current density, and the decreasing of electrode distance, an acceleration of PPL degradation efficiency was observed. Additionally, maintaining a neutral pH was found to be beneficial for the degradation of PPL. Furthermore, the degradation pathways of PPL were elucidated based on density-functional theory and LC-MS detection. Quantitative structure–activity relationship (QSAR) analyses revealed a significant reduction in the toxicity of PPL products after the degradation by EC/PAA. The results suggest that EC/PAA-MMO/MMO is a promising technology for the removal of naphthyl-containing pollutants that are difficult to be degraded by OH.