☆ 4.8 Article

Comparison of the degradation of multiple amine-containing pharmaceuticals during electroindirect oxidation and electrochlorination processes in continuous system

WATER RESEARCH (2021)

Journal

WATER RESEARCH

Volume 203, Issue -, Pages -

Publisher

PERGAMON-ELSEVIER SCIENCE LTD

DOI: 10.1016/j.watres.2021.117517

Keywords

Multiple amine-containing pharmaceuticals; Dimer; Electroindirect oxidation; Electrochlorination; Toxicity; Scavenger

Funding

National Taiwan University via the Excellence Research Program-Core Consortiums [NTUCCP-107 L891301, NTU-108 L8806, NTU-108 L4000, NTU-109 L4000]
NTU Research Center for the Future Earth via the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE)
Ministry of Science and Technology in Taiwan [MOST108-2621-M-002-024-MY2]

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Abstract

This study compared the degradation of pharmaceuticals by electrochemical oxidation in batch and continuous reactors, revealing different removal sequences in systems with and without chloride. The presence of residual chlorine in electrochlorination systems significantly affected the degradation pathways of pharmaceuticals.

The degradation of pharmaceuticals by electrochemical oxidation (EO) in simulated wastewater containing multiple pharmaceuticals was compared between batch and continuous reactors. Despite the excellent efficiencies achieved in batch experiments, the practical/large-scale applications of EO-degrading amine-containing pharmaceuticals has not yet been accomplished. This paper presents the results of continuous experiments with one of the most promising electrochemical configurations of Pt/Ti electrodes before proceeding to application. In the continuous electrooxidation system (without chloride), direct oxidation on the electrode surface and oxidation by hydroxyl radicals were the main pathways. Due to their short lifespans, the radicals could not be transferred to the bulk solution, and the removal of pharmaceuticals followed the order of sulfamethoxazole (SMX) > paracetamol (PAR) > diclofenac (DIC). In the electrochlorination system (with chloride), oxidation by residual chlorine was the main pathway. The removal of pharmaceuticals followed the order of sulfamethoxazole (SMX) > diclofenac (DIC) > paracetamol (PAR). High SMX removal was realized because of the high reaction rate of SMX with free chlorine. Among the pharmaceuticals, PAR had the lowest removal because it is a neutral species with a low mass transfer rate without the attraction of electrostatic force. These results are consistent with the predictions from our previous batch-scale study, which showed that the reaction rate of dissociated compounds could be increased by the addition of electrostatic force. Furthermore, multiple coexisting pharmaceuticals, such as SMX and PAR or DIC, may form dimers that can be transferred to complex structures and cause higher toxicity.

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Elimination of pesticide from high salinity wastewater by electrochlorination process: Active chlorine species and scale-up performance

Zhiyong Wang, Kuiling Li, Jingjing Guo, Chengfeng Yang, Liu Yan, Wei Feng, Yong Zhang, Jun Wang

Summary: The electrochemical process mediated by active chlorine species is a promising strategy for the removal of refractory pollutants and ammonia in high salinity organic wastewater. In this study, an electrochlorination (E-Cl) process was constructed using the high concentration of chloride ions in the wastewater, and it showed efficient removal of pesticide wastewater. The E-Cl process produced active chlorine species, including free chlorine, reactive chlorine species, and hydroxyl radical, during electrolysis, resulting in excellent removal efficiency of chemical oxygen demand (COD) and atrazine (ATZ) in the pesticide wastewater.

SEPARATION AND PURIFICATION TECHNOLOGY (2023)