Methadone degradation and reduced nitrosamine formation in synthetic human urine by the photoelectrochemical process using GOTiO2 film photoelectrodes
Journal
Chemical Engineering Journal
Journal Volume
524
Start Page
168977
ISSN
13858947
Date Issued
2025-11-15
Author(s)
Abstract
Source-separated urine treatment offers an efficient approach to minimizing pharmaceutical contaminants released into aquatic environments while simultaneously recovering valuable nutrients, offering a sustainable strategy for resource reclamation. This study investigated methadone degradation in synthetic human urine using the photoelectrochemical (PEC) process with graphene oxide‑titanium dioxide (GOTiO2) film photoelectrodes under UV-A irradiation. The study is the first to comprehensively elucidate the degradation mechanism of methadone and assess the generation of nitrosamine byproducts within the urine matrix. Among other processes (photolysis, photocatalysis, photochemical, electrochemical (EC), and PEC processes), the PEC process demonstrated the highest methadone degradation rates at a current density of 4 mA/cm2 and an electrode distance of 0.5 cm, with rates of 0.0116 min−1 in fresh urine (pH 5.6) and 0.0113 min−1 in hydrolyzed urine (pH 9.4). The generated reactive species including •OH, •O2−, 1O2, •Cl, OCl−, and ozone were identified in both PEC and EC processes. 1O2 was the dominant contributing to methadone degradation in hydrolyzed urine (PEC: 38.3 %; EC: 63.7 %), while •OH, •O2−, •Cl, and OCl− also involved degradation. The presence of chloride and ammonia enhanced methadone degradation, while bicarbonate hindered the reaction through scavenging effects. Three nitrosamine byproducts (N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and 2-Ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine perchlorate (EDDP)) were detected during operation. The inhibition of the highly toxic carcinogen NDMA in hydrolyzed urine during PEC process under UV-A irradiation was observed, compared to EC process. This study further provides insight into that this PEC process is not only capable of rapidly degrading recalcitrant micropollutants, but also potentially controlling the formation of byproducts, making it a promising treatment for urine while further reuse.
Subjects
Human urine
Methadone
Nitrosamine byproducts
Photoelectrochemical
Reaction kinetics
SDGs
Publisher
Elsevier B.V.
Type
journal article