Far-UVC Radiation Activating Percarbonate to Accelerate the Removal of Methotrexate: Degradation Efficiency, Mechanisms, and Moiety-Dependence Transformation
Jiawei Chen, Lin Du, Jian Liu, Lifeng Lin, Min Zhao, Lei Wang, Shaohua Chen, Jianzhi Huang
Abstract
This study investigated innovative advanced oxidation processes (AOPs) combining far-UVC radiation at 222 nm with sodium percarbonate (SPC) to effectively remove methotrexate (MTX). UV 222 significantly enhanced the direct photolysis and AOP degradation of MTX. •OH, CO 3 •–, and direct photolysis were primarily involved in the degradation, with their relative contribution being in the order •OH > CO 3 •– > direct photolysis. The fluence-normalized steady-state concentrations of both CO 3 •– and •OH in UV 222 /SPC were 7.76 and 4.05 times higher, respectively, than those in UV 254 /SPC. Transformation product analysis revealed distinct MTX degradation pathways and varied degradation rates of MTX substructures between the systems, with the order in UV 254 /SPC being 4-aminobenzamide (ABZ) > 2,4-diamino-6-(hydroxymethyl) pteridine (DHP) > l -glutamic acid (LG) and that in UV 222 /SPC being DHP > ABZ > LG, suggesting different reactivities of MTX moieties under each system. The presence of HCO 3 – and HA inhibited the MTX degradation, whereas NO 3 – promoted it, in the UV 222 /SPC system. In addition, UV 222 /SPC demonstrated a lower energy consumption compared to UV 254 /SPC, highlighting its potential for cost-effective wastewater treatment applications. This study offers new insights into the mechanisms of UV 222 /SPC systems and provides guidance for the development of technologies for the removal of emerging contaminants.