Degradation of ribavirin by Fe2+/PS oxidation technology: performance, mechanism and toxicity control

During the COVID-19 pandemic, the extensive use of ribavirin (RBV) raised concerns about its environmental residues and associated risks, necessitating remedial actions. This study investigates the degradation efficiency, mechanism, and biotoxicity of RBV using ferrous (Fe 2+ ) activated persulfate (PS) advanced oxidation technology (Fe 2+ /PS oxidation). Experiments conducted under various conditions revealed that at pH = 3, PS concentration of 4 mM, PS/Fe 2+ molar ratio of 2:1, and citric acid of 0.5 mM with Fe 2+ added twice, the degradation rate of RBV reached 98.70 %. The degradation process of RBV by Fe 2+ /PS from 0 to 5 mins followed a first-order reaction kinetics model. The presence of halide ions (Cl - , Br - , I - ) was found to inhibit the degradation efficiency. The active species involved were identified as SO 4 - ·, ·OH, 1 O 2 , and FeO 2+ , with SO 4 - · and ·OH being the most significant. Moreover, the products of ribavirin were determined and their degradation pathways were proposed. Dehydration, deamidation, C-N bond breaking and hydroxylation were the major pathways. Additionally, toxicity assessment showed that Fe 2+ /PS oxidation reduced the inhibition rate of bioluminescence in Vibrio fischeri from 31.58 % to 3.88 %, effectively controlling RBV toxicity during the reaction. This study provides insights into managing water environmental risks associated with pharmaceutical residues in the post-pandemic era.