Oxidation of indometacin by ferrate (VI): kinetics, degradation pathways, and toxicity assessment

• Published in: Environmental science and pollution research international 2017-04, Vol.24 (11), p.10786-10795
• Main Authors: Huang, Junlei, Wang, Yahui, Liu, Guoguang, Chen, Ping, Wang, Fengliang, Ma, Jingshuai, Li, Fuhua, Liu, Haijin, Lv, Wenying
• Format: Article
• Language: English
• Subjects: Algae; Aquatic plants; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bacteria; Biodegradation; Chronic toxicity; Degradation; Deionization; Earth and Environmental Science; Ecological monitoring; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Fulvic acids; Hydrogen-Ion Concentration; Hydroxyl groups; Indomethacin; Iron - chemistry; Kinetics; Lakes; Linkages; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Microtox; Oxidation; Oxidation-Reduction; pH effects; Rate constants; Reaction kinetics; Research Article; Structure-activity relationships; Tandem Mass Spectrometry; Toxicity; Vibrio fischeri; Waste Water Technology; Water analysis; Water Management; Water Pollution Control; Water sampling; Waterborne diseases
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-017-8750-x

The oxidation of indometacin (IDM) by ferrate(VI) (Fe(VI)) was investigated to determine the reaction kinetics, transformation products, and changes in toxicity. The reaction between IDM and Fe(VI) followed first-order kinetics with respect to each reactant. The apparent second-order rate constants ( k app ) decreased from 9.35 to 6.52 M −1  s −1 , as the pH of the solution increased from 7.0 to 10.0. The pH dependence of k app might be well explained by considering the species-specific rate constants of the reactions of IDM with Fe(VI). Detailed product studies using liquid chromatography-tandem mass spectrometry (LC-MS/MS) indicated that the oxidation products were primarily derived from the hydrolysis of amide linkages, the addition of hydroxyl groups, and electrophilic oxidation. The toxicity of the oxidation products was evaluated using the Microtox test, which indicated that transformation products exhibited less toxicity to the Vibrio fischeri bacteria. Quantitative structure-activity relationship (QSAR) analysis calculated by the ecological structure activity relationship (ECOSAR) revealed that all of the identified products exhibited lower acute and chronic toxicity than the parent pharmaceutical for fish, daphnid, and green algae. Furthermore, Fe(VI) was effective in the degradation IDM in water containing carbonate ions or fulvic acid (FA), and in lake water samples; however, higher Fe(VI) dosages would be required to completely remove IDM in lake water in contrast to deionized water.