Three degradation pathways of 1-octyl-3-methylimidazolium cation by activated sludge from wastewater treatment process

The biodegradability and degradation pathways of 1-octyl-3-methylimidazolium cation [OMIM]⁺ by microbial community of wastewater treatment plant in Jeonju city, Korea were investigated. It was found that [OMIM]⁺ could be easily degraded by the microbial community. New degradation products and pathways of [OMIM]⁺ were identified, which are partially different from previous results (Green Chem. 2008, 10, 214-224). For the analysis of the degradation pathways and intermediates, the mass peaks observed in the range m/z of 50-300 were screened by using a tandem mass spectrometer (MS), and their fragmentation patterns were investigated by MS/MS. Surprisingly, we found three different degradation pathways of [OMIM]⁺, which were separated according to the initially oxidized position i.e. middle of the long alkyl chain, end of the long alkyl chain, and end of the short alkyl chain. The degradation pathways showed that the long and short alkyl chains of [OMIM]⁺ gradually degraded by repeating oxidation and carbon release. The results presented here shows that [OMIM]⁺ can be easily biodegraded through three different degradation pathways in wastewater treatment plants.