The complex biopolymer lignin makes up approximately 25% of the organic carbon in the biosphere and plays a key role in the global C cycle that sustains the Earth by being an integral component of modern organic matter and in the past by its involvement in the formation of coal and other fossil fuels. Reactive oxygen species (ROS) have been implicated in oxidative transformations of lignin in the environment and this leads to both mineralization (to CO2 and H2O) as well as chemical rearrangement to new molecules which contribute to previously uncharacterized natural organic matter (e.g., humic substances). Examination of these new molecules by ultrahigh resolution mass spectrometry, FTIR, and synchrotron X-ray absorption spectroscopy indicates that the oxidative degradation and rearrangement appears to be catalyzed by transition metals (mainly Fe and possibly Mn). We subjected natural lignin concentrates to oxidative decomposition by ROS and Fe (II) salts (Fenton chemistry) and mimicked the manner in which lignin is naturally degraded to humic substances in the environment by photochemical, mineral-catalyzed oxidations, and biological oxidation.

Interaction of lignin with Fe (II) in the environment leads to the production of humic substances in natural waters, sediments, and soils via Fenton chemistry

253rd National Meeting (2017)

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