Pathways and selectivity of Fenton degradation of different precursor species of dissolved organic matter.

Fenton has become one of the dominant technologies for the treatment of recalcitrantly degradable wastewater. Fenton reaction inevitably generates massive amounts of secondary dissolved organic matter (DOM). However, the pathways and selectivity of reaction remain unclear when Fenton is applied in a complex environmental system with different DOM molecules. Here, we design five levels of Fenton reactions based on typical precursor monomers of different DOM species and their stable isotope-labeled monomers combined with actual DOM media. The molecular information of the Fenton-derived DOM for all reactions is obtained based on ultra-high resolution mass spectrometry. The exact mass difference calculations demonstrate that Fenton degrades eight DOM precursor species by different pathways. The temporal gradient changes in the co-molecular characteristics of the Fenton-derived DOM between individual monomer reactions and gradient mixed monomer reactions confirm Fenton degradation selectivity toward eight DOM precursor species. These findings may provide a theoretical basis for using the Fenton process in the targeted degradation of organics.