Tuning the reactivity of permanganate by naturally occurring DNA bases: Enhanced efficiency of micropollutant abatement

The transformation of extracellular DNA (e.g., antibiotic resistance genes) in water has attracted increasing attention over the last decades. To date, the effect of the resulting byproducts (e.g., DNA bases) on the degradation of micropollutants by oxidants remains largely unknown. In this study, four DNA bases (i.e., deoxyadenosine (dA), deoxythymidine (dT), deoxycytidine (dC), and deoxyguanosine (dG)) were investigated as potential permanganate (Mn(VII)) activators for the oxidation of tetracycline (TC) in water. The dC exhibited the best performance, e.g., the first-order rate constant of TC increased from 0.082 min −1 in the absence of dC (i.e., Mn(VII) alone) to 0.290 min −1 in the presence of 500 µM dC (i.e., Mn(VII)/dC system). The degradation of three other emerging micopollutants (i.e., bisphenol F (BPF), bisphenol S (BPS), and methotrexate (MTX)) by Mn(VII)/dC was also greater than Mn(VII) alone. Multiple lines of evidence suggested that the synergistic effect of in-situ formed MnO 2 colloids and Mn(VII) had a major role in the observed enhancement compared to radicals, Mn(VI), Mn(V) or Mn(III). The transformation products (TPs) of TC by Mn(VII) with and without dC were tentatively identified, from which the reaction pathways were proposed. Despite the high degradation of micropollutants by Mn(VII)/dC system, the majority of TPs were recalcitrant to biodegradation with multi-endpoint adverse health effects on different aquatic organisms, as indicated by in silico prediction software. Overall, this study unveiled the free DNA bases as in-situ Mn(VII) activators for removing emerging contaminants of global concern from water. However, the secondary environmental risks related to the TPs need to be considered in terms of water safety assessment.