UV-activated persulfate oxidation of the insensitive munitions compound 2,4-dinitroanisole in water: Kinetics, products, and influence of natural photoinducers

Abstract

2,4-Dinitroanisole (DNAN) is an emerging organic contaminant that may pose potential risks to both human health and ecological system. In this contribution, we attempt to investigate the degradation of DNAN in water by UV-based advanced oxidation processes, including UV/H2O2 and UV/persulfate (UV/PS). Both UV/H2O2 and UV/PS were capable of degrading DNAN; however, the latter appeared to be more efficient than the former, especially when high dosage of peroxide was utilized. An increase in the degradation rate of DNAN was observed with increasing concentration of PS. Kinetic modeling based on the assumption of steady-state concentration of sulfate radical (SO4−) underestimated the removal of DNAN, most likely due to an decrease in PS concentration and significant formation of by-products. Time-dependent evolution of 2,4-dinitrophenol (2,4-DNP), the major intermediate product of DNAN, can be well described by a sequential kinetic model. Solution pH had negligible impact on DNAN degradation. The presence of natural occurring photoinducers, such as Suwannee River fulvic acid (SRFA) and nitrate (NO3−), inhibited the degradation of DNAN appreciably, possibly due to light screening and/or radical scavenging effects. However, high concentration of NO3− mitigate the inhibitory effect, presumably due to the reactive nitrogen species (RNS) generated by NO3− photolysis. Experimental results suggest that DNAN was amenable to oxidation by UV/PS; however, the treatment efficiency could be remarkably influenced by natural photoinducers present in waters such as natural organic matter (NOM) and NO3−.