Degradation of 2,4-dinitrotoluene by persulfate activated with iron sulfides

Of the many oxidants studied to date for subsurface remediation, persulfate (S2O82−) is particularly attractive for its stability under ambient conditions and high reactivity upon activation. In this study we evaluated a new approach to activate persulfate, namely using pyrite (FeS2) or iron sulfide (FeS), with 2,4-dinitrotoluene (DNT) as a model contaminant. Pyrite was able to activate persulfate to degrade DNT. However, DNT degradation was rapidly halted presumably due to the low water solubility of pyrite and the presence of trace dissolved oxygen. In contrast, FeS was effective in activating persulfate to continuously and completely degrade DNT. Separate experiments with Fe2+ and HS− suggest that Fe2+, rather than HS−, released from FeS was involved in persulfate activation and was necessary for rapid degradation of DNT. Further experiments show that reduction products of DNT were oxidized much faster than DNT by FeS-activated persulfate. These findings and their implications are discussed in the context of subsurface remediation strategies for hydrocarbons and reducible contaminants such as nitroaromatic compounds.

• FeS is effective in activating persulfate to continuously and completely degrade DNT. • Fe2+ released from FeS is involved in persulfate activation and is necessary for rapid degradation of DNT. • Reduction products of DNT are oxidized much faster than DNT by FeS-activated persulfate. • Chemical oxidation by FeS-activated persulfate is a potentially feasible technology for in situ remediation and/or ex situ treatment.