Molecular-level comparison study on microwave irradiation-activated persulfate and hydrogen peroxide processes for the treatment of refractory organics in mature landfill leachate.

This study investigated the degradation of organics in mature leachate treated by microwave radiation-activated persulfate (MW/PS) and hydrogen peroxide (MW/H2O2) processes. Obvious synergistic effects existed in both the MW/PS and MW/H2O2 processes, but were significantly higher in the MW/PS process. Refractory organics were better degraded by the MW/PS process than the MW/H2O2 process due to the major contribution of SO4-. Moreover, according to Fourier transform-ion cyclotron resonance mass spectrometry coupled with electrospray ionization analysis results, the refractory organics (e.g. polycyclic aromatics (AI > 0.66), polyphenols (0.66 ≥ AI > 0.50)) were greatly degraded by both the MW/H2O2 and MW/PS processes, but the MW/PS process degraded dissolved organic matter (DOM) over a wider range than the MW/H2O2 process due to the different dominant radicals in the two processes. In addition, after reaction in the MW/PS process, the O/C ratio of DOM in the treated effluent showed an obvious increase, which can be mainly attributed to the reaction of sulfate radicals with the N- and S- containing compounds via single electron transfer.