Manganese dioxide as a catalyst for oxygen-independent atrazine dealkylation

The herbicide atrazine is widely distributed in the environment, and its reactivity with soil minerals is an important issue. We have studied atrazine degradation on the surface of synthetic hydrous (10% H2O) δ-MnO2 (birnessite) using UV resonance Raman spectroscopy and gas chromatography. The products are mainly mono- and didealkyl atrazine. Atrazine disappearance is rapid (τ1/2 approximately 5 h at 30 °C), independent of whether O2 is present or not. MnO2 reduction is a minor reaction, and the alkyl chains are converted mainly to the alkenes, in a nonredox process. A novel dealkylation mechanism is proposed involving proton transfer to Mn(IV)-stabilized oxo and imido bonds. When O2 is present, olefin oxidation and ring mineralization are also observed as secondary reactions in addition to those discussed above. Thus δ-MnO2, a common soil constituent, is found to promote efficient N-dealkylation of the herbicide atrazine at 30 °C, via a nonoxidative mechanism.