MN-CATALYZED OXIDATION OF MULTIPLE-RINGED AROMATICS

The role of manganese (Mn) oxides in catalyzing the abiotic oxidation of polynuclear aromatic compounds (PNAs) has been investigated by moni toring the oxidation of dihydrodiol and dione PNAs and corresponding r eduction of Mn in an aqueous environment. 1,4-, 1,3-, and 2,3-naphthal enediol, 1,4-naphthoquinone, and 1,4-dihydroxy-9,10-anthracenedione (Q uinizarin) were oxidized in an oxic, aqueous environment, where each o f these organic compounds is soluble in water, except Quinizarin. A ma thematical model is presented, which describes the redox reactions, an d suggests that electron transfer/organic release from the oxide surfa ce is rate limiting with the reaction apparently proceeding through a free-radical formation. Results indicate significant oxidation of the organics, that the oxidation of the diols is kinetically more favorabl e than that of the dione, and that lower molecular weight PNAs contain ing diol and dione functional groups are susceptible to abiotic-cataly zed oxidation, thereby suggesting that progressively more complex PNA molecules may also be susceptible to oxidation.