MN-CATALYZED OXIDATION OF NAPHTHALENEDIOL

This study investigates the effects that manganese(IV) dioxide particl es have on 2,3-naphthalenediol at varying pH levels (i.e., initial pH of 4.58, 5.85, and 8.75) and under different organic concentration con ditions (4x10(-3), 4x10(-4), and 4x10(-5) M), and assesses the importa nce of Mn oxides on abiotic catalysis of the multiple-ringed aromatic compound. Proton concentration affected the rates of reductive dissolu tion; as the pH values increased, the rate of reductive dissolution de creased, as predicted by theory. Also, as the concentration of naphtha lenediol increased, the rate of reductive dissolution increased, altho ugh not proportionally; thus indicating that a majority of the active sites had been occupied. In addition, the results tend to confirm that electron transfer/organic release from the oxide surface is the rate- limiting step. This study demonstrates that in an oxic environment and in the presence of 2,3-naphthalenediol, MnO2 particles undergo reduct ive dissolution; in the process, naphthalenediol is oxidized. An oxida tion by-product of reductive dissolution is an insoluble polymerized o rganic. The organic by-product was deep-brown in appearance, very simi lar to that of ''humified'' material. Using infrared spectroscopy, ene rgy-dispersive x-ray analysis, and a microelemental analysis, the ''hu mified'' products appeared to be comprised mainly of constituents orig inating from naphthalenediol.