Degradation of metronidazole by radio frequency discharge in an aqueous solution

Degradation of metronidazole (MNZ) by radio frequency discharge in water was examined. Results showed that (OH)-O-center dot, H-center dot, and O-center dot were produced. Decay of MNZ followed pseudo-first order kinetics, where the apparent rate constant was independent of its initial concentration in the range 0-0.5 mM, decreased in the range 0.5-1.0 mM, and leveled off in the range higher than 1.0 mM. pH had no effects on MNZ degradation. (OH)-O-center dot scavengers enhanced the MNZ removal. Formic acid, nitrite ion, oxalic acid, nitrate ion, and acetic acid were determined as the primary intermediate byproducts. The eventual products were ammonia and inorganic carbon. Both (OH)-O-center dot and H-center dot participated in the MNZ degradation. H-center dot played more efficient role than (OH)-O-center dot in the early stage.