ALKALI-INDUCED AND METAL-INDUCED DECOMPOSITION OF PEROXYMONOSULFATE

If trace metals are sequestered, the rate of alkali-induced decomposit ion of peroxymonosulfate (HSO5-) is negligible below pH 6 Above that p H, the kinetic data are consistent with the mechanism involving reacti on between undissociated and dissociated peroxides (HSO5- and SO5=). I n this research, hydroxyl radicals were detected and quantified by the ir hydroxylation of an aromatic amide. The hydroxyl radical nor any ot her highly reactive free radical is involved in alkali-induced decompo sition. Metal-induced decomposition was investigated at pH 1.0, 2.0, 5 .0, and 8.0. Six transition metals (Mn, Fe, Cu, Ni, V, Co) were added to solutions at concentrations typical of those that would be encounte red in kraft pulp bleaching. With the exception of Cu at pH 8 and high concentrations of Co (approximately 50 times higher than would be enc ountered in pulp bleaching), none of the metals resulted in a high rat e of decomposition. Rates of decomposition were higher at pH 5 and 8, but less reactive free radicals were generated. Degradation of cellulo se was significant at pH 1.0 and 2.0. Higher viscosities were obtained by the addition of Ag+ which trapped the sulfate radical anion (SO4-. ).