ALKALI-INDUCED AND METAL-INDUCED DECOMPOSITION OF PEROXYMONOSULFATE

If trace metals are sequestered, the rate of alkali-induced decomposition of peroxymonosulfate (HSO5-) is negligible below pH 6 Above that pH, the kinetic data are consistent with the mechanism involving reaction between undissociated and dissociated peroxides (HSO5- and SO5=). In this research, hydroxyl radicals were detected and quantified by their hydroxylation of an aromatic amide. The hydroxyl radical nor any other highly reactive free radical is involved in alkali-induced decomposition. 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 encountered in kraft pulp bleaching. With the exception of Cu at pH 8 and high concentrations of Co (approximately 50 times higher than would be encountered in pulp bleaching), none of the metals resulted in a high rate of decomposition. Rates of decomposition were higher at pH 5 and 8, but less reactive free radicals were generated. Degradation of cellulose 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-.).