Decomposition of Carboxylic Acids in Water by O3, O3/H2O2, and O3/Catalyst

This paper studies the decomposition of formic, oxalic and maleic acids by O3, O3/catalyst, and O3/H2O2. The catalytic effect of Co2+, Ni2+, Cu2+, Mn2+, Zn2+, Cr3+, and Fe2+ ions is investigated. The results showed that—Co2+ and Mn2+ have the highest catalytic activity for the decomposition of oxalic acid while the catalytic effect of the studied ions is insignificant on the rate of decomposition of formic acid. Maleic acid decomposes by ozone into formic acid and glyoxylic acid, which subsequently oxidizes to oxalic acid. Though the studied ions have no effect on the decomposition of maleic acid, they have a significant effect on the produced oxalic and glyoxylic acids. In the presence of Cu2+ ions glyoxylic acid is mainly transformed into formic acid and traces of oxalic acid. In such case, a complete decomposition of maleic acid and its degradation products is achieved within 45 min. The results also show that combining H2O2 with O3 results in an increase in the rate of decomposition of oxalic acid. However, O3/H2O2 system is less active than O3/Co2+ or O3/Mn2+.