Effects and mechanism of ozonation for degradation of sodium acetate in aqueous solution

Abstract

The degradation efficiencies and mechanism of ozonation for the degradation of sodium acetate in aqueous solution were investigated under atmospheric pressure at room temperature (293 K). The effects of the initial pH value, reaction time, and concentrations of HCO3−, CO32− CaCl2 and Ca(OH)2 on the removal rate of chemical oxygen demand (COD) were studied. The results indicated that ozonation obviously improved the degradation rate of sodium acetate when the pH value of the solution was not less than 8.5. A suitable long reaction time may be helpful in increasing the COD removal rate, and a removal rate of 36.36% can be obtained after a 30-minute treatment. The COD removal rate increased firstly and decreased subsequently with the increase of the HCO3− concentration (from 0 to 200 mg/L), and under the same experimental condition it reached the optimum 34.66% at the HCO3− concentration of 100 mg/L. The COD removal rate was 5.26% lower when the concentration of HCO3− was 200 mg/L than when there was no HCO3−. The COD removal rate decreased by 15.68% when the CO32− concentration increased from 0 to 200 mg/L. CO32− has a more obvious scavenging effect in inhibiting the formation of hydroxyl radicals than HCO3−. CaCl2 and Ca(OH)2 could increase the degradation efficiency of sodium acetate greatly, and the COD removal rates reached 65.73% and 83.46%, respectively, after a 30-minute treatment, 29.37% and 47.10% higher, respectively, than with single ozone oxidation. It was proved that the degradation of sodium acetate in the ozonation process followed the mechanism of oxidization with hydroxyl free radicals (·OH).