Abstract
Optimal hydrogen peroxide dose for ozone/hydrogen peroxide (03/H2O2) process was investigated based on the difference of the reactivity of target compounds (i. e., malonate and oxalate ions) with hydroxyl radical (HO·) and their initial concentration (i. e., 0.05 and 0.50 mM). All experiments were conducted at pH7.5 and ozone dose was 0.021 mM·min-1. The optimal H2O2 doses at which the decomposition ratio of these target compounds becomes maximum with the reaction time of five and ten minutes existed in the range of 0.025-0.14 mM. At five minute reaction time, the optimal H2O2 dose for malonate ion, highly reactive compound with HO·, was greater than that for oxalate ion, lowly reactive compound with HO·. On the other hand, the optimal H2O2 dose became more dependent on the time-course of H2O2 concentration in the process at ten minute reaction time. Especially, in the case of oxalate ion, the optimal H2O2 dose greatly increased with the elapse of time. Bicarbonate ion not only prevented the decomposition of target compounds but also enhanced the decrease of H2O2 concentration. Also, the optimal H2O2 dose increased with the increase of initial bicarbonate ion concentration.
