Abstract
ABSTRACT
The oxidation of 1,2-dichlorobenzene (DCB), 1,3,5-trichlorobenzene (TCB) and pentanoic acid (PA) by ozone, ozone/UV, ozone/H2O2 and ozone/UV/H2O2 was studied. The greatest removal of TCB using ozone/H2O2 treatment was achieved using a H2O2 concentration of 60 μM. At pH values < 6, ozone/UV performed significantly better than the other processes. However, at circumneutral pH, the removal efficiencies of TCB and DCB by the three AOPs were nearly equal (∼ 97% for TCB; 98% for DCB). At high pH (> 9) the removal efficiencies for all processes studied were nearly equal.
The DCB and TCB removal efficiencies for all the processes studied were usually lower when humic acid was present, however, at a concentration of 1.6 mg/L humic acid slightly enhanced the rate of TCB and PA degradation by ozone. For all the processes studied the rates of oxidation of TCB and DCB were significantly slower in the presence of added bicarbonate.
In the systems studied, it appears that the reaction of DCB, TCB and PA with OH is primarily responsible for the degradation of these compounds. Estimates of the steady-state OH concentrations were made using the PA data. The concentration of OH ranged from 6 × 10−14 to 6 × 10−12 M.
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