Is catalytic ozonation always an efficient treatment for refractory pollutant in various water matrices?

Abstract

In this study, surrogate indicators (·OH yield and Rct value) were developed to identify whether homogeneous and heterogeneous catalysts should be added during ozonation of refractory pollutants. The abatement of atrazine (ATZ) was in the order of O3/H2O2 process (94 %) > O3/γ-Al2O3 process (70 %) > ozonation alone process (55 %) in synthetic water samples at pH 7, which was in agreement with the order of ·OH yield and Rct value. However, the abatement of ATZ during ozonation alone process (0.64–0.62) was higher than O3/H2O2 process (0.63–0.60) and O3/γ-Al2O3 process (0.48–0.49) in the presence of high dosage of humic acid (HA, 3.38 × 10−1–4.50 × 10−1 mg C/L) at pH 7. The abatement of ATZ was linearly proportional to ·OH yield, whereas it was not linearly proportional to Rct value in the synthetic water samples containing HA at pH7. The abatement of ATZ during ozonation alone process was higher than that during catalytic ozonation process by one-time ozone dosing method in real water. The abatement of ATZ during O3/H2O2 process and O3/γ-Al2O3 process were higher than that during ozonation alone process by three-time ozone dosing method in real water, which was linearly proportional to ·OH yield and Rct value. The residual DOM in phase III become recalcitrant to ozone, which could be decomposed by catalyst forming ·OH. Overall, this result implies that the comparison of ·OH yield and Rct value between ozone decay by DOM in various water matrices and by catalyst should be concerned before the addition of catalyst during ozonation process was applied in real water.