Deethylatrazine as a more appropriate hydroxyl radical probe compound during ozonation: Comparison with the widely used p-chlorobenzoic acid

Abstract

This study proposed deethylatrazine (DEA) as the OH probe compound during ozonation and compared with the widely used p-chlorobenzoic acid (pCBA) for the first time. Results showed the ozone decay was not affected by DEA, but largely accelerated by pCBA as compared to the control. The DEA degradation was exclusively attributed to OH formation from ozonation of the tested waters, while pCBA was partially degraded by OH formation from the pCBA-derived propagation reactions. In synthetic waters with different OH scavenging capacities, the ozone decay rates with DEA were almost consistent with the control. The ozone decay rates with pCBA remained consistent with the control only in the synthetic waters with high OH scavenging capacities. For the synthetic waters with low OH scavenging capacities, pCBA led to higher ozone decay rates and OH exposures, and thus gave overestimated Rct values. The two OH probe compounds were also investigated in four authentic waters with different OH scavenging capacities. DEA exhibited no detectable effect on the ozone decay in all four authentic waters as compared to the control. The enhancing effects of pCBA on the ozone decay and OH formation were observed in the tap and reservoir water, which led to an overestimation of Rct as compared to the presence of DEA. In the ground water and wastewater, similar values were observed in ozone decay rates and Rct for the presence of pCBA and DEA. Thus, the use of pCBA as the OH probe compound should be carefully examined or avoided to prevent its interrupts in determining the Rct during ozonation of waters with different OH scavenging capacities. DEA is a more appropriate OH probe compound during ozonation.