Identification of intermediates and assessment of ecotoxicity in the oxidation products generated during the ozonation of clofibric acid

Treatment of micropollutants in municipal wastewater: Ozone or powdered activated carbon?

“…§3.5.3), meaning that micropollutants were presumably transformed to (unknown) oxidation products. The transformation products are expected to lose their biological activity (Dodd et al, 2009;Larcher et al, 2012), but higher toxicity of the metabolites has also been reported in some cases (Larcher et al, 2012;LusterTeasley et al, 2002;Rosal et al, 2009). Unlike ozone, PAC physically removes the micropollutant from the water, which avoids the release of unknown transformation products.…”

Mechanism for enhanced degradation of clofibric acid in aqueous by catalytic ozonation over MnO /SBA-15

“…In ozonation alone, ozone molecules are well known to be the main reactive species in acidic and weakly acidic conditions. Although the reaction rate constant of ozone with CA (lower than 20 is much lower than that of • OH (5.5 × 10 9 ± 8 × 10 8 M −1 s −1 ) [26], due to its relatively higher concentration in solution, O 3 is believed to be sufficient for the initial degradation of CA [25,33]. Meanwhile, during the first 15 min, the reaction rate of CA in ozonation alone was distinctly higher than in O 3 /MnO x /SBA-15.…”

“…The reason may lie in that • OH, a kind of non-selective oxidant for most organic matters, is the main active species in catalytic ozonation. In the initial period of O 3 /MnO x /SBA-15, the generated intermediates could also readily react with • OH [26], thus retarding the degradation of CA by • OH.…”

“…Similar to CA degradation, TOC remarkably decreased during the first 15 min and then reached to a slower removal in the following 45 min, in both ozonation processes. It has been suggested that various kinds of acidic intermediates can be generated in ozonation processes for organics and the degradation of easily oxidizable intermediates into hard oxidizable ones, e.g., small molecular carboxylic acid, can be promoted [26,27]. In the early stage, CA and some easily oxidizable intermediates were the dominating reactants and readily degraded, leading to the simultaneously pronounced removal of CA and TOC.…”

“…However, the study on heterogeneous catalytic ozonation for CA removal, especially on the reaction mechanism, is relatively rare. Rosal et al [26] applied TiO 2 in ozonation of CA and suggested that the production of • OH was enhanced. Yalfani et al [27] observed that the catalytic ozonation was more effective when the surface of Cu-dawsonite was charged.…”