Clofibric acid degradation in UV 254/H 2O 2 process: Effect of temperature

Abstract

The degradation of clofibric acid (CA) in UV 254/H 2O 2 process under three temperature ranges, i.e. T1 (9.0–11.5 °C), T2 (19.0–21.0 °C) and T3 (29.0–30.0 °C) was investigated. The effects of solution constituents including NO 3 − and HCO 3 − anions, and humic acid (HA) on CA degradation were evaluated in Milli-Q waters. CA degradation behaviors were simulated with the pseudo-first-order kinetic model and the apparent rate constant ( k ap ) and half-life time ( t 1/2) were calculated. The results showed that higher temperature would favor CA degradation, and CA degradation was taken place mostly by indirect oxidation through the formation of OH radicals in UV 254/H 2O 2 process. In addition, the effects of both NO 3 − and HCO 3 − anions at two selected concentrations (1.0 × 10 −3 and 0.1 mol L −1) and HA (20 mg L −1) on CA degradation were investigated. The results showed that HA had negative effect on CA degradation, and this effect was much more apparent under low temperature condition. On the other hand, the inhibitive effect on CA degradation at both lower and higher concentrations of bicarbonate was observed, and this inhibitive effect was much more apparent at higher bicarbonate concentration and lower temperature condition. While, at higher nitrate concentration the inhibitive effect on CA degradation under three temperature ranges was observed, and with the temperature increase this negative effect was apparently weakened. However, at lower nitrate concentration a slightly positive effect on CA degradation was found under T2 and T3 conditions. Moreover, when using a real wastewater treatment plant (WWTP) effluent spiked with CA over 99% of CA removal could be achieved under 30 °C within only 15 min compared with 40 and 80 min under 20 and 10 °C respectively, suggesting a significant promotion in CA degradation under higher temperature condition. Therefore, it can be concluded that temperature plays an important role in CA degradation in UV/H 2O 2 process.