No abstract

This study examined the reaction mechanism, influencing factors and toxicity of diclofenac sodium (DS) degradation by ultraviolet (UV)/chlorine process. The UV/chlorine was capable of eliminating DS from water. The DS degradation during the UV/chlorine process followed a pseudo-first-order kinetic model that was influenced by chlorine dosage, solution pH, humic acid and bicarbonate concentrations. The free chlorine affects not only DS elimination, but the contribution of various active species as well. Increasing free chlorine dosage from 1 to 7 mg·L-1 increased the first-order rate constant of NaClO, ·OH and reactive chlorine species (RCS) from 0.00063, 0.00328 and 0.00203 min−1 to 0.00233, 0.0101 and 0.0974 min−1, respectively, and increased the contribution of RCS from 8.20% to 75.71%, while the contribution of UV, NaClO, and ·OH were declined from 76.02%, 2.54% and 13.24% to 14.63%, 1.81%, and 7.85%, respectively. The contribution of RCS became increasingly prominence with the increment of free chlorine dosage. The kobs,UV/chlorine,DS value decreased from 0.0797 to 0.0445 min-1 as pH increased from 5.0 to 8.0. The presence of bicarbonate and natural organic matter both exerted an inhibitory effect on DS degradation. Eleven intermediate products were identified and the degradation pathway involved C-N cleavage, condensation, hydroxylation, and decarboxylation was proposed. The UV/chlorine process effectively reduced acute toxicity and was superior to chlorination. The genotoxicity induced by a chlorinated solution treated by the UV/chlorine process exhibited negative genotoxicity. These results show that the UV/chlorine process is capable for the degradation and detoxification of DS.

In this paper, the removal performance of Triamcinolone acetonide (TA) by ClO2, NaClO, O3, K2FeO4, and KMnO4 oxidation was assessed. The effects of pH value and humic acid (HA) on TA removal during KMnO4 oxidation process were also investigated. The results showed that ClO2, NaClO, and O3 were not sufficient for TA elinimation. However, K2FeO4 can capable of removing TA effectively, and the removal rate of TA can be achieved 84.6% at 60 min while K2FeO4 dosing at 10 mg/L. However, the removal effect of TA in water was inhibited as the concentration of K2FeO4 overdosed. KMnO4 can degradate TA effectivly. TA can be completely removed after 90 minutes while the initial concentration of TA is 250μg/L and the KMnO4 dosage at 50mg/L.Weakly acidic and neutral conditions can promote TA removal, the effect of Humid acid (HA) on TA removal was based on the HA dosage, an inhibitory effect was obsearved when the dosage of HA from 1mg/L to 5mg/L, however when CHA≥7mg/L, HA can accelerate TA removal.

This study investigated the effect of water quality parameters during simultaneous chlorine dioxide disinfection and low pressure ultraviolet (LPUV) irradiation on TCS degradation.The TCS degradation by the co-exposure process was sensitive to chlorine dioxide dosage, concentration of TCS, pH, and NOM.The removal efficiency increases as the pH increases.Neutral and slightly alkaline environments is conductive to promote TCS elimination, The removal rate within 1 minute of pH 5 was only 95.02%.The smaller the removal rate of TCS was decreased as the concentration of humic acid increasing. The higher the concentration of TCS lead to the lower the experimental removal. 2, 4-DCP was generated during UV/ClO2, ClO2 and UV, however, the production of 2, 8-Cl2DD was not detected during UV/ClO2 process.