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UV/persulfate (UV/PS) has been as an efficient method to remove many organic contaminants in water. However, little is known about the impact of UV/PS pretrement on the formation of disinfection byproducts (DBPs) during chlorination of 2,4-Di-tert-butylphenol (2,4-D). This research evaluated that UV/PS preoxidation of 2,4-D greatly decreased the DBPs generation during following chlorination. In the 2,4-D solution without any treatment system (O system), trichloromethane (TCM) as the only detected DBP increased with the increase of chlorine dosage. While the formation of TCM declined with the increase of PS dosage in the PS and UV/PS preoxidation systems and decreased the estimated toxicity accordingly. And it was found the residual PS in system could combine free chlorine to further oxidize 2,4-D. And intermediate products were analysed by high-performance liquid chromatography combined with triple quadrupole mass spectroscopy analysis. In the presence of bromine, the bromodichloromethane augmented first and then slowly decreased while dibromochloromethane and tribromethane increased both in O and UV/PS systems with the increase of [Br − ]. Bromine substitution was decreased by preoxidation of UV/PS. UV/PS could decrease the total-DBPs formation when used in the real water matrix contained 100 μg/L 2,4-D. [ABSTRACT FROM AUTHOR]

In this study, the degradation performance of 2,4-Di-tert-butylphenol (2,4-D) by the ultraviolet/persulfate (UV/PS) process was evaluated for the first time. To better understand the possible degradation mechanism in the UV/PS advance oxidation process system, a kinetic model involved hydroxyl and sulfate radicals was developed for predicting pseudo-first order rate constants (k o ) and radical contributions. The results showed that the degradation of 2,4-D was promoted by increasing dosages of PS. H 2 PO 4 - almost had no significant impact on the degradation of 2,4-D, whereas the removal of 2,4-D was suppressed when NO 3 - dosage was added up to 50 mM. HCO 3 - , HPO 4 2 - and natural organic matter significantly inhibited the degradation of 2,4-D. The reaction rate constants between SO 4 - and 2,4-D were not affected by pH. However, the degradation was suppressed with the increasing pH due to the increasing HPO 4 2 - from the phosphate buffer in alkaline. The degradation of 2,4-D was promoted by adding Cl − . The proposed degradation pathways were elucidated on the basis of results obtained by high-performance liquid chromatography combined with triple quadrupole mass spectroscopy analysis. [ABSTRACT FROM AUTHOR]

UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS) processes as alternative methods for removal of imidacloprid (IMP) were conducted for the first time. The reaction rate constants between IMP and the sulfate or hydroxyl radical were calculated as 2.33 × 10 9 or 2.42 × 10 10 M − 1 s − 1 , respectively. The degradation of IMP was greatly improved by UV/PS and UV/PMS compared with only UV or oxidant. At any given dosage, UV/PS achieved higher IMP removal rate than UV/PMS. The pH range affecting the degradation in the UV/PS and UV/PMS systems were different in the ranges of 6–8 and 9 to 10. SO 4 2 − , F− and NO 3 − had no obvious effect on the degradation in the UV/PS and UV/PMS systems. CO 3 2 − and PO 4 3 − inhibited the degradation of IMP in the UV/PS system, while they enhanced the degradation in the UV/PMS system. Algae organic matters (AOM) were used to consider the impact of the degradation of IMP for the first time. The removal of IMP were restrained by both AOM and natural organic matters. The higher removal rate of IMP demonstrated that both UV/PS and UV/PMS were suitable for treating the water containing IMP, while UV/PS was cost-effective than UV/PMS based on the total cost calculation. Finally, the degradation pathways of IMP were proposed. Image 1 • Imidacloprid (IMP) was degraded by UV/PS and UV/PMS for the first time. • Reaction rate between IMP and Image 3 was calculated as 2.33 × 10 9 M − 1 s − 1 . • Reaction rates between IMP and Image 2 was calculated as 2.42 × 10 10 M − 1 s − 1 . • AOM restrained removal of IMP in the oxidation systems studied for the first time. • UV/PS was more cost-effective than UV/PMS based on the total cost calculation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The combination of UV irradiation and chlorine significantly facilitated VEN degradation. • Kinecus software could simulated the VEN degradation well. • HO· was the dominant radical species responsible for the loss of VEN at acidic pH. • Transformation of VEN in UV/chlorine process can occur via four dominant reactions. • The toxicity of the products are generally lower than that of VEN. The presence of serotonin-norepinephrine reuptake inhibitors (SNRIs) such as venlafaxine (VEN) in surface waters has caused some concerns due to their harmful impacts on the human health and environment security. In the study, ultraviolet (UV) coupled with chlorine was developed for degrading VEN. Among the experiments, the UV/chlorine process demonstrated the highest performance in eliminating VEN. UV irradiation alone played a negligible role in VEN degradation. 39.56% of VEN was degraded by dark chlorination in 30 min, while 76.02% of VEN was decayed by UV/chlorine treatment within 30 min. Adding chlorine dosage and raising solution pH both facilitated the VEN removal. HCO 3 −, Cl− and HA inhibited VEN degradation during UV/chlorine treatment in accordance with predicted data. Furthermore, Kintecus software was applied to simulate the process of VEN degradation. Under UV/chlorine co-exposure, hydroxyl radical (HO·), chlorine and reactive chlorine species (RCS) were all proved to provide significant contribution to VEN oxidation. Note that both experimental and predicted contributions of HO· decreased as solution pH increased from 5.0 to 8.0. Four transformation pathways of VEN during UV/chlorine process were elucidated on basis of the DFT calculation and LC/MS analysis. Moreover, ECOSAR model program showed that UV/chlorine process reduced ecological toxicity of VEN obviously. Considering the influence of various factors, the most economical experimental conditions consist of chlorine (2.0–4.0 mg L−1) and pH (7.0–8.0). [ABSTRACT FROM AUTHOR]