Study Of UV-photolysis Behavior And Toxicity Of Waterborne Tricyclic Antidepressant Amitriptyline(AMT)

As an important part of pharmaceuticals and personal care products(PPCPs), psychiatric medications have been widely used. The remnants of psychiatric medications can simply enter the environment, which would not only result in eco-environmental deterioration but also contaminate drinking water and threaten the human health. Amitriptyline(AMT), a representative tricyclic psychiatric medicine, is mostly used to treat depression and several neuropathic illnesses. The removal efficiency of AMT by traditional sewage treatment methods is limited, and previous studies have demonstrated that UV irradiation is an effective way in organic wastewater treatment. In this study, AMT was selected as the target compound, and the photodegradation efficiency of AMT by simulated sunlight and UV irradiation was mesured. Moreover, the toxicity of AMT before and after UV treatment was determined. The results in this study shoud provide a reference for treatment method of AMT and other psychiatric medictions by UV irradiation in waste water treatment process; the study of the toxicity of AMT is of great significance for its ecological risk assessment.The degradation efficiency of AMT by simulated sunlight alone was limited, and the degradation rate of 10.0 mg/L AMT was only 26.9% in 8 h under simulated sunlight, while it could be significantly increased by the additon of H2O2 in treatment solution. The degradation rate of AMT under the UV irradiation was much higher than that under the simulated sunlight, and the removal rate was 49.8% in 180 min under UV condition by which the degradation of AMT followed pseudo-first-order kinetics in aqueous solution. AMT degradation was enhanced with the increase of H2O2 concentrations and the decrease of initial AMT concentrations in UV/H2O2 process; the degradation rate of AMT increased with the increasing concentration of Fe SO4 under UV/Fe2+ process, and the best concentration of Fe2+ is at 0.5 m M in UV/Fe2+ process in this experiment. The results demonstrated that the UV/Fenton system was more effective for AMT degradation than the UV/H2O2 process and UV/Fe2+ process. It only took 5 minutes to degrade all the AMT at a molar ratio of 1:1(H2O2=0.1 m M; Fe2+=0.1 m M) under UV/Fenton process. Considering the cost efficiency of UV treatment, the optimum molar ratio of H2O2: Fe2+ should be set from 1:1 to 3:1 in the UV/Fenton system. It was also found that the degradation rate of AMT decreased with the increase of initial AMT concentration by UV irradiation alone, and it is more favorable for AMT degradation with the alkaline p H in the river surface water. Finally, the primary degradation intermediates and the end products of AMT were determined using LC/MS and possible pathways under UV irradiation were analyzed.Using zebrafish embryos as a testing model, we found that AMT caused significant influence on the mortality rate and aberration rate of zebrafish embryos/ larvae at the level of mg/L. At the environmental relavent concentrations of μg/L and ng/L, AMT had limited effects on mortality rate and aberration rate of zebrafish embryos/larvae, but it obviously increased the hatching rate of zebrafish embryos, moreover, AMT had significant impact on the heart rate of zebrafish larvae. After 3 h UV-photolysis, the removal rate of 0.5 mg/L AMT in solution was 85%, which indicated that the concentration of AMT after UV irradiation is 75 μg/L; while, 50.0 mg/L AMT was reduced to 42.0 mg/L after 3 h irradiation. By comparing the toxicity of AMT on zebrafish embryos/larvae before and after UV irradiation, we found that there were no significant differences between the 0.5 mg/L treatment group after irradiation and control in the mortality rate and hatching rate of zebrafish; the mortality rate of zebrafish embryos/larvae in the 50.0 mg/L group after irradiationwas lower than the untreated 50.0 mg/L AMT exposed group. These results demonstrated that the primary intermediates and the end products of AMT after degradation didn’t have obvious toxic effects on zebrafish embyos, which suggested that the toxicity of AMT most possibly came from the parent chemical but not the intermediates and the end products, and proved that UV-photolysis process could be a safe and effective method for the removal of AMT in aqueous solution.