Transformation And Mechanism Of Representative Anticancer Drugs In Chloride Oxidation Process

Due to poor living habits and environmental pollution,the incidence of cancer has increased year by year,more and more anticancer drugs are used for the treatment of cancer.Most of the drugs are excreted backout the body as the prototype or active metabolites,which are stable in the environment with good water solubility and mobility.At the same time,many anticancer drugs have been proved to have?carcinogenic,teratogenic and mutagenic?characteristics and endocrine disrupting activity.In this work,aiming at the problem of anticancer drug pollution,the representative anticancer drug is selected as the target to study the kinetics,influencing factors,and transformation mechanism of several chloride oxidation processes in the water plant.The main contents and conclusions are as follows:The kinetics of the transformation of representative anticancer drugs in chloride oxidation process were investigated.The transformation of representative anticancer drugs in NaClO,ClO₂ and UV/NaClO systems all conformed with the second-order kinetic model.The reaction activation energy of Cytarabine?Ara-C?and Capecitabine?CAP?were 82.45 and 88.81 kJ·mol^-1 in NaClO system,and 50.68 and 45.76kJ·mol^-1 in UV/NaClO system,respectively.While for imatinib?IMA-3?and mitoxantrone?MA?,the reaction activation energy were 58.26 and 56.51 kJ·mol^-1 in ClO₂ system,repectively.The transformation rate of Ara-C and CAP in the UV/NaClO system were more efficiently than that in NaClO system.There were significant differences in the transformation rate of different anticancer drugs in the ClO₂ system.The second order rate constant(k_app)for IMA-3 and MA were 14.33 M^-1s^-1 and 20.14M^-1s^-1 in the ClO₂ system at T=25?,pH=6.0,respective.However Ara-C,CAP,and5-FU were hardly ever transformation in the ClO₂ system.The effects of environmental conditions on the transformation of representative anticancer drugs in chloride oxidation process were investigated.The pH has a significant effect on the transformation process.In NaClO system and UV/NaClO system,the transformation rate of Ara-C and CAP,respectively,were faster under acidic and neutral conditions.While,in ClO₂ system,the rate of transformation of IMA-3 and MA increased significantly with the improve of pH.HCO₃^-/CO₃^2-had slightly promoted the transformation of Ara-C and CAP in the UV/NaClO system,IMA-3 and MA in the ClO₂ system.The transformation of anticancer drugs were slightly inhibited by NO₃^-in UV/NaClO system.The presence of Cl^-had remarkably promoted the transformation of CAP in UV/NaClO system.The transformation of anticancer drugs were inhibited by humic acid in ClO₂ and UV/NaClO systems.And stronger inhibition was observed in UV/NaClO system with the addition of humic acid.The transformation of anticancer drugs in the surface water and the effluent of wastewater treatment plant were inhibited to some extent.The transformation mechanisms of representative anticancer drugs in the chloride oxidation process were investigated.Representative anticancer drugs were commonly hydroxylation and carboxylation in the process of chlorine oxidation.In the NaClO system and the ClO₂ system,the main reaction way was electron transfer.While in the UV/NaClO system,relatively complex transformation mechanism combined electrophilic addition,electron transfer and hydrogen substitution was observed.In the process of the transformation of antiseptic drugs,chlorinated disinfection by-products were not detected,and the final products were mainly organic acids such as small molecule organic acids.