Transformation Mechanism And Environmental Implication Of Typical Drugs In Aqueous Phase

Recently,the trace drug contaminants in waters have attracted considerable attention,as the abundant consumption,relatively persistence,and adverse effects on humans and animals,are accepted to be the emerging contaminants(ECs)in the environments.Given the importance of refractory drugs as ECs,a comprehensive analysis and reveal of the transformation behaviors and environmental impacts regarding refractory drugs is needed.The research content of this paper is divided into the following three parts:1.Indirect photochemical transformation mechanism and environmental implication of Lamotrigine in surface waterThe direct photolysis of Lamotrigine(LAM)has been proved to be negligible,and the reactive oxygen species(ROS)generated by sensitizers deserves attention.In this work,three common ROS(·OH,HO2·and 1O2)were selected to investigated the indirect photochemical transformation behaviors of LAM in surface water.Results show that the C6 site of LAM represents the global reactive active site,two dialdehyde products of 1O2 oxidation appear to be harmless,while all OH-initiated products vary degrees of toxicity.When[·OH]ss ≤ 2.06 × 10-16 M or[1O2]ss≤ 2.53 × 10-16 M,LAM has significant water environmental persistence in natural water.These results emphasize the importance of management and control for such trace contaminants.2.Transformation mechanism and potential risk of 5-Fluorouracil in ozonation system and·OH-based oxidation systemThe existences of non-biodegradable 5-Fluorouracil(5-FU)in waters and its aquatic toxicity have caused widespread concern.In this work,two typical oxidants(O3 and ·OH)were selected to investigate the mechanism,kinetics,and the potential ecotoxicology assessment of 5-FU.Results show that 5-FU can be degraded rapidly by O3 and·OH,which subsequently undergoes ring-opening,decomposition,defluorination,and hydroxylation steps.The half-lives of 5-FU determined by O3 and·OH are on the order of seconds in the advanced oxidation processes.Aquatic toxicity decreased gradually with the process of reaction,but the developmental toxicity and mutagenicity of several products still exist.In addition,the main products have been found to decompose into NO,Formic acid,Acetic acid,and so on.These results provide theoretical basis for the design of industrial infrastructure.3.Experimental and theoretical insight into the transformation behaviors and risk assessment of Flutamide in UV/O3/PMS systemNowadays,the widespread existence and adverse effects of ECs in waters have prompted the search for effective treatment methods.In this study,the feasibility of UV/O3/PMS(peroxymonosulfate)method for the elimination of Flutamide(FLU)was comprehensively investigated.The results showed that the UV/O3/PMS method achieved the FLU elimination efficiency of 83.68%within 40 min.The radical(-OH and SO4-·)oxidation occupies greater advantages in the initiation reaction pathways of FLU compared to non-radical(O3 and 1O2)oxidation.With the participation of H2O2,H2O,O2,and·OH,eleven TPs are generated through hydroxylation,demethylation,and decomposition reactions.In addition,the toxicity of most TPs gradually decreased,but the residual developmental toxicity could not be ignored.These findings provide a basis for the practical application of ECs in water treatment.Combined with theoretical chemisty,computational toxicology,and experimental simulation,the transformation behavior of ECs in various environmental systems was unveiled,and the water environmental persistence and advanced oxidation efficiency of ECs were evaluated using LAM,5-FU,and FLU as examples.These studies provide theoretical basis for ECs control and advanced oxidation processes selection.