Ozonation And Mechanism Of Fluoxetine And Its Metabolite Product Norfluoxetine

Pharmaceuticals and Personal Care Products?PPCPs?is a kind of emerging contaminants.Because of its large comsumption and characteristic of hardly degradable by conventional wastewater treatment processes,PPCPs has been detected widely in the water environment,which has pototential risk to ecological system and human health.As a kind of important PPCPs,antidepressants,along with their human metabolites have become the emphasis in the environmental study.Ozonation has been investigated to be a kind of very efficient process in removing organic contaminant.However,studies have been proved that ozonation could hardly be capable of fully mineralization,thus leading to the formation of the oxidation products which have greater toxicity than parent compounds.In this study,ozonation of an antidepressant fluoxetine and its principle metabolite product norfluoxetine were investigated to provide theoretical and technical support.Experimental results of the ozonation of fluoxetine showed that despite the quickly removal of mother compounds within 3 min,the TOC could not be decreased during ozonaiton.Furthermore,the ozonation rates of fluoxetine varied strongly with pH.The kinetic constants of fluoxetine increased by 6 orders of magnitude from 3.0 M^-1 s^-1 to1.7×10⁶ M^-1 s^-11 with the increase of pH from 3 to 12.Nine degradation intermediates,including defluorination products,were observed for fluoxetine ozonation by Orbitrap mass spectrometers.Ozonation mechanism were proposed as hydroxylation,demethylation,carbonylation and cleavage of the benzene ring.Secondary amino functional group and benzene ring were supposed to be the main attack site during ozonation.Three organic acids and three aldehydes were detected during the ozonaiton of fluoxetine.The constitution of organic carbon during ozonation showed that carboxylic acids made a great contribution to TOC after 60 min ozonation.Finally,Vibrio fischeri experiments were used to assess toxicity evolutions during ozonation.The toxicity decreased after ozonation,but cannot be fully removed.The experiments results proved that the formation of aldehyde byproducts may lead to the obstinate toxicity.Similar to the degradation of fluoxetine by ozonaiton,the experimental results of the ozonation of norfluoxetine also showed the easily-removed and the hardly-decreased TOC.The kinetic constants of norfluoxetine increased by 5 orders of magnitude from 3.9 M^-1 s^-1 to 3.5×10⁵ M^-1 s^-11 with the increase of pH from 3 to 12.At the similar ratio of pH species,the k value of NFX is at least one order of magnitude lower than that of FX.This is due to the reactivity difference of the primary and the secondary amino functional group.Six degradation intermediates were observed for norfluoxetine ozonation by Orbitrap mass spectrometers.Ozonation pathways were proposed as hydroxylation and carbonylation.Benzene ring were speculated to be the main attack site during ozonation.Finally,the concentration of the small molecular products and the toxicity during the ozonation of norfluoxetine were also detected.The results showed the similar results of those of fluoxetine ozonation.