Degradation Of Trimethoprim By Permonosulfate Catalyzed By Mn(?):Performance And Mechanism

Trimethoprim?TMP?is a kind of antibacterial agent,which is widely used due to its excellent efficacy and low cost.While 75% of TMP intake by humans and animals couldn't be metabolized and absorbed.Moreover,common wastewater treatment plants?WWTPs?cannot remove the residual TMP effectively,leading to its frequently detection in surface water.Since the persistence of TMP in water is harmful to aquatic organisms,what's more,causing the generation and spread of antibiotic resistance.That would be great threat to human health.Thus,developing a water treatment technique which could degrade TMP has drawn increasing scrutiny.In this study,Mn²⁺activated permonosulfate?PMS?process was set up to degrade TMP.The advantage of this method is PMS is stable,easy to control,and generating strong oxidants.Moreover,Mn²⁺ could exist stably and activate PMS under neutral conditions,impact lightly to environment.The degradation efficiency and mechanism of TMP were studied,investigating factors that impacted the efficiency of TMP degradation.The degradation of TMP in Mn²⁺/PMS process accorded with the pseudo first order kinetic model,main factors affecting the TMP degradation efficiency are PMS concentration,Mn²⁺concentration,initial p H value of the solution.TMP degradation efficiency was obviously better under acidic conditions than the alkaline condition,indicting that pH was a significant factors.Reasons are that Mn²⁺ were not stable in under alkaline condition.In addition,p H effected the state of TMP,since TMP would dissociate under acidic conditions,therefore more active to oxidants.Study on changes of nitrogen showed that Mn²⁺/PMS process degraded TMP effectively.The oxidizing species generated in Mn²⁺/PMS process were determined in a variety of ways.Singlet oxygen?1O2?,sulfate radicals?SO·-4?and Mn???were generated in Mn²⁺-PMS process,while SO·-4and Mn???played the main role in the oxidation of TMP.The activation mechanism is proposed based on these conclusions.Molecular calculations were conducted based on density functional theory?DFT?.optimization of the molecular structure of TMP was conducted to calculate charge distribution.Fukui function?FF?was applied to judge active sites to SO·-4and Mn???,results showed that 7C,8C and N atoms,these sites are concentrated in the pyrimidine ring of TMP.UPLC-MS/MS detected intermediates with m/z values of 323,311,307,197,143.The degradation pathway of TMP in Mn²⁺/PMS processwas proposed in this study,synthesizing the computing and test results.the pathway involved hydroxylation,demethylation,oxidative cleavage of the C ? C double bond and C-C single bond.Moreover,the reduction of products with m/z value of143 and the increase of the proportion of inorganic nitrogen indicated that the pyrimidine ring was degraded to small inorganic molecules.