Study On The Photo-dation Of Iodinated X-rav Contrast Media Via Electromagnetic Induction Electrodeless Lamp

In recent years,many treatment techniques were investigated to deal with iodinated X-ray contrast media(ICM)due to their incomplete removal in sewage treatment plants,ubiquitous occurrence and potential adverse toxic effects to living species.Among them,UV advanced oxidation processes(AOPs)are effective approaches against ICM.Most of studies concentrated on the addition of oxidants and catalysts to improve the removal efficiency,whereas problems of the low light efficiency and metal electrodes loses need to be solved.In this work,an electromagnetic induction electrodeless lamp(EIEL)was introduced into UV AOPs to overcome these shortages.Diatrizoate(DTZ),a typical ICM,which could be hardly removed in some oxidative treatment processes,was selected as target compound.Direct photolysis of DTZ demonstrated that EIEL was more competitive than Hg lamps due to the high removal efficiency and low energy cost.In this sense,the combination of EIEL and oxidants(O2,H2O2 and S2O82-(PS))was further investigated.Increased photodegradation rates were obviously observed in UV/PS system.The production of radicals and the second-order rate constants of DTZ with SO4·-and·OH were determined,from which the primary contribution of SO4·-was calculated as 62.5%in UV/PS system.Therefore,due to the high efficiency of UV/PS system in photodegradation of DTZ,the effect of water parameters such as inorganic ions and natural organic materials(DOMs)were further investigated.The inhibition effects of Cl-and HCO3-and promoting effects of Fe2+and Cu2+ on photodegradation were observed at low concentration of PS.Besides,the effect of DOMs was investigated based on the contribution ratios of light screening effect and quenching.Photodegradation products were identified by LC-HRMS and five possible transformation pathways were proposed in UV/PS system including deiodination,intramolecular cyclization,decarboxylation,deacetylation and deamination,which were further confirmed by frontier electron density calculations.Toxicities of DTZ and each product were evaluated by EC OSAR program using three aquatic organisms including fish,daphnid and green algaeMoreover,a nonionic ICM,Iohexol,was subjected to treatment by 3 AOPs(UV,UV/H2O2,UV/H2O2/Fe2+).In order to investigate the treatment efficiency of AOPs,optimization of the treatment conditions,as well as modeling of the degradation was performed,by step-wise constructed quadratic or product models,and determination of the optimal operational regions was achieved through desirability functions.Through HPLC/MS analysis the degradation pathway and the effects the operational parameters were monitored,thus attributing the pathways the respective modifications.The addition of iron in the UV/H2O2 process inflicted additional pathways beneficial for both Iohexol and organics removal from the matrix.These findings could enhance the general understanding on the photodegradation of ICM and supply a novel method for removal of contaminations using the combination of EIEL and oxidants.