| Iodinated X-Ray Constrast Media(ICM)is a class of Iodinated organic compounds derived from 2,4,6-triiodized benzoic acid in which the side chains contain hydroxyl(-OH)and carboxyl(-COOH)groups,which is used in enhancing the CT and MRI detection.Recently,ICM was detected frequently in the surface,underground water and even drinking water.ICM itself is not toxic,but its metabolites increase the concentration of iodine in water and promote the generation of iodate disinfects byproducts with high genetic toxicity and cytotoxicity,which presents potential environmental risks.Therefore,it is of great importance to study the effective removal technology of ICM.In this paper,sodium panatrizoate(DTZ)and lopamidol(IPM)were selected as the target pollutants,the degradation under Ultrasound(US)activated Potassium peroxymonosulfate(PMS)system were studied.The main contents are as follows:(1)Ultrasound can effectively activate PMSand they have significant synergistic effect on DTZ oxidation,with DTZ degradation rate achieving 83.24%whenDTZ concentration was 10 mg/L,PMS concentration was 10 mmol/L,power was 195 W,25℃,pH was 6.5 ±0.2.Ultrasound power existed optimum value in the range of 135-235 W.Initial pH had a significant and complex effect on DTZ oxidation,which was affected by DTZ morphology,PMS disintegration,the type and contribution of the active species.The degradation rate of DTZ increased with PMS concentration(1-15 mmol/L),decreased with DTZ concentration(5-12.5 mg/L).DTZ degradation process was followed the quasi-first order reaction kinetics(R2>0.96)in range of 15-45℃,and the reaction activation energy(Ea)was calculated as 22.03 kJ/mol.Expected for HO·and SO4-·,O2-·and 1O2 were the main active species for DTZ oxidation under US/PMS system.The production of IO3-and I2 increased with DTZ degradation rate.Ten byproducts were detected by HPLC/MS/MS during DTZ dgradation.Combined with the advanced molecular orbital theory(FEDs)and Gaussian calculations,DTZ degradation pathway under US/PMS system mainly included deiodination,electrophilic reaction,intramolecular cycylation,decarboxylation and deacetylation.In addition,the toxicity change of DTZ under US/PMS system were assessed by the transcriptional effect level index(TELI).(2)DTZ degradation rate was taken as the response value,four factors such as DTZ concentration,PMS concentration,ultrasonic power and initial pH were considered,a response surface optimization model with four factors and three levels was established.The model fitted good with the determination coefficient of 0.9571..(3)DTZ oxidation under US/PMS system were affected by the water quality factors to some extent,which depended on their repective concentration.Cl’ inhibited DTZ degradation in range of 1-2.5 mmol/L,and promoted when its concentration was in range of 5-10 mmol/L.HCO3-had a slight inhibitory effect in 1.0-5.0 mmol/L and promoted DTZ degradation at 10 mmol/L.Humic acid(HA)significantly inhibited DTZ degradation,and the inhibition increased with HA concentration(1-10 mg/L).(4)Similar to the oxidation of ionic ICM-DTZ,US/PMS showed significant oxidation effect on non-ionic ICM-IPM as well.IPM degradation rate reached 83.06%under the same experimental conditions as DTZ.IPM degradation rate increased with PMS concentration(1-10 mg/L),reaching the maximum(83.06%)at ultrasound power of 195 W.The reaction activation energy of IPM oxidation under US/PMS system was calculated to be 20.29 KJ/mol.O2-·and 1O2 were the main active substances for IPM degradation under US/PMS system.Five products were detected in IPM degradation process,one of which was deiodinated product.Genotoxicological analysis also showed that the toxicity of IPM solution increased with the reaction time. |
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