The integration of ZVI-dehalogenation and electrochemical oxidation for the treatment of complex effluents polluted with iodinated compounds

• Main Authors: Cañizares, P. (Author), Correia, S.E (Author), Cotillas, S. (Author), Lacasa, E. (Author), Moratalla, Á (Author), Rodrigo, M.A (Author), Sáez, C. (Author)
• Format: Article
• Language: English
• Published: Elsevier Ltd 2022
• Subjects: Degradation; Degradation rate; Effluents; Electrochemical oxidation; Electrolysis; Hydroxyl radicals; Iodinated X-ray contrast media; Iodine; Iodine species; Iopamidol; Iron; Large amounts; Organic carbon; Oxidation process; Pollution; Pre-treatments; Urine; Zero valent iron; Zero-valent iron
• Online Access: View Fulltext in Publisher

 This work evaluates the integration of dehalogenation with Zero Valent Iron (ZVI) and electrochemical oxidation (EO) for the treatment of urines polluted with iodinated X-ray contrast media (ICM). To do this, different strategies were evaluated: pretreatment with ZVI followed by EO (ZVI-EO) or electrolysis enhanced with ZVI-dehalogenation (EO/ZVI). For comparison purposes, single electrolysis was also performed to check the best treatment strategy. Results showed that EO was less efficient than EO/ZVI and ZVI-EO processes. Removal percentages of 74.9%, 87.6% and 99.5% were reached after passing 13.8 Ah dm−3 at 10 mA cm−2 during EO, EO/ZVI and ZVI-EO, respectively. EO/ZVI process favored the production of large amounts of hydroxyl radicals in the effluent through Fenton´s reaction, enhancing the degradation rate of iopamidol (IPM). The pretreatment with ZVI allowed to transform up to 95% of IPM to C17H25N3O8. Then, electrolysis attained the almost complete removal of the raw pollutant (ZVI-EO). The different iodine species formed at the end of the treatment were also monitored, finding similar proportions of organic iodine species for EO and EO/ZVI processes, although single EO promoted the formation of the stable inorganic iodine (IO3-) and EO/ZVI favored the release of I-. Total organic carbon removal percentages lower than 20% were achieved, suggesting that the technologies employed were selective for the removal of the target pollutant under the operating conditions studied. Finally, the organic IPM by-products were also identified by LC-MS and the chromatographic area profiles showed higher values for EO/ZVI followed by ZVI-EO and EO. © 2022 The Authors