ELECTROCHEMICAL IODINATION AND DEIODINATION PROCESSES FOR GREEN SYNTHESIS AND WATER REMEDIATION

This project is devoted to highlight the importance and the great innovation that the application of electrochemistry could bring in the protection of the environment. The aim was to develop cost-effective and eco-friendly methods in both environmental remediation and green chemistry fields, to make electrochemistry considered as a valid alternative to classical methods in the contrast media industry. The first part of the thesis is focused on the study of the electrochemical iodination of N,N’-(2,3-dihydroxypropyl)-5-hydroxy-1,3-benzenedicarboxamide (idroamide, IA), an important intermediate for the synthesis of iomeprol (IMP). It has been demonstrated that the use of a carbonaceous anode can successfully transform I-/I2 in iodinating species, leading to a complete iodination of the reagent and almost no by-products. The experimental conditions have been optimized and the potentiostatic electrolysis in a recirculating divided cell (cation exchange membrane) has been successfully scaled for the treatment of 0.8 L of IA 23.5% w/w. A pre-pilot system has been designed and installed and the first tests showed the way forward from here. Parameters related to increasing volumes will be studied, also optimising them for flow chemistry. The success of the scale-up of this study will provide a concrete, as well as green, alternative to the current use of ICl, a highly corrosive iodinating agent that must be handled with great caution. The second part of this work is instead focus on iodinated contrast media (ICM) electrochemical degradation, and, in particular, on reductive processes. Gold was found to be a powerful electrocatalyst in the case of C-I bond breaking and a preliminary study on sputtered 10 nm bilayer films showed promising results about a powerful synergy between gold and silver. The reductive mechanism was also investigated for IMP deiodination, allowing the optimization of the experimental parameters in conditions similar to those of real polluted matrices. Iodine was almost completely recovered as iodides in this case, while in simulated urine and industrial wastewater, where an undivided cell was chosen to promote mineralization, it was accumulated as iodates. Further development will be focused on iodides separation from the polluted matrix, in a iodine circular economy perspective.