Elimination of radiocontrast agent diatrizoic acid by photo-Fenton process and enhanced treatment by coupling with electro-Fenton process.

Abstract

The removal of radiocontrast agent diatrizoic acid (DIA) from water was performed using photo-Fenton (PF) process. First, the effect of H2O2 dosage on mineralization efficiency was determined using ultraviolet (UV) irradiation. The system reached a maximum mineralization degree of 60% total organic carbon (TOC) removal at 4h with 20mM initial H2O2 concentration while further concentration values led to a decrease in TOC abatement efficiency. Then, the effect of different concentrations of Fenton's reagents was studied for homogeneous Fenton process. Obtained results revealed that 0.25mM Fe(3+) and 20mM H2O2 were the best conditions, achieving 80% TOC removal efficiency at 4h treatment. Furthermore, heterogeneous PF treatment was developed using iron-activated carbon as catalyst. It was demonstrated that this catalyst is a promising option, reaching 67% of TOC removal within 4h treatment without formation of iron leachate in the medium. In addition, two strategies of enhancement for process efficiency are proposed: coupling of PF with electro-Fenton (EF) process in two ways: photoelectro-Fenton (PEF) or PF followed by EF (PF-EF) treatments, achieving in both cases the complete mineralization of DIA solution within only 2h. Finally, the Microtox tests revealed the formation of more toxic compounds than the initial DIA during PF process, while, it was possible to reach total mineralization by both proposed alternatives (PEF or PF-EF) and thus to remove the toxicity of DIA solution.