RESEARCH ARTICLE Elimination of radiocontrast agent diatrizoic acid by photo-Fenton process and enhanced treatment by coupling with electro-Fenton process Elvira Bocos 1,2 & Nihal Oturan 2 & Marta Pazos 1 & M. Ángeles Sanromán 1 & Mehmet A. Oturan 2 Received: 6 May 2016 /Accepted: 7 June 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract The removal of radiocontrast agent diatrizoic acid (DIA) from water was performed using photo-Fenton (PF) process. First, the effect of H 2 O 2 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 4 h with 20 mM initial H 2 O 2 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 0.25 mM Fe 3+ and 20 mM H 2 O 2 were the best conditions, achieving 80 % TOC removal efficiency at 4 h treatment. Furthermore, heterogeneous PF treatment was de- veloped using iron-activated carbon as catalyst. It was dem- onstrated that this catalyst is a promising option, reaching 67 % of TOC removal within 4 h 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, achiev- ing in both cases the complete mineralization of DIA solution within only 2 h. Finally, the Microtox tests revealed the forma- tion 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. Keywords Diatrizoic acid . Photo-Fenton . Mineralization . Heterogeneous process . Activated carbon . Photoelectro-Fenton Introduction Over the past decades, pharmaceuticals have become prob- lematic pollutants in both surface and groundwater. The pres- ence of these pollutants in water streams is overall caused by pharmaceutical industrial streams, hospital waste and munic- ipal wastewater effluents. Although they have been present in water from many years ago, the pollution of water has been highlighted in the 1960s when the presence of these com- pounds on the environment was detected in the USA and Europe (Stumm-Zollinger and Fair 1965). Usually, pharma- ceuticals are found in very low quantities (ng L -1 to μgL -1 ), and their behaviour in biotic and abiotic environments is still unknown (Daughton and Ternes 1999). Recently, some stud- ies have demonstrated their potential hazards (Rastogi et al. 2014; Tiehm et al. 2011) even at low concentrations, and thus concerns about their potential risk became worrying. Therefore, the problem of their elimination has arisen. To protect the envi- ronment from adverse effects of such pollutants, it is important Responsible editor: Vítor Pais Vilar Highlights • Optimization of key parameters in photo-Fenton (PF) removal of diatrizoic acid (DIA) • Eighty per cent TOC removal under homogeneous PF using 0.25 mM Fe 3+ and 20 mM H 2 O 2 • Sixty-seven per cent TOC removal under heterogeneous PF using iron- activated carbon • Complete mineralization by photoelectro-Fenton (PEF) or PF followed by EF process (PF-EF) • Removal of the toxicity of DIA solution by PEF or PF-EF * Mehmet A. Oturan mehmet.oturan@univ-paris-est.fr 1 Department of Chemical Engineering, University of Vigo, Isaac Newton Building, Campus As Lagoas Marcosende, 36310 Vigo, Spain 2 Laboratoire Géomatériaux et Environnement (LGE), Université Paris-Est, EA 4508, 77454 Marne-la-Vallée, France Environ Sci Pollut Res DOI 10.1007/s11356-016-7054-x