Open the way to turnover frequency determination in (photo)Fenton processes for catalytic activities comparison

The design of new catalysts represents a crucial aspect for future applications of advanced oxidation processes for tertiary wastewater treatment and the development of active catalysts for (photo-)Fenton processes is a sector of enormous interest for both scientific and industrial sectors. Notwithstanding, critical evaluation of the catalytic activity needed to compare different catalysts under the same conditions has been poorly addressed so far in the scientific literature. To date, researchers' attention has been mainly devoted investigate optimal reaction conditions to degrade a target pollutant in aqueous matrices excluding a critical evaluation of general aspects of catalysis. In this work we report on the necessity of introducing the turnover frequency number determination for each investigated catalyst in order to evaluate the corresponding activity and to improve the benign-by-design approach for further catalytic improvements. For this purpose, we discussed the comparison between two Iminodisuccinic acid-based metal complexes in the phenol degradation through photo-Fenton process. Experiments were carried out under the same reaction conditions ([phenol]=50 mg/L; [H2O2] =5.3 mM; 2 h; UV-C radiation) and the best results were obtained in the presence of Fe-IDS (COD removal = 73 %; TOF=17.6) whereas Cu-IDS is not active for phenol degradation. TOF determination was further discussed considering literature data (phenol degradation using Fe2+ and Fe-EDTA as catalysts) with the scope of enlarge the results discussion on the basis of TOF determination.