Parametric optimization of individual and hybridized AOPs of Fe2+/H2O2 and UV/S2O82− for rapid dye destruction in aqueous media

The aim of the study was to assess and optimize the UV/S2O82− (activated persulfate ion), Fe2+/H2O2 (Fenton), UV/Fe2+/H2O2 (photo-Fenton), and their hybridized processes for discoloration, degradation and mineralization of an azo dye, Direct Red 16, as a model pollutant, in aqueous media. A special air bubbling photo-reactor, with a perfect photon utilizing of an only 6 W, UV-C light source, was employed and a promising hybridized homogeneous AOP, as: UV/S2O82−/Fe2+/H2O2, under initial natural pH of 6.0, was introduced. This process exhibits a rapid discoloration (100% in 30 min), as well as aromatic rings degradation (more than 86% in 40 min) and mineralization (more than 50% in 60 min) of DR16 with 30 mg/L initial concentration at 25 °C. The optimum parameters of initial pH, initial reagents dosage and temperature were reported for each process. The ferrous ion catalyst concentration was much less than its standard limit. Different processes kinetic relationships were introduced in a power law model and as a function of dye concentration and temperature. Moreover, synergism impact of UV light on the catalytic center of Fenton process was proved based on a kinetic analysis.

Research highlights
► Fenton process works nice with low reagents dosages, much less than standard limit.
► A new hybrid homogeneous UV/S2O82−/Fe2+/H2O2 process under natural pH is disclosed.
► Rapid 100% dye discoloration or 86% degradation attainable with low energy consumption.
► Contribution of individual branches in the global function is determined.
► UV light and catalytic Fe2+ function degree of synergism reaches to 18 after 15 min.