Boosting peroxydisulfate Fenton-like reaction by protocatechuic acid chelated-Fe2+ with broad pH range

In this study, a boosted peroxydisulfate (PDS)/Fe2+ Fenton-like system that employing protocatechuic acid (PCA) as complexing reagent to mediate Fe3+/ Fe2+ circulation was established. The outcomes presented typical dyes and antibiotics, such as methyl orange (MO), rhodamine B tetracycline, and metronidazole all can be efficiently eliminated in this synergistic process. Under the optimal conditions (1 mmol L-1 PDS, 30 µmol L-1 Fe2+ and 30 µmol L-1 PCA), the MO removal reached 100% within 80 min at pH 6.7. Furthermore, this system could perform well under the broad pH span (3–7) and realize the effective Fe3+/Fe2+ cycle. The masking test and electron paramagnetic resonance demonstrated sulfate radical (SO4·-), hydroxyl radical, and singlet oxygen were responsible for MO elimination in the cooperative process, and SO4·- was the dominant active substance. The MO decomposition byproducts and their evolutions were researched based on the mass spectrum analysis. The effect of inorganic anions in natural water on the PDS/Fe2+/PCA system was conducted, and the consequences indicated that Cl-, HCO3– and NO3– all negatively influenced the MO elimination. The proposed organic co-catalytic Fenton-like method could promote the development of advanced oxidation processes in water treatment.