Synthesis of Cu2O-CuFe2O4 microparticles from Fenton sludge and its application in the Fenton process: the key role of Cu2O in the catalytic degradation of phenol

This paper presents the key role of Cu2O in Fenton catalysis using Cu2O-CuFe2O4 magnetic microparticles, which were prepared using Fenton sludge as an iron source. The catalytic activity of the as-prepared Cu2O-CuFe2O4 and CuFe2O4 microparticles was evaluated in a heterogeneous Fenton system for the degradation of recalcitrant phenol. The Cu2O-CuFe2O4 microparticles demonstrated relatively superior catalytic performance as compared to CuFe2O4 microparticles when used as a Fenton catalyst. The relatively higher catalytic activity of Cu2O-CuFe2O4 for phenol degradation during the Fenton process could be attributed to the availability of both monovalent [Cu(I)] and divalent [Cu(II)] as well as Fe(II)/Fe(III) redox pairs, which could react quickly with H2O2 to generate hydroxyl radicals (HO center dot). An electron bridge was formed between Cu(I) and Fe(III), which accelerates the formation of Fe(II) species in order to boost the reaction rate. Highly reactive and excessively available Cu(I) species for as prepared Cu2O-CuFe2O4 microparticles could be considered to be rather crucial for the generation of highly reactive HO center dot radical species. In addition, the as-prepared Cu2O-CuFe2O4 magnetic microparticles exhibited sound stability and reusability.