Synthesis of Cu(2)O–CuFe(2)O(4) microparticles from Fenton sludge and its application in the Fenton process: the key role of Cu(2)O in the catalytic degradation of phenol

This paper presents the key role of Cu(2)O in Fenton catalysis using Cu(2)O–CuFe(2)O(4) magnetic microparticles, which were prepared using Fenton sludge as an iron source. The catalytic activity of the as-prepared Cu(2)O–CuFe(2)O(4) and CuFe(2)O(4) microparticles was evaluated in a heterogeneous Fenton system for the degradation of recalcitrant phenol. The Cu(2)O–CuFe(2)O(4) microparticles demonstrated relatively superior catalytic performance as compared to CuFe(2)O(4) microparticles when used as a Fenton catalyst. The relatively higher catalytic activity of Cu(2)O–CuFe(2)O(4) 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 H(2)O(2) to generate hydroxyl radicals (HO˙). 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 Cu(2)O–CuFe(2)O(4) microparticles could be considered to be rather crucial for the generation of highly reactive HO˙ radical species. In addition, the as-prepared Cu(2)O–CuFe(2)O(4) magnetic microparticles exhibited sound stability and reusability.