Photo-Fenton degradation of methylene blue by synergistic action of oxalic acid and hydrogen peroxide with NiFe2O4 hollow nanospheres catalyst

Abstract

NiFe2O4 hollow nanospheres (NHNS) with diameters of 155–185 nm were successfully synthesized by a solvothermal process and were used in heterogeneous photo-Fenton degradation of Methylene Blue (MB) as catalysts. The obtained products were characterized by XRD, SEM, TEM, XPS, BET and so on. It was found that the NHNS is highly porous and assembled by oriented attachment of magnetic NiFe2O4 nanocrystal building blocks. And the NHNS exhibited a good degradation effect. Under the conditions of 0.2 g L−1 NHNS, 5 mM H2O2, 0.06 g L−1 H2C2O4 and natural pH, almost up to 98.5% degradation of 0.03 g L−1 MB solution was achieved only within 50 min. Moreover, the stability of NHNS was estimated by studying the iron leaching and nickel leaching in three cyclic tests. In addition, a possible mechanism for the degradation of MB had been presumed. To assess the degree of decomposition, the COD was tested and the degradation intermediates were identified by LC–MS.