Remarkable effect of Co and Mn on the activity of Fe3-xMxO4 promoted oxidation of organic contaminants in aqueous medium with H2O2

In this work substituted magnetites Fe3-xMnxO4 (x = 0.21, 0.26 and 0.53), Fe3-xCoxO4 (x = 0: 0. 19: 0.38; 0.75) and Fe3-xNixO4 (x = 0: 0. 10; 0.28:0.54) have been used to promote two different reactions involving H2O2: (i) the oxidation of organic molecules namely phenol, hydroquinone and methylene blue dye in aqueous medium and (ii) the peroxide decomposition to 0,. The presence of Co or Mn in the magnetite structure strongly increased the rate of H2O2 decomposition and the oxidation of the organic molecules whereas the presence of Ni inhibited both reactions. Kinetic data and CEMS Mossbauer spectroscopy suggest that the H2O2 decomposition and the organic oxidation are competitive reactions involving oxidizing species generated by surface M2+ (M = Fe, Co or Mn). (C) 2003 Elsevier B.V. All rights reserved.