Abstract:Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. Different compositions of ferrite, Zn_(1-x)Cu_xFe₂O₄ (x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety .The rate constant k has the highest value with x=0.75 and 5% (mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu²⁺-Fe ⁺ and/or Cu⁺-Fe²⁺ ion pairs besides the one component sites Cu²⁺-Cu⁺, Fe³⁺-Fe²⁺, as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.

Key words: mixed ferrite; spinel; valence induction; catalyst activity; rate constant; lanthanum oxalate