Influence of the synthesis conditions on the catalytic efficiency of NiFe2O4 and ZnFe2O4 nanoparticles towards the wet peroxide oxidation of 4-chlorophenol

Abstract

Catalytic wet peroxide oxidation of 4-chlorophenol solution was studied over nickel and zinc ferrite nanoparticles at mild conditions. The catalysts were prepared by sol–gel auto combustion method using ethylene glycol and citric acid as gelling agents at different calcination temperatures. Complete removal of 4-chlorophenol (25 ml of 1 g/l 4-chlorophenol solution) was achieved within 60 min at ambient conditions. Studies on the effect of reaction variables revealed that only a small amount of the oxidant (1 ml) is required for the complete degradation of 4-chlorophenol. 100 % of the target pollutant was removed at catalyst concentrations of 300 mg. The catalysts were reusable and the activity as well as the single phasic nature of the ferrite catalysts remained the same after five successive runs. Leaching of iron from ferrite nanoparticles was not observed after five consecutive cycles indicating the mechanism to be heterogeneous. The samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results underline the effect of preparation conditions on the morphology, crystallite size and catalytic efficiency of nanoferrites.