Manganese zinc ferrite nanoparticles as efficient catalysts for wet peroxide oxidation of organic aqueous wastes

Manganese substituted zinc nanoparticles, MnxZn1-xFe2O4 (x = 0.0, 0.25, 0.5, 0.75, 1.0) prepared by sol gel method were found to be efficient catalysts for wet peroxide oxidation of 4-chlorophenol. Complete degradation of the target pollutant occurred within 90 min at 70 degrees C. Zinc substitution enhanced the catalytic efficiency and the unsubstituted ZnFe2O4 oxidized the target compound completely within 45 min. Studies on the effect of reaction variables revealed that only a small amount of the oxidant, H2O2 (3-4 mL) is required for complete degradation of 4-chlorophenol. More than 80% of 4-chlorophenol was removed at catalyst concentrations of 100 mg/L. Direct correlation between the amount of catalyst present and the extent of degradation of 4-chlorophenol was observed, ruling out hesterogeneous-homogeneous mechanism. The catalysts are reusable and complete degradation of target pollutant occurred after five successive runs. The extent of iron leaching was fairly low after five consecutive cycles indicating the mechanism to be heterogeneous.