Adsorption and catalytic degradation of organic dyes in water using ZnO/ZnxFe3−xO4 mixed oxides

• Zinc/Iron mixed oxides comprising of ZnO and ZnxFe3−xO4 (ZFOs) are synthesized.
• Adsorption/catalytic degradation of azo-dyes are investigated using the ZFOs.
• ZFOs proved to be highly efficient photocatalysts for removal of azo-dyes in water.
• The ZFOs could be regenerated and reused in multiple treatment cycles.

Adsorption and catalytic degradation of organic dyes were investigated using ZnO/ZnxFe3−xO4 mixed oxides (ZFOs). Two ZFOs with varying ratio of zinc:iron were synthesized by co-precipitation technique and their physico-chemical properties were studied using N2 adsorption–desorption, X-ray diffraction, thermo-gravimetric analysis, scanning electron microscope, transmission electron microscope, vibrating sample magnetometer, and Zetasizer. The synthesized ZFOs were evaluated for the removal of two azo dyes, Acid Blue 113 (AB-113) and Orange II (OR-II), from water by adsorption and by catalytic degradation. The influence of the factors such as adsorbent/catalyst dosage, amount of the oxidant (H2O2), solution pH and reaction temperature on removal of the dyes by the ZFOs was investigated. Increase in reaction temperature led to significant increase in degradation of the dyes by the ZFOs. Regeneration and reuse of the catalysts were also studied up to five cycles.

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