Photocatalytic activity of spinel ZnFe2−xCrxO4 nanoparticles on removal Orange I azo dye from aqueous solution

• Photodegradation of aqueous solution of pollutant Orange I is reported.
• Dye removal efficiency was enhanced with increase in Cr3+ content in ZnFe2O4.
• The decolorization rate under visible light is two times lower that under UV light.
• Under UV irradiation, first order kinetic rate constant k was 5.85 × 10−2/min.

In this study the photodegradation of aqueous solution of recalcitrant organic pollutant Orange I was investigated by using chromium substituted zinc ferrite, ZnFe2−xCrxO4 (x = 0, 0.25, 0.5, 1.0, 1.50, 2.0) catalysts, for the first time, under both UV and visible light irradiation. The photocatalytic process was promoted when Fe3+ cations were substituted with Cr3+ cations. Therefore, the dye removal efficiency was enhanced up to 92.8% for x = 1.50 composition when Cr3+ cations were introduced in octahedral lattice of ZnFe2O4, showing that this material contains chromium optimal dosage for photocatalytic degradation of Orange I. Further, we studied photocatalytic activity under both UV and visible light irradiation of ZnFe0.50Cr1.50O4 above Orange I dye solution. The investigation of removal kinetics of Orange I indicates that the removal processes, under both UV and visible light, obeys the rate of first-order kinetic equation. The best photocatalytic performance was achieved after 45 min of UV light irradiation, with first order kinetic rate constant k of 5.85 × 10−2/min. Anyway, the decolorization rate under UV light is two times higher that afforded under visible light.