Characterization of the hetero-system ZnCo2O4/ZnO prepared by sol gel: application to the degradation of Ponceau 4R under solar light

Ponceau 4R is successfully oxidized on the hetero-system ZnCo2O4/ZnO under the solar light. The spinel with a nano-morphology is elaborated by the sol gel method at similar to 850 degrees C. The X-ray diffraction pattern exhibits narrow peak characteristics that reveals a good crystallization. The capacitance(-2)-potential (C-2-E) plot of the semiconductor ZnCo2O4 indicates p type behavior from which a flat band potential of +0.30 V-SCE is determined. The energy band diagram, built from the physic-chemical properties, clearly predicts the electron transfer from the conduction band of ZnCo2O4 toward dissolved oxygen via ZnO. Indeed, the ZnCo2O4/ZnO composite improves the photocatalytic performance, where the colloidal photochemical hetero-system is successfully used for the light induced Ponceau 4R oxidation. The spinel dose and Ponceau 4R concentration are optimized. The conversion rate is controlled by UV-Visible spectrophotometry and, under the ideal conditions, the oxidation of 70% of Ponceau 4R (15 ppm) is obtained in aerated solution for less than 4 h when exposed to the solar light. The oxidation obeys a first order kinetic with a half-photocatalytic life of 130 min (k similar to 52 x 10(-4) min(-1)).