Photo-electrochemical and Physical Characterizations of the Hetero-System FeAlO 3 /ZnO and its Application for the Oxydation of Remazol Under Sunlight

Remazol (REM), a hazardous dye, is successfully oxidized on the hetero-system FeAlO 3 /ZnO under the solar light. The ilmenite FeAlO 3 with a nano morphological structure is synthesized by nitrate route followed by treatment at 850 °C. The X-ray diffraction pattern exhibits narrow peaks, characteristic of a good crystallization. A direct optical transition at 2.03 eV, determined from the diffuse reflectance is due to degeneracy lifting of Fe 3+ : 3d level in octahedral site. The valence band derives from the cationic t 2g orbital (5.23 eV). The conduction takes place by electron-hopping mechanism and an activation energy (E a ) of 0.15 eV is calculated from the slope dσ/dT −1 . The capacitance − - potential (C −2 - E) curve of FeAlO 3 indicates p type conduction with a flat band potential of + 0.18 V SCE and hole density of 1.08 × 10 16 cm −3 . The energy diagram, drawn from the physic-chemical properties, predicts the electron transfer from the conduction band of FeAlO 3 to dissolved oxygen via ZnO. Indeed, the hetero-system FeAlO 3 /ZnO enhances considerably the photoactivity through the photochemical REM oxidation. The ilmenite dose and initial REM concentration are optimized. The oxidation is monitored by UV–Visible spectrophotometry and, under the ideal conditions, a conversion abatement of 80% of REM (15 ppm) is obtained in aerated solution under solar light. The kinetic data are well fitted by a first order model with a half-photocatalytic life of 2 h under the optimal conditions (pH ~ 7, FeAlO 3 25%/ZnO, 200 mL).