Synthesis and characterization of semiconductor CoAl2O4 for optical and dielectric studies: Application to photodegradation of organic pollutants under visible light

The objective of this work is to investigate the optical and dielectric properties of the synthesized cobalt aluminate (CoAl2O4) by chemical route using nitrates as reagents. The X-ray diffraction shows a single spinel phase with a good crystallinity. The diffuse reflectance spectrum R (lambda) recorded in the range (200-900 nm) enable us to calculate the refractive index n (lambda), optical conductivity (sigma(opt)), extinction coefficient (k), dissipation factor (tan delta) and relaxation time (tau). The optical gap (E-g = 1.83 eV), was evaluated and confirmed by several methods. The n-type conductivity is evidenced from the capacitance-potential plots, which leads to flat band potential of -0.43 V-SCE and an electron density of 1.44 x 10(17) cm(-3). As application, the photo-degradation of Congo Red (CR) a persistent and hazardous dye was successfully realized, yielding a de-pollution parentage of 94 % within 240 min for an initial concentration of 10 mg L-1.