Abstract
An approach involving ultrasonic irradiation/hydrothermal route was employed for fabricating a series of ZnO nanospheres-carbon nanotubes (Z/CNT) and reduced graphene oxides (Z/GO) nanocomposites, at different weight % ratios of both. The synthesized catalysts were tested in heterogeneous photocatalytic degradation of 4-nitrophenol (4-NP, 10 ppm) via Fenton approach in the attendance of visible light irradiation (160 W, lambda > 420), ultrasonic illumination (60 W, 20 kHz) and during coupling the latter irradiations (sonophotocatalysis). The experimental parameters for the Photo-Fenton degradation of 4-NP at the surface of the Z(70)/CNT(30) catalyst were 40 mM H2O2, pH 4, catalyst dosage of 1.75 g/L and at 25 degrees C. The rate constants of 4-NP degradation using the sonophotocatalytic approach (0.3 min(-1)); that takes 15 min to accomplish, exceeded those of sonocatalytic (0.15 min(-1)) and photocatalytic (0.06 min(-1)) systems, unveiling the synergistic performance of the former system. These values were lower when performing the reaction at the same conditions but at pH 11 to elucidate the importance of the slow releasing of center dot OH in the acid range. The sono- and photo- coupled irradiations induced a synergy percentage comprised of 30 to demonstrate the efficacy of the adopted approach and the catalyst in the degradation of 4-NP.