Solar/visible photocatalytic degradation kinetics and mechanism of RB5 dye by g-C3N4 nanosheets

The photodegradation of an azo dye, Reactive Black 5 (RB5), as a model pollutant by graphitic carbon nitride, g-C3N4 nanosheets under visible and solar light irradiations was evaluated. The g-C3N4 nanosheets with the band gap of 2.7 eV was prepared by via the thermal condensation of urea. The photodegradation of RB5 dye by prepared g-C3N4 nanosheets was performed under different conditions including photocatalyst loading, pH, initial dye concentration, and irradiation source (Xe lamp and sunlight). Fig. 1 shows the influence of pH (3.4-9.0) on the degradation efficiency of RB5 by g-C3N4 nanosheets at 25 oC under 90 min sunlight irradiation. The optimum photodegradation conditions were achieved by 0.04 gl-1 of g-C3N4, 10 ppm of RB5, and pH 3.4 under sunlight irradiation. The photocatalytic degradation of RB5 over g-C3N4 nanosheets under sunlight light irradiation followed the pseudo-first-order kinetics with the rate coefficient of 0.0058 s-1. To elucidate which of the active species has a major role in the photodegradation of RB5 dye by g-C3N4 nanosheets under visible light irradiation, different radical scavengers with the same concentration of 60 mM were used. It was found that the influence of superoxide radical is the most important