3.7. Photodegradation Measurements

The photocatalytic performance of as-obtained samples was tested by degradation experiments of NOR in aqueous solution. The visible-light source was provided by a 500 W xenon lamp equipped with a 420 nm cut filter.

Typically, 20 mg of the sample as-obtained was added into 100 mL 20 mg/L NOR solution with magnetic stirring in a quartz tube reactor with a water circulation facility. Before light irradiation, the mixture suspension was remained in the dark for 30 min to reach the adsorption-desorption equilibrium between photocatalysts and degradation product. During the photodegradation process, 10 mL of the suspension was withdrawn and centrifuged to remove the photocatalyst each 20 min. The absorbance of the supernatant was examined at a wavelength of 280 nm. The photodegradation ratio for NOR was tested by the formula below:

where η is the photodegradation ratio for NOR, C_t and C₀ represent the initial and remaining NOR in aqueous solution, t is the light irradiation time, respectively.