Impact of operating conditions for the continuous-flow degradation of diclofenac with immobilized carbon nitride photocatalysts

Abstract

In the current paper, the continuous-flow photodegradation of diclofenac (DCF) as an aqueous model pollutant was investigated using porous carbon nitride (mp-CN), immobilized onto stainless steel (SS) plates, as the photocatalyst, and a homemade cubic photoreactor for the degradation reaction. X-ray diffraction (XRD) and N2 adsorption/desorption characterization (BET) were conducted to determine the structural features of the mp-CN photocatalyst. The effect of operating reaction conditions on DCF photodegradation efficiency, such as the loaded amount of mp-CN photocatalyst (0.8–4.1 mg/cm2), initial DCF concentration (10–200 mg/L), and type of irradiation source (LED, solar-simulator, and Xenon lamp), was studied in detail. The highest DCF photodegradation efficiency of about 71% was obtained for a DCF concentration of 10 mg/L, Xenon lamp irradiation, and mp-CN loading of 2.041 mg/cm2. The kinetic studies indicated a pseudo-first-order reaction that was fitted with the experimental data completely (R2 > 0.96). The reaction rate constant for the highest DCF degradation efficiency was determined to be k = 0.0049 min−1). The stability and reusability experiments proved that the immobilized mp-CN photocatalyst could be used for four times in the continuous-flow mode without a notable decline of the photodegradation performance. The studied photoreactor with the immobilized photocatalyst particles could be an acceptable alternative for photodegradation processes of aqueous contaminants in a continuous-flow mode.