Photocatalytic degradation of norfloxacin and its intermediate degradation products using nitrogen-doped activated carbon-CuS nanocomposite assisted by visible irradiation

We have synthesized a nitrogen-doped activated carbon (NAC) derived from oak using KOH and N-2 thermal treatment at 400 degrees C as well as CuS nanoparticles. The NAC was decorated with the synthesized CuS to apply as a photocatalyst for degradation of norfloxacin (NOR). Before its application for photodegradation, the adsorbent/photocatalyst structural properties were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy. The photocatalytic degradation of NOR was successfully done under visible light using NAC-CuS. The results revealed that the investigated fluoroquinolone degraded very efficiently and pseudo-first-order kinetics was adopted for the photodegradation process. In addition, isothermal studies showed that the adsorption process in darkness followed the Langmuir model. The degradation characteristics of the NAC-CuS photocatalyst were studied for 120 min and 15 h under visible light for degradation of NOR, exhibiting a good efficiency for NOR removal. During 120 min of degradation, some intermediate degradation products that can be considered as secondary pollutants were produced. Then, to degrade these pollutants the radiation time was increased up to 15 h. The results displayed a perfect degradation of NOR and its secondary pollutants. The effective variables including pH, degradation time and photocatalyst dosage were optimized and studied in a multivariate method using Design Expert 7. Determination of photodegradation products was carried out using liquid chromatography-mass spectrometry. The results are of significance for estimating the environmental fate of NOR in aqueous media.