Photocatalytic activity of NiS, NiO and coupled NiS–NiO for degradation of pharmaceutical pollutant cephalexin under visible light

摘要

In this research, a magnetic core–shell catalyst support was prepared by polymerization of pyrrole in the presence of Fe₃O₄ nanoparticles. The magnetic support was employed for the implementation of NiS, NiO and coupled NiS–NiO. The synthesized photocatalysts were characterized by FTIR, TG, XRD, DRS, BET, TEM and SEM techniques and then used for the degradation of pharmaceutical pollutant cephalexin under visible light irradiation. The results indicated that the efficiency of the coupled photocatalyst (Fe₃O₄@PPY–NiO–NiS) was considerably higher than that of Fe₃O₄@PPY–NiO and Fe₃O₄@PPY–NiS. This can be explained by the lower band gap energy of the photocatalysts, obtained after coupling and immobilization on the support. Magnetization of the photocatalyst evaluated by VSM technique showed that the magnetized photocatalyst properly and quickly separated from the reaction solution with the aid of an external magnetic field. Upon regeneration, the photocatalyst retained most of its initial efficiency. The enhancing effect of H₂O₂ and the inhibition effects of some reagents on the degradation efficiency were studied. The photodegradation products were identified by GC-MS technique.