Photocatalytic degradation of antibiotics using a novel Ag/Ag2S/Bi2MoO6 plasmonic p-n heterojunction photocatalyst: Mineralization activity, degradation pathways and boosted charge separation mechanism

A new 3D Ag/Ag2S/Bi2MoO6 plasmonic p-n heterojunction photocatalyst has been designed and applied for efficiently visible-light photocatalytic degradation of pharmaceutical antibiotics. [Display omitted] •Ag/Ag2S/Bi2MoO6 (AAS/BMO) plasmonic p-n heterojunction was constructed.•AAS/BMO displayed superior catalytic activity and great stability for antibiotics removal.•Effects of various factors on levofloxacin removal were studied systematically.•A plausible degradation pathway for levofloxacin was proposed.•Plasmonic p-n heterojunction greatly promotes charge separation and ROS production. A novel Ag/Ag2S/Bi2MoO6 plasmonic p-n heterojunction has been constructed via the in-situ growth of p-type Ag2S nanoparticles on n-type Bi2MoO6 microspheres, followed by the photo-reduction treatment. Simultaneously, the Ag0 loading percentage in the heterojunction could be finely controlled by tuning the photo-reduction time. The optimized Ag/Ag2S/Bi2MoO6 (AAS/BMO-4) manifests the highest photocatalytic performance towards degrading levofloxacin (LEV) and tetracycline hydrochloride (TC), which degradation efficiencies are 87.3% and 92.8%, respectively. Such improvement mechanism could be due to the improved light absorption in the visible-light region induced by localized surface plasmon resonance (LSPR) and the efficient interfacial separation and transport of charge carriers in Ag/Ag2S/Bi2MoO6. The impacts of some key parameters (e.g., various inorganic anions, representative organic substances and various water resources) are systematically investigated. Ag/Ag2S/Bi2MoO6 also exhibits excellent mineralization capability and recycling performance in degrading LEV. Moreover, photo-generated h+, OH, and O2– are identified as the dominant reactive species accounting for the degradation of antibiotics. The photodegradation pathway of LEV has also been elucidated based on the intermediate identification. Therefore, this study not only reports an innovative plasmonic p-n heterojunction but also the new design of photocatalysts capable of efficiently degrading pharmaceutical antibiotics under visible-light irradiation.