The photocatalyst with a strong internal electric field grown in situ on the surface of copper foam collaborates with peroxymonosulfate to enhance directional charge transfer and achieve ultra-fast Mn+/M(n+1)+ cycling

Abstract

To address three pressing problems that limit the application of photocatalytic synergic peroxymonosulfate (PMS) technology, namely difficult reuse, low photogenerated carrier separation efficiency, and sluggish metallic ions redox cycle, we utilized an in-situ growth method to construct a vertical nanosheet heterojunction on the surface of copper foam (CF). This heterojunction is characterized by a strong internal electric field (IEF) that serves as both a “pump” for the rapid and efficient migration of electrons and a driving force for the activation of PMS by these electrons. In the CF@CCS@CO-3/7/Vis/PMS system, the photoelectrons generated by photocatalysis quickly replenish the high valence metals activated by PMS, allowing for highly efficient cycling of differently valenced metal ions and reducing the dissolution of high valence metal ions produced by PMS. As a result, close to 100 % of ciprofloxacin (CIP) was degraded within 60 min in the CF@CCS@CO-3/7/Vis/PMS system with a reaction rate constant k of 0.0621 min−1, which is about 3.22 times higher than that of the CF@CCS@CO-3/7/Vis system and 2.65 times higher than that of the CF@CCS@CO-3/7/PMS system. Moreover, the in-situ growth of active ingredients with vertical nanosheet structure on the CF surface can well maintain structure and reactivity in complex environments, allowing more than 10 cycles to be realized. The results of the free radical burst assay and EPR analysis indicated that SO4∙−, ∙O2− and h+ were the main reactive species involved in the catalytic process. Building upon CF@CCS@CO-3/7, we assembled a fixed-bed continuous treatment device that enables high mineralization flow treatment of pharmaceutical wastewater (after Secondary biological treatment).