Construction of a new cascade photogenerated charge transfer system for the efficient removal of bio-toxic levofloxacin and rhodamine B from aqueous solution: Mechanism, degradation pathways and intermediates study.

In this work, a novel cascade system (i.e., SnTCPP/g-C3N4/Bi2WO6) is successfully constructed using stannum (II) meso-tetra (4-carboxyphenyl) porphyrin (SnTCPP) as the key photovoltaic agent for the first time. Visible light driven photocatalytic experiments indicated that wt. 12% SnTCPP and 30% Bi2WO6 codecorated g-C3N4 demonstrates the highest photodecomposition capabilities for levofloxacin and rhodamine B, achieving 85.64% and 93.64% degradation rates, respectively. The dramatically enhanced photocatalytic performance mainly raised from the synergetic co-effects among SnTCPP, g-C3N4 and Bi2WO6, including: i) the incorporation of SnTCPP extends the visible light response of the binary Bi2WO6/g-C3N4 heterojunctions, resulting in the highly efficient visible light harvesting; ii) we find that the g-C3N4 not only serves as a promising supporter to trap electrons from Bi2WO6, but also as an interfacial electron-hole pairs transfer moderator, like "volleyball setter" to facilitate the charges transfer between Bi2WO6 and SnTCPP. The presence of the "setter" endows a cascade system for boosting the photodegradation efficiency of levofloxacin and rhodamine B. This study provides a promising design strategy to construct efficient g-C3N4 based heterojunctions suitable for removing pharmaceutical antibiotics and hazardous dyes from various real wastewaters.