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-C 3 N 4 /Bi 2 WO 6 ) 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% Bi 2 WO 6 codecorated g-C 3 N 4 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-C 3 N 4 and Bi 2 WO 6 , including: i) the incorporation of SnTCPP extends the visible light response of the binary Bi 2 WO 6 /g-C 3 N 4 heterojunctions , resulting in the highly efficient visible light harvesting; ii) we find that the g-C 3 N 4 not only serves as a promising supporter to trap electrons from Bi 2 WO 6 , but also as an interfacial electron-hole pairs transfer moderator, like “volleyball setter” to facilitate the charges transfer between Bi 2 WO 6 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-C 3 N 4 based heterojunctions suitable for removing pharmaceutical antibiotics and hazardous dyes from various real wastewaters .