Cu-doped g-C3N4 catalyst with stable Cu0 and Cu+ for enhanced amoxicillin degradation by heterogeneous electro-Fenton process at neutral pH

The development of new heterogeneous Cu-based solid catalysts for hydroxyl radical (center dot OH) generation plays a crucial role in degradation of pollutants at neutral pH circumstance. In this work, a Cu-doped graphitic carbon nitride (g-C3N4) complex was synthesized in one-step pyrolysis process using copper chloride dihydrate and dicyandiamide as precursors. The results reveal that after Cu doping, the bulk structure of g-C3N4 was destroyed with fragmentary morphology formation. Besides, Cu-0 and Cu+ were successfully embedded in g-C3N4 sheet. Moreover, amoxicillin (AMX) removal by heterogeneous electro-Fenton process was performed to evaluate the catalytic activity of the Cu-doped g-C3N4. 99.1% AMX removal efficiency was obtained after 60 min electrolysis under neutral pH condition when the current density was 12 mA cm(2) and the catalyst dosage was 0.3 g L-1. Both Cu-0 and Cu+ were stably retained in the Cu-doped g-C3N4 catalyst and AMX removal efficiency reached 91.1%, even after 5 cycles, manifesting the remarkable stability of Cu-doped g-C3N4. Also, Cu-doped g-C3N4 possessed excellent catalytic activities for AMX removal in various waterbodies. According to the catalytic mechanism analysis, the center dot OH was proved to be the primary reactive species for AMX removal in heterogeneous electro-Fenton process. Based on the identification of sixteen different intermediate products, the possible degradation pathways were proposed. This work provides a simple method to synthesize a Cu-based solid catalyst containing stable Cu-0 and Cu+ for degradation of pollutants in wastewater.