Microwave-assisted method synthesis of Ag/CNQDs/g-C3N4 with excellent photocatalytic activity for the degradation of norfloxacin

In this paper, through microwave-assisted process combined with a chemical reduction method, the novel ternary photocatalysts Ag/CNQDs/g-C3N4 composites were prepared successfully for the norfloxacin removal. The Ag/CNQDs/g-C3N4 composites possessed the suitable specific surface area, better crystal structure and excellent stability. Furthermore, forming an internal electric field, the isotype heterojunction structure between CNQDs and g-C3N4 could promote effective carrier separation. Unexpectedly, the Ag/CNQDs/g-C3N4 with the synergistic effect of the up-conversion fluorescent properties of CNQDs and the surface plasmon resonance (SPR) effect of Ag NPs, showed the excellent photocatalytic property. As a result, the optimized Ag/CNQDs/g-C3N4 composites exhibit excellent photocatalytic degradation of norfloxacin under visible light irradiation. The norfloxacin removal rate was reached almost 100% within 120 min, and the quasi-first-order kinetic constant (k) value was 0.04233 min 1, which was more than 4 times higher than that of g-C3N4. Moreover, the center dot O-2(-) and h(+) were the dominant active species involved in the photo-degradation of norfloxacin. In the mineralization process, the toxicity of norfloxacin degradation intermediates gradually reduced. This work not only provides new insights for the design of g-C3N4-based composites for photocatalysis applications, but also affords an effective strategy in the environmental remediation field.