Strategic combination of nitrogen-doped carbon quantum dots and g-C3N4: Efficient photocatalytic peroxydisulfate for the degradation of tetracycline hydrochloride and mechanism insight

Photo-assisted peroxydisulfate (PDS) activation has exhibited a great potential for pollution control. In this study, metal-free nitrogen-doped carbon quantum dots (N-CQDs) modified g-C3N4 composite was fabricated and used to activate PDS under visible light to effectively remove tetracycline hydrochloride (HTC) in wastewater. Specifically, almost 90% of HTC (20 mg/L) was removed in 60 min under the conditions of an initial value of catalysis dose of 0.5 g/L and PDS dose of 0.6 g/L. Electron spin resonance analysis and trapping experiments confirmed that center dot SO4-, center dot O-2(-) and h(+) were found as the dominant contributors to the HTC degradation. PDS and N-CQDs acted as an electron acceptor to transfer the photogenerated charges, resulting in the successful activation of PDS. The promoting visible light absorption can be ascribed to up-conversion effect of N-CQDs. The combination strategy provides an innovative approach to synthesize binary metal-free carbonaceous photocatalysts for implementing PDS-based oxidative degradation of pollutants.

Automated summary

Photo-assisted peroxydisulfate (PDS) activation has shown great potential in pollution control, and in this study, a metal-free nitrogen-doped carbon quantum dots (N-CQDs) modified g-C3N4 composite was used to effectively remove tetracycline hydrochloride (HTC) in wastewater under visible light. The combination of PDS and N-CQDs acted as electron acceptors, transferring photogenerated charges and successfully activating PDS for pollutant degradation. The up-conversion effect of N-CQDs contributed to enhanced visible light absorption, providing an innovative approach for synthesizing binary metal-free carbonaceous photocatalysts.