Efficient photo-oxidation of bisphenol a and tetracycline through sulfur-doped g-C3N4/CD heterojunctions

Abstract

The synergistic effects of sulfur-doped g-C₃N₄ (SCN) and carbon dots (CD) in nanocomposite photocatalysts were explored for the degradation of contaminants of emerging concern (CECs), particularly phenolic pollutants such as bisphenol A (BPA) and tetracycline (TC). Various SCN/CD nanocomposites were synthesized via thermal polymerization by mixing with different CD concentrations with thiourea (1, 2, 3, and 4 by wt%), denoted as SCN/CD1, SCN/CD2, SCN/CD3, and SCN/CD4, respectively. The embedded CD functions as an intrinsic surface modifier on the surface of the SCN which facilitated the suppression of electron–hole recombination and promoted photocatalytic activity. Among the synthesized catalysts, SCN/CD3 exhibited remarkable efficiency, degrading a 50-ppm solution of BPA to 92.5% and TC to 90.7% within 60 minutes, utilizing 50 mg of catalyst. Moreover, SCN/CD3 demonstrated exceptional reusability over five cycles without significant degradation in efficiency. Radical scavenging experiments identified holes (h⁺) and superoxide radicals (O₂˙⁻) as the primary radical species responsible for pollutant degradation. This work highlights the potential of SCN/CD composite photocatalysts in solving water pollution concerns by elucidating a promising photocatalytic degradation process for CECs.