Electrostatic self-assembly of hydrotalcite-based g-C3N4 composites for adsorption and photocatalytic degradation of aqueous norfloxacin

Abstract

Norfloxacin, a quinolone antibiotic pollutant, posed a significant threat to environment and human being health. In this study, hydrotalcite-based g-C₃N₄ composites were produced using electrostatic self-assembly and the structural memory effect of hydrotalcite to optimize their adsorption-degradation of norfloxacin under visible-light illumination. Optimized hydrotalcite and g-C₃N₄ composite (750°C, 40 wt% of g-C₃N₄) exhibited a highest photo-degradation rate constant of 1.8×10⁻² min⁻¹ with 83.98 % norfloxacin degradation achieved within 1.5 h under visible-light, surpassing that of bare g-C₃N₄ and hydrotalcite photocatalysts. The synergistic effects of the composite, such as uniform flower-like micro-morphology and rich mesoporous structure, resulted in a large specific surface area (58.67 m²/g), abundant active sites, and good photo-generated charge separation efficiency. All these facilitated both sorption (7.95 mg/g) and subsequent visible-light degradation of norfloxacin. Furthermore, the superior photocatalytic performance observed in the degradation of norfloxacin under visible-light illumination was assigned to the effective transport of photogenerated electrons and holes between hydrotalcite and g-C₃N₄ components. The work highlights the potentials of hydrotalcite and g-C₃N₄ composites as an excellent photocatalyst for environment remediation and water treatment.