Three-dimensional porous La(OH)3/g-C3N4 adsorption-photocatalytic synergistic removal of tetracycline

Abstract

La(OH)₃/g-C₃N₄ composites were successfully synthesized via one-step calcination using urea, melamine, and La(NO₃)₃·nH₂O as raw materials, and applied to UV-induced photocatalytic tetracycline (TC) removal. Comprehensive characterization by an X-ray diffraction (XRD), Fourier transform infrared reflection (FT-IR), high-resolution transmission electron microscope (HRTEM), and other techniques analyzed effects of La³⁺ doping, especially N vacancies and cyano groups as active sites. Compared to pure g-C₃N₄ and La(OH)₃, synthesized La(OH)₃/g-C₃N₄ composites exhibited a three-dimensional porous nanosheet structure with specific surface area of 83.62 m²/g and equilibrium TC adsorption capacity up to 285.59 mg/g; La(OH)₃ doping significantly improved composite structure. After dispersing 10 mg La-CN-0.5 photocatalyst in 60 mL 40 mg/L TC solution, TC removal reached 91.08% in 30 min under UV irradiation, exhibiting excellent performance. Additionally, La-CN-0.5 showed significant adsorption-photocatalytic synergism, with the quasi-primary kinetic constant increased by 1.83-fold. The efficiency of high tetracycline (TC) concentration treatment through adsorption photocatalytic degradation by La-CN-0.5 was confirmed by the utilization of free radical trapping and electron spin resonance (ESR) tests. The significant involvement of ∙O₂^-, ∙OH, and h⁺ in this process was observed. These findings propose that the prepared La-CN-0.5 material exhibits a unique capability for adsorption photocatalysis, providing a promising approach for the efficient removal of high TC concentrations.

Keywords: Active sites; Adsorption; One-step calcination; Photocatalysis; Removal; Synergy; Tetracycline.