Photocatalytic degradation of tetracycline hydrochloride by lanthanum doped TiO2@g-C3N4 activated persulfate under visible light irradiation

Abstract

In this work, a visible light-driven La/TiO₂@g-C₃N₄ photocatalyst was synthesized for the photodegradation of tetracycline hydrochloride (TCH) in the presence of peroxydisulfate (PDS) in an internal loop-lift reactor. The surface morphology and structure of La/TiO₂@g-C₃N₄ have been characterized by XRD, SEM-EDS, FTIR, XPS, and UV/vis DRS. La/TiO₂@g-C₃N₄ displays outstanding photocatalytic performance and reusability. After four reuse cycles of the vis/La/TiO₂@g-C₃N₄/PDS system, the TCH degradation rate and efficiency still reached 0.083 min⁻¹ and 97.68%, respectively. Reactive species in this system included free radicals SO₄˙⁻, ˙OH, and ˙O₂⁻, as well as non-radicals e⁻, and h⁺, as established from the results of chemical quenching experiments. Moreover, a mechanism of action of the vis/La/TiO₂@g-C₃N₄/PDS system for TCH degradation was proposed. The acute toxicity of the reaction solution towards Photobacterium phosphoreum T3 spp. in the vis/La/TiO₂@g-C₃N₄/PDS process increased during the first 60 min and then decreased, illustrating that vis/La/TiO₂@g-C₃N₄/PDS provided an effective and safe method for the removal of TCH.