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

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.