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 SO4Ë-, ËOH, and ËO2 -, 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.
ABSTRACT
Solid waste resource utilization and the treatment of wastewater are two important aspects in environmental protection. Here, biochar (BC) derived from municipal sewage sludge has been combined with ZnFe2O4 to form the photocatalyst ZnFe2O4/biochar (ZnFe/BC), and it was used to degrade sulfadiazine (SDZ) in the presence of peroxymonosulfate (PMS) under visible (Vis) light irradiation in an internal loop-airlift reactor (ALR). The surface morphology and structure of ZnFe/BC have been characterized by X-ray diffraction (XRD), scanning electron microscopy equipped with an attachment for energy-dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). ZnFe/BC displays outstanding photocatalytic performance and reusability. After four reuse cycles of ZnFe/BC in the Vis/ZnFe/BC/PMS system, the SDZ degradation rate and efficiency still reached 0.082 min-1 and 99.05%, respectively. Reactive species in this system included free radicals SO4Ë-, ËOH, and ËO2 -, as well as non-radicals 1O2, e-, and h+, as established from the results of chemical quenching experiments and electron paramagnetic resonance (EPR) analyses. Moreover, a mechanism of action of the Vis/ZnFe/BC/PMS system for SDZ degradation was proposed. The acute toxicity of the reaction solution towards Photobacterium phosphoreum T3 spp. in the Vis/ZnFe/BC/PMS process increased during the first 40 min and then decreased, illustrating that Vis/ZnFe/BC/PMS provided an effective and safe method for the removal of SDZ.
