Construction of a novel S-type γ-Bi2O3/CeO2 heterojunction for highly efficient photocatalytic degradation of antibiotics.

ABSTRACT

Cubic nanoparticles of CeO2 were partly covered on the tetrahedron surface of γ-Bi2O3 through a hydrothermal reaction and then a calcination process to construct a novel S-type γ-Bi2O3/CeO2 heterojunction. The optimized sample removed 96% of lomefloxacin and 81% of tetracycline. During the cycling test, the photocatalytic efficiency of lomefloxacin and tetracycline was maintained above 87% and 80%, respectively, for five consecutive cycles. According to XRD and Raman spectra characterization, the sample after cycling held a stable crystal structure. Holes, OH-˙, O2˙, and electrons participated in the degradation of lomefloxacin, while tetracycline was removed via the effect of the former three active substances. Based on theoretical calculation and experimental tests, the excellent photocatalytic activity of γ-Bi2O3/CeO2 came from the fast transfer of charge carriers along the S-type path. Moreover, the CB electrons of γ-Bi2O3 and VB holes of CeO2 were preserved to generate free radicals for antibiotic degradation. The colony numbers of Escherichia coli were 1.50 × 10-6 CFU mL-1 and 1.39 × 10-6 CFU mL-1 in solutions after the degradation of the two pollutants, which represents the non-toxicity of the final products. The γ-Bi2O3/CeO2 sample has a potential application for antibiotic removal from modern sewage.