High efficiency degradation of tetracycline and rhodamine B using Z-type BaTiO3/γ-Bi2O3 heterojunction

Z-scheme BaTiO 3 /γ-Bi 2 O 3 heterojunction for high efficiency photodegradation of tetracycline and rhodamine B. • BaTiO 3 /g-Bi 2 O 3 was synthesized by hydrothermal, coprecipitation, and calcination. • Degradation efficiency of tetracycline is above 93% after 90 minutes. • Catalyst mass, water body, and pH values have a weak effect on tetracycline removal. • Rhodamine B is completely degraded using the optimal samples. • Photogenerated electrons transfer from g-Bi 2 O 3 CB to BaTiO 3 VB. Thirteen BaTiO 3 /γ-Bi 2 O 3 heterojunctions (labeled as HS1 to HS13) were synthesized via solid phase method under different raw material ratio, calcination temperatures, and times with XRD, SEM, EDS mapping, TEM, XPS, and Raman spectra characterizations. The degradation efficiency of all samples is above 93% after 90 min upon initial concentration 10 mg/L tetracycline with the optimal HS6 as 97.95%. The first order reaction rate is above 0.059 min -1 , faster than 0.031 min -1 of BaTiO 3 and 0.011 min -1 of γ-Bi 2 O 3 . The catalyst masses, different water bodies, and pH values have a little effect on the final removal efficiency of tetracycline. Under the same test environment, the removal efficiency of 10 mg/L rhodamine B is over 73.62%, higher than BaTiO 3 45.35% and γ-Bi 2 O 3 63.34% and the best HS3, HS4, and HS5 samples have 100% degradation efficiency. The heterojunction can be recycled with excellent structural stability. The superior catalytic activity is attributed to electrons transfer along Z-type from γ-Bi 2 O 3 conductor band (CB) to BaTiO 3 valence band (VB) via work function and charge density difference analysis. The superoxide radical and hole are active substance in the process of tetracycline degradation while the rhodamine B removal is ascribed to superoxide and hydroxyl radicals attacking. The decomposition paths of two pollutants are revealed using high performance liquid chromatography mass spectroscopy (HPLC-MS).