Study on highly enhanced photocatalytic tetracycline degradation of type Ⅱ AgI/CuBi2O4 and Z-scheme AgBr/CuBi2O4 heterojunction photocatalysts.

Removal of antibiotics from aqueous solutions by photocatalysis is an advanced technology for environmental remediation. Herein, we have fabricated a series of AgX (X = I, Br)/CuBi2O4 composites through an in-situ precipitation method. The photocatalytic activity of the obtained photocatalysts was measured by the degradation of tetracycline (TC) under visible light irradiation (λ > 420 nm). All the AgX (X = I, Br)/CuBi2O4 composites exhibit much higher photocatalytic activity than that of pure CuBi2O4. The enhanced photocatalytic activity is mainly attributed to the efficient interfacial charge separation and migration in the AgX (X = I, Br)/CuBi2O4 heterojunctions. Meanwhile, AgX (X = I, Br)/CuBi2O4 heterojunctions display excellent photocatalytic stability, and the photocatalytic degradation rates were not obvious decreased even after five successive cycles. Based on the energy band structure, the radicals trapping and electronic spin resonance (ESR) experiments, the Z-scheme mechanism of AgBr/CuBi2O4 and type II mechanism of AgI/CuBi2O4 heterojunction photocatalysts were tentatively discussed, respectively.