Acetic acid-assisted fabrication of hierarchical flower-like Bi2O3 for photocatalytic degradation of sulfamethoxazole and rhodamine B under solar irradiation

With the assistance of acetic acid (CH 3 COOH), a novel 3D flower-like Bi 2 O 3 was synthesized via hydrothermal process followed by calcination. For the first time, the role of CH 3 COOH as a capping agent in the formation of flower-like structure was investigated. The as-prepared flower-like Bi 2 O 3 had a high activity on the degradation of sulfamethoxazole (SMX) under simulated solar light irradiation due to the narrow band gap of 2.69 eV, high percentage of β-Bi 2 O 3 as well as high intensity of polar facets (1 2 0) and (2 0 0). Meanwhile, the photocatalytic degradation followed apparent pseudo-first-order kinetics. The rate constant ( k ) increased from 0.7 × 10 −2 to 3.0 × 10 −2 min −1 with the catalyst loading varying from 0.5 to 2.0 g L −1 . Increasing pH values from 3 to 11 led to the decrease of k from 2.2 × 10 −2 to 0.2 × 10 −2 min −1 , which could be attributed to the electrostatic adsorption between SMX molecules and Bi 2 O 3 . The radical quenching experiments showed both direct (h + ) and indirect oxidation ( OH and O 2 - ) happened in this process.