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

With the assistance of acetic acid (CHCOOH), a novel 3D flower-like BiO was synthesized via hydrothermal process followed by calcination. For the first time, the role of CHCOOH as a capping agent in the formation of flower-like structure was investigated. The as-prepared flower-like BiO had a high activity on the degradation of sulfamethoxazole (SMX) under simulated solar light irradiation due to the narrow band gap of 2.69eV, high percentage of β-BiO as well as high intensity of polar facets (120) and (200). Meanwhile, the photocatalytic degradation followed apparent pseudo-first-order kinetics. The rate constant (k) increased from 0.7×10 to 3.0×10min with the catalyst loading varying from 0.5 to 2.0gL. Increasing pH values from 3 to 11 led to the decrease of k from 2.2×10 to 0.2×10min, which could be attributed to the electrostatic adsorption between SMX molecules and BiO. The radical quenching experiments showed both direct (h) and indirect oxidation (OH and O) happened in this process.