Efficient adsorption and visible-light photocatalytic degradation of tetracycline hydrochloride using mesoporous BiOI microspheres

A novel microsphere-like BiOI hierarchical material was successfully synthesized by a one-step solution method at room temperature using polyvinylpyrrolidone (PVP) as structure directing reagent, its morphology, structure, surface area, photoabsorption were characterized, and the removal of tetracycline hydrochloride (TC) was evaluated under dark adsorption and visible light irradiation. It was shown that the BiOI microspheres formed in the precursor solution with PVP exhibit a mesoporous surface layer, 28.1m(2)g(-1) surface area, 1.91 eV band gap energy (E(g) value), and twofold removal ability to tetracycline hydrochloride (TC), i.e. adsorptive separation and visible light photocatalytic degradation. The adsorption process of TC on BiOI microspheres can be described by pseudo-second-order kinetics model and both Freundlich and Langmuir equations well described the adsorption isotherm but the former is better. More importantly, the BiOI microspheres exhibit an excellent photocatalytic degradation and mineralization capability to TC under visible light irradiation, which comes from its electronic band structure, high surface area and high surface-to-volume ratio. In addition, the BiOI microspheres are stable during the reaction and can be used repeatedly, showing promising prospect for the treatment of TCs in future industrial application.