Room-temperature synthesis of flower-like hierarchical architecture of BiOI and enhanced photocatalytic activity: Application of response surface methodology

Flower-like bismuth oxyiodide (BiOI) hierarchical microspheres were synthesized successfully at room temperature in the presence of ethylene glycol and KI as solvent and iodide source, respectively and applied for the photocatalytic degradation of levofloxacin from aqueous media under visible light irradiation. Optimal conditions for the synthesis and photocatalytic processes were obtained by using the response surface methodology (RSM) combined with central composite design (CCD). Based on the CCD, the quadratic model represents the relationship between the following factors: reactant concentration (0.009-0.116 mol/L), percentage of ethylene glycol (15%-85%) for synthesis processes and contact time (12-108 min), BiOI dosage (0.05-2.45 g/L), and initial concentration (1.1-5.9 mg/L) for photocatalytic processes. The obtained BiOI structures were characterized by scanning electron microscopy (SEM), nitrogen adsorption (BET), X-ray diffraction (XRD), and UV-Vis absorption spectroscopy. The results show that the proposed quadratic model in accordance with the experiment results in an R-2 value and lack of fit F-values of 0.9987 and 2.79 for synthesis processes, and 0.9977 and 3.06 for photocatalytic processes. It was observed that ethylene glycol not only acted as a solvent but was also a soft temple for the fabrication of flower-like BiOI hierarchical microspheres. The optimum conditions of reactant concentration and percentage of ethylene glycol for synthesis processes were obtained at 0.063 mol/L and 85%, respectively. Additionally, under visible light irradiation, the synthesized flower-like BiOI hierarchical microspheres can remove levofloxacin up to 99%. The optimum conditions of contact time, BiOI dosage, and levofloxacin initial concentration for photocatalytic processes were obtained at 90 min, 2 g/L, and 2 mg/L, respectively.