Dr. Valdés-Morales, Héctor

Recently, bismuth oxyiodide (BiOI) is an attractive semiconductor to use in heterogeneous photocatalysis processes. Unfortunately, BiOI individually shows limited photocatalytic efficiency, instability, and a quick recombination of electron/holes. Considering the practical application of this semiconductor, some studies show that synthetic zeolites provide good support for this photocatalyst. This support material permits a better photocatalytic efficiency because it prevents the quick recombination of photogenerated pairs. However, the optimal conditions (time and temperature) to obtain composites (BiOI/ synthetic zeolite) with high photocatalytic efficiency using a coprecipitation-solvothermal growth method have not yet been reported. In this study, a response surface methodology (RSM) based on a central composite design (CCD) was applied to optimize the synthesis conditions of BiOI/mordenite composites. For this purpose, eleven BiOI/mordenite composites were synthesized using a combined coprecipitation-solvothermal method under different time and temperature conditions. The photocatalytic activities of the synthesized composites were evaluated after 20 min of photocatalytic oxidation of caffeic acid, a typical organic pollutant found in agro-industrial wastewater. Moreover, BiOI/mordenite composites with the highest and lowest photocatalytic activity were physically and chemically characterized using nitrogen adsorption isotherms, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and diffuse reflectance spectroscopy (DRS). The optimal synthesis conditions prove to be 187 ◦C and 9 h. In addition, the changes applied to the experimental conditions led to surface property modifications that influenced the photocatalytic degradation efficiency of the BiOI/mordenite composite toward caffeic acid photodegradation.

This study describes theoretical and experimental considerations to optimize the photocatalytic degradation of caffeic acid in water using 3D-BiOBr based materials under visible light irradiation. Three BiOBr materials were synthesized through the solvothermal method using different bromide sources, namely potassium bromide (KBr) and the ionic liquid (IL) 1-butyl-3-methylimidazolium bromide. Morphological and chemical changes were observed in IL based 3D-BiOBr materials. The theoretical optimization of the experimental conditions in heterogeneous photocatalysis tests (pH and dose of catalyst) were simulated using the MODDE 12.0.1 software. A central composite design (CCD) was applied to obtain a response surface to elucidate the optimal conditions. This model predicted that the maximum photocatalytic degradation can be achieved at pH of 6.7 and a photocatalyst dose of 344 mg L−1. The optimal experimental conditions were tested using the three synthesized 3D-BiOBr materials. The results showed that the highest degradation efficiency and mineralization yield were obtained using the BiOBr microspheres synthesized with the IL at 145 °C.