Co-precipitation synthesis of BiOI/(BiO)2CO3: Brief characterization and the kinetic study in the photodegradation and mineralization of sulfasalazine

Abstract

A binary BiOI/(BiO)2CO3 catalyst was prepared via the co-precipitation process as a typical bismuth-based photocatalyst. The XRD data confirmed the tetragonal crystals of BiOI and (BiO)2CO3 had been produced. The crystallite size of BiOI, (BiO)2CO3, and BiOI/(BiO)2CO3 samples were 28.94, 23.24, and 25.11 ​nm (Scherrer formula), and 86.26, 28.28, and 39.60 ​nm (Williamson formula), respectively. FTIR bands for the Bi–O and Bi–I in BiOI, the stretching vibrations bands of the Bi–O, the C–O and CO bonds in (BiO)2CO3 were detected, confirming the formation of the proposed semiconductors. DRS results showed the absorption wavelength edges of 684, 362, and 509 ​nm correspond to the band gap values of 1.81, 3.43, 2.44 ​eV for BiOI, (BiO)2CO3, and BiOI/(BiO)2CO3, respectively. This confirms that the binary catalyst is a visible-light-driven photocatalyst. Some lump and plate-like segments were depicted in the SEM images. About 1% and 5% of a 10 ​ppm SSZ solution were removed by direct photolysis and surface adsorption, while photodegradation by BiOI, (BiO)2CO3, and BiOI/(BiO)2CO3 catalysts removed 62, 75, and 81% SSZ molecules during 30 ​min visible irradiation, confirming the high efficiency of the photocatalysis in SSZ removal by the proposed photocatalyst, especially the binary system. The Hinshelwood formula studied the kinetics of the photodegradation process, and a rate constant of 0.106 min−1 (slope) with a t1/2 value of 7.1 ​min was obtained. When the photodegraded SSZ solutions were subjected to the COD experiment y= −0.085–0.106x, r2=0.9725, and k= 0.106 min−1 (t1/2 ​= ​6.5 ​min) were obtained for the mineralized SSZ molecules.