Optimization and modeling of the photocatalytic activities of a novel visible driven CNT/TiO2/BiOBr/Bi2S3 nanocomposite

Abstract

In this work, the photocatalytic degradation of Acid black 1721 (AB1721) in the presence of a novel photocatalyst (TiO2 - titanium dioxide) TiO2/CNT/BiOBr/Bi2S3 under visible light irradiation was investigated. The effect of different loadings of carbon nanotubes (CNT) (1%, 2%, 4%, 6% and 8%), BiOBr (10, 20, 30 and 40 wt.%) and Bi2S3 (5, 10, 15 and 20 wt.%) on the photocatalytic activities of the prepared nanocomposites was investigated. The structural properties of the nanocomposites have been characterized by X-ray diffraction, Brunauer-Emmett-Teller, diffuse reflectance spectra (DRS), Field-emission scanning electron microscopy, photoluminescence spectroscopy (PL) and Fourier-transform infrared spectroscopy. The results show that the photodegradation efficiency of TiO2/4-CNT/20-BiOBr/10-Bi2S3 photocatalyst was better than the samples. Results of DRS show a visible shift when TiO2/CNT was modified with BiOBr and Bi2S3. Also, PL spectra for all the prepared samples indicated that TiO2/4-CNT/20-BiOBr/10-Bi2S3 had the lowest recombining of electron and holes. The effect of independent variables including initial dye concentration (30, 60 and 90 mg/L), pH (3, 6 and 9), irradiation time (20, 30 and 40 min) and catalyst loading (0.5, 0.75 and 1 g/L) on dye removal was determined by response surface methodology. The optimum condition was AB1721 concentration of 30 mg/L, initial pH of 3, the reaction time of 40 min, and catalyst loading of 1 g/L.