Synthesis of a new visible driven photocatalyst TiO2/a-CNT/b-BiOBr/c-Bi2S3 and its application for RB19 removal: modeling and process optimization

Abstract

In present study, new visible driven photocatalysts (TiO2/4-CNT/20-BiOBr/10-Bi2S3) with various loading of CNT (2, 4, 6 and 8 wt%), (10, 20, 30 and 40 wt%) and Bi2S3 (5, 10, 15 and 20 wt%) were successfully synthesized and characterized by XRD, FTIR, FESEM, PL, and DRS analysis. The DRS and PL analysis confirmed a redshift of modified TiO2 into a visible light range and the reduction of the recombination rate of electron/hole. The photodegradation results showed the optimum weight percentage of CNT, BiOBr, and Bi2S3 was 4%, 20%, and 10% respectively. Besides, the central composite design (CCD) was applied to model and optimize the photocatalytic activity of nanocatalyst for photodegradation of reactive blue 19 (RB19) and assess the effects of four independent variables including RB19 concentration, catalyst concentration, pH, and irradiation time on the response. The photocatalytic activity performance of TiO2/4-CNT/20-BiOBr/10-Bi2S3 under visible light irradiation for RB19 removal showed that 97.2% dye removal efficiency was obtained at optimum conditions of pH 4, catalyst dosage 1 g/L, RB19 concentration 50 mg/L, and contact time 60 min. The investigation of the effect of processing factors on the dye removal efficiency confirmed that increasing the catalyst concentration and time while decreasing pH and dye concentration resulted in the dye removal efficiency in a short time. The reusability of the catalyst was studied under optimum conditions ([RB19] = 50 mg/L, [TiO2/4-CNT/20-BiOBr/10-Bi2S3] = 1 g/L, pH = 4 and irradiation time = 60 min).