The promoted photodegradation of mixture of textile dyes under visible-light using CdS-SiO2-TiO2/TiO2 nanotube arrays heterojunction – Studying photocatalyst properties and determinants influencing efficiency

چکیده مقاله

The development of innovative photocatalysts powered by visible light is an effective strategy to solve the problems related to environmental pollution. In this study, a ternary heterostructure photocatalyst with high photocatalytic performance was synthesized. For this purpose, CdS nanoparticles were deposited on the surface of SiO2-TiO2/TiO2 nanotube arrays (CST/TNTs) by the process of successive ionic layer adsorption and reaction (SILAR). Samples were characterized using a variety of techniques including XRD, FTIR, UV–Vis/DRS, EIS, Mott–Schottky analysis, BET and FESEM-EDS. The photocatalytic degradation results showed that C4S4T/TNTs has a rate constant about 3 times higher than SiO2-TiO2/TNTs (ST/TNTs), leading to a remarkable efficiency in degrading a mixture of Maxilon Blue GRL (MB-GRL) and Maxilon Red GRL (MR-GRL) in an aqueous solution. The successful formation of C4S4T/TNTs is highly desirable as it increases the photoabsorption capacity and improves the charge transfer pathways to prevent electron-hole recombination at the interface between the two components. Using the Mott–Schottky plot, the donor density of C4S4T/TNTs was determined to be 1.50 × 107 cm???? 3, which was higher than the 2.60 × 107 cm???? 3 of ST/TNTs. The RSM-CCRD method was used to optimize the degradation process. A highly statistically significant quadratic model with a 95 % confidence level (p < 0.0001, R2 = 0.9931 and R2adj = 0.9850 for MB-GRL and p < 0.0001, R2 = 0.9875 and R2adj = 0.9730 for MR-GRL, respectively) was constructed to characterize the influence of variables on the degradation efficiency. Analyzed by gas chromatography–mass spectrometry (GC/MS), the intermediate product distributions of dye degradation were determined.