Synthesis, characterization and investigation of methyl orange dye degradation using Ag/MoO3/TiO2 nanocomposite under UV-irradiation

Abstract

Advanced oxidation processes (AOPs) are considered as the most efficient and highly attractive process for the degradation of azo dyes from textile wastewater. In this process, a strong oxidizing radical known as hydroxyl radical (˙OH) is produced, which can react with organics unselectively until mineralization. Titanium dioxide (TiO2) based photocatalytic process has been utilized widely in last few decades because of its higher photocatalytic activity to degrade organics from textile wastewater. Doping of TiO2 with noble metals (Ag, MoO3) can increase the performance of TiO2. Therefore, the major objectives of this study were to synthesize Ag/MoO3/TiO2 nanocomposite, design and construction of UV-Ag/MoO3/TiO2 nanocomposite immobilized reactor using borosilicate glass (BG), and finally investigation and optimization of the UV-Ag/MoO3/TiO2 nanocomposite reactor performance for the treatemt of methyl orange (MO) dye. The photocatalysts of TiO2, MoO3/TiO2, Ag/TiO2, and Ag/MoO3/TiO2 were synthesized by sol-gel and heat treatment methods. The physico-chemical properties of all the photocatalysts were analyzed by applying X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis/DRS), and Brunauer–Emmett–Teller (BET). The XRD showed the increased amount of anatase phase of Ag/MoO3/TiO2 nanocomposite compared to TiO2 nanoparticles and MoO3/TiO2 and Ag/TiO2 nanocomposites. The photocatalytic removals of MO dye (10 ppm) were found 59.5%, 63.1%, 70.6% and 75.8%, for TiO2, MoO3/TiO2, Ag/TiO2, and Ag/MoO3/TiO2, respectively, for a particular dose of photocatalyst (0.120 g) at pH 7.0 with 5.5 h of contact time. The impact of operating parameters such as initial dye concentration, pH and hydrogen peroxide (H2O2) dose was evaluated. The photocatalytic performance was decreased with increase of pH and initial dye concentration, and increased with the addition of photocatalyst and H2O2 in the reactor. The reaction kinetics were consistent with the first-order kinetic model and rate constant values were 0.003 min-1, 0.002 min-1, 0.003 min-1, and 0.004 min-1 for TiO2, MoO3/TiO2, Ag/TiO2, and Ag/MoO3/TiO2, respectively, for 0.120 g of photocatalyst dose. Thus, the outcomes from the current study suggest that the synthesized Ag/MoO3/TiO2 nanocomposite has a great potential for the treatment of organics present in textile wastewater under UV-radiation.