Synthesis of bi-metallic oxides nanotubes for fast removal of dye using adsorption and sonocatalysis process

•Synthesis of ZnO–TiO2 NTs using ultrasound-assisted sol–gel and hydrothermal method.•ZnO–TiO2 NTs has large specific surface area and high pore volume than ZnO and TiO2.•ZnO–TiO2 NTs is better than pure ZnO and TiO2 for adsorption and sonocatalysis.•Simultaneous application of sonolysis and adsorption gives highest decolorization.•Approximately 97% decolorization of MB was achieved within 10 min of treatment.

In this study, ultrasound-assisted synthesis of bi-metallic oxides nanotubes (ZnO–TiO2 NTs) using sol–gel method followed by hydrothermal method is reported. Essentially, an attempt was made to investigate the simultaneous adsorption and sonocatalysis process for fast removal of dye using ZnO–TiO2 NTs. The results of characterization revealed that ZnO–TiO2 NTs were hollow nanotubular structure in shape with tube diameter of ∼10 nm and open ended. It has large specific surface area of 336.9 m2/g as compared to ZnO (30.5 m2/g) and TiO2 (12.3 m2/g). The band-gap energy of NTs is 2.95 eV which is much lower than the pure ZnO (3.18 eV) and TiO2 nanoparticles (3.15 eV). Activity of ZnO–TiO2 NTs was assessed using decolorization process as model reaction system involving adsorption and sonocatalysis processes. The results were also compared with their counterparts, viz. ZnO and TiO2. Experimental results revealed that large specific surface area and surface charges on ZnO–TiO2 NTs promote the adsorption efficiency, while the high pore volume helps dye molecules to diffuse rapidly during the sonocatalysis process. Approximately, 97% of decolorization was achieved within 10 min of treatment with sonocatalysis process. These experimental results presented in this paper could form a useful tool for further research in degradation of other bio-recalcitrant pollutants using ZnO–TiO2 NTs.

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