Continuous ultrasonic stimulation based direct green synthesis of pure anatase-TiO2 nanoparticles with better separability and reusability for photocatalytic water decontamination

Abstract

Titanium dioxide nanoparticles have shown a tremendous potential in various fields such as photocatalysis, solar-photovoltaics, electrodes, sensors, implants and pigments. Due to these versatile applications, their synthesis routes have gained a vast attraction and demand for being frugal and eco-friendly with better control over the anatase and rutile phase ratio. Comprehensively, the sol-gel method is a widely used technique for the synthesis of TiO2 nanoparticles that requires several additional chemical entities such as organic solvents, acids and capping agents. It makes this process quite uneconomical and hazardous in nature. In the present study, non-hazardous microwave and/or ultrasound based one-pot synthesis approaches have been studied for the production of phase controlled TiO2 nanoparticles and compared with the sol-gel synthesized and commercially available TiO2 nanoparticles. These comparisons have been validated through several material characterization techniques. The obtained results have shown that the ultrasound based synthesis followed by suitable thermal processing alone has tremendous potential to produce phase controlled TiO2 nanoparticles (preferably anatase phase), mostly in the form of nano-micro aggregates. In addition, the photocatalytic activity of ultrasonically synthesized TiO2 nanoparticles has also been examined and compared with that of the commercially available TiO2 nanoparticles. It is interesting to observe that, ultrasonically synthesized TiO2 nanoparticles have not only shown improvised photocatalytic degradation activity, but also shown a significant improvement on their separability and recyclability for water treatment applications, in comparison to that of the commercially available TiO2 nanoparticles (TiO2-P25).