Synthesis of flower-like titania nanoparticles for photocatalytic decolourization of methylene blue

Abstract

In recent times, industrial dye effluent has produced adverse effects towards human health and the environment, majorly due to its high level of toxicity. Among the various techniques for treatment of the dye effluents, photocatalytic decolourization proves to be highly promising owing to its safety, low energy consumption and high efficiency. Titanium dioxide (TiO2) is the most well-known photocatalyst. However, due to its large band-gap and agglomeration tendency, a lot of researches such as modification of its morphology have been reported in attempt to resolve this problem. In this study, the flower-like titanium dioxide nanoparticle (FTN) photocatalyst was prepared under different concentrations (2M-4M) of hydrochloric acid (HCl) via hydrothermal method and subsequently tested for decolourization of methylene blue (MB). The properties of the catalysts were characterized using x-ray diffraction, field emission scanning electron microscope, Fourier transform infrared, electron spin resonance, ultraviolet-visible spectrophotometer diffuse reflectance spectroscopy and nitrogen adsorption-desorption. The increase in HCl concentration was observed to result in more enhancement of the pure crystalline rutile TiO2 with the more open structure of its individual nanospindle. The highest distribution of hydroxyl group, oxygen vacancy and Ti3+ surface defect was observed for the catalyst synthesized using 3M HCl concentration, thereby increasing its potential use in visible light irradiation. The photocatalytic activity of the catalysts towards decolourization of 10 mg L-1 MB at pH 11 with 0.25 g L-1 catalyst after 1 hour 30 minute under visible light irradiation was in the following order: FTN-3M (98%) > FTN-4M (92%) > FTN-2M (86%). The kinetics study specified that decolourization of MB followed the pseudo first order Langmuir-Hinshelwood model. The regeneration study showed that the catalyst remained stable after 5 cycles. Lastly, the synthesized catalyst has displayed remarkable performance (above 80%) in decolourization of simulated dyes which consist of rhodamine B, MB, methyl orange and congo red, and has potential use as catalyst for wastewater treatment in textile industry