Facile and eco-friendly synthesis of TiO2 NPs using extracts of Verbascum thapsus plant: an efficient photocatalyst for reduction of Cr(VI) ions in the aqueous solution

In this study, a fast and green synthesis of TiO 2 nanoparticles (TiO 2 NPs) is investigated using Verbascum thapsus ( V. thapsus ) plant aqueous extract as a reducing and stabilizing agent at room temperature. The TiO 2 NPs formation and the optical properties were followed by the absorption spectra in ultraviolet–visible spectroscopy. This spectrum showed a strong absorption peak of around 356 nm. Moreover, the green synthesized TiO 2 NPs were characterized by different techniques, for example, X-ray powder diffraction was used to analyze the phase and crystal structure, Fourier-transform infrared spectroscopy was conducted to know the functional groups involved in the NPs TiO 2 , and transmission electron microscopy was carried out to determine the morphology and size. The results showed a successful synthesis and anatase phase with spherical shape and smaller than 13 nm and also the presence of a few phytochemicals of the extracts around the synthesized TiO 2 NPs, which acted as stabilizing the NPs. X-ray photoelectron spectroscopy analysis was carried out to characterize TiO 2 NPs for evaluating the chemical states of the elements. The catalytic activity of the green synthesized TiO 2 NPs was examined on photoreduction of Cr(VI) ions in the aqueous solution. The found conditions are as follows: [TiO 2 NPs] = 750 mg/L, pH = 3.5, T = 25 °C and after 120 min of reaction photocatalytic reduction of Cr(VI) ions, 79.6% reduction efficacy (RE) was achieved. It was found that the reduction kinetic fitted the pseudo-first-order model. Finally, the photocatalyst reusability was investigated after five times of recovery; RE was reduced to 78.1%.