Efficient and recyclable visible light-active nickel–phosphorus co-doped TiO2 nanocatalysts for the abatement of methylene blue dye

The present investigation aimed to design a best performing improved photocatalytic-active material of extensive implications and suitable to achieve the emerging needs of water pollution abatement. In view of the above, the present research work planned to synthesized nickel and phosphorus double-doped TiO2 (NPT’s) by the sol–gel process, characterized by advanced instrumental techniques and applied for the abatement of methylene blue (MB) under visible light. Characterization results demonstrated that nickel and phosphorus co-doped TiO2 samples showed anatase phase determined by XRD. Structural aspects such as smooth surface with spherical shape morphology, less band gap, less particle size, and high surface area when compared with bare TiO2 were determined by SEM, UV–Vis. DRS, TEM and BET, respectively. The elemental composition and oxidation states were identified by XPS analysis. The substitutional doping of Ti4+ ion by Ni2+, P5+ ion and P3− ion with oxygen in the TiO2 lattice was evaluated by FT-IR spectroscopy. Based on the characterization results, the catalyst NPT5 was applied for the abatement of MB at various optimum reaction conditions, with pH 10, catalyst weight 0.1 g/l and starting MB concentration 10 mg/l. At these reaction conditions, the degradation was completed within 75 min in the visible light. The photostability of the NPT5 was verified by recycling up to five cycles. Finally, this research work was concluded with a plausible mechanism, using reactive species generated during the degradation process and these species were simultaneously tested using scavenger reagents.