Visible light photocatalytic activity of sol–gel Ni-doped TiO₂ on p-arsanilic acid degradation

Nickel-doped TiO₂ (0.1, 0.5, 1.0, 2.5, 5.0, and 10.0 wt%) photocatalysts were prepared by the sol–gel method. Physicochemical properties were determined by the characterization using X-ray diffraction, Raman and UV–vis diffuse reflectance spectroscopies, N₂ physisorption, and zeta potential determination (PZC). The synthesized materials exhibited the photocatalytically active anatase crystalline phase and the catalysts exhibited stronger absorption in the visible light region with a red shift in the adsorption edge with the increase of Ni doping. The photocatalytic evaluation of TiO₂−Ni materials was carried out on p-arsanilic acid (p-ASA, 10 mg L⁻¹) degradation in aqueous suspension under visible radiation. Compared with bare TiO₂, the TiO₂–Ni 1.0 material (1 wt% Ni-doped TiO₂) exhibited higher photocatalytic activity on p-ASA degradation under visible light irradiation allowing a 76% degradation percentage in 180 min reaction time while 60% degradation percentage was achieved with undoped TiO₂. The TiO₂–Ni 1.0 material showed the highest surface area in comparison with the other prepared materials. Meanwhile, the photocatalytic activity of TiO₂–Ni 1.0 can keep even after three cycles with not loss of activity since nickel was not leached from the TiO₂-based catalyst into the solution during photocatalytic reaction. Therefore, the doping of the nickel into the TiO₂ lattice by the sol–gel method allowed its activation under visible radiation and an efficient photoexcited charge separation to prevent electron-hole recombination showing high chemical stability.