Degradation and Mineralization of Benzohydroxamic Acid by Synthesized Mesoporous La/TiO₂

Rare earth element La-doped TiO₂ (La/TiO₂) was synthesized by the sol-gel method. Benzohydroxamic acid was used as the objective pollutant to investigate the photocatalytic activity of La/TiO₂. The physicochemical properties of the prepared materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, specific surface area and porosity, scanning electron microscopy and transmission electron microscopy. As a result, the doping of La could inhibit the crystal growth of TiO₂, increase its specific surface area and expand its response to visible light, thus improving its photocatalytic activity. La/TiO₂ with the doping ratio of 0.75% calcined at 500 °C, showing the highest photocatalytic activity to degrade benzohydroxamic acid under the irradiation of 300 W mercury lamp. About 94.1% of benzohydroxamic acid with the original concentration at 30 mg·L^-1 was removed after 120 min in a solution of pH 4.4 with an La/TiO₂ amount of 0.5 g·L^-1. Furthermore, 88.5% of the total organic carbon was eliminated after 120 min irradiation. In addition, after four recycling runs, La/TiO₂ still kept high photocatalytic activity on the photodegradation of benzohydroxamic acid. The interfacial charge transfer processes were also hypothesized.