UV–VIS photocatalytic degradation of nitrobenzene from water using heavy metal doped titania

The photocatalytic degradation of nitrobenzene (NB) under UV–VIS irradiation with un-doped TiO2 and various heavy metals doped TiO2 powders were studied for aerated solutions. The dopant type (Fe, Co, Ni) and its concentration (0.5–5 wt.% TiO2) influence on pollutant degradation efficiency were investigated. The photocatalyst with lowest Fe content (0.5 wt.%) showed a considerable better behaviour in respect to pollutant degradation than catalyst with higher Fe content and Co and Ni doped titania catalysts. The experiments were carried out for solutions with (0.37–8.45) × 10−4 M NB initial content, using 50–250 mg/L catalyst dose, at various pHs (4–10) and irradiation time between 30 and 240 min. The kinetics of NB degradation and organic nitrogen mineralization was assessed and pseudo-first order rate constants were calculated. For optimum working conditions (0.5 wt.% Fe doped-TiO2 loading of 250 mg/L, 2.52 × 10−4 M pollutant initial concentration, pH = 7 and 240 min irradiation time) NB removal and organic nitrogen mineralization efficiencies were 99% and 85%, respectively. It was also demonstrated that degradation process occurs on catalyst surface, so experimental results are in accordance with Langmuir–Hinshalwood model.