Adsorption kinetics of Direct Black 38 on nitrogen-doped TiO2

In this work, three samples of nitrogen-doped TiO₂ prepared at different calcination temperatures (400, 450 and 500 °C) were applied for the adsorption of Direct Black 38. Kinetic studies about the adsorption of Direct Black 38 on nitrogen-doped TiO₂ were performed under different initial dye concentrations
(75-175 mg l^-1). Pseudo-first and pseudo-second order models were fitted with the experimental data. The results revealed that nitrogen-doped TiO₂ synthesized at 400 °C presented the more adequate characteristics for adsorption purposes, such as specific surface area of 151 m² g^-1. The adsorption kinetics agreed with the pseudo-second order model, at initial dye concentrations from 75 to 175 mg l^-1. The maximum adsorption capacity predicted by the pseudo-second order model was 138.3 mg g^-1, and was obtained using nitrogen-doped TiO₂ synthesized at 400 °C. In summary, these results revealed that nitrogen-doped TiO₂ is a good material for the removal Direct Black 38 from aqueous solutions by adsorption.