Lanthanum enriched aminosilane-grafted mesoporous carbon material for efficient adsorption of tartrazine azo dye

For the first time the synthesis of mesoporous carbon of cubic structure modified with 3-aminopropyltriethoxysilane and lanthanum chloride, and its ability to remove tartrazine azo dye from aqueous solutions, have been described. The physicochemical properties of the adsorbent were characterized by X-ray diffraction, low-temperature nitrogen sorption, transmission electron microscopy, FT-IR spectroscopy and Boehm titration. The carbon functionalization was found to significantly change its porosity, structure ordering and acid-base character of its surface. The effect of different key parameters such as contact time, temperature, initial concentration and pH of azo dye solution on the effectiveness of tartrazine adsorption was evaluated. Sorption capacity of mesoporous material was found to increase with increasing initial dye concentration and contact time but decreases with increasing temperature of the system, from 25 to 60 degrees C. The effectiveness of tartrazine removal by La/CKIT-6-A material was compared with that of pristine carbon (CKIT-6) and the aminosilane-grafted sample CKIT-6-A. The introduction of lanthanum on the surface of sample functionalized with 3-aminopropyltriethoxysilane increased its sorption capacity towards tartrazine. The best fit to experimental data was obtained for the Langmuir isotherm model, suggesting homogeneous distribution of adsorption sites on the surface of mesoporous carbon. The adsorption kinetic data were well described with the pseudo-second-order kinetic model. On the basis of the detail analysis of the interactions between the carbon material and tartrazine, a mechanism of dye adsorption was proposed.