Adsorptive removal of Congo Red dye from aqueous solution using TiO2 nanoparticles: Kinetics, thermodynamics and isothermal insights

Abstract

TiO2 nanoparticles have been synthesized by co-precipitation method and is used as an adsorbent for removal of toxic Congo Red (CR) dye. The resulting adsorbent TiO2 was characterized by X-ray powder diffraction pattern, confirming the rutile phase of TiO2 nanoparticle. Adsorption equilibrium data were evaluated by Langmuir isotherm and Freundlich adsorption isotherm. The kinetic data were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion equations. Kinetics result revealed that the adsorption of CR is of pseudo second-order and chemisorption type. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated and the positive value of ΔH° (2.64 kJmol−1) corresponds to an endothermic nature of the adsorption process and the positive value of ΔS° (0.162 Jmol−1 K−1) reveals the increased randomness of the dye during adsorption process.