Equilibrium, kinetic and thermodynamic adsorptions of the environmental pollutant tannic acid onto activated carbon

Polymeric waste, which is the main waste from textural industry in Turkey, was used as the raw material for the preparation of activated carbon by chemical activation with KOH. The pore properties, such as BET surface area, pore volume, pore-size distribution, and pore diameter, of the activated carbon were characterized by the t-plot based on the N2-adsorption isotherm. The BET surface area of activated carbon (SK) was determined as 2390 m2/g. Activated carbon has been used for the removal of tannic acid from aqueous solutions. Adsorption experiments were carried out as a function of initial tannic acid concentration, contact time, and pH. Adsorption data were modeled using the Langmuir and Freundlich adsorption isotherms. The kinetic studies showed that the adsorption followed a pseudo second-order reaction. The intraparticle diffusion rate constant, external mass transfer coefficient, film and pore diffusion coefficients at various temperatures were evaluated. The thermodynamic parameters, such as ΔG0, ΔS0, and ΔH0, were calculated. The thermodynamics of tannic acid–SK system indicates endothermic process.