Kinetics, thermodynamics and equilibrium evaluation of direct yellow 12 removal by adsorption onto silver nanoparticles loaded activated carbon

The efficiency and performance of silver nanoparticles loaded activated carbon (SNP-AC), as a new adsorbent, for the adsorptive removal of direct yellow 12 (DY12) from aqueous solutions, has been evaluated with respect to several experimental conditions including initial solution pH, contact time, initial DY12 concentration, temperature, ionic strength, and adsorbent dosage. The maximum removal percentage (approximately 98%) was observed when used 0.1 g L-1 of SNP-AC suspension, 25 mg L-1 of initial DY12 concentration at initial pH 1.0, and contact time of 10 min. The experimental data were analyzed by the Langmuir, Freundlich, and Tempkin isotherm models. The monolayer adsorption capacity of SNP-AC was found to be 454.54 mg g(-1) by using Langmuir isotherm model. The calculation of the thermodynamic parameters such as Gibbs free energy, entropy and enthalpy changes of the on-going adsorption process indicated the feasibility and endothermic nature of DY12 adsorption. The kinetics study suggested that the adsorption of DY12 onto SNP-AC proceeds according to the pseudo-second order model. (C) 2012 Elsevier B.V. All rights reserved.