Adsorption behavior of zinc and cadmium ion on granular activated carbon in singular and binary systems and the influence of nitrilotricetic acid as a complexing agent.

Adsorption characteristics of zinc and cadmium ion on granular activated carbon have been studied in dynamic and equilibrium aspects and singular and binary adsorption behavior were compared. Based on the van't Hoff equation, reaction orders and rate constants were observed to increase as initial concentration of adsorbate was raised for both metal ions. Adsorption of Zn and Cd ion was found to increase with temperature, and this endothermic nature of adsorption reaction was further verified by thermodynamic calculation. Taking nitrilotriacetic acid (NTA) as a ligand, the influence of complexing agent was examined and the variation of adsorption percentage was found to closely relate with the change in ionic form of NTA depending upon pH conditions and amount of complexing agent used. Features of binary adsorption are discussed for several influential parameters and experimental observations for both ions were correlated with a predicted adsorption isotherm based on a Langmuir multi-component model.