Selective silver ion adsorption onto mesoporous graphitic carbon nitride

A 3D cubic structure of mesoporous graphitic carbon nitride (3D-g-CN) was fabricated by nano casting using the mesoporous silica hard template KIT-6. The abundant intrinsic amine functionalities of 3D-g-CN were applied as a selective adsorbent for silver ions using the unique affinity of silver and amine functionalities. The large surface area of 3D-g-CN resulted in increased amine functionalities at the surface and enabled it to form complexes with silver ions. As a result, almost 400 mg/g of silver ion could be removed from 100 mM of initial solution at 293.15 K. The isotherm of silver ion adsorption onto 3D-g-CN was described by the Freundlich and Sips models and indicated heterogeneity of the adsorbent surface. Thermodynamic parameters determined from temperature dependent isotherms were verified by the endothermic silver ion adsorption process of 3D-g-CN. The adsorption capacity of silver ion on 3D-g-CN was maintained during several reuses without a significant decrease in capacity. Overall, the results indicate that 3D-g-CN has intrinsic amine functional groups with a large surface area and could therefore be utilized as an efficient selective adsorbent of silver ions for water purification. (C) 2015 Elsevier Ltd. All rights reserved.