Metal Adsorption by Activated Carbon: Effect of Complexing Ligands, Competing Adsorbates, Ionic Strength, and Background Electrolyte

Abstract

Cadmium and nickel adsorption isotherms were performed using three activated carbons in ligand-free systems and in the presence of EDTA, succinic acid, PO₄ (Ni only), NH₄BF₄ (Cd only), competing metals (Ni and Cd), and differing ionic strengths and background electrolytes. Generally, all carbons removed metals from the ligand-free systems. Four scenarios were forwarded which described metal adsorption in the presence of various organic and inorganic compounds. The effect of organic and inorganic ligands on metal removal was dependent on the carbon, metal, and ligand type and concentration. The presence of a second heavy metal did not affect removal of the primary metal ion. Increasing ionic strength decreased metal removal for all carbons and metals investigated while the type of background electrolyte had no effect on metal removal.