Adsorption of Metal Ions on an Activated Carbon/ L ‐Lysine Derivative Hybrid Compound

The new compound N ϵ ‐(4‐amino‐1,6‐dihydro‐1‐methyl‐5‐nitroso‐6‐oxopyrimidin‐2‐yl)‐ L ‐lysine (H 2 L) has been synthesised and its molecular structure determined by single‐crystal X‐ray diffraction methods. The Brönsted acid/base character of H 2 L has been determined in water in the pH range 2.5–10.0, and the nature of the observed protonation steps determined by potentiometric and spectrophotometric methods. The adsorption of H 2 L on a commercial activated carbon (AC) in aqueous solution is irreversible, mainly due to the electronic behaviour of the π system of the pyrimidine moiety. The adsorption of H 2 L on the AC provides a route to develop NH 3 + ‐CHR‐COO – ‐type functions on the AC surface, thereby yielding a new hybrid material with an enhanced adsorption capacity for metal ions in aqueous solution. The adsorption of Ni II , Cu II , Zn II and Cd II ions on the functionalised AC has been studied and the results analysed on the basis of the reactivity data for several pyrimidine ligand/metal ion systems. The results, which show an enhancement of the adsorption capacity of the new material with respect to the unfunctionalised AC, are compared with analogous materials studied previously.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)