Co‐Adsorption of Copper(II) and 3‐Amino‐1,2,4‐triazole at a Water–Natural Macromolecular Compound Interface: Molecular Structure from Adsorption Isotherms Combined with X‐ray Absorption Measurements

Abstract

AbstractThe co‐adsorption of CuII and amitrole at a water–natural macromolecular compound interface was studied by means of batch adsorption experiments, Fourier transform infrared, and X‐ray absorption spectroscopy. The binary systems, aqueous amitrole–CuII complex, and amitrole and CuII adsorbed on the surface of the solid were studied. The ternary system was investigated over the pH range 2–10 and at varying metal concentrations. The combination of macroscopic and molecular information shows that CuII and amitrole interact directly at the water–solid interface to form ternary surface complexes. A two‐step mechanism is proposed whereby initial formation of a CuII–amitrole aqueous complex is followed by the sorption of this complex onto the surface. The structure of the ternary complex was elucidated. Copper(II) is bound to the surface in an inner‐sphere mode, while two amitrole ligands simultaneously bonded in a monodentate fashion to CuII to form a six‐membered coordination sphere around the metal cation. The copper coordination sphere is completed by two water molecules. This structure and the mechanism proposed are supported by a combination of potentiometric data, IR and UV/visible spectroscopies and XAS measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)