Synthesis, structural characterization and Pb(II) adsorption behavior of K- and H-birnessite samples

Abstract

This paper presents the synthesis, structural characterization and Pb(II) adsorption behavior of K-birnessite and H-birnessite samples. Changes in the surfaces and structure of birnessite samples were characterized by means of infrared spectroscopy (IR), N-2 gas adsorption and thermal analysis (TG-DTA) techniques. Adsorption of Pb(II) by samples was investigated as a function of the initial Pb(II) concentration, solution pH, ionic strength, temperature and inorganic ligand (NO3-, Cl-). The Langmuir monolayer adsorption capacities of K-birnessite and H-birnessite samples in 0.1 M NaNO3 solution at 298 K were estimated as 164.30 and 133.17 mg/g, respectively. Thermodynamic parameters such as change in free energy (Delta G), enthalpy (Delta H) and entropy (Delta S) were evaluated for K-birnessite and H-birnessite to be -22.43 kymol (at 298 K), 23.90 kJ/mol, 155 J/mol K, and -18.50 kJ/mol (at 298 K), 10.57 kJ/mol, 98 J/mol K, respectively. (C) 2011 Elsevier B.V. All rights reserved.