Equilibrium and thermodynamic studies of Cu(II) removal by iron oxide modified sepiolite Original Research Article

This paper presents the adsorption of Cu(II) from aqueous solution by raw sepiolite (RS) and iron oxide-coated sepiolite (ICS) samples. Adsorption of Cu(II) by sepiolite samples was investigated as a function of the initial Cu(II) concentration, solution pH, ionic strength, temperature and the presence of an inorganic ligand (Cl−, SO42− and HPO42−). Changes in the surface and structure were characterized by means of XRD, IR and XRF techniques. The Langmuir monolayer adsorption capacities of RS and ICS in 0.1 M NaNO3 solution at 298 K were estimated to be 14.96 and 21.56 mg/g, respectively. ΔG, ΔH and ΔS were evaluated for RS and ICS to be −14.14 kJ/mol (at 298 K), 39.03 kJ/mol and 178 J/mol K, and −16.09 kJ/mol (at 298 K), 32.99 kJ/mol and 165 J/mol K, respectively.