ORIGINAL PAPER Adsorption of copper and zinc onto natural clay in single and binary systems A. T. Sdiri • T. Higashi • F. Jamoussi Received: 14 August 2012 / Revised: 27 September 2012 / Accepted: 23 April 2013 / Published online: 17 May 2013 Ó Islamic Azad University (IAU) 2013 Abstract Calcareous and smectitic clay samples from the Coniacian–Lower Campanian system, Tunisia, were used as adsorbents for the removal of copper and zinc from aqueous solutions in single and binary systems. Calcareous clay sample was treated with acetic acid to obtain car- bonate-free sample that was also used for metals removal. The adsorption of metal ions onto natural clay was tested in a batch method by mixing 1 g/L of each sample with a metal ion solution of zinc (300 lmol/L) and/or copper 600 lmol/L under the operating pH of 6, and agitation speed of 200 rpm within the equilibrium time of 60 min at 25 °C for single and binary systems. Our results showed that natural clay samples were mainly composed of silica, alumina, iron, and magnesium oxides. Adsorption data showed that the studied clay samples removed substantial amounts of heavy metals in single and mixed systems. Initial solution pH and carbonates contents enhanced the removal capacities of the studied clay samples, confirming their strong influencing effects. Thermodynamic parame- ters indicated an endothermic adsorption for metals removal by calcareous clay, but exothermic process for the smectitic sample. These results suggest that the Late Cretaceous clays, Tunisia, can be effectively used as nat- ural adsorbents for the removal of toxic heavy metals in aqueous systems. Keywords Clays  Competitive Langmuir model  Heavy metals  Thermodynamic  Sorption Introduction Various industrial processes, including metal plating, fer- tilizer production, mining, metallurgy, battery manufac- turing and textile dyeing, and others, are the main sources of heavy metals (Barhoumi et al. 2009; Messaoudi et al. 2009; Eloussaief and Benzina 2010). The fate of the metals in aquatic system can be variable, depending upon their initial form and the chemical and physical charac- teristics of the receiving water body. Metals may be in solution as free ions, soluble salts, associated ions with dissolved inorganic or organic ligands, or bound to par- ticulate matter. Unlike organic contaminants, heavy metals are non-biodegradable; they accumulate in living organ- isms causing adverse effects to many vital functions. That is why toxic metals like zinc, copper, nickel, mercury, cadmium, lead, and chromium have to be removed from industrial wastewaters before being discharged in the ecosystem. Remediation of metal-contaminated media is a time-consuming and expensive process. The use of natural clays in the removal of Cu(II) and Zn(II) from aqueous solutions is of particular interest for environmental clean- up since the use of natural adsorbents is particularly beneficial for the development of cost-effective process for heavy metal removal from wastewaters. Adsorption is the most preferred method for removal of heavy metals from aqueous solutions due to its simplicity and its high A. T. Sdiri (&)  T. Higashi Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan e-mail: alisdiri@yahoo.fr A. T. Sdiri National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan A. T. Sdiri  F. Jamoussi National Center for Materials Science, 273-8020 Borj Ce ´dria, Soliman, Tunisia 123 Int. J. Environ. Sci. Technol. (2014) 11:1081–1092 DOI 10.1007/s13762-013-0305-1