IntroductionMontmorillonites, as clay minerals, are used on a large scale industrially in many different fields, such as oil drilling, building industry and agriculture. 1 These minerals consist of silicate layers stacked on one another. Their physical and chemical properties mainly depend on their large surface area and multi-layered structure. 1 Therefore, it is very interesting to modify the surface of the mineral, e.g. by the adsorption of organic molecules. 2 Clays obtained by adsorption of this kind of organic material, at the maximum degree of hydrophobicity, are called organo-clays, and are used in a wide range of practical applications, such as in drilling muds, paints and inks. [3][4][5] An organophilic surface and interlayer environment can be produced by replacing naturally occurring inorganic exchange cations with a variety of organic cations. Replacement of the inorganic cations in montmorillonite by alkylammonium cations opens up the lamellae and causes profound changes in the sorption and intercalation of organic molecules. [6][7][8] In contrast to natural montmorillonites, organic molecules are now freely sorbed between the montmorillonite lamellae, and the sorptive capacity is greatly increased. The montmorillonites are much more organophilic than the same crystals before exchange. 9,10 Numerous studies have been devoted to clay-organic complexes. However, only a small amount of data has been assembled out to study the quantitative aspects of adsorption of heavy metal ions from aqueous solutions by organo-clay minerals.
11It is known that regular organo-clay minerals are ineffective sorbents of aqueous-phase heavy-metal ions. Based on the fact that organo-clays exhibit strong sorptive capabilities for organic molecules, organofunctional groups with potential usefulness in chemical analysis can be incorporated on their surface. The physically adsorbed reagents do not present any restrictions in coordinating with the metal ions on the surface. Quantitative retention of the metal ion complex species on the surface is possible because they are insoluble in a solvent.In this context, organofunctional groups loaded on an organoclay surface can perfectly be used in the preconcentration process of metal ions present in water samples as well as in the voltammetric determination of mercury at a chemically modified carbon-paste electrode (CMCPE).Clay modified electrodes (CMEs) possess distinct advantages over conventional electrodes in numerous application areas, including electrocatalysis, electrochemical sensors and preconcentration.These electrodes naturally have an exceptional attractiveness for the electrochemical detection of A montmorillonite from Wyoming-USA was used to prepare an organo-clay complex, named 2-thiazoline-2-thiolhexadecyltrimethylammonium-clay (TZT-HDTA-clay), for the purpose of the selective adsorption of the heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). Adsorption isotherms of Hg 2+ , Pb 2+ , Cd 2+ , Cu 2+ , and Zn 2+ from aqueous solu...