ADSORPTION OF COPPER AT AQUEOUS ILLITE SURFACES

In this paper, we conducted potentiometric titrations, batch adsorptio n experiments and FT-IR analysis to study the uptake of copper in illi te/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous illite surfaces. Our research shows that the copper adsorption at the se surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copp er in the carbonate-free illite suspensions can be explained by the fo rmation of mononuclear surface complexes, =SOCu+ and =SOCuOH, and a mu ltinuclear surface complex, =SOCu2(OH)(+)(2), followed by the formatio n of a bulk precipitate, Cu(OH)(2)(s), or a surface precipitate, =SOCu 2(OH)(3)(sp). For the illite suspensions containing carbonates, we pro pose that the copper-illite interaction can be depicted by the formati on of mononuclear surface complexes, =SOCu+ and =SOCuOH, followed by t he formation of a copper hydroxylcarbonate precipitate, Cu-2(OH)(2)CO3 (s), rather than a copper hydroxide precipitate. The existence of Cu-2 (OH)(2)CO3(s) in the carbonate-containing illite suspensions was ident ified by FT-IR analysis. (C) 1997 Academic Press.