Cu (II) Adsorption on Aluminium Pillared Clay in Aqueous-ammoniacal Solutions(Activated Clays and Porous Materials,Proceedings of the 13^<th> International Clay Conference)

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Pillared clays are excellent candidates for adsorption of transition metal ions because of the presence of an ultra dispersed oxyhydroxide phase between the clay layers. On the basis of both macroscopic (adsorption at variable pHs and the speciation of Cu(II) complexes) and microscopic (ESR of Cu(II)) data, we propose a model of adsorption of Cu(II)) ([Cu(NO_3)_2]=10^<-2> mol L^<-1>) from aqueous ammoniacal solution ([NH_3]+[NH_4^+]=1mol L^<-1>) on a pillared saponite by hydroxyaluminium polycations. When the concentration of NH_4^+ is high, it seems that the Cu(OH)_<2aq>, Cu(OH)^+ and Cu_2(OH)_2^<2+> complexes have more affinity for adsorption than [Cu(NH_3)_n(H_2O)_<6-n>]^<2+>. On the other hand when the pH is above 9 the concentrations of NH_4^+ and of the hydroxo copper complexes are very low and the majority adsorbed form becomes [Cu(NH_3)_4(H_2O)_2]^<2+>.
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