Meta-clay interactions at low temperature : reactivity of nontronite temperature : reactivity of nontronite with different metals.

Interactions between metals and smectites have been studied with the aim to predict the reactivity of clayey engineered barriers with the metallic container used for the radioactive waste confinement. Recent results (Lantenois, 2003) has showed that the reactivity of the reaction between metallic iron and Garfield nontronite depends of the pH. They were done at 80C during 45 days. We present in this work, results obtained with titanium, chromium, manganese, cobalt, nickel, copper and zinc metals. Clay sample is the Garfield nontronite (Na0.05Ca0.23K0.01) (Si3.5Al0.49) (Fe3+1.86 Al0.18 Mg0.02)O10OH2. The reactions have been realised at pH 5 and 9. Experiments have been performed with a 1/2/50 ratio for the clay / metal powder / MilliQ water. pH of the solutions have been fixed at 5 and 9 with NaOH or HCl add. The mixture have been placed in a Teflon reactor and heating at 80C during 45 days. At the end of the reaction, solutions have been filtered and analyzed by ICP-AES and solid phases were characterized by XRD and infrared spectroscopy. Results : XRD pattern analysis show that nontronite reacted with the seven studied metals. Oxides or hydroxides has been identified. Two main modifications of Garfield nontronite have been observed. - Modification of smectite interlayer space : after the reaction, (chromium, cobalt, nickel, copper) cations are in the interlayer space. They can be hydrated or hydroxyled. In the case of hydroxyled cations, interlayer brucitic sheets can be identified because (00ℓ) reflections are identical to chlorites ones. - Destabilisation of the smectite phase : The reaction with zinc and tin cations lead to the formation of new silicate phases. For example, willemite (Zn2SiO4) and varlamoffite (Sn,Fe)(O,OH)2 phases have been obtained after the reaction with zinc and tin metals respectively