Resumen de Formación de filipsita en la alteración hidrotermal de la bentonita de la Serrata de Níjar (Almería) a pH básico
Raquel Vigil de la Villa Mencía, Susana Ramírez Martín, Jaime Cuevas Rodríguez, Santiago Leguey Jiménez
The cement-bentonite interface is a highly dynamic region in the engineered barrier systems (EBS) designed to isolate radioactive wastes. Two very different chemical environments are held toghether: a near-neutral clay minerals-calcite equililibrium-dominated system (hydrated bentonite system) and a very unstable hiperalcaline porous one. The system is then in a permanent disequilibrium due to the pH changing conditions that are related to the various degradation steps of the cement. The formation o f phillipsite, (Na-K-zeolite; Si/AI ratio o f 1.8-2.4), has been found in series o f closed-system tests at 35-90-C when the resulting pH was between 11.7 and 12.6. The chemistry of the resulting solutions, rather than the crystallization substrata, controls the Si/AI atomic ratio and the type of zeolite that has been formed. This based in the decrease o f Si/AI at higher pHs and the predominance o f Na-phillipsite.
