Mineralogical and technical characterization of zeolitic and smectitic material from the Puno Area (South-East Perù)

This paper presents the results of an investigation carried out on the ignimbritic formations in the Puno area in SE Peru, associated with the Tertiary volcanism. Mineralogical characterization, conducted by means of diffractometric analysis and scanning electron microscopy revealed the presence of heulandite together with smectite, quartz, mordenite, cristobalite and feldspar. Laboratory analysis carried out on representative samples of the investigated deposit, showed a cation exchange capacity (CEC) of about 50 meq per 100 grams of zeolitic material and a specific surface area, determined using the N2-BET method, of about 33.56 m2/g. Cation exchange capacity tests using solutions containing different concentrations of NH4+, Pb2+, Cd2+, Cu2+, Zn2+ and Mn2+, considered singly, have shown the following selectivity order: NH4+>Pb2+> Zn2+> Cu2+> Cd2+> Mn2+. Furthermore to increase cation exchange capacity, the zeolitic material was pretreated with a 2N NaCl solution. The results obtained demonstrate the efficiency of preconditioning that yields a substantial increase in exchange capacity for all the cations examined.