Hydroxy-Chromium Smectite: Influence of Cr Added

C. Volzone
Centro de Tecnología de Recursos Minerales y Cerámica, Cno. Centenario y 506, CC 49 (1897) M.B. Gonnet Buenos Aires, Argentina. FAX 54-21-710075

Abstract: OH-Cr smectites were prepared with different mmol Cr/g smectite: 0.5, 1.5, 3.5, 5, 10 and 20 by treatment with hydroxy-chromium solution prepared at 60°C and one day of hydrolysis with OH/Cr = 2. The samples were characterized by X-ray diffraction (XRD), differential thermal analyses (DTA) and N2 adsorption-desorption isotherms.

The d(001) spacings of OH-Cr-smectite were different according to Cr added/g smectite. Larger d(001) spacings: 1.95, 2.05 and 2.07 nm were obtained with 5, 10 and 20 mmol Cr per gram of sample. DTA diagrams of smectite treated with OH-Cr solution showed exothermic peak at 420°C corresponding to Cr2O3 (confirmed by XRD). N2 adsorption-desorption isotherms of smectite treated with different amounts of Cr preserved the same slit-shaped pores than original sample, but with different micropore volume. This behavior was maintained until treatment temperature of 380°C. The specific area of smectite was increased from 36 to 175 m2/g after treatment with OH-Cr solution. The textural characteristics of OH-Cr smectite heated up to 420°C were changed. The specific area decreased and mesopore volume was produced. The different Cr added modified the structural and textural behavior.

Key Words: DTA • Pillared clays • Smectite • XRD

Clays and Clay Minerals; June 1995 v. 43; no. 3; p. 377-382; DOI: 10.1346/CCMN.1995.0430312
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)