has been reported by Komarneni & Roy (1983). ... Roy, 1983) were used for this study. Two of the zeolites, .... Nevada; (D) clinoptilolite, Castle Creek, Idaho.
Clay Minerals (1985) 20, 181-188
CHARACTERIZATION OF S M E C T I T E S SYNTHESISED FROM ZEOLITES AND M E C H A N I S M OF S M E C T I T E S Y N T H E S I S S. K O M A R N E N I
AND E. B R E V A L
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA
Received 24 May 1984; rev&ed 10 August 1984)
A B ST R A C T: Smectites were synthesised hydrothermally from zeolites in an Mg-rich brine at 300~ under a confining pressure of 30 MPa and characterized by XRD using the Greene-Kelley Li-saturation test and the K+-saturation/glycolation test. The synthetic smectites were found to be dioctahedral with only tetrahedral negative layer charge; the layer charge was also deduced to be low and they are classified as beidellites. The mechanism of formation includes H + saturation of zeolites by the hydrolysis of Mg2+ under hydrothermal conditions, followed by decomposition of the zeolites and recrystallization to beidellites. These results show that solution chemistry is an important factor affecting stability of zeolites under hydrothermal conditions.
Transformation of zeolites to smectites in an Mg-rich brine under hydrothermal conditions has been reported by Komarneni & R o y (1983). The objectives of this investigation were (i) to elucidate the mechanisms of smectite formation from zeolites and (ii) to characterize these synthetic smectites. Understanding the mechanism of smectite formation from zeolites is helpful in determining the precise conditions for possible commercial manufacture of smectites and also in the interpretation of zeolite diagenesis. Characterization of these synthetic smectites could indicate likely industrial applications, e.g. viscosity control agents or in catalysis.
EXPERIMENTAL Materials
Six smectites synthesised earlier from six different zeolites in Mg-rich brine (Komarneni & Roy, 1983) were used for this study. Two of the zeolites, namely phillipsite from Pine Valley, Nevada (reference zeolite 27134) and erionite from Shoshone, California (reference zeolite 27104), were again hydrothermally treated to synthesise smectite in order to investigate the mechanism of smectite formation. The zeolite samples were supplied as < 200 mesh (
