Author
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Laird, David |
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Submitted to: Clay Minerals Society Meeting
Publication Type: Abstract Only Publication Acceptance Date: 6/13/2002 Publication Date: 6/13/2002 Citation: LAIRD, D.A. REVISED ALKYLAMMONIUM METHOD OF DETERMINING LAYER CHARGE. CLAY MINERALS SOCIETY MEETING. 2002. ABSTRACT P. 109. Interpretive Summary: Technical Abstract: Layer charge is one of the primary criteria used in classification of 2:1 phyllosilicates. Furthermore, layer charge strongly influences numerous properties of 2:1 phyllosilicates, including; hydration, swelling, sorption affinity for organic molecules, surface reactivity, and both cation exchange capacity and selectivity. Despite the importance, determination of layer charge is still not routine. The two primary methods for determining layer charge, the structural formula method and the alkylammonium method, both have serious limitations. In this study, a new approach for estimating layer charge from results of X-ray diffraction (XRD) analysis of alkylammonium saturated clays is proposed. For most samples, layer charge can be accurately (r**2 = 0.96) estimated using; LC = -0.3485 + 0.1915(d/n**0.577), where d is the measured basal spacing in angstroms and n is the C chain length for the saturating alkylammonium cation. A critical requirement for using this equation is that the measured basal spacing be between 14 and 17 angstroms, within the mono-layer to bi-layer transition region. Using this equation, layer charge can be estimated from XRD results for a single alkylammonium-clay sample, although the accuracy is improved if results for several samples within the mono-layer to bi-layer transition region are averaged. |