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Lecture12-14(2008) - CLAY MINERALS Clay minerals have a...

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CLAY MINERALS Clay minerals have a layer structure, each layer is composed of silica and alumina sublayers or sheets. Within the Si sheet, each silicon ion is surrounded by four oxygen ions — comprising a tetrahedron (Tetrahedral Sheet).
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The metallic ion in these sheets can vary, i.e., Si 4+ , Al 3+ , Mg 2+ , or Fe 2+ These can be replaced with similar size cations,--That is Al 3+ can replace Si 4+ . This is called isomor phous substitution . This results in a negatively charged clay surface. The surface charge varies depending on the type of clay present in a soil. CLAY MINERALS (cont.) Within the Al sheet, each aluminum ion is surrounded by six hydroxyl (OH) ions comprising an octahedron (Octahedral Sheet).
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