Heterogeneity of Montmorillonite Surface and Its Effect on the Nature of Hydroxy-Aluminum Interlayers

Abstract

Abstract--A specimen montmorillonite (Arizona bentonite) was treated with hydroxy-aluminum solutions of various basicity. The cation exchange sites of this clay were found not to be homogeneous in their strength of retaining hydroxy-aluminum polymers; this strength varied from very weak, with which the A1 polymers were only loosely held, to very strong, with which stable interlayer AI-clay complexes were formed. When a large amount of clay was treated with a small amount of solution, the polymers were held only in positions of strong affinity; the polymers were difficult to extract with neutral salt solutions and did not change to crystalline AI(OH)3 during prolonged aging. When a small amount of clay was treated with a large amount of solution, the exchange sites were completely occupied by polymers; a portion of these polymers was easily extractable with neutral salt solutions and, during aging, changed to AI(OH)3. This contrast is significant in any attempt to compare results obtained under different experimental conditions and to correlate laboratory experimentation with the occurrence of gibbsite and interlayer AI-clay complexes in nature.

Charge Heterogeneity and Nanostructure of 2:1 Layer Silicates by High-Resolution Transmission Electron Microscopy

“…The net result of charge heterogeneity is to affect the rate of mineral transformation and the physical and chemical properties of a clay. Charge heterogeneities in smectite and vermiculites have been deduced 1) by reacting the clay with hydroxy Al-polymer solution and determining the ease with which these polymeric cations are exchanged with small inorganic cations (Hsu, 1968) and 2) by exchanging with alkylammonium ions followed by determining the packing of these cations in the clay interlayers by X R D (Lagaly and Weiss, 1970;Lagaly, 1982;Malla andDouglas, 1987a, 1987b). Alkylammonium ions in the interlayers of2:1 clays may assume a monolayer (13.6/~), a bilayer (17.7/~), a pseudotrimolecular layer (21.7 ~), or a paraffin-type configuration depending on the magnitude of the layer charge and the size of the alkyl chain.…”

Reduction of the Cation-Exchange Capacity of Montmorillonite by Take-Up of Hydroxy-Al Polymers

“…Inasmuch as no C1-or other anions (except OH-) were present in the clay suspensions, a neutralization fraction of < 1 indicates that part of the negative charge of the clay was compensated by A1 ions. Barnhisel and Rich (1963) and Hsu (1968) also suggested that AI 3+ is the only major exchangeable AI species on the basis of partially neutralized Al-treated clay systems. For example, when 10% and 50% of the CEC of Ca-montmorillonite were saturated by A1 ions, the amount of untitrated A1 was 10 and 30 mmole/kg, respectively (Tables 1 and 3).…”

Properties and Quantitative Estimation of Poorly Crystalline Components in Sesquioxidic Soil Clays

“…The basicity of interlayer hydroxyalumina appears, for optimum retention by clay minerals, to range between 2.5 and 2.7 in synthetic systems (Turner, 1965;Hsu, 1968), while a range of 2.3-2.5 has been estimated for chloritized Canadian prairie soil clays (Huang and Lee, 1969). Based on these findings it would seem reasonable as an approximation, to assume an average basicity of 2.5 for amorphous hydroxyalumina in the Oxisol clays.…”