Charge and adsorption characteristics of hydroxy-interlayered 2 : 1 clays

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Hydroxyaluminum (HyA) and hydroxyaluminosilicate (HAS) type interlayers with different basicity and degree of silication were synthesized in the montmorillonite (Mt) and vermiculite (Vt) clays. The synthesized interlayers were characterized from chemical, electrochemical, and mineralogical points of view.The interlayer materials of naturally occurring 2 : 1 to 2 : 1 : 1 layer silicate intergrades have hitherto been regarded as HyA polymers, without taking into account the reaction of HyA polymers with Si(OH)ィイD24ィエD2 to form HAS ions in solution and their subsequent adsorption in the interlayer spaces of expandable layer silicates. It was provided evidence that the interlayer surfaces of Mt were able to adsorb a substantial amount of HAS ions, forming siliceous Al interlayers. The present results show that in addition to Mt, interlayer adsorption of HAS ions is also possible with Vt. The adsorption of HAS ions by expandable days was found to inhibit transformation of HAS ions to protoimogolite allophane. Therefore, the expandable 2 : 1 layer silicates such as Mt and Vt, which occur in soils, sediments, and suspended loads in natural waters, can affect the transport and transformation of HyA or HAS ions. Consequently, the fixation of HyA or HAS ions on Mt and Vt can influence the levels of Al species and related ecological and toxicological problems in acid-vulnerable terrestrial and aquatic environments.The fixation of HyA and HAS ions on Mt and Vt with a concomitant alteration of charge and surface characteristics, phosphate adsorption behavior, and cation fixation and exchange properties of the host clays as observed in the present study merit vital pedogenic, soil fertility management, and environmental implications in acid vulnerable aquatic and terrestrial ecosystems.