Enhanced layer charge modification in smectites by using microwaves

摘要

Smectites are a class of layered minerals composed of stacks of 1 nm thick units, consisting of two silica tetrahedral sheets with a central alumina octahedral sheet. The most important feature of this type of minerals is an unbalanced lattice charge due to isomorphic substitution of alumina for silica in the tetrahedral sheet and of iron and magnesium for alumina in the octahedral sheet. Therefore the solvated cations localised between the layers compensate negative charges of the octahedral sheet. The attractive forces between the layers in the stacks are weak and cause the layers to expand with water. Typically, the layer charge affects several physical-chemical properties of clays such as hydration of interlayer cations, swelling and sedimentation volumes, coagulation, rheology etc. which may be relevant for a large variety of industrial applications. Recently the research was focused on the modification of the layer charge of typical smectites. Such a treatment can result in the alteration of the required properties of the parent clay for its variable applications. The modification of the layer charge of smectites is known as Hofmann-Klemens effect [1]. Upon exchange of the exchangeable cations of dioctahedral smectite by Li{sup}+ cations, the material heated to 100-200°C for about 21 days reveal the loss of cation exchange capacity and the ability to swell.