Transformation of Structure and Adsorption Properties of Montmorillonite under Thermochemical Treatment

Resumo

Abstract—Complex studies revealed transformations of composition, structure, and properties of bentonite clays of the Taganskoe (Kazakhstan) and Dahskovskoe (Moscow oblast) deposits under thermochemical treatment. Leaching of cations from interlayer and octahedral sites, protonation of interlayer and OH-groups lead to the modification of interlayer and 2 : 1 layer composition. This, in turn, causes significant changes of properties: a decrease of cation exchange capacity owing to the decrease of layer charge and increase of specific surface through the decomposition and partial amorphization of structure. Bentonites of the Dashkovskoe deposit showed the higher resistance to the thermochemical impact than bentonites of the Taganskoe deposit owing to the isolating action of organic matter. Obtained results demonstrated that bentonite clays preserve most of adsorption properties even under such strong thermochemical influence (13 М HNO₃, 90°С, 5 h).