Influencing parameters of direct homogenization intercalation of kaolinite with urea, dimethyl sulfoxide, formamide, and N-methylformamide

A detailed investigation of the influencing parameters of the homogenization intercalation method was carried out for a medium-defect kaolinite (Hinckley index = 0.8). The direct synthesis of kaolinite-urea, kaolinite-dimethyl sulfoxide, kaolinite-formamide, and kaolinite-N-methylformamide complexes was systematically studied and the effect of the reaction parameters was analyzed. The Avrami-Erofeev equation modified for diffusion was applied to describe the intercalation kinetics. The present study revealed that the homogenization method reduces the shortcomings of the conventional solution and mechanochemical methods. The homogenization method requires an order of magnitude lower amount of reagents, and results in low-defect complex structures identical to those obtained by the solution method, with a high degree of intercalation. Comparing the studied reaction parameters, the intercalation of kaolinite with urea, dimethyl sulfoxide, and N-methylformamide strongly depends on the aging temperature. Heating at slightly above room temperature (60 degrees C or 80 degrees C) makes it possible to complete the intercalation in a short time, while at room temperature the maximum intercalation can take ten times longer. In the case of formamide, the aging temperature has a weaker effect; the reaction rate constant of its intercalation did not increase significantly up to 50 degrees C.