Expansion characteristics of organo montmorillonites during the intercalation, aging, drying and rehydration processes: Effect of surfactant/CEC ratio

Understanding microstructure of organo montmorillonites (OMts) under wet condition is of high importance in clarifying their adsorption characteristics towards hydrophobic organic compounds in water. In this work, we investigated the basal spacing evolution of a series of OMt with various cetyltrimethylammonium (CTMA) loading during the intercalation, aging, drying and rehydration processes. The aim of this work is to provide novel information for exploring microstructure of wet OMt. X-ray diffraction results show that basal spacing value of the OMt does not change evidently after 30 min during the CTMA intercalation process, and then it decreases slightly in the following aging process. Drying causes dehydration and further decrease of basal spacing value. Rehydration of the dried OMt will cause the swelling of basal spacing again, but only the samples with relatively low CTMA loading amounts can recover the large values as those before drying. At relatively high CTMA loading level, OMt always show two (0 0 1) diffraction reflections, which indicates a heterogeneous interlayer structure for these samples. Moreover, this heterogeneous interlayer structure seems to be more evident in water. Our results also show that with increasing CTMA loading amounts, the rehydrated OMt show stepwise increase of basal spacing values, i.e., from 1.90 nm to 2.70 nm, and then to 2.76 nm. Finally, the possible interlayer structures of the rehydrated OMt are proposed.

Graphical abstractThe possible structure models of the wet organo montmorillonites corresponding to basal spacing values of ∼1.90 nm (a) and ∼2.70 nm (b) are proposed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Structure changes during intercalation, dehydration and rehydration processes. ► Drying causes organo montmorillonites dehydration and decrease of basal spacing. ► Rehydration of organo montmorillonites will cause the swelling of basal spacing.