Ionic liquids as modifiers for cationic and anionic nanoclays

As part of a broader effort to develop nanoclays functionalized with different heterocyclic aromatic structures for novel applications, preliminary data are reported on the modification of sodium montmorillonite, a cationic clay, and hydrotalcite, an anionic clay, with four low molecular weight pyridinium and imidazolium-based ionic liquids. Commercially available unmodified montmorilonite was treated with aqueous solutions of three ionic liquids: N-ethyl pyridinium tetrafluoroborate, 1-ethyl 3-methyl imidazolium bromide and 1-hexyl 3-methyl imidazolium chloride. Commercially available hydrotalcite was treated with N-ethyl pyridinium tetrafluoroborate and its amorphous calcined version was regenerated in the presence of N-ethyl pyridinium tetrafluoroborate and N-ethyl pyridinium trifluoroacetate aqueous solutions The modified materials were characterized qualitatively and quantitatively by FTIR, TGA, EDX, WXRD and elemental analysis. The cationic clay data show an overall increase in interlamellar spacing as a result of sodium cation exchange with the cations of the ionic liquids (in spite of their relative small size) and improved thermal stability vs. commercial nanoclays modified with long chain quaternary ammonium salts. The effects were dependent on the type of the ionic liquid. The anionic clay data showed no anion intercalation for the commercial hydrotalcite and mostly surface absorption, rather than intercalation, for the calcined clay; this is possibly due to the relatively small size of the anions and the presence of a strongly bound carbonate anion, not easily amenable to exchange.