Cyclic carbonate–sodium smectite intercalates

• Cylcic carbate solvents are of interest for improving saline resistance of bentonites.
• Various cyclic carbonate can be derived from glycerol carbonate.
• Intercalates of glycerol carbonate and some of its derivatives with Mt were studied.
• XRD and IR results indicated strong interactions between intercalate and Mt interlayers.
• Stable and highly ordered glycerol carbonate–Mt complex formed at 1:1 ratios.

Five-membered cyclic organic carbonates (COC) are of interest for their ability to modify the surface properties of smectites and enhance the hydraulic resistance of bentonites to saline leachates. The mechanism of interaction of glycerol carbonate (GC) and several other hydroxyl containing cyclic organic carbonates (generally having progressively greater molecular masses) with sodium montmorillonite (Na+-Mt) was studied using powder X-ray diffraction and infrared spectroscopy. The 001 reflection for GC/Na+-Mt intercalates varied with the amount COC added, and the measured d001 value increased from 1.29 nm to as large as 2.22 nm at equal-mass coverage of the COC to Na+-Mt. In general, when intercalated, the cyclic carbonyl (CO) stretch and the fundamental hydroxyl (O–H) stretch bands of COC derivatives were red-shifted with respect to these bands for neat COC, indicating strong ion-dipole interaction of the carbonyl group with interlayer Na+, and H-bonding of the OH group with both interlayer water and Mt surfaces. A stable and highly ordered intercalate was produced at a 1:1 mass loading with Mt in which about 6 GC molecules per unit cell (~ 7 molecules per Na+ ion) replaced most of the interlayer water.

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