| Abstract
| - Using a mixed solution of HCl−NaCl, deintercalation of carbonate ions from a hydrotalcite-like compound (MgAl-LDH) was extremely enhanced, yielding Cl--LDH which has higher anion-exchangeability. The carbonate ions were deintercalated very rapidly at 25 °C without any weight loss or any morphological change.
- Because of the high affinity of the carbonate ion (CO32-) to the hydrotalcite-like compoundsor LDHs (layered double hydroxides), it was difficult to deintercalate carbonate ions andconvert them into other LDHs with an easier anion-exchangeability. By treatment with diluteacids such as HCl, the conversion is limited, and, at higher concentrations, changes in shapeand weight loss occurred. We found that the addition of NaCl dramatically enhanced thedeintercalation of carbonate ions by dilute HCl solution (0.0025−0.005 N). It made thecarbonate ions very rapidly deintercalate from the hydrotalcite-like compounds at 25 °Cwithout any weight loss. Scanning electron microscopy (SEM) revealed that no morphologicalchange occurred. Furthermore, by changing the HCl/NaCl ratio, it was possible to regulatethe exchange ratio. Protonation of carbonate ions in the interlayer space and successive ionexchange with a large excess of Cl- ions was assumed to be the mechanism for this enhanceddeintercalation.
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