Effects of thermal treatment on the micro-structures of co-precipitated and sol–gel synthesized (Mg–Al) hydrotalcites

Mg–Al hydrotalcite prepared from sol–gel technique after calcination at 600 °C designated as HTsg-(600) exhibited mesoporous structure with cylindrical pores as observed from N2 adsorption/desorption analysis. The pore size data for HTsg-(600) were 5.15 nm with 268.3 m2/g specific surface area and 0.28 cm3/g pore volume. This accounts for 84% higher surface area and 3.5 times higher for pore volume than the sample prepared from co-precipitation method. Surface fractal dimension (D) for HTsg-(600) was found to be 2.49 and 2.44 for HTcp-(600) sample, indicating that HTsg-(600) exhibited a relatively rougher surface than hydrotalcite prepared from co-precipitation method. HTsg-(600) showed appreciably higher CO2 adsorption capacity compared to HTcp-(600). The CO2 adsorption capacity for HTsg-(600) and HTcp-(600) were 635 and 27.2 mol/g, respectively under similar conditions.