• Shivanna Marappa

      Articles written in Bulletin of Materials Science

    • Interaction of pristine hydrotalcite-like layered double hydroxides with CO2: a thermogravimetric study

      Shivanna Marappa P Vishnu Kamath

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      Metal oxides in general have surface acidic sites, but for exceptional circumstances, are not expected to mineralize CO2. Given their intrinsic basicity and an expandable interlayer gallery, the hydrotalcite-like layered double hydroxides (LDHs) are expected to be superior candidate materials for CO2 mineralization. However, the incorporation of Al3+ adversely impacts the ability of the metal hydroxide layer to interact with CO2 in the gas phase in comparison with the unitary Mg(OH)2. Thermogravimetric analysis shows that the decomposition reaction of the [Mg–Al–CO3] LDH is only marginally delayed in flowing CO2 in comparison with flowing N2, showing only an apparent marginal CO2 uptake. Al3+ ion severely attenuates the surface basicity of the LDHs, as the unitary Al(OH)3 is acidic in comparison with Mg(OH)2 and shows little or no interaction with CO2 in the gas phase.

    • NO$^−_2$ and SCN$^−$-intercalated layered double hydroxides: structure and orientation of anions in the interlayer gallery

      SHIVANNA MARAPPA P VISHNU KAMATH

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      NO$^−_2$ and SCN$^−$ are two common small inorganic anions. The former is a common industrial pollutant. Thelatter is linear and is a good mimic for the toxic CN$^−$ ion. The structures of these two anions are refined within the gallery ofthe [Zn–Al]-layered double hydroxide (LDH). Both LDHs crystallize as mixed anion phases. The nitrite is found to co-existwith the nitrate ion. The nitrite ion is intercalated with its molecular plane inclined to the metal hydroxide layer. In the caseof the SCN$^−$ intercalated LDH, no other anion was detected by ion chromatography, suggesting that the SCN$^−$ deficiencyis compensated by intercalated hydroxyl ions. In this case, the SCN$^−$ ion is found to be intercalated with its molecular axisinclined to the metal hydroxide layer.

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