New insights in MgAl and MgFe-LDH affinity towards carbon dioxide – role of the hydrophilic character on CO2 retention strength

Abstract The surface basicity and hydrophilic character of Mg and Al or Fe-based layered double hydroxides were assessed through thermal programmed desorption (TPD) of CO2 and H2O in terms of CO2 and water retention capacity (CRC and WRC), respectively. LDH calcination up to 450 °C produced slightly irreversible and detrimental effects on both properties, much less pronounced for Fe-based samples. These properties turned out to be completely revived after calcination below 200 °C. Iron-based LDH showed higher hydrophilic character but lower surface basicity than MgAl-2. Both CRC and WRC increased simultaneously with increasing PNLCO beyond a certain level. Water and CO2 adsorb via competitive interactions with weak to medium adsorption sites, but favor mutually their retention on strong basic sites. These results allow predicting LDH behavior in the adsorption of acidic gases and potential large-scale CO2 capture in humid conditions without previous dehydration.