Microwave treatment effect on the enhanced basicity of porous clay heterostructured composites derived from Laponite

Abstract

Porous clay heterostructured composites (PCH) derived from layered hydrous magnesium silicate, Laponite, were functionalized by Fe(NO3)3x9H2O with the use of mechano-chemical impregnation followed by microwave irradiation or hydrothermal treatment to evoke new base properties, active in CO2 sorption. It resulted in the progressive leaching of the Mg2+ from the octahedral sheets of the Laponite structure and their capture on the surface of PCH composites increasing the Mg/Si ratio. The increase of Mg/Si ratio was accompanied by the decline of the (Mg3OH) absorption bands intensity attributed to Laponite and discussed regarding the formation of dispersed nanostructured MgO moieties capable of adsorbing CO2. CO2-TPD temperature-programmed desorption technique revealed that sorption and stabilization of CO2 molecules are related to the coordination of oxygen sites in the formed MgO lattice and that edge and corner sites facilitate the interaction of CO2 molecules with O2− sites on MgO. Doping of PCH resulted also in the nucleation of nanocrystalline α-Fe2O3 able to capture CO2 with strength and stability higher than MgO. Microwave irradiation resulted in significant development of the surface basicity as part of the transformation of clay structure. This study confirms the importance of clay minerals in the uptake and retention of CO2.