The non-micellar template model for porous clay heterostructures: A perspective from the layer charge of base clay

Abstract

In this paper, the effect of layer charge (LC) of base clay on the structural properties of porous clay heterostructures (PCHs) was studied. Three natural montmorillonites (Mt) with different LC and a series of reduced-charge Mt were used in the synthesis of PCH to discuss the non-micellar template model for PCH from the perspective of base clay. The PCH samples are the intergrowth of a porous silica-intercalated clay and an amorphous silica component. The XRD and TEM studies revealed that the d001-values of PCH samples prepared from natural Mt (simply as “natural PCH” for short) were larger than 3nm. The interstratified structures in PCH samples from reduced-charge Mt (simply as “reduced-charge PCH” for short) were the result of the collapse of interlayer spaces caused by the inhomogeneous LC reduction. The organic carbon contents (fOC) of organo-montmorillonite (OMt) were negatively correlated with the bulk silica contents (fSiO2-b) of the corresponding PCH samples. For the natural PCH, the extra spaces from decreased surfactant within interlayer were occupied by amorphous silica in the pillaring reaction. The decreased specific surface area (SSA), porosity and the invariant dominant pore size (1.3–1.4nm) of PCH suggested that blocking the pore channels in the interlayer spaces with increased silica was more pronounced than propping the layers permanently apart and building porous structures. Based on the effect of organic template and base clay on the structural properties in our previous and present work, Mt-based PCH probably is a type of porous materials with invariant pore size.