Effect of Adding Bentonite to Porous Silica via the Sol-Gel Method.

The control of specific surface area and pore size of porous materials is essential for applications such as optics, medicine, and food technology. Here, the interspace between nanomaterials such as nanoparticles and nanosheets was studied. Nanoparticle-nanosheet interspaces were formed by incorporating bentonite nanosheets to the preparation of porous silica by the sol-gel method. The product had micropore and mesopores, which originated from internanoparticle space and nanoparticle-nanosheet spaces, respectively. These two types of pores had not only different sizes but also different aspect ratios. Time-domain nuclear magnetic resonance evaluation of the bentonite dispersion revealed that the dispersion state of bentonite in water prior to composite fabrication affected the formation of the pore structure. The pore size distribution could be easily changed by adding two-dimensional and flexible nanosheets owing to the change in the physical properties of the product. The silica-bentonite composite had a significantly larger specific surface area and pore volume than porous silica without bentonite. Water vapor adsorption measurements showed that the composite exhibited a larger maximum adsorption in comparison to porous silica. Therefore, a large improvement in the physical properties can be achieved by combining nanomaterials with different geometries.