Synthesis and characterization of hierarchical porous clay heterostructure from Al, Fe -pillared nano-bentonite using microwave and ultrasonic techniques

Abstract

Abstract The present research is focused on the textural, structural and surface properties of Al, Fe and Si hierarchical porous nano-bentonite heterostructure (PBH) derivated from Al, Fe pillared nano-bentonite (Al, Fe-PILB). The application of Al, Fe-PILB as a precursor to prepare porous clay minimized the use of cationic surfactant, water consumption, synthetic time and organic wastes. Furthermore, the incorporation of Al and Fe species from Al, Fe-PILB in the silica framework was performed in one step reaction compared to the conventional method required the continuous control for hydrolysis and condensation in the synthesize of PBH. Besides using Al, Fe-PILB as a precursor, the ultrasonic and microwave techniques were firstly assisted to the synthesis of PBH for opening bentonite layers with breaking pillars resulted in the increasing basal spacing and improving mesoporous silica formation in interlayer space of Al, Fe-PILB in little synthetic time. The LPSD, XRD, UV–Vis spectra, N2 adsorption-desorption, FESEM-EDS, TEM, and FTIR analyses allowed for a better understanding of PBH behaviors under different synthetic conditions. The results showed that the use of pillared clays in the conventional method did not lead to the formation of PBH due to the strong interaction between the Al, Fe species and the clay layers. The synergism effect of ultrasonic waves and microwave irradiation reduced the structural damage of nano-bentonite and improved BET surface area (867 m2/g), micropore and mesopore volume (0.62 cm3/g) compared to the only application of ultrasonic or microwave techniques. These properties make PBH as an attractive candidate for catalysis and adsorption applications.