The effect of microwave irradiation and conventional acid activation on the textural properties of smectite: Comparative study

In this work, the activation clay employing “traditional or conventional” heating and microwave (MW) irradiation is reported. This paper is an extension of a previous paper where the natural and purified clay in the homoionic Na form were activated by microwave irradiation and physico-chemically characterized (Korichi et al., 2009).The influence of conventional and microwave irradiation on smectite activation was investigated. Preparation time of the conventional activation took about 8 h, whereas a highly porous structure is obtained, when operating at a power of 500 W for 20 min in case of microwave irradiation. To find changes in physicochemical properties, the following techniques were used: Laser granulometry, N2 adsorption/desorption, Mercury porosimetry, X-ray diffraction, Chemical analysis, FT-IR spectroscopy, Scanning Electron Microscopy (SEM), Thermo Gravimetric (TGA) and Differential Thermal Analysis (DTA). Characterization results confirm the general smectite character of the natural sample.The properties of the compounds obtained by these two methods are comparable. The clay materials were composed of microporous and mesoporous structures. The total surface area and pore volume of samples prepared with conventional method are 173.17 m2/g and 0.1597 cm3/g, respectively. The total surface area and pore volume of samples prepared under microwave are 165.80 m2/g and 0.1919 cm3/g, respectively. The results of this study showed that small pores were created in the prepared materials with both methods: conventional heating and microwave irradiation.

Scanning Electron Microscopy images of sample exhibited the structure typical of smectite clays. Treated sample (this figure) has larger pores between particles than natural sample. The second shows the X-ray Energy Dispersive Spectrometry spectra of sample clay powder; this result was confirmed by the chemical analysis of natural sample.Figure optionsDownload as PowerPoint slideHighlights
► Studies have shown that acid activation by HCl under microwave and conventional methods produce mesoporous smectites.
► The specific surface area increases as the acid activation increases under microwave irradiation.
► Changes in surface properties the clay after microwave irradiation are similar to those obtained by conventional method.
► Microwave method is more powerful and can achieve the same results with a shorter time compared to the conventional method.
► Microwave irradiation is rapid alternative method to conventional acid activation for preparing mesoporous smectites.