Physical properties of mesoporous scoria and pumice volcanic rocks

Abstract

In this study, the chemical composition, crystal structure, texture properties, and thermal properties of five powdered samples of scoria and pumice volcanic rock from different Harrats were investigated. It was observed that volcanic rocks show variations in chemical compositions, crystal structure, texture, and thermal properties. All samples comprised SiO2, Al2O3, CaO, and Fe2O3 as the major elements and contained both amorphous and crystalline phases. Textural parameters such as surface area and porosity were determined using various calculation models. The surface area of scoria samples was between 0.85 and 1.71 m2 g−1 (Brunauer–Emmett–Teller and Single point model), 0.293–1.028 m2 g−1 (Barrett–Joyner–Halenda model), and 1.02–2.35 m2 g−1 (Langmuir model). While for pumice, the calculated values of the surface area were 1.67 m2 g−1 (Brunauer–Emmett–Teller and Single point model), 0.763 m2 g−1 (Barrett–Joyner–Halenda model), and 2.24 m2 g−1 (Langmuir model). The adsorption-desorption isotherm curves reveal that the scoria and pumice particles under study have mesoporous sizes between 7.89 and 9.81 nm, respectively. The differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results of scoria and pumice samples illustrate a thermally stable material at high temperatures. TGA results show a weight gain by about 1.0% has been observed in the scoria samples in the region beyond 600 °C that may indicate a probable oxidation phenomenon with a change in color. While the DSC results of the red scoria and pumice did not show any recrystallization or oxidation, but only showed a small loss of weight in the TGA result. The diversity in molecular composition, texture, and structure of scoria and pumice volcanic rock samples provide for promising natural stable mesoporous materials that can be used in various mesoporous technologies or applications such as solar cells.