Physicochemical characterization of biogenic silica of the upper Numidian babouchite siliceous rocks, northwestern Tunisia

Abstract

Physicochemical features (surface area, structural functional groups, thermal behavior), of the babouchite siliceous rocks from the upper Numidian formation, were explored in order to determine their possible uses. A suite of twelve-powder and fragments form were taken from Tabarka and Babouch areas, northwestern of Tunisia. The properties of the studied biogenic silica was measured using several techniques such as Scanning Electron Microscopy (SEM), Nitrogen physisorption measurements (N2-sorption), Fourier Transform Infrared Spectroscopy (FTIR) and Simultaneous Thermal Analysis (TGA-DSC). The studied siliceous rocks exhibited finely parallel-layered surfaces of microcrystalline quartz. Furthermore, the textural parameters of the babouchite samples showed the presence of mesopores with dissimilar size and distribution, which is demonstrated by SEM micrographs of the different fragments indicating pores with a size up to 4 μm. As well, the structure of the resulting adsorbents was characterized by specific surface area between 25 and 30 cm2g-1 and the average pore volume (V) is around 0.08 cm3g-1. The FTIR spectroscopy has clearly showed the predominance of quartz phase by the characteristic spectral bands of SiO2 crystal, mostly located between 1400 and 400 cm−1. Thermally, at above 900 °C, the babouchite siliceous rocks have a high thermal stability due to the dehydroxylation of kaolinite and other clay minerals minerals contained in these siliceous rocks.