Physicochemical, mineralogical, and thermogravimetric characterizations were carried out to assess the potential technological benefits of natural sand deposits from El-Oued district (eastern Algeria). The use of granulometric analysis, FTIR spectroscopy, X-ray fluorescence (WDXRF), X-ray diffraction (XRD), scanning electron microscope (SEM/EDX), and thermogravimetric (TGA) analysis was necessary to further highlight the main physical and chemical properties of the studied sands. The grain size distribution suggests fine-to-medium sands with a mean grain size ranged from 207 to 261 μm. However, the grain micro-texture features indicate aeolian nature of El-Oued sand, and the chemical analysis reveals that all samples contain a high ratio of silica (SiO 2 ) reaching 94% with low content of CaO, Al 2 O 3 , Fe 2 O 3 , Na 2 O, and K 2 O oxides, which reflects the siliceous nature of El-Oued sand. The mineralogy of the El-Oued sand consists mainly of α-quartz (≤ 93% SiO 2 ) with minor calcite (CaCO 3 ) and very small amounts of feldspar mineral. Furthermore, the crystallite size of Quartz in all sand samples was determined to be in the range of nanometric scale. Thermal analysis (TGA) showed that El-Oued sand was relatively stable upon 800 °C. These characteristics corroborate the interesting and promising uses of El-Oued sand in the industry and nanotechnology. KeywordsSand • Mineralogical and chemical characterization • α-Quartz • Rietveld refinement • Industrial applications

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This study synthesized highly pure silica nanoparticles from the northeast Algerian Sahara dunes sand as a low-cost silica source using a simple and environmentally friendly method. The silica nanoparticles were extracted using a sodium silicate solution as a precursor without employing any additive agents. The extracted silica’s crystalline structure, chemical composition, chemical bonding, microstructure, elemental analysis, thermal analysis, and optical characteristics were investigated. The X-ray diffraction patterns demonstrate the amorphous nature of the extracted silica. Furthermore, the X-ray fluorescence spectroscopy (XRF) and energy dispersive X-ray (EDX) results prove the high purity of the extracted silica (99% SiO 2 ). However, the Fourier-transform infrared spectroscopy (FTIR) results corroborate the presence of silanol and siloxane groups. According to the SEM image analysis, the produced silica has an average particle size in the range of nanometers. Thermal analysis (TGA/DTA) exhibited the high thermal stability of the silica, and the optical band gap energy for silica nanoparticles was determined to be 3.75 eV. Therefore, dunes sand is an alternative source for developing high-purity silica nanoparticles, which have great potential for advanced material applications.

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