Extracting High Purity Nano-silica from Oil Shale: Valorising a Neglected Natural Resource

Abstract

Silica nanoparticles are indispensable materials in modern industries because of their versatility. However, conventional production sources are intensive and environmentally burdensome. Given these considerations, this manuscript presents a novel, abundant, and inexpensive natural resource for extracting high-purity nano-silica. Indeed, a chemical extraction method was applied to a neglected Moroccan oil shale. The synthesized silica nanoparticles were thoroughly characterized using a range of analytical techniques. The nitrogen adsorptiondesorption isotherms exhibited a Type IV profile with a surface area of 381.0582 m²/g, X-ray diffraction (XRD) confirmed its amorphous structure with a broad peak centered at 2θ ≈ 22.5◦, while energy-dispersive Xray spectroscopy-mapping (EDX-mapping) validated the exceptional purity reaching up to 99.99 %. Additionally, scanning and transmission electron microscopy (SEM and TEM) revealed dense agglomerates of nanoparticles ranging from 9 to 15 nm in diameter. Fourier-transform infrared spectroscopy (FTIR) indicated the presence of silanol (Si–O–H) and Siloxane (Si–O–Si) characteristic bands, indicating the formation of silica. Thermal analysis (DSC and TGA) demonstrated the thermal stability of the mesoporous structure up to 900 ◦C and the presence of both physically adsorbed and chemically bound water. This high yield of silica (92 %) makes this underexploited oil shale resource commercially viable for large-scale applications in catalysis, water treatment, and nanotechnology. Environmentally, the process promotes waste valorization by transforming shale byproducts into amorphous nano-silica and supports circular economy principles, enabling developing economies to locally produce advanced materials with minimal ecological impact.