Novel geopolymer composite based on oil shale and chitosan for enhanced uranium (VI) adsorption: Experimental and theoretical approaches

This study introduces an innovative geopolymer composite (Ch@GPol), synthesized from oil shale and chitosan (Ch), tailored to improve Uranium (VI) adsorption. Experimental and theoretical methods were applied to explore the distinct characteristics and potential applications of the composite. Various techniques were employed, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). The interaction between chitosan and the geopolymer was scrutinized through FTIR and XRD analyses, revealing substantial alterations in the composite structure. Adsorption experiments highlighted the exceptional U(VI) removal performance of the composite from aqueous solutions. Comparative to materials in the literature, the Ch@GPol exhibited a notably high adsorption capacity of 0.236 mol kg(-1). The maximum adsorption capacity was observed at the natural pH of the uranium(VI) solution. showcasing the composite's versatility. Textural analyses of the Ch@GPol, encompassing surface area and pore size distribution, revealed enhanced porosity and favorable adsorption characteristics. The determination of the point of zero charge (pHPZC) provided insights into surface charge distribution, emphasizing the composite's applicability across a broad pH range. Kinetic studies demonstrated rapid adsorption kinetics, with the pseudo-second-order model best describing the adsorption process. Density Functional Theory (DFT) analysis offered structural insights into the interaction between the composite and Uranium (VI), confirming robust binding capabilities.