Modified fibrous silica for enhanced carbon dioxide adsorption: Role of metal oxides on physicochemical properties and adsorption performance

Highlights: • Metal oxides–fibrous silica (FS) was prepared by ultrasound assisted impregnation. • Fibrous morphology increases the accessibility of CO₂ in FS. • Alkaline earth metal (CaO and MgO) increases the basic active sites of FS. • High CO₂ physisorption: CaO-FS (0.76mmol/g); High CO₂ chemisorption: MgO-FS (9.77mmol/g). • Porosity and basicity played important roles on CO₂ adsorption performances. This work investigates the effectiveness of FS loaded with CaO, MgO, and CeO₂ for CO₂ adsorption. Different techniques such as XRD, ATR–FTIR, Raman, CO₂–TPD, in situ FTIR, FESEM, and TEM were employed. Upon the metal oxides loading, the alteration of textural properties, increases in the weak and moderate basic strength and quantity of basic active sites as well as disappearance of the dendritic structures in CaO/FS were observed. The in situ FTIR studies confirmed the formation of different carbonates species upon the interaction with CO₂. The greatest CO₂ physisorption capacity was demonstrated by CaO-FS (0.76mmol/g), while the highest CO₂ chemisorption uptake was shown by MgO-FS (9.77mmol/g). The CO₂ physisorption activity depends mainly on the porosity and basic strength of the adsorbents. On the contrary, the CO₂ chemisorption performance is determined by the basic strength and basic sites as well as CO₂ affinity of the adsorbents.