Synthesis of amino-functionalized mesoporous alumina with enhanced affinity towards Cr(VI) and CO₂

Amino-functionalized mesoporous alumina (MA) with enhanced affinity towards Cr(VI) and CO₂ was successfully synthesized by Pluronic P123-assisted sol-gel method, followed by impregnation process to extract the polymeric template and load tetraethylenepentamine (TEPA) simultaneously. The physicochemical and adsorption properties of MA without and with TEPA were comparatively characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), N₂ adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV/Vis and temperature programmed desorption of CO₂ (CO₂-TPD) techniques. Adsorption kinetics for Cr(VI) on mesoporous P123-alumina composites before (PA) and after (PA-TEPA) treatment with TEPA were described by pseudo-second-order and pseudo-first-order kinetics, respectively; while, their adsorption equilibrium isotherms were described reasonably well by Langmuir model. PA-TEPA with specific surface area of 67.4m²g^-1 could be considered as a bifunctional adsorbent showing high adsorption capacity of 59.5mgg^-1 and extremely fast adsorption kinetics with percentage removal of 92% within 0.5min for Cr(VI) at an optimal pH=2, and decent adsorption capacity of 0.7mmolg^-1 for CO₂ at room temperature. The presence of amino functionality in PA-TEPA is essential for both Cr(VI) and CO₂ adsorption, which make this material an effective bifunctional adsorbent for environmental applications.