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

•Synthesis of bifunctional mesostructured alumina via amino-functionalization.•P123 extraction and tetraethylenepentamine loading were simultaneously realized.•The amino-functionalized alumina shows excellent mesostructure centering at 7.3 nm.•Good adsorptive capability of the amino-functionalized alumina for Cr(VI) and CO2.•The amino-functionalized alumina shows very fast adsorption kinetics for Cr(VI).

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 67.4 m2 g−1 could be considered as a bifunctional adsorbent showing high adsorption capacity of 59.5 mg g−1 and extremely fast adsorption kinetics with percentage removal of 92% within 0.5 min for Cr(VI) at an optimal pH = 2, and decent adsorption capacity of 0.7 mmol g−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.

Graphical abstractA novel amino-functionalized mesostructured alumina with amorphous walls was successfully synthesized by a facile two-step procedure involving P123-assisted sol–gel method, and followed by simultaneous extraction of Pluronic P123 and immobilization of tetraethylenepentamine. The as-prepared alumina shows a much faster adsorption kinetics and higher adsorption capacity for Cr(VI), and a higher adsorption capacity for CO2 at room temperature than those of the alumina without amino modification mainly due to its unique amino-functionalized mesostructure. This new synthetic strategy for the preparation of amine-modified mesoporous alumina not only can save much energy and increase efficiency, but also has great potential to remove heavy metal ions such as Cr(VI), and to capture CO2 for consecutive desorption of gas.Figure optionsDownload full-size imageDownload as PowerPoint slide