Highly-efficient removal of Pb (II) from water by mesoporous amino functionalized silica aerogels: Experimental, DFT investigations and Life Cycle Assessment

Mesoporous amino functionalized silica aerogels (MASA-X) with high adsorption capacity were prepared at ambient pressure conditions for removal of Pb (II) ions from water. Supported by SEM images and FTIR spectra, the presence of –NH2 groups and porous structures on the surface of MASA-X were demonstrated, which played a critical role in promoting the interfacial adsorption process. The adsorption isotherm fitted well by Langmuir model, indicating that the adsorption occurred on a homogeneous surface and the maximum adsorption capacity of MASA-1, MASA-2, MASA-3, MASA-4 were 444.4 mg/g, 628.93 mg/g, 549.45 mg/g and 286.53 mg/g, respectively, and MASA-2 demonstrated optimal adsorption performance. The kinetic data showed good correlation coefficient with the pseudo-second order kinetic model, and the adsorption equilibrium of MASA-1, MASA-2, MASA-3, MASA-4 were reached in 120 min, 60 min, 20 min and 20 min, respectively. And raising temperature facilitated the adsorption of Pb (II) as it was a spontaneous and endothermic process. It was noteworthy that MASA-2 showed satisfactory reusability after eight adsorption-desorption cycles. FTIR, XPS coupled with Density Functional Theory (DFT) calculation revealed that the involvement of monodentate N atoms in the coordination with Pb (II) on adsorption of Pb (II) by MASA-2. The environmental impact of the MASA-2 preparation process was calculated through Life Cycle Assessment (LCA) and by analyzing the contribution of each material in the production of MASA-2, a more environmentally friendly and effective production strategy has been finally proposed, which could facilitate the promotion of MASA-X adsorbents in the heavy metal contaminated water market.