Use
of Ball Drop Casting and Surface Modification
for the Development of Amine-Functionalized Silica Aerogel Globules
for Dynamic and Efficient Direct Air Capture
posted on 2024-03-13, 07:29authored byYong Kong, Quan Liu, Zhiyuan Liu, Xiaodong Shen
Amine-functionalized
silica aerogel globules (AFSAGs) were first
synthesized via a simple ball drop casting method followed by amine
grafting. The effect of grafting time on the structure and CO2 adsorption performance of the AFSAGs was investigated. The
CO2 adsorption performance was comprehensively studied
by breakthrough curves, adsorption capacity and rates, surface amine
loading and density, amine efficiency, adsorption halftime, and cyclic
stability. The results demonstrate that prolonging the grafting time
does not lead to a significant increase in surface amine content owing
to pore space blockage by superabundant amine groups. The CO2 adsorption performance shows obvious dependence on surface amine
density, determined by both the surface amine content and specific
surface area, and working temperature. AFSAGs with a grafting time
of 24 h (AFSAG24) with a moderate surface amine density have optimal
CO2 adsorption capacities, which are 1.78 and 2.14 mmol/g
at 25 °C with dry and humid 400 ppm CO2, respectively.
The amine efficiency of AFSAG24 with low CO2 concentrations,
0.38–0.63 with dry 400 ppm−1% CO2, is the
highest among the reported amine-functionalized adsorbents. After
estimation with different diffusion models, the CO2 adsorption
process of AFSAG24 is governed by film diffusion and intraparticle
diffusion. In the range of 1–4 mm, the ball size does not affect
the CO2 adsorption capacity of AFSAG24 obviously. AFSAG24
offers significant advantages for practical direct air capture compared
with its state-of-the-art counterparts, such as high dynamic adsorption
capacity and amine efficiency, excellent stability, and outstanding
adaptation to the environment.