Issue 8, 2015

Sol–gel hydrothermal synthesis of microstructured CaO-based adsorbents for CO2 capture

Abstract

In this study, microstructured CaO-based adsorbents were synthesized by a sol–gel hydrothermal method using calcium nitrate tetrahydrate, citric acid and sodium hydroxide as precursors. Experiments with different NaOH concentrations (2, 6 and 10 M) were carried out to investigate the effects on the morphologies and CO2 adsorption activities of the synthesized adsorbents. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) results showed that different NaOH concentrations resulted in different crystal phases and morphologies. A novel three-dimensional (3D) hierarchical calcite (CaCO3) hollow microspherical adsorbent composed of one-dimensional (1D) spike-shaped nanorods was obtained with 2 M NaOH. XRD analyses confirmed that the hierarchical CaCO3 hollow microspheres were characteristic of the calcite phase. The FESEM image revealed that the microspheres were composed of 1D spike-shaped nanorods with an average length of 500 nm. The cross-sectional FESEM image showed that the microspheres had hollow structures with an average inner cavity of 2 μm and a shell thickness of approximately 0.5 μm. The CO2 adsorption performance of the synthesized adsorbents was investigated using thermogravimetry-differential thermal analysis (TG-DTA) apparatus. The results indicated that the novel hierarchical calcite (CaCO3) hollow microspherical adsorbent composed of one-dimensional (1D) spike-shaped nanorods possessed higher carbonation conversion of 45% after 15 cycles, which was about 22% higher than that of other adsorbents synthesized with 6 and 10 M NaOH concentration and limestone. This property could be attributed to the 3D hierarchical hollow microsphere structure, 1D spike-shaped nanorod structure, trimodal pore size distribution and large BET surface area (44.85 m2 g−1) of the novel adsorbent.

Graphical abstract: Sol–gel hydrothermal synthesis of microstructured CaO-based adsorbents for CO2 capture

Supplementary files

Article information

Article type
Paper
Submitted
12 Nov 2014
Accepted
15 Dec 2014
First published
15 Dec 2014

RSC Adv., 2015,5, 6051-6060

Author version available

Sol–gel hydrothermal synthesis of microstructured CaO-based adsorbents for CO2 capture

N. N. Hlaing, S. Sreekantan, R. Othman, S. Pung, H. Hinode, W. Kurniawan, A. A. Thant, A. R. Mohamed and C. Salime, RSC Adv., 2015, 5, 6051 DOI: 10.1039/C4RA14355H

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