Layered Double Hydroxides for CO_2 Capture in Cementitious Materials:Experiment Investigation and Thermodynamic Analyses

【Author】

Ping Duan;Wei Chen;Guowei Chen;Zhonghe Shui;

【Abstract】

<正>The development of new or modified cementitious materials is an important part of existing strategies to improve performance and minimize life-cycle costs.The high anion exchange capacity of layered double h~(88)ydroxides(LDHs) materials makes their interlayer ion exchange by organic and inorganic anions versatile and easily achieved LDH-like materials could be used in cementitious materials for their CO_3~(2-) capturing capacity and to enhance carbonation resistance of cementitious materials. In this work,original LDHs were synthesized,LDHs calcinated at 500,550 and 600℃respectively were prepared Power X-ray diffraction(XRD),IR-spectroscopy and thermal analysis (TG-DSC) were employed to characterize the component and structural changes of these types of LDHs before and after CO_2 capture.Carbonation resistance of cement paste incorporating LDHs was experimental evaluated for assessment of CO_2 capture capacity of LDHs.Ion exchange mechanism of LDHs was also analyzed from thermodynamic calculation. The results show that all the prepared LDHs solids display powder X-ray diffraction spectra typical of LDH materials.Thermal decomposition of LDHs includes three main stages.Calcineted LDHs fulfill the structure regeneration after CO_2 capture.LDHs have positive effect on improvement of carbonation resistance of cement paste especially at later curing stages. Carbonate-bearing hydrotalcite-like compounds will be less soluble than hydrotalcite-like compounds bearing other anions and carbonate-bearing hydrotalcite-like compounds will be the most stable due to the minimum Gibbs free energies. Originality In this article we conduct experimental and theoretical studies of the component,structure and mophology of LDHs used in concrete. A detailed understanding of the component,structure and mophology of LDHs as well as the mechanism of the formation process should facilitate the design of materials with properties precisely tailored for specific applications,especially for concrete. This study also aims to catch carbonate ions in concrete and to fix them in intercalation layers,in order to improve carbonation resistance by means of the properties of anion-exchange and structure re-construction of the intercalated layered materials(LDHs).Ion exchange mechanism of LDHs was also analyzed from thermodynamic calculation.

【Keywords】

layered double hydroxides(LDHs):anion exchange;;carbonation;;cementitious materials;;thermodynamic

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