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Origin of Gypsum Growth Habit Difference as Revealed by Molecular Conformations of Surface-Bound Citrate and Tartarate

Abstract

The introduction of various organic acids during gypsum (CaSO4∙2H2O) crystallization could change the crystallization behavior of gypsum leading to different macroscopic properties. Understanding the origin of organic acids on gypsum crystallization at an atomic level is the key step for us to rationalize the design of gypsum-related products. Here, citric acid (CA) and L-(+)-tartaric acid (LTA) were selected as two model compounds to investigate such organic-inorganic interactions. CA has the stronger retarding effect of gypsum precipitation as compared with LTA. The introduction of CA in aqueous solution results in final plate-like gypsum crystal with the smaller specific surface area. However, the presence of LTA does not change gypsum crystal morphology and the specific surface area remains almost the same as that of pure gypsum. AFM was firstly used to characterize the surface roughness of gypsum (010) plane, and it was found that only monolayer organic-inorganic structure is formed on top of gypsum (010) plane for both LTA and CA. Afterwards, the synchrotron μ-FTIR was utilized to obtain the atomic structure information, and the results further confirm the mono-tartarate structure is formed. Finally, the advanced metadynamics simulation (MD) was employed to obtain detailed organic-inorganic structure information and the free energy landscape. The simulation results show CA owns stronger affinity as compared with LTA. CA and LTA were found to prefer to stand up conformation on top of gypsum (010) plane. The combination of numerous characterization techniques with MD simulations, for the first time, clarify the organic-inorganic interfacial structure in gypsum system.

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Publication details

The article was accepted on 11 May 2018 and first published on 15 May 2018


Article type: Paper
DOI: 10.1039/C8CE00669E
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Origin of Gypsum Growth Habit Difference as Revealed by Molecular Conformations of Surface-Bound Citrate and Tartarate

    W. Chen, W. Zhao, Y. Wu, Y. Wang, B. Zhang, F. Li, Q. Chen, Z. Qi and Z. Xu, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C8CE00669E

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