Energies of the Adsorption of Functional Groups to Calcium Carbonate Polymorphs: The Importance of 鈭扥H and 鈭扖OOH Groups

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• 作者：D. V. Okhrimenko ; J. Nissenbaum ; M. P. Andersson ; M. H. M. Olsson ; S. L. S. Stipp
• 刊名：Langmuir
• 出版年：2013
• 出版时间：September 3, 2013
• 年：2013
• 卷：29
• 期：35
• 页码：11062-11073
• 全文大小：607K
• 年卷期：v.29,no.35(September 3, 2013)
• ISSN：1520-5827

文摘

The adsorption behavior of calcium carbonate is an important factor in many processes in nature, industry, and biological systems. We determined and compared the adsorption energies for a series of small molecules of different sizes and polarities (i.e., water, several alcohols, and acetic acid) on three synthetic CaCO₃ polymorphs (calcite, aragonite, and vaterite). We measured isosteric heats of adsorption from vapor adsorption isotherms for 273 < T < 293 K, and we used XRD and SEM to confirm that samples did not change phase during the experiments. Density functional calculations and molecular dynamics simulations complemented the experimental results and aided interpretation. Alcohols with molecular mass greater than that of methanol bind more strongly to the calcium carbonate polymorphs than water and acetic acid. The adsorption energies for the alcohols are typical of chemisorption and indicate alcohol displacement of water from calcium carbonate surfaces. This explains why organisms favor biomolecules that contain alcohol functional groups (鈭扥H) to control which polymorph they use, the crystal face and orientation, and the particle shape and size in biomineralization processes. This new insight is also very useful in understanding organic molecule adsorption mechanisms in soils, sediments, and rocks, which is important for predicting the behavior of mineral鈥揻luid interactions when the challenge is to remediate contaminated groundwater aquifers or to produce oil and gas from reservoirs.