Role of Aspartic Acid in the Synthesis of Spherical Vaterite by the Ca(OH)₂–CO₂ Reaction

Abstract

Vaterite crystals with a spherical shape were successfully obtained by the addition of aspartic acid (Asp) in the calcium hydroxide (Ca(OH) 2 )−carbon dioxide reaction system. Crystalline products were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry (TG-DSC). The experimental results indicate that the addition of Asp can inhibit the growth of calcite but promote the formation of vaterite, and the spherical vaterite CaCO 3 is gradually dominant along with the increase of Asp. Meanwhile the content of the vaterite phase is prominently influenced by the reaction temperature, and the optimal temperature for vaterite is at 40 °C. It is proposed that vaterite is induced through the intermediate chelated by Asp and Ca(OH) 2 , and then Asp is adsorbed on the surface of vaterite by chelation, preventing the metastable vaterite from transforming to calcite via a dissolution−recrystallization process. Further, the decrease of pH in the solution could reduce the chelation between Asp and Ca 2+ , leading to the transformation from vaterite to calcite. Hence, the study on the formation and transformation of vaterite will provide additional insight into biomineralization mechanism and industrial production.

Synthesis and Adsorbing Properties of Tabular {001} Calcite Crystals

“…On the other hand, no data reporting Li + distribution into the vaterite crystals are available, to the best of our knowledge. Therefore, we hypothesize that in the systems with higher Li + content, the increasing adsorption onto the vaterite surface cause its slower dissolution and kinetic stabilization, which consequently postpone the formation of calcite, as already reported for organic molecules [46]. However, the adsorption of Li + onto the calcite can also inhibit its growth, which influences the overall course of transformation.…”

Formation and Phase Selection of CaCO3 in the Intervention of Lignin Monomer Model Compounds

“…The existence of carboxyls was benefit to the formation of vaterite. [ 40,41 ] As presented in Figure , the spectra of all the ACCs formed at pH 11 exhibited a new peak at 1797 cm −1 which corresponded to C═O. This illustrated that the carboxyls in the PCA, FA, and SA were transformed to C═O with the increase of pH from 7 to 11.…”

Corrosion Protection of Q235 Steel Using Epoxy Coatings Loaded with Calcium Carbonate Microparticles Modified by Sodium Lignosulfonate in Simulated Concrete Pore Solutions

“…Sixteen diffraction peaks in the XRD patterns at 2θ = 22.944, 29.311, 31.409, 35.849, 39.314, 43.045, 47.034, 47.455, 48.414, 56.463, 57.275, 60.535, 61.310, 62.909, 64.525, and 65.616° correspond to the respective planes of (012), (104), (006), (110), (113), (202), (024), (018), (116), (211), (122), (214), (119), (125), (300), (0012) of vaterite and the peaks at 2θ = 20.880, 24.883, 26.973, 32.711, 42.613, 43.767, 49.098, 49.946, and 55.768° correspond to the respective planes of (002), (100), (101), (102), (004), (110), (112), (104), and (202) for calcite. We estimated that the vaterite and calcite relative mole fractions in the CaCO 3 microparticles can be correlated to the X-ray diffraction intensity from the following expression [ 37 ]: where, C and V are the calcite and vaterite mole fractions, respectively, I C is the X-ray diffraction intensity of the corresponding planes of calcite, and I V is the X-ray diffraction intensity of planes of vaterite.…”