Regulation of Calcite Morphology by Low‐Molecular‐Weight Organic Acids: Alcohol Hydroxyl and Carboxyl Matters

Abstract

Replicating the key structural feature of calcium carbonate (CaCO3) by biomolecules provides unique inspiration for synthesis of CaCO3 suitable for industry application. The biomolecule‐based morphological strategies generally contain the strong interaction between crystal and functional groups, such as carboxyl group and alcohol hydroxyl group. Here, a comparative study of low‐molecular‐weight organic acids (OAs) with structural similarity on calcite crystallization is presented. The morphological evolution of calcite from rhombohedron to ellipsoid is observed, needle‐like or dumbbell‐like in the presence of monohydroxy OAs of lactic acid, malic acid, or citric acid, suggesting carboxyl group shows more remarkable effect on the morphologies of calcite than that of Li+. The strong adsorption behavior of carboxyl group on calcite can decrease the crystallinity with increased number of carboxyl groups. In contrast, the dicarboxylic OA of tartaric acid showed stronger effects on the phase transition process from vaterite to calcite than that of succinic acid and monohydroxy OAs. These findings will aid in synthesizing CaCO3 with specific morphology and polymorph by biochemical methods and are of great significance to the industrial application of CaCO3.

Effect of carboxylate additives on CaCO3 particle size by precipitation method using scallop shell

“…In addition, the pH values of the solutions after particle generation using the above mixtures of ( 1) and ( 5), and 0.1 mol/L CaSC solution were pH 7.80 and pH 7.29, respectively. The dissociation constant (pK) of tartric acid, citric acid, and oxalic acid have been reported as tartric acid (pK 1 = 3.03, pK 2 = 4.37) 39 , citric acid (pK 1 = 3.13, pK 2 = 4.76, pK 3 = 6.4) 39 , and oxalic acid (pK 1 = 1.25, pK 2 = 3.67) 36 , respectively. Judging from the pH values of the solution after particle generation, and the reported dissociation constant values, the added dicarboxylate ions should be perfectly bared, that is, all these ions should charge negatively, so the added dicarboxylate ions could be enough to bind to calcium ion.…”