Abstract
We have investigated dissolution and surface reaction of calcite and aragonite in amino acid solutions of L-glutamic (L-glu) and L-aspartic acid (L-asp) at weak acidity of above pH 3. The surface reactions of calcite and aragonite were related with the dissolution. Calcite was dissolved in both solutions but the dissolution was limited by an adsorption of Ca-carboxylate salt. Aragonite was neither dissolved nor reacted in amino acid solutions because the crystal surface consisted of a hard to dissolve structure.
Highlights
The dissolution of calcium carbonate has been researched extensively for several decades because calcium carbonate plays an important role in carbonate buffering in natural water
The present study aims to compare dissolution and surface reactions of synthesized calcite and aragonite in amino acids such as L-aspartic (L-asp) and L-glutamic (L-glu) acid
The dissolution of calcite resulted from the hydrogen attack as shown in reaction (1) and the Ca concentration from dissolved calcite would be equal to a half of the initial concentration of the acidic solution by charge balancing
Summary
The dissolution of calcium carbonate has been researched extensively for several decades because calcium carbonate plays an important role in carbonate buffering in natural water. The dissolution of calcite occurred by the transport of reactant to the surface, surface reaction, and the transport of product from the surface. The dissolution kinetics of calcite have been studied with various additives in the solutions such as chelating agents, sodium dichromate, and polymaleic acid, phosphoric acid, or oxalic acid [9,11,12]. The hydrogen ion attack of equation (1) did not occur, but the dissolution of calcite happened with the surface reaction between the chelating agent and calcite. In the neutral pH region between 6 and 7, calcite was dissolved and the dissolution rate was affected by the presence of carbon dioxide, which retards its dissolution [11]. Dissolution is related to surface characters, we analyzed filtrates and the surface of solids after reactions
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