方解石与柠檬酸/酒石酸模拟实验中的反应规律.

Citric acid/tartaric acid can cause mineral dissolution and biomineralization of calcite, so the study on reaction pattern between them is of great significance for the assessment of the stability of calcite minerals and the study on the corresponding geochemical effects in organic acid-rich environments. The reaction between calcite and citric acid/tartaric acid and the corresponding solution chemistry change were studied by batch equilibrium method under open system conditions. The results show that at the initial concentration of 20 mg.L-1, the reaction removal of citric acid and tartaric acid decreases significantly when the initial pH value increases from 7.7 to 9.7; this is attributed to the electrostatic effect on the surface of calcite and the increasing competition between HCO-3 and CO2-3 in the solution, which inhibit the surface adsorption reaction of the two acids on calcite. At the initial pH of 7.7 and 8.3, the reaction of the two acids with an initial concentration of 20 mg.L-1 and calcite reaches equilibrium after 7 h; compared with the blank values, the pH and Ca concentration have little change, which prove that the dominant mechanism of the reaction is surface adsorption. In the concentration range of 0-900 mg.L-1, the reaction removal results of citric acid and tartaric acid at the initial pH of 8.3 could be well fitted by the Langmuir adsorption model, which proves that both of the above removal mechanisms are surface adsorption; at the initial pH of 7.7, the reaction removal results of citric acid still could be fitted by the Langmuir adsorption model, and the removal mechanism is still surface adsorption; while the removal of tartaric acid shows a continuous steep increase, which cannot be fitted by the Langmuir or Freundlich adsorption model, and this is due to the fact that the dominant mechanism of tartaric acid removal by reaction is precipitation reaction. At an initial pH of 8.3, a concentration range of 0-900 mg.L-1 and the temperatures of 5 ℃, 20 ℃, and 35℃, the removal results of both acids could be fitted by the Langmuir adsorption model, and the removal mechanism is still surface adsorption; the increase in the saturation adsorption of citric acid with increasing temperature is greater than that of tartaric acid; meanwhile, citric acid at all three temperatures brings about a greater increase in pH and Ca concentration than that of tartaric acid. [ABSTRACT FROM AUTHOR]