碳酸镁结晶过程离子团簇与扩散成核机制

doi:10.19964/j.issn.1006-4990.2021-0344

摘要/Abstract

摘要：

理解离子的团簇演化成核机制可以更好地进行结晶过程的调控。基于分子动力学模拟研究了结晶温区、溶质离子浓度等对溶液结晶成核与生长过程的影响,并探讨了溶质离子的团簇演化规律。结果表明,溶质离子的扩散速率与物质结构和分子间作用力有关,并且与成核或晶界生长过程的团簇演化相互影响。在此研究范围内,溶质离子浓度一定（1.71 mol/L）时,388 K体系的成核与生长能力最强,是晶界引导无水碳酸镁生长、干扰镁离子和水分子结合的最佳温度,吸附在晶界的溶质离子分数为28.33%;一定温度下（298 K）,溶质离子浓度为3.99 mol/L时最有利于晶体生长,吸附在晶界的溶质离子分数为32.14%,且该浓度起到了最佳的脱水效果,有利于形成无水碳酸镁。这为获得结晶良好、形貌均匀的无水碳酸镁等工艺技术提供了理论依据和指导。

关键词: 团簇演化, 成核与生长, 分子动力学模拟, 碳酸镁溶液, 晶体表面

Abstract:

Understanding the nucleation mechanism of ion cluster evolution can better regulate the crystallization process.The effect of crystallization temperature zone and concentration on the nucleation and growth process of solution crystallization was studied based on molecular dynamics simulation,and the evolution of solute ion clusters was discussed.The results showed that the diffusion rate of solute ions was related to the material structure and intermolecular forces,and interacted with cluster evolution during nucleation or grain boundary growth.Within the scope of this study,at the certain solute ion concen-tration（1.71 mol/L）,the system had the strongest nucleation and growth ability at 388 K,which was the best temperature for the grain boundary to guide the growth of AMC and interfere with the combination of Mg²⁺ and H₂O,and the ratio of solute ions adsorbed on the grain boundary was 28.33%.At the certain temperature（298 K）,the ion concentration of 3.99 mol/L was the most conducive to crystal growth.Under this concentration,the ratio of solute ions adsorbed on the grain boundary was 32.14%,and it had the best dehydration effect,which was beneficial to formate anhydrous magnesium carbonate.It provided theoretical basis and guidance for the technological process of obtaining anhydrous magnesium carbonate with good crystallization and uniform morphology.

Key words: cluster evolution, nucleation and growth, molecular dynamics simulation, magnesium carbonate solution, crystal surface

中图分类号:

TQ174

任文芝,强伟丽,廉士俊,兰忠. 碳酸镁结晶过程离子团簇与扩散成核机制[J]. 无机盐工业, 2022, 54(3): 51-58.

REN Wenzhi,QIANG Weili,LIAN Shijun,LAN Zhong. Ionic clusters and diffusion nucleation mechanism during crystallization of magnesium carbonate[J]. Inorganic Chemicals Industry, 2022, 54(3): 51-58.

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c（MgCO₃）/ （mol·L^-1）	离子数/个		密度/ （g·cm^-3）
c（MgCO₃）/ （mol·L^-1）	CO₃^2-	Mg²⁺	密度/ （g·cm^-3）
0.057	1	1	1.030
0.57	10	10	1.073
1.14	20	20	1.121
1.71	30	30	1.170
2.28	40	40	1.217
2.85	50	50	1.265
3.42	60	60	1.313
3.99	70	70	1.361
4.56	80	80	1.409

项目	原子类型	力场类型	电荷/C
CO₃^2-	C	c3i	+0.395 1
CO₃^2-	O	o1-	-0.798 4
Mg²⁺	Mg	mg+2	+2.000 0
H₂O	H	h1o	+0.410 0
H₂O	O	o2*	-0.820 0

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