物理化学学报 >> 2016, Vol. 32 >> Issue (2): 405-414.doi: 10.3866/PKU.WHXB201511192

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拉曼光谱法研究Na+, Mg2+//SO42-, Cl-, H2O四元体系中SO42-离子缔合结构特征及其变化规律

阎波1,周桓2,*(),李文轩2   

  1. 1 天津科技大学海洋与环境学院, 天津市海洋资源与化学重点实验室, 天津 300457
    2 天津科技大学化工与材料学院, 天津市海洋资源与化学重点实验室, 天津 300457
  • 收稿日期:2015-07-27 发布日期:2016-01-30
  • 通讯作者: 周桓 E-mail:zhouhuan@tust.edu.cn
  • 基金资助:
    国家自然科学基金(21176189, U1407204);天津市应用基础与前沿技术研究计划(15JCYBJC23200);教育部科研创新团队培育计划([2013]373);天津市高等学校创新团队培养计划(TD12-5004)

Studies on the Characteristics and Behaviors of the Ion Association Structures of SO42- in Na+, Mg2+//SO42-, Cl-, H2O System by Raman Spectroscopy

Bo YAN1,Huan ZHOU2,*(),Wen-Xuan LI2   

  1. 1 Tianjin Key Laboratory of Marine Resource and Chemistry, College of Marine and Environmental Sciences, Tianjin University of Science & Technology, Tianjin 300457, P. R. China
    2 Tianjin Key Laboratory of Marine Resource and Chemistry, College of Chemical Engineering and Materials Sciences, Tianjin University of Science & Technology, Tianjin 300457, P. R. China
  • Received:2015-07-27 Published:2016-01-30
  • Contact: Huan ZHOU E-mail:zhouhuan@tust.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21176189, U1407204);Natural Science Foundation of Tianjin,China(15JCYBJC23200);Training Program for Changjiang Scholars and Innovative Research Teams in University, China([2013]373);Innovative Research Team of Tianjin Municipral Education Commission, China(TD12-5004)

摘要:

复杂水盐体系存在稳态和介稳固液相平衡以及复杂的成盐规律。为了解固液平衡状态下液相的结构特征,本文采用拉曼光谱技术并结合高斯-洛伦兹去卷积分峰拟合程序对Na+, Mg2+//SO42-, Cl-, H2O四元体系及其二元和三元子体系中ν1-SO42-的离子缔合结构特征进行了分析。研究结果表明:SO42-在Na2SO4-H2O体系存在自由态SO42-和SO42-离子簇两种结构,在MgSO4-H2O, MgSO4-MgCl2-H2O及Na+, Mg2+//SO42-, Cl-, H2O等含镁体系中,还有Mg2+-H2O-SO42-和Mg2+-OSO32-两种缔合结构。在二元和三元体系中ν1-SO42-的离子缔合结构以自由态SO42-为主,随着SO42-离子总浓度的变化,上述四种结构所占比例会发生规律性变化。Na+, Mg2+//SO42-, Cl-, H2O四元体系在NaCl减少及等温蒸发过程中,自由态SO42-结构比例逐步降低, Mg2+和SO42-相结合形成Mg2+-H2O-SO42-或Mg2+-OSO32-结构的机会增多,在复盐区还会形成SO42-离子簇结构。由此判断溶液结构的适应性变化是导致介稳现象的重要原因。进一步的相关分析表明:SO42-的浓度和耶涅克指数Jν1-SO42-峰的峰强度和峰面积存在正相关关系, Mg2+浓度是影响ν1-SO42-峰中四种缔合结构的比例发生变化的主要因素。

关键词: SO42-, 离子缔合结构, 拉曼光谱, 固液相平衡

Abstract:

Stable and metastable solid-liquid equilibria phenomena and complex salt-forming behaviors exist in complex salt-water systems. To realize the relationship between salt-forming behavior and liquid structure, the characteristics of ion association structures of SO42- in Na+, Mg2+//SO42-, Cl-, H2O system and its binary, ternary subsystems were studied by Raman spectroscopy, combined with a Gauss-Lorentz peak fitting program. The spectrum experimental results show that there were two ion association structures of SO42- as non-associated SO42- and SO42- groups in the Na2SO4-H2O system, while in the MgSO4-H2O, MgSO4-MgCl2-H2O, and Na+, Mg2+//SO42-, Cl-, H2O systems, there were also Mg2+-H2O-SO42- and Mg2+-OSO32- structures. Non-associated SO42- was the main structure in the ν1-SO42- band of binary (MgSO4 Na2SO4) and ternary (MgSO4-MgCl2-H2O) subsystems, and with varying SO42- concentration, these four types of SO42- ion association structure varied regularly. Likewise, the ion association structures of SO42- in the Na+, Mg2+//SO42-, Cl-, H2O system changed regularly during both the processes of NaCl crystallization and isothermal evaporation. This was evident when, during the process of decreasing NaCl concentration and increasing MgSO4, the content of non-associated SO42- decreased, the chance of Mg2+-H2O-SO42- and Mg2+-OSO32- structure formation increased, and the SO42- group structure appeared in the astrachanite region. More importantly, the adaptive changes in solution structure during the progress of evaporation can result in the appearance of metastable phenomena. Further linear analysis showed that the concentration and Jänecke index (J) value of SO42- were positively related to the intensity and peak area of the ν1-SO42- band, and the concentration of Mg2+ affected the contents of four ion association structures in the ν1-SO42- band mainly.

Key words: SO42-, Ion association structure, Raman spectroscopy, Solid-liquid phase equilibrium

MSC2000: 

  • O642.5