【摘要】 以MgSO₄、ZnSO₄、CdSO₄和Li₂SO₄-H₂SO₄溶液为例,描述了熔融毛细硅管中硫酸盐-水体系的高温液-液相分离现象,即均一的溶液相分离为富集硫酸盐和贫硫酸盐的两个液相。相行为观测和原位拉曼光谱分析表明,金属离子和SO₄^2–之间复杂的络合作用是导致液-液相分离发生的主要原因。首先,液-液相分离的发生温度在低浓度溶液中随浓度升高而降低,而在高浓度溶液中则随浓度升高而升高,并呈现典型的临界相转变现象,而临界相转变现象是聚合物溶液的典型宏观特征;其次,ν₁(SO₄^2–)光谱随温度升高逐渐变宽,且不对称性加强,表明离子络合作用随温度升高而加强。以MgSO₄水/重水溶液为例,随着温度升高,先后在溶液相中检出"自由"SO₄^2–(⁹80 cm^–1)、接触离子对MgSO₄0(⁹92 cm^–1)和三离子离子对Mg₂SO₄²⁺(¹003 cm^–1)的信号,而相分离发生后在富集硫酸盐的液相中检测到位于¹020 cm^–1新的ν₁(SO₄^2–)组分,其代表了更为复杂的Mg²⁺-SO₄^2–络合物。关于Mg²⁺-SO₄^2–络合作用和硫酸盐-水体系液-液相分离的研究,有助于深化白云岩成因和海底热液系统中SO₄^2–在多孔岩石中迁移及还原为S2–的研究。受溶液组分影响,硫酸盐溶液呈现较为宽广的液-液相分离发生温度范围（150³60℃）,对特定组分的硫酸盐溶液来讲,液-液相分离发生温度可重复性强,能够作为热台温度校准的标样。结合熔融毛细硅管合成流体包裹体技术,提出了一种新的热台温度校准方法。更多还原

【Abstract】 Taking aqueous MgSO₄, ZnSO₄, CdSO₄ and Li₂SO₄-H₂SO₄ solutions as examples, we described an unusual liquid-liquid phase separation in aqueous sulfate solutions contained in fused silica capillary tubes; the aqueous solution was separated into a sulfate-rich liquid phase and a sulfate-depleted liquid phase at elevated temperatures. In situ optical and Raman spectroscopic observations revealed that the liquid-liquid phase separation was triggered by the strong and complex ion association between cations and sulfate. The major evidences include（1） the liquid-liquid phase separation temperature decreased with increasing sulfate concentrations in dilute solutions but increased with increasing sulfate concentrations in concentrated solutions, showing a typical critical phase transition phenomenon. The critical phase transition phenomenon was considered to be a macro-scale property of polymer solutions; and（2） the ν₁(SO₄^2–) spectra shifted to higher wavenumbers and became broader with increasing temperature, indicating increasing ion association between cations and sulfate. For the MgSO₄-H₂O/D₂O system, with increasing temperature, the ν₁(SO₄^2–) components of "free" sulfate(⁹80 cm^–1), MgSO₄0(⁹92 cm^–1) and Mg₂SO₄²⁺(¹003 cm^–1) were successively identified in the aqueous phase. After the liquid-liquid phase separation, a new ν₁(SO₄^2–) component at ¹020 cm^–1 was detected in the sulfate-rich liquid phase. This ν₁(SO₄^2–) component should be ascribed to more complex Mg²⁺-SO₄^2– associations than Mg₂SO₄²⁺. The results can help to better study the origin of dolomite and the transport and reduction of sulfate in porous rocks of submarine hydrothermal systems. The liquid-liquid phase separation temperature was mainly affected by the composition of the sulfate solutions. Current studies show that sulfate solutions exhibit a wide range of liquid-liquid phase separation temperatures（e.g., 150³60 ℃）. The liquid-liquid phase separation temperature was relatively stable and could be highly reproduced for a given sulfate solution. Then, the liquid-liquid phase separation temperature can be used as a reference to calibrate the temperature of a heating stage. Using a fused silica capillary tube to construct optical cells containing various sulfate solutions, we have proposed a new method for calibrating the temperature of a heating stage.更多还原