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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Raman Spectroscopic Observations of the Ion Association between Mg2+ and SO42- in MgSO4-Saturated Droplets at Temperatures of = 380 degrees C
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Raman Spectroscopic Observations of the Ion Association between Mg2+ and SO42- in MgSO4-Saturated Droplets at Temperatures of = 380 degrees C

机译：在<= 380摄氏度的温度下MgSO4饱和液滴中Mg2 +和SO42-之间的离子缔合的拉曼光谱观察

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摘要

Liquid-liquid phase separation was observed in aqueous MgSO4 solutions with excess H2SO4 at elevated temperatures; the aqueous MgSO4/H2SO4 solutions separated into MgSO4-rich droplets (fluid F1) and a MgSO4-poor phase (fluid F2) during heating. The phase separation temperature increases with SO42-/Mg2+ ratio at a constant MgSO4 concentration. At a MgSO4/H2SO4 ratio of 5, the liquid-liquid phase separation temperature decreases with an increase in MgSO4 concentration up to similar to 1.0 mol/kg and then increases at higher concentrations, showing a typical macroscale property of polymer solutions with a lower critical solution temperature (LCST) of similar to 271.4 degrees C. In situ Raman spectroscopic analyses show that the MgSO4 concentration in fluid Fl increases with an increase in temperature, whereas that in fluid F2 decreases with an increase in temperature. In addition, HSO4-, which does not readily form complexes with Mg2+, tends to accumulate in fluid F2. Analyses of the v(1)(SO42-) bands confirmed the presence of four-sulfate species of unassociated SO42- (similar to 980 cm(-1)), contact ion pairs (CIPs; similar to 995 cm(-1), and triple ion pairs (TIPs; similar to 1005 cm(-1)) in aqueous solution, and more complex ion pair chain structure (similar to 1020 cm-1) in fluid Fl. Comparison of the sulfate species in fluids Fl and F2 at 280 degrees C suggests that SO42- in fluid F2 is less associated with Mg2+. On the basis of in situ visual and Raman spectroscopic observations, we suggest that the formation of the complex Mg2+-SO42- ion association might be responsible for the liquid-liquid phase separation. In addition, Raman spectroscopic analyses of the OH stretching bands indicate that the hydrogen bonding in fluid F1 is stronger than that in fluid F2, which might be ascribed to the increasing probability of collision of H2O with Mg2+ and SO42- in fluid F1.
机译：在升高的温度下，在含有过量H2SO4的MgSO4水溶液中观察到液-液相分离。在加热过程中，MgSO4 / H2SO4水溶液分离为富含MgSO4的液滴（流体F1）和缺少MgSO4的相（流体F2）。在恒定的MgSO4浓度下，相分离温度随SO42- / Mg2 +的比例而增加。在MgSO4 / H2SO4比率为5时，液相-液相分离温度随着MgSO4浓度的增加而降低，直至接近1.0 mol / kg，然后在较高的浓度下增加，这显示出临界值较低的聚合物溶液的典型宏观性质。溶液温度（LCST）接近271.4摄氏度。原位拉曼光谱分析表明，流体F1中的MgSO4浓度随温度升高而增加，而流体F2中的MgSO4浓度随温度升高而降低。此外，不易与Mg2 +形成络合物的HSO4-往往会积聚在流体F2中。对v（1）（SO42-）谱带的分析证实存在未结合的SO42-（类似于980 cm（-1）），接触离子对（CIPs;类似于995 cm（-1），和三重离子对（TIPs;类似于1005 cm（-1）），以及流体Fl中更复杂的离子对链结构（类似于1020 cm-1）。比较流体Fl和F2中的硫酸盐种类280℃表明流体F2中的SO42-与Mg2 +的联系较少，根据原位视觉和拉曼光谱观察，我们建议形成复杂的Mg2 + -SO42-离子缔合可能是液-液此外，OH伸缩带的拉曼光谱分析表明，流体F1中的氢键比流体F2中的氢键强，这可能是由于H2O与流体F1中的Mg2 +和SO42-碰撞的可能性增加。 。

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