光散射学报, 2018, 30 (3): 251, 网络出版: 2018-10-06  

拉曼光谱法研究硝酸钙溶液的离子缔合

A Study on Ion Association of Calcium Nitrate Solution by Raman Spectroscopy
作者单位
青海师范大学化学与化工学院,西宁 810000
摘要
采用显微拉曼光谱技术研究水盐摩尔比(WSR)为4.0~160.0的硝酸钙溶液中的缔合物种分布情况及物种间的转换关系。研究表明当WSR从160.0降低到4.0时溶液中硝酸根离子的对称伸缩振动频率(v1-NO-3)从1048.3 cm-1蓝移至1052.9 cm-1,半峰高宽(FWHM)从7.6 cm-1增大到15.3 cm-1。采用组分分析方法对v1-NO-3峰分析得出,WSR≥16.3时为第一浓度区域,主要物种为溶剂共享离子对(shared ion pair,SIP),次要物种为接触离子对(contact ion pair,CIP)和自由水合离子(free hydrated ion,Free ion),且WSR=16.3时,SIP和CIP的量相等;当8.4≤WSR<16.3时为第二浓度区域,主要物种为CIP,复杂离子簇(complex ion cluster,Complex)的量快速增加;当WSR<8.4时为第三浓度区域,主要物种为Complex,CIP和SIP的量快速下降;WSR<4时,由曲线拟合得出溶液中CIP和SIP均逐渐转换为Complex,Complex的量趋近于1。硝酸钙溶液过饱和度越高,结晶越困难,溶液的结构构型与四水硝酸钙熔融盐结构相似,即推测出过饱和硝酸钙溶液(1≤WSR≤4,没有新相生成)的结构构型是单齿六配位[(H2O)m(HO3)nCa(NO3)Ca(NO3)p(H2O)q](m+n=p+q=5)。
Abstract
Association species distribution and the transformation relationship among species in the calcium nitrate solution with water and salt molar ratio(WSR) of 4.0 ~ 160.0 were studied by mcroscopic Raman spectroscopy.The results showed that the symmetric stretching vibration frequency(v1-NO-3) of nitrate ions in solution was shifted from 1048.3 cm-1 to 1052.9 cm-1,and FWHM(the full width at half-maximum) was changed from 7.6 cm-1 to 15.3 cm-1 with the WSR decreased from 160.0 to 4.0 The v1-NO- peak was studied by the component analysis method.It was found that WSR≥16.3 was the first concentration region,the main species was shared ion pair(SIP),the second species was contact ion pair(CIP) and free hydrated ion(free ion),there were the same amount of SIP and CIP when WSR=16.3;it was the second concentration region when 8.4≤WSR<16.3,The main species was CIP,the amount of complex structure(Complex) was increased;it was the third concentration region when WSR<8.4,The main species was Complex,the amounts of CIP and SIP was decreased rapidly;When WSR <4,CIP and SIP were transformed rapidly into Complex,the amount of Complex approached 1.The higher the supersaturation of calcium nitrate solution is,the more difficult the crystallization be.The structure of this solution was similar to molten salt of calcium nitrate tetrahydrate,the structural configuration of the calcium nitrate solution(1≤WSR≤4,new phase is not generated)might be monodentate hexacoordination[(H2O)m(HO3)nCa(NO3)Ca(NO3)p(H2O)q](m+n=p+q=5).

王琼瑶, 张文华, 赵继颖, 杨林. 拉曼光谱法研究硝酸钙溶液的离子缔合[J]. 光散射学报, 2018, 30(3): 251. WANG Qiongyao, ZHANG Wenhua, ZHAO Jiying, YANG Lin. A Study on Ion Association of Calcium Nitrate Solution by Raman Spectroscopy[J]. The Journal of Light Scattering, 2018, 30(3): 251.

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