The Phase Equilibrium Study Of Alkali Metal Bromide In Various Mixed Solvents Of Amide And Water

Adding organic solvent into the aqueous solution of the salts can usually reduce the solubility of salt. It is often used for separation and purification of salts in traditional field of phase chemistry. As a continuous work of our research group, in this paper, alkali metal bromide+ amide+ water systems was selected, the solubility, density and refractive index of the saturated solution were determined. The result in this work could provide basic thermodynamic data in solution chemistry, which is expected to be applied into the chemistry, engineering, and also scientific research.1. The choice of the amide:according to the structure and the properties of the amide, we select the formamide(FA), N-dimethylformamide(NMF), N,N-dimethyl-formamide(DMF), N-methylacetamide(NMA), N,N-dimethylacetamide(DMA) and N,N-diethylformamide(DEF) as the organic solvent in this work.2. The solubility, density and refraction index of the MBr (M=Na, K, Rb, Cs)+ amide+H2O ternary systems were systematically investigated at (283.15,298.15, 308.15,313.15,318.15) K. The experimental results show that all the systems are simple solid-liquid equilibrium. The solubility of alkalimetal bromides in the mixture increased with the increasing of the temperature and decreased with the increasing of amides. The density of ternary systems showed similar trend as that of the solubility. However, the variation of refractive index is much different from that of the solubility and density. Moreover, the structure effect of amides on the properties was discussed.3. The solubility, density and refraction index were correlated by a four-parameter empirical equation. Moreover, NRTL model and UNIQUAC model were fit the solubility. The mean activity coefficients of the ternary systems were successfully obtained by the UNIQUAC model at the experimental temperature.4. The solubility at multiple temperatures was measured from 283.15 K to 333.15K. The ?h equation and Apelblat equation were used to fit the experimental solubility data. The related thermodynamic parameters, such as enthalpy and entropy were calculated and used to explain the dissolvation process thermodynamically.