Study On The Behavior Of MCl (M = Na, K, Rb, Cs) Solution Under Amide Control

The phase equilibrium of the aqueous solutions containing salts are of increasing importance for the separation and purification processes in chemical engineering. However, selection of solvents is the major problem in a basic extractive crystallization process. The Amides (formamide FA/N-dimethylformamide NMF/ N,N-dimethylformamide DMF/N,N-dimethylacetamide DMA/N,N-diethylformamide DEF)+MCI (M= Na, K, Rb, Cs)+Water ternary systems were studied. The main research and conclusions are as follows:(1) The SLE of the (FA/NMF/DMF/DMA/DEF)+MCl (M= Na, K, Rb, Cs)+ H2O ternary systems were investigated by a semimicro phase equilibrium installation, including:the isothermal solubility, density and refraction index, In general, the temperature, the contents of amides and salts were three main reasons. A combination of the ternary system with two binary systems was uitilizd to explain the tendency intuitively.(2) Aside from the NRTL model, the UNIQUAC model was successfully utilized to evaluate the solubility and showed better agreement. The Jouyban-Acree model can be successfully used to predict the experiment data. A linear fitting formula of temperature was utilized to correlate the density and refraction index. The mean activity coefficients were obtained by the UNIQUAC model. Herein, a combination of the thermodynamics and phase equilibrium through the UNIQUAC model was established.(3) The dynamic solubility measurement system was used to determine the solubility at multiple temperatures. The λh equation, the Apelblat equation, and the Van’t Hoffe equation have been applied. The equilibrium solubility in the binary solvent and the related dissolution thermodynamic analysis are introduced by the Van’t Hoffe equations, aiming at investigating the mechanisms of the electrolyte solution phase equilibrium.(4) As the increasement of alkyl chain, temperature and salt content, the DEF+RbCl/ CsCl+H2O were stratified. The critical temperature of DEF+RbCl+H2O was also determined. The binodal curves and tie lines of DEF+CsCl+H2O were investigated. The (liquid+liquid) region was magnified as the temperature increased. The results indicate that the critical temperature rises with the increasing w1’. The three-parameter equation, Othmer-Tobias equation, and Bancroft equation were succesfully applied to correlated the binodal curves and tie lines.