Study On Liquid-liquid Phase Equilibrium Of Water/mixture Solvent System And Applications Of Extraction And Separation

Water/mixture solvent system is a novel extraction and separation system, which can be applied to the fields of biological product separation, functional ingredient extraction from herbal medicine and natural products, sample enrichment and separation in analytical chemistry, solvent separation and environmental protection, etc. It is an extraction and separation system of potential industrial applications.This dissertation studies on the liquid-liquid equilibrium (LLE) of water/ ethanol/ isobutanol system in detail, and investigated the partition coefficients for dipotassium glycyrrhizinat in the system. The main contents were following:1) The liquid-liquid equilibrium data of water/isobutanol binary system were determined according to the turbidity analysis method. The binary interactive parameters of NRTL equation were regressed and correlated with genetic algorithm. The results show that the correlation precision is high, temperature affects the model parameter to some extent. The correlate precision is the highest when considering the linear relationship between model parameters and temperature. Meanwhile the correlation precision can be satisfied while only the constants non-related to temperature are used.The solubility and liquid-liquid equilibrium data of water/ethanol/isobutanol ternary system were measured with turbidity-density analysis method under 30℃ and 35℃. The results indicate that within 30—35 ℃ the moler ratio range between the two phases is: water 0.44~0.99, ethanol 0~0.105, isobutanol 0~0.55. In some region the system can form a mild extraction environment with high water content and can be used to the separation and purification of material with biological activity.NRTL model and Othmer-Tobias/Bancroft equation were used for correction and prediction of the liquid-liquid equilibria of water/ethanol/isobutanol. The results indicated that both binary interactive parameters of water/isobutanol system from this work and the parameters of water/ethanol from literature can be used to precdict the liquid-liquid equilibria of water/ethanol/isobutanol. But the parameters of ethanol/isobutanol from the literature were not appropriate for the prediction. Furthermore, the model parameters from 30℃ can can be used to predict the liquid-liquid equilibria under 35 ℃ . The model parameters of water/isobutanol are independent on the temperatures, so constant parameters irrelative to temperature can meet prediction accuracy. Othmer-Tobias/Bancroft equation was also used to fit the liquid-liquid data of water/ethanol/isobutanol system, but it didn't possess the performance of predicting the liquid-liquid equilibria.The partition coefficients of dipotassium glycyrrhizinat were determined in the liquid-liquid two-phase system of water/ethanol/isobutanol and corrected by experiential equation. Some factors effecting on partition coefficients was investigated, and the extraction product is characterized with Infrared Analysis and TG. The results indicate that the nearer the start point close to the critical point, the higher the partition coefficient of dipotassium glycyrrhizinat elevated to. The temperature affects partition of dipotassium glycyrrhizinat but the effect is minor. On the same time pH has major impact on the partition of dipotassium glycyrrhizinat. The coefficient is eight times higher when pH reaches 2. The improved Diamond-Hsu model can be used to correlate the partition coefficient of dipotassium glycyrrhizinat in the system of water/ethanol/isobutanol. The result of Infrared and TG analysis indicate the extraction product has the same characteristic features with dipotassium glycyrrhizinat.