| This article optimized supercritical fluid extraction process conditions of paeoniflorin by using response surface methodolog at first, and then established the mathematical model of supercritical fluid extraction, finally summarized mass transfer process of supercritical CO2 extraction containing entrainer.On the basis of one-factor tests and the Box-Behnken center-united experimental design principle, the method of response surface analysis with 3 factors and 3 levels was adopted. A second order quadratic equation for supercritical fluid extraction of paeoniflorin was built. Response surface and contour were graphed with the extraction rate of paeoniflorin as the response value. Based on the analysis of the response surface plots and their corresponding contour plots, the effects of extraction pressure, extraction temperature, and methanol concentration were explored. By using the new method discussed above, the optimum extraction condition was obtained as follows: extraction pressure 18.9MPa, extraction temperature 59.9℃, methanol concentration 68.5%, the flow rate of cosolvent mehtanol 0.4mL·min-1, and extraction time 60min. Under the optimized condition, extraction rate of paeoniflorin on theoretical value was 7.85mg·g-1. And the experimental extraction rate was 7.48mg·g-1 with relative error 4.71%, compared with the predictive value.Through the analysis of response surface and contour lines, we can obtain the conclusion that the interaction between methanol concentration and extraction pressure or methanol concentration and extraction temperature is obvious, while is not obvious between pressure and temperature, indicating that methanol concentration has very significant impact on the extraction process. Compared with the soxhlet extraction and ultrasonic extraction, we can see that supercritical fluid extraction is an effective, high extraction rate and shorten time extraction method.According to fractional mass transfer mechanism on the basis of response surface analysis, established a mathematical model of supercritical fluid extraction about paeoniflorin. Through simulation obtained model parameters such as the solute concentration of difficult extraction xk=5.243×10-4kg·kg-1, the mass transfercoefficient of the outer surface of sample particles Kf=8.598×10-8m·s-1, and the mass transfer coefficient of internal surface of sample particles Ks=7.811×10-10m·s-1. Through model checking, this model can reflect the process of extraction, it can be use as a reference for further optimizing the model parameters and technology research.
|
PDF Full Text Request