| Erythromycin is an important macrolide antibiotic, which has a huge demand in market. It is mainly produced by fermentation rather than chemical synthesis. As a result, extraction of erythromycin from broth plays an important role in yield and quality. At present, the methods to extract erythromycin include solvent extraction, resin adsorption, ion exchange, membrane separation and so on. However, there are obvious drawbacks in these processes. In this paper, based on knowledge of complex extraction, operating conditions of complex extraction was investigated. Besides, stripping dispersion and supported liquid membrane was combined to extract erythromycin. In the research, reaction kinetics of complex extraction was researched and the model of overall mass transfer resistance was established. The research was aimed at providing guidance for the applying complex extraction and membrane technology to erythromycin.Based on the mechanism of complex extraction, complex extraction system suitable for erythromycin was selected. The composition of complex was ascertained by slope method. Factors affecting distribution coefficient such as concentration of extractant, pH of feed solution, phase ratio temperature and so on were analyzed. What’s more, the effects of phase ratio and pH of stripping solution on stripping rate were also taken into consideration. The results showed that the suitable operation conditions were as follows: octanol and cyclohexane formed complex extraction system and their volume ratio was 1:1, the pH of feed solution was from 10 to 11, phase ratio was 1:2, the suitable temperature was 298 K, the stripping solution was sodium acetate-acetic acid buffer solution, whose pH was from 4 to 5 and the ratio between stripping and organic phase was 1:1. The complex extraction was an endothermic reaction. Erythromycin and octanol formed complex through a intermolecular hydrogen bond. The extraction rate was still more than 90% after the regeneration of extractant to be recycled 6 times.According to the result of bulk membrane, supported liquid membrane with stripping dispersion was adopted. Factors affecting extraction rate such as membrane dipping time, pH of feed solution, stirring rate, transmembrane pressure, volume rate and so on were investigated. The results showed that the extraction rate could reach 92.9% at optimum parameters. The suitable operation conditions were as follows: membrane dipping time was 2h, pH of feed solution was 11, stirring rate was 350 rpm, transmembrane pressure was 25 kPa and volume rate of tube and shell was separately 500ml/min and 400ml/min. The kinetics of erythromycin complex extraction could be well described by second order kinetics. The stability of liquid membrane was improved by stripping dispersion.The model of overall mass transfer resistance was established to analyze mass transfer in liquid membrane extraction process and the accuracy of model was verified through experimental data. The effects of operating parameters on overall mass transfer were studied. The results showed that model results were in good agreement with experimental data, mass transfer resistance mainly existed in tube side and liquid membrane and the effects of operating parameters on extraction rate could be explained through the analysis of operating parameters’ effects on overall mass transfer, which could provide guidance for mass transfer optimization.Erythromycin can be extracted by complex extraction with low water extraction. It is effective to extract erythromycin through hollow fiber supported liquid membrane with stripping dispersion and the established model can be used to analyze the mass transfer process. |
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