| 6-aminopenicillanic acid(6-APA) is an important intermediate of semi-synthetic penicillins synthesis, which is widely used and has a broad market. The main industrial production methods for 6-APA is enzymatic synthesis, which has a mild reaction conditions, a higher conversion rate as well as a less pollution.The crystallization process is the main method for the separation and purification of 6-APA, while the mother solution still contains a small amount of 6-APA. The direct emission of the solution not only resulted in a waste of resources, but also improved the expenses of the environmental protection. In this paper, the application of liquid membrane technology was investigated to deal with the low concentration of 6-APA solution, aiming at a more efficient recovery of 6-APA.First, the mass transfer process of complex extraction was studied through the thick membrane complex extraction experiment for the low concentration of 6-APA solution. The influence factors were optimized, besides the thick film complex extraction kinetics was studied. The results showed that the best pH of feed phase for the extraction is 6.2, the optimal concentration of TOMAC in the mixed extraction solvent is 0.70 mol/L, the suitable volume ratio is for the mixed extraction solvent to feed phase and stripping phase is 0.8: 1: 1, the optimum pH of stripping phase is about 1.5, and the best concentration of Cl- in stripping phase in is 1mol/L.Second, the extraction technique of HFSLM-SD was investigated to deal with low concentration 6-APA process solution. The influence factors of HFSLM-SD were optimized. The results showed that the best stirring rate of the stripping phase is 300 rpm, the best tube side flow is 150 ml / min, the best shell side flow is 125 ml / min and the most suitable transmembrane pressure is 6psi. Besides, the stability of liquid membrane was studied through four continuous experiments, and it illustrated the process has a good liquid film stability and continuity.Finally,some reasonable assumptions were raised through the mass transfer analysis of the HFSLM-SD process of 6-APA, and the overall mass transfer coefficient model was established based on some the assumptions. Then got the results that the Individual mass transfer coefficient of the feed solution(ka), membrane(km) and the stripping solution(ks) were respectively 6.99×10-6m/s, 1.5×10-6m/s, 6.681×10-5m/s, and the total mass transfer coefficient K was 3.891×10-6m/s. It proved that the resistance of hollow fiber membrane complex extraction process of 6-APA existed mainly in the transmembrane mass transfer process. By comparing the concentration changes of 6-APA in feed phase, the accuracy of the model was verified.The liquid film technology coupled complex extraction was applied to deal with low concentration 6-APA in the experimental research, and achieved certain results, which I think may be provided for other scholars in low concentration of 6-APA treatment process research and application of liquid film technology. |
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