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L-lactic acid as a green platform chemicals, has great application prospects. Study and solve the key technology in the separation of L-lactic acid, is of great significance for strengthening renewable comprehensive utilization of resources, and enhance environmental protection. In view of the membrane separation technology has no phase change, low energy consumption, does not destroy the biological activity and a simple feature, paper, film Combined Process of L-lactic acid fermentation broth. For the membrane separation process in the membrane flux attenuation and membrane fouling, the study of the L-lactic acid fermentation liquor flocculation - sedimentation decolorization pretreatment process, optimization of the operation of ultrafiltration and reverse osmosis membrane process conditions, the establishment of the membrane pass The mathematical model of the amount of the operating process parameters, explored the mechanism of membrane fouling, and establishes the film's best cleaning conditions. (1) by a single factor and orthogonal test, optimize flocculation - sedimentation process: the amount of Ca 4.5 ‰ hydroxide established L-lactic acid fermentation broth, add the amount of 7.5 ‰ of activated carbon, the amount of magnesium sulfate add 3 ‰ flocculation temperature of 70 ° C. , flocculation time 45 min. Under these conditions, the bacteria removal rate was 99.48%, protein removal rate was 84.42%, 39.80% removal of residual sugar, the loss rate of 1.88% lactic acid. (2) Comparative bleaching effect of the powder and granular activated carbon, preferably a powdered activated carbon as a bleaching agent. Ternary quadratic orthogonal rotation combination acidolysis decoloration powdered activated carbon, on the basis of single factor to optimize the design of activated carbon decolorization process and the establishment of a mathematical model, the optimum conditions are as follows: 0.318% of the amount of active carbon, bleaching temperature. 43.18 ℃, the bleaching time 18.83 min, decolorizing total efficiency of 80.23%; obtained by frequency analysis having a probability of 95% to ensure the decolorization overall efficiency greater than 70% of the range of parameters, i.e. 0.395-0.695% of the added amount of activated carbon, bleaching temperature 56.88-69.84 ° C decolorization time 15.68-22.58min. Established by verifying the known mathematical model. (3) by a single factor and orthogonal test, optimize established the best ultrafiltration process conditions: operation pressure 0.9MPa, feed the concentration of 50 g / L, the operating temperature of 35 ° C. At this time, the membrane flux to 7.913 L · m-2 h-1, protein retention rate of 98.93%, lactic transmittance of 97.52%; through the single factor experiment, to determine reverse osmosis process conditions: operating pressure of 1.0 MPa, into feed concentration of 40 g / L, the operating temperature of 30 ° C. (4) The the membrane flux attenuation empirical formula better simulation of ultrafiltration and reverse osmosis process membrane flux decay with time quantitative relationship; resistance superposition model and preferential adsorption - pores flow model for the prototype to explore ultra mathematical model of the process of filtration and reverse osmosis membrane flux and operation of process parameters, as follows: reverse osmosis process: J = 42.136 exp (-0.1455, P-0.0305 Cf) · [the P-0.0043RCf] verify the results show that the , they can be better described ultrafiltration and reverse osmosis process. (5) ultrafiltration membrane and reverse osmosis membrane cleaning conditions Univariate: EDTA · 2Na concentration of 0.75%, 0.75%, sodium polyphosphate concentration cleaning time 50 min, the pH of the cleaning agent 11, the cleaning temperature 35 ° C.
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