Study On Heatable L-lactic Acid Extraction Using Ceramic Membrane

Almost all the technics of lactic acid extraction adopt the method of lacti-calcium crystal at present, it has many working procedure, such as basification, flocculation, acidification, ion exchange, active carbon decolor. The technics was mature, but it need a lot labor intensity, high environment pollution, low product rate. How to advance the product rate, depress the produce cost, preparation high quality L- lactic acid have become the research keystone in the lactic acid industry. In this paper the aim was to use ceramic membrane in heatable L-lactic acid extraction, replace the basification and flocculation in the original technics, and compared the physicochemical index of filtrate by ceramic membrane and flocculation.In this thesis, use 0.01μm aperture ceramic membrane to filtrate the fermentation of L- lactic acid in the lab. And compared the physicochemical index of filtrate between new technics and original technics, test the concentration of glucose, amino acid, protein and iron, and test the variation of heat stability of lactic acid in extraction. Results showed that, the ceramic membrane has well filtration impression on amino acid and protein, but it has little filtration impression on glucose and no filtration impression on iron. After ion exchange, the physicochemical index of filtrate by ceramic membrane and flocculation was same. So the ceramic membrane technics could completely produce heat stability of lactic acid.The conditions during filtering have been studied and the optimum conditions are as follows: a 0.01μm ceramic membrane, initial flux of clean water above 500 L·m-2·h-1 (0.1 MPa), operating pressure 0.2MPa, operating temperature above 70℃. And the stable flux would be above 250 L·m-2·h-1.Serious pollution of the membrane, mainly through plugging the pores, occurred during the primary filtrating stage. The plugging resistance, which controlled the variation of the steady flux, occupied 70~80% of the total resistance.And the reasonable cleaning process was cleaning the membrane orderly with different agents, firstly water, then sodium hydroxide 30 min, subsequently water, nitric acid(1%)15 min and finally water. As a result, the flux of water could come back to about 700 L·m-2·h-1 and the repeatability of the cleaning effects was fine.