Study On The Producing Of Tea Polyphenols By Precipitation-adsorption Process

In this paper, ultrafiltration process of tea extract, decaffeine process by precipitation and adsorption process with XDA-1 macroporus adsorbent resins are studied. Through experimental work in detail, a new technolygy for producing TP(Tea Polyphenols) using precipitation -adsorption united process is developed, it proved to be simple, feasible and nontoxic.For the complex biochemical system of extracted liquid of tea leaves, ANDEUF-01 ultrafiltration pilot unit is used to refine it. The resistance -in-serials model are applied to the correlation of flux of ultrafiltration with operation parameters such as operation pressure , feed concentration and operation velocity. Also, parameters in the model are correlated. Results show that the calculating data go well with experimental ones in the whole operation range of ultrafiltration.Target on the decaffeine rate, factors which affect precipitation process are discussed, for example, the mass of precipitating agent, precipitating temperature, pH of the precipitating solution, centrifuge rate, agitating rate and time. Then the optimum conditions are obtained, this new decaffeine method can remove no less than 40% percent caffeine(caf) from the feed. Also, it can avoid using toxic organic solvent and raising the safety of production process.Through experiments of adsorption, XDA-1 resin is determined for the separation of TP and caffeine. Adsorption model for TP mass transfer with XDA-1 resin is also set up , the height of mass transfer zone and total mass transfer coefficient in different operation conditions are caculated, whichcan provide important reference to the design of adsorber.At the same time, modified resins are studied. Composite resins of XDA coated with PA membrane are prepared and apply to the separation of TP and caffeine from tea extract. The effects of such factors as proportion of casting solution, amounts of the supported PA and additive are studied in detail, thus got the optimum compound technology. These composite resins have good adsorption and desorption performances.Cao Li (Chemical Engineering) Directed by Professor Zhang Xiaolin Professor Kang Maode...