Research On Bacterial Cellulose Production In Airlift Tank And The Attapulgite Clays/Bacterial Cellulose Composites

Bacterial cellulose is a natural compound with high purity and high degree of polymerization,it will get light in weight and have high porosity with good mechanical properties after being dried.It has been regarding as the material which has great potential in functional material due to these excellent properties.Since the bacterial cellulose was found,one of the most important research direction is improving its production.In this paper,we expanded the scale of culturing by using airlift tank based on the optimization of culture medium and other conditions.According to the characteristics of airlift tank,we picked out three major influence factors by taking Plackett-Burman design:aeration rate,amount of inoculation and tank pressure.To find the best optimum value of these three factors,we used response surface methodology.The result showed when we set aeration rate at 1.68 Nm3h-1,amount of inoculation at 7.3%,tank pressure at 0.057 MPa,we can get about 3.63 g dried bacterial cellulose from each liter of fermentation broth.Attapulgite clay is a natural mineral soil with excellent properties of adsorption,ion exchange,catalysis and so on.Relatively stable chemical properties make it possible that attapulgite clay can be applied to composite materials.In this paper,we tried to combine bacterial cellulose with attapulgite clay through three different methods:static culture,modified static culture and dynamic culture.The effect of three methods was characterized and investigated by SEM,FT-IR,XPS,TGA and XRD.By analyzing the results,we find that dynamic culture can make them combine well,by taking modified static culture method,only a little attapulgite clay can be coated on nanofibers,original static culture can hardly work.Attapulgite clay/bacterial cellulose aerogels obtained by dynamic culture were used to study the adsorption of heavy metal ions Pb2+ in water.We investigated the effect caused by time,temperature and pH on adsorption.When it comes to 60 minutes,the adsorption result can be excellent.At the same time,lower the temperature(0-100℃)and raise pH(5.0-8.0)can improve adsorption rate.The adsorption process of Pb2+accords with the pseudo two order kinetic equation.In terms of thermodynamic adsorption Pb2+ adsorbed by composite aerogels can be fitted by the Freundich model.It means the effect between aerogels and Pb2+ happens on a non-uniform surface with both physical and chemical adsorption.Bacterial cellulose can provide well mechanical support in composite aerogels and simplify recovery process.Heated and eluted by dilute base for five times,the adsorption rate of Pb2+ the material can be maintained above 85%.