| Fiber materials play an important role in filtration for their superior performances.Among them,the ultrafine fibers and assemblies has been current research direction for which can significantly improve filtration efficiency and reduce filtration resistance.Bacterial cellulose is a kind of fiber assembly produced by microorganisms with ultrafine network structure,production controllability and biodegradable ability.However,its development and application are restricted because of brittleness and low yield.In this work,biological composition method was used to prepare bacterial cellulose/cellulose diacetate(BC/CDA)fiber composite materials with diacetate spunlace nonwoven(100 g/m~2)and short fibers used as base materials by static co-culture.The main research contents and conclusions are as follows:In this paper,K.xylinus was used to produce BC membranes under static culture conditions.The effects of carbon and nitrogen sources of fermentation medium and cluture temperature on the dry weight of BC membranes were investigated.On this basis,the growth and film formation process of bacterial cellulose were analyzed,and the relations of surface morphology,pore size,gas permeability and filtration performance of BC with culture time were investigated.The experimental results showed that the optimized fermentation conditions were:mannose concentration 50 g/L yeast extract concentration 16 g/L,cultivation temperature 30°C.The morphological characterization showed that BC membrane was assembled by subtle reticulation structure layer by layer,with pore size of 0.05~6?m and single fiber diameter of 90~300 nm.As the culture time increased,fibers gradually accumulated,average pore size decreased,the porosity decreased and pore size tended to be uniform finally,and the filtration efficiency and resistance of BC membrane increased.The BC membranes with culture time of 3 d,5 d,7 d on the particle size?1.0?m of filtration efficiency were over 99%,filtration efficiency on the particle size?0.3?m and resistance of BC membrane with 7 d culture time were respectively 98.82%and 780 Pa.Based on the research of BC membrane,the microfiber membrane was self-grown on the surface of diacetate spunlace nonwoven,and the structure,mechanics,filtration properties of composites prepared by different culture time were studied.The results showed that the diacetate nonwoven can be used as flexible carrier for bacterial cellulose.The molecular structure indicated that they were connected by hydrogen bonding.The morphological characterization showed that BC was coated on the surface of diacetate fiber and filled with openness between fibers,resulting in thick and fine fiber structure.The breaking strength and average pore size of composites under 5 d culture time were 13.23 MPa and 22.4?m,132%higher and 75%lower respectively than CDA spunlace nonwoven.The filtration efficiency on the particle size?0.3?m and resistance of diacetate nonwoven were respectively 24.29%and16 Pa.As compounding time was 2 d,3 d and 5 d,they respectively were 42.46% and 92 Pa,77.16% and 146 Pa,90.34%and 407 Pa.Finally,the diacetate short fiber was reinforced by fiber entanglement between BC and diacetate fiber under static co-culture,therefore BC/CDA composite membrane was prepared.The composite structure and entanglement principle were explored,and the effects of length,gram weight of diacetate fiber and co-culture time on gas permeability,mechanical properties,pore structure and filtration quality were investigated.The results showed that the surface and cross section morphology of composite films were continuous structures with coarse-fine fiber distribution.As co-culture time was 3 d,the length and weight of diacetate were 40 mm and 3 g,the filtration efficiency on the particle size?0.3?m and?2.0?m respectively 89.37%and 98.65%,and filtration resistance was 350 Pa.As co-culture time was 2 d,the length and weight of diacetate were 40 mm and 2 g,the filtration efficiency on the particle size?0.3?m and?2.0?m respectively 84.14%and 98.63%,and filtration resistance was 102 Pa,... |
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