Study On Preparation Of Ultrafiltration Membrane By Cellulose Dissolution And Regeneration

Ultrafiltration is a highly efficient separation method in membrane separation technology.Ultrafiltration membrane materials are often derived from petrochemical derived polymers.With the increasing depletion of petroleum resources and the aggravation of environmental pollution caused by petrochemical products,it is urgent to seek petroleum substitutes and develop new materials.The use of abundant,huge,renewable and biodegradable biomass raw materials and the development of ultrafiltration membrane materials by physical and chemical methods have attracted more and more attention.Cellulose is the most abundant renewable and biodegradable environment-friendly material on earth.Cellulose membrane products based on cellulose have been widely used in various fields such as industrial production and daily life.Among them,alkali urea system is different from the traditional preparation process of regenerated cellulose membrane.It has the advantages of simple cellulose dissolution steps,no pollution and low cost.It is one of the green preparation ways of regenerated cellulose membrane.However,the dissolution efficiency of cellulose in this system is very low,which also affects the strength and cost of regenerated membrane and limits its industrial application.In this paper,cotton linter was used as the main raw material to improve the dissolution efficiency of Na OH / urea / aqueous solution system through ultrasonic pretreatment.The regenerated cellulose membrane was prepared by template phase conversion method and suction filtration method in order to obtain high-throughput ultrafiltration membrane.Firstly,the technological conditions of ultrasonic assisted cotton fiber dissolution were studied,and the scheme of maximum dissolution efficiency of cotton pulp fiber was obtained.Secondly,the effects of the type,temperature and concentration of precipitation solution and coagulation bath on the average pore size,pure water flux,porosity and molecular retention of the membrane were studied.Finally,the characteristics of the film were analyzed and characterized by scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD).Under the optimum dissolving conditions of alkali urea system,the maximum dissolving rate of cotton linter can reach 48%,after ultrasonic pretreatment,the maximum solubility can reach 64.8%,and the dissolving rate can be increased by 16.8%.The ultrafiltration membrane with minimum pore diameter of 58 nm,average pore diameter of 360.9 nm,porosity of 19.5% and pure water flux of 793.2 LMH can be prepared by suction filtration.The regenerated cellulose membrane with average pore diameter of 152 nm and pure water flux of 146.8 LMH can be prepared by template method.Compared with the suction filtration method,the cellulose membrane prepared by the template method has smaller average pore size and more pores,but the surface morphology and dimensional stability of the membrane are poor.The results show that cellulose films with different microstructure can be prepared by adjusting the type,concentration and temperature of coagulation bath,which can meet the needs of different scenes.