Preparation And Performance Of Electrospun Polymer Ultrafine Fibrous Membranes Containing Quinoxaline Rings

With the rapid development of the alumina industry,the discharge of red mud,the solid waste produced during the production of alumina,is also increasing.Because red mud is extremely harmful to the environment,the research on effective utilization of red mud has received extensive attention in recent years.However,the high alkalinity of red mud slurry has become a technical problem for the comprehensive utilization of red mud.Therefore,the filtration membrane material with high-temperature and alkali-hydrolysis resistance,flexibility,and porosity has become the key to effective utilization of red mud.In this paper,in response to the application requirements of the comprehensive utilization of red mud for high-performance filter membrane materials,quinoxaline rings are introduced into the structure of polymer molecular,and a series of advanced polymer ultrafine fibrous membranes containing quinoxaline rings are prepared by electrospinning,and the relationship between their structure and performance was systematically studied.First,a type of poly(ether-quinoxaline)(PEQ)resin containing ether bond and quinoxaline ring was synthesized according to the literature,and PEQ ultrafine fibrous membrane was prepared by electrospinning.The microstructure,high-temperature,and alkali-hydrolysis resistance of the PEQ membrane were systematically studied.PEQ electrospun membrane showed flexible porous structure,and exhibited good thermal stability(glass transition temperature T_gis 189.9?)and alkali-hydrolysis resistance;Secondly,in order to further improve the thermal stability of the fibrous membrane,a series of poly(imide-phenylquinoxaline)(PIPQ)resins were synthesized by introducing the phenylquinoxaline structure into the polyimide through molecular design.And PIPQ ultrafine fibrous membranes were prepared by electrospinning,and their microstructure,thermal stability,and alkali-hydrolysis resistance were systematically studied.The results showed that PIPQ membranes have a flexible porous structure and good alkali-hydrolysis resistance.In addition,the thermal stability of PIPQ membranes had been greatly improved(T_gis higher than 250?,and temperature at 5%weight loss is more than 500?)compared with PEQ fibrous membranes;Finally,a series of standard PPQ resins were synthesized using several aromatic tetraketone and tetraamine monomers,including PPQ-?_a(ODB-DAB),PPQ-?_b(ODB-TADPE),PPQ-?_a(DBOB-DAB),and PPQ-?_b(DBOB-TADPE),and PPQ ultrafine fibrous membranes were prepared by electrospinning.The effects of quinoxaline rings on the microstructure,thermal stability,and alkali-hydrolysis resistance of PPQ membranes were systematically investigated.Then,the experimental study on the filtration and separation of red mud samples was carried out.As a result,PPQ-?_bfibrous membrane showed the best comprehensive performance.The red mud was separated with high efficiency and could be easily separated from the membrane.