Preparation Of Polyacrylonitrile-Based High-Performance Fiber Membrane And Its Application In Water Treatment

Due to its high separation purity,low process cost,simple process conditions,low pollution discharge and other characteristics,membrane separation technology can effectively solve the water pollution and biological enrichment of heavy metal ions caused by wastewater discharge from electroplating,printing and dyeing,mineral resources and other industries.This study first used hydrophilic pore forming agents to regulate the microporous structure and performance of flat membrane.Then,using melt blown cloth as the substrate,a composite membrane was prepared by immersion rolling method,and amine oximation modification was carried out to construct a pre process for high concentration metal ion wastewater treatment.Then,an amine oximation polyacrylonitrile hollow fiber membrane and its column membrane components were prepared to construct a post process for trace metal ion wastewater treatment,achieving a stepwise filtration effect,Finally,pilot studies were conducted on columnar membrane modules.The main tasks include:（1）Using hydrophilic pore forming agents such as polyvinyl pyrrolidone（PVP）and polyethylene glycol（PEG）to regulate the microporous structure of polyacrylonitrile and polyurethane（PAN/PU）flat membrane,the effects of different proportions of pore forming agents on the water flux and retention rate of the flat membrane were investigated.Through scanning electron microscopy analysis,pure water flux testing,and viscosity testing,it was found that when the content of pore forming agent PVP was 6%and PEG was 4%,the microporous structure of the flat membrane was the best,forming obvious finger like through-holes,The water flux reaches 213 L·m^-2·h^-1;After amine oximation modification,the flux of the flat film coating layer significantly decreases and the mechanical properties weaken.In order to improve the pollution resistance of the flat film,the polyacrylonitrile/polyurethane（PAN/PU）melt blown composite film was prepared by immersion coating method,and the amine oximation polyacrylonitrile/polyurethane（AOPAN/PU）melt blown composite film was modified to prepare it.The composite membrane was characterized by scanning electron microscopy and infrared spectroscopy,and its hydrophilicity was measured;Research has shown that the water flux of the modified AOPAN/PU melt blown composite membrane increased from 349 L·m^-2·h^-1to 435 L·m^-2·h^-1.After three dynamic cycles of filtration of a 100 mg/L Cu²⁺,Fe³⁺,Zn²⁺mixed metal solution,it was found that the removal rates of all three metal ions in the filtrate were above 90%.（2）Polyacrylonitrile/polyurethane（PAN/PU）hollow fiber membrane was prepared by dry-wet spinning,and the amine oxime polyacrylonitrile/polyurethane（AOPAN/PU）hollow fiber membrane was modified to study the changes in hydrophilicity and metal ion adsorption performance of the hollow fiber membrane.The hollow fiber membrane was characterized by scanning electron microscopy and infrared spectroscopy,and its hydrophilicity was measured.Research has shown that when the content of pore forming agent PVP is 6%and PEG is 4%,the microporous structure of PAN/PU hollow fiber membrane is the best.The hydrophilicity of AOPAN/PU hollow fiber membrane modified by amine oxime is greatly improved,and it has efficient metal ion retention performance.After three adsorption cycles of 10 mg/L Cu²⁺,Fe³⁺,Zn²⁺mixed metal solution,it was found that the concentration of three metal ions in the filtrate meets the sanitary standards for drinking water.（3）Produce AOPAN/PU hollow fiber membranes into columnar membrane modules,and use pilot sewage treatment equipment to explore the attenuation of membrane module flux under long-term operation,changes in module flux under different operating pressures,the impact of membrane module cleaning on flux recovery rate,and the ability to treat metal ion wastewater on a large scale.Research has shown that when the module is used to treat industrial wastewater,after running for more than24 hours,the membrane module experiences a certain degree of membrane fouling,but the flux recovery rate of the module after backwashing reaches 80.6%.The membrane module had a retention rate of over 90%within 2 hours of initial operation on a mixture of Cu²⁺,Fe³⁺,Zn²⁺metal ions at 100 mg/L.After two series cycles of treatment on a mixture of Cu²⁺,Fe³⁺,Zn²⁺metal ions at 10 mg/L,the emission concentrations of all three metal ions in the membrane module met the standards for drinking water.