Microscale Transport Mechanism Of Fibrous Membranes In Membrane Separation Applications

In this paper,the electrospinning fibrous membrane is used for membrane separation research,and the microscale problem in the gas phase-liquid phase separation process is deeply studied.In this paper,according to the phase transition in the separation process,the research is divided into two aspect:one is the process of separating air and aerosol oil droplets without phase change,and the other is the process of separating waste acid by membrane distillation with phase change.This paper explores the transport mechanism of fibrous membrane separation of micro-nanoscale materials?micron-scale aerosol oil droplets and nano-scale molecules?and the effect of the corresponding thermodynamic parameters or membrane parameters on the experiment.In this paper,the fibrous membrane is taken as the research object,and the enrichment behavior and transport mechanism of micron-sized aerosol oil droplets on the fibrous membrane and modified fibrous membrane are studied.The experimental results show that aerosol oil droplets exhibit different structures and evolution behaviors on fibrous webs with different surface energy.Aerosol oil droplets form axisymmetric structures on PAN fibers and non-axisymmetric structures on modified PAN fibers.During the growth of aerosol oil droplets on the fibers,non-axisymmetric structure of aerosol oil droplets on modified PAN fibers switches to axisymmetric structure.The final structure of aerosol oil droplets on the modified PAN fibers and PAN fibers do not form the liquid film on the fibers.Instead,they form large axisymmetric aerosol oil droplets.In this study,it was found by measuring the pressure drop of the fiber membrane and the liquid entry pressure that the oil droplets can enter the interior of the PAN fibrous membrane and be adsorbed together by the inner and outer fibrous membranes.For the modified PAN fibrous membrane,the oil droplets could only be surface-coated.The fibrous membrane is adsorbed to form an oil film on the surface.Modified PAN fibrous membranes can prevent aerosol oil droplets from infiltrating compared to original PAN fibrous membranes and have the function of blocking aerosol oil droplets from invading the fibrous membranes.In this paper,the fibrous membrane is used as a gas-liquid barrier,and the mass transfer mechanism of the membrane distillation technique using the fibrous membrane in the process of treating the hot-dip galvanized waste acid solution was studied and the thermodynamic analysis of the membrane distillation process was carried out.The experimental results show that it is feasible to treat galvanizing waste acid solution with hydrophobic modified fibrous membrane.The rejection ratio for Fe²⁺contained in the waste acid solution is higher than99.9%.The higher temperature of the waste acid solution,the bigger the permeation flux.During the membrane distillation process,the HCl gas in the waste acid solution diffuses through the fiber membrane and condenses into hydrochloric acid.The present of FeCl₂ in the waste acid solution increases the partial pressure of HCl,which increases the permeate flux of HCl and decreases the total permeation flux.Therefore,the HCl concentration in the permeate increases,which is beneficial to recover HCl acid.The mass transfer mechanism of HCl gas molecules and H₂O gas molecules passing through the pores of the membrane belongs to the transitional diffusion.As the temperature increases,the diffusion coefficient increases almost linearly but the increase is small,and the slopes of the diffusion coefficients of different components are almost the same.As the temperature of the feed liquid increases,the STEC of the membrane distillation system gradually decreases,and the GOR gradually increases.