Preparation Of High-performance Electrospinning PTFE Hollow Fiber Membrane For Ammonia Removal With Membrane Absorption

Ammonia nitrogen is a common type of pollutant in wastewater.The discharge of ammonia nitrogen usually comes from industrial,agricultural and domestic sewage.Overcharged ammonia nitrogen in wastewater seriously endangers the human health and environment.Membrane absorption has attracted widespread attention in recent years as its advantages of low energy consumption,controllable scale,simple equipment structure and high ammonia removal efficiency.In this research,PTFE hollow fiber membrane was prepared by using two different spinning liquid systems through electrospinning method,and the preparation process was optimized by controlling the processes parameter of electrospinning and sintering.The PTFE hollow fiber membrane with high porosity,strong hydrophobicity and excellent mechanical properties was obtained.Combined with deamination mass transfer theory and deamination experiment,the high mass transfer coefficient and flux of the self-made membrane were verified.（1）Pullulan-PTFE as-spun membrane was prepared by electrospinning using the biopolymer Pullulan as the precursor material（binder）.Nanofiber membrane composed of pure PTFE was obtained by removing the precursor material through sintering.By single factor experiment,the optimal preparation conditions were obtained,and successfully fabricated PTFE hollow fiber membrane with high porosity,high LEP and good mechanical properties.In subsequent experiments,the deamination performance of the self-made membrane was investigated,which showed high mass transfer coefficient and membrane flux.（2）PTFE nanofiber membrane with PVA as precursor materials were fabricated by electrospinning and controlled sintering process.The effects of the ratio of spinning emulsion,electrospinning parameters,sintering temperature and cooling mode on the morphology,structure and mechanical properties of the membrane were investigated.By optimizing the original materials,the ratio of PVA to PTFE in the spinning emulsion was reduced to a minimum,and the optimal preparation conditions were obtained through adjust the preparation process parameters:the ratio of PVA to PTFE was 1:17,the injection speed of the syring-pump was 0.5m L/h,the relative humidity was 23%,the positive voltage was 11k V,and the sintering temperature was 380℃.Further research shows that the sintering temperature and cooling rate have effects on the mechanical properties of the membrane.The PTFE hollow fiber membrane fabricated under the optimal experimental conditions showed superior hydrophobicity（CA=154°）,tensile strength up to 12MPa,lower fracture strain（118%）and higher Young’s modulus（72MPa）.（3）Based on the resistances-in-series model,a series of experiments were carried out to investigate the deamination performance of the self-made membrane and the influencing factors in the process of deamination.Under the conditions of pH 11 and temperature 313K,the mass transfer coefficient and flux reach to 3.73×10^-5·m·s^-1and4.17×10^-3kg·m^-2·h^-1,which are 2.6～2.9 times as much as those of commercial membranes under the same deamination conditions.Combined with the theory of mass transfer of deamination,the effects of pH,temperature and circulating flow rate on the deamination process were studied.The results show that the best deamination effect can be achieved under the conditions of pH 11,temperature 313K and circulating flow rate 0.1L/min.