Preparation Of High-performance Electrospun Hollow Fiber Membrane For Ammonia Removal With Membrane Absorption Process

Excessive ammonia nitrogen in wastewater seriously endangers the environment and human health.Membrane absorption has recently received increasing attention due to low energy cost and suitable to a wide concentration range of ammonia nitrogen.However,the main difficulty of membrane absorption is the lack of high-performance membrane.For example,the flux and selectivity are low,and low-selectivity membrane will result in recovery of low ammonia concentration.In this paper,high-flux and high-selectivity membrane was prepared by electrospinning,and post-treatment with solvent-vapor welding was investigated to improve the mechanical strength.The theoretical model of liquid-vapor-liquid mass transfer and the rule of membrane absorption for ammonia removal in wastewater were studied.The main results are as follows:（1）The hollow fiber membrane was prepared based on electrospinning,and post-treatment of solvent-vapor welding for improving mechanical properties was studied.N,N-dimethylformamide was used as the welding solvent,and the influence of temperature,solvent volume and time on membrane performance was investigated.The optimal conditions were obtained,namely temperature of 70℃,solvent volume of 99.2μL and time of 100min.The Young’s modulus of treated membrane was2.12±0.4 MPa,which showed 103.8%higher than the pristine membrane.（2）The resistances-in-series model was used as the theoretical mass transfer model to explore the effects of different factors on ammonia removal,including p H,temperature of feed solution and membrane thickness.The results showed that the mass transfer coefficient of self-made module could reach 1.35×10^-5 m·s^-1 at p H=11,which was 1.63 times higher than that of polypropylene commercial module.The flux of self-made module was 2.43×10^-3·m^-2·h^-1,which was 1.70 times higher than that of the commercial module at 35°C.The mass transfer coefficient can reach 2×10^-5m·s^-1,when the membrane thickness was 55±5μm.（3）Furthermore,the effects of different factors（p H,temperature and membrane thickness）on the selectivity for ammonia removal were investigated.The results showed that the selectivity coefficient of self-made module exhibited higher performance compared with commercial module at the same conditions of p H and temperature.In addition,it was found that the membrane thickness has a significant influence on the selectivity.When the thickness was 115±5μm,the selectivity coefficient was 9.74,which was 1.41 times higher than that of 55±5μm.