聚乙烯亚胺改性聚酰胺反渗透膜的CO_(2)/N_(2)分离性能

Study on CO_(2)/N_(2)separation performance of polyethyleneimine-modified polyamide thin-film composite reverse osmosis membrane

传统二氧化碳(CO_(2))分离膜受“Trade-off”效应制约难以实现渗透性及分离选择性的同步提升,本文将聚乙烯亚胺(PEI)胺基载体分子通过静电作用负载于商业化聚酰胺(PA)复合反渗透膜表面,制备具有促进CO_(2)传递功能的PEI-PA复合膜材料,并系统探究了膜制备与分离工艺对PEI-PA复合膜CO_(2)/N_(2)分离性能的影响规律.膜制备研究表明,复合膜的CO_(2)渗透性能在一定范围内随PEI分子浓度提升而增大,且PEI改性层中胺基在pH中性环境中具有理想的CO_(2)转运活性,在最佳改性条件下(改性溶液中PEI质量分数2.0%、分子量1800 g/mol、pH值7),复合膜CO_(2)渗透性和CO_(2)/N_(2)分离选择性可达96.9 GPU和90.0,较改性前分别提升37.8%和22.4%.分离实验表明,复合膜CO_(2)渗透速率在一定范围内随压力升高而增大,过高压力下CO_(2)渗透速率趋近饱和且低于N_(2)提升幅度,导致CO_(2)渗透速率和气体分离选择性衰减;而气体温度与流速升高将显著提高N_(2)渗透速率,导致气体分离选择性下降.研究结果验证了将反渗透水处理膜转化为CO_(2)气体分离膜的可行性,为工业化放大实践提供了可靠依据.

Traditional carbon dioxide(CO_(2))separation membranes are subject to the“Trade-off”effect,which makes it difficult to realize the simultaneous improvement of permeability and separation selectivity.In this study,polyethyleneimine(PEI)was selected as amine-based carrier molecules and loaded onto the surface of commercial polyamide(PA)composite reverse osmosis membrane by electrostatic deposition to prepare composite PEI-PA membrane for the facilitated transport of CO_(2).The influences of membrane fabrication and separation process conditions on the CO_(2)/N_(2)separation performance of the obtained PEI-PA membrane were systematically investigated.The study of membrane preparation showed that the CO_(2)permeability of the composite membrane increased with the concentration of PEI in a certain range.And the amine groups in the PEI modified layer had ideal transport activity of CO_(2)at the neutral pH.Under the optimal modification conditions(2.0%mass fraction of PEI with molecular mass of 1800 g/mol,pH=7),the CO_(2)permeability and CO_(2)/N_(2)selectivity of the composite membrane could reach 96.9 GPU and 90.0,which were 37.8%and 22.4%higher than unmodified membranes,respectively.Separation performance test showed that the CO_(2)permeation increased with the pressure in a certain range.But it would approach saturation and become lower in growth proportion than N_(2),resulting in attenuation of the CO_(2)permeation ratio and CO_(2)/N_(2)selectivity.Besides,the increase of gas temperature and flow rate significantly increased N_(2)permeation,resulting in selectivity decline.Above results verify the feasibility of transforming reverse osmosis membranes into CO_(2)separation membranes,which provides a reliable basis for industrial scale-up practice.