凝固浴温度对纤维素中空纤维膜结构及气体渗透分离性能影响研究

EFFECT OF COAGULATION BATH TEMPERATURE ON STRUCTURE AND GAS SEPARATION PROPERTIES OF CELLULOSE HOLLOW FIBER MEMBRANES

利用新型溶解工艺,在不同的凝固浴温度(0～60℃)下制备了纤维素中空纤维膜,考察了凝固浴温度对纤维素中空纤维膜结晶结构、机械性能和气体渗透分离性能的影响.扫描电镜表征表明凝固浴温度的升高使得纤维素中空纤维膜更加疏松,并且内侧的指状孔变大变多;膜的机械性能随凝固浴温度的升高而变差;XRD谱图显示凝固浴温度对纤维素中空纤维膜的结晶度没有明显影响.气体渗透分离性能测试结果表明,随着凝固浴温度的升高,干态纤维素中空纤维膜气体渗透速率增加明显,表现出"Knudson扩散"控制行为;与干态纤维素膜相比,加湿状态下的纤维素中空纤维膜气体渗透性能都有大幅度的下降,而且较低凝固浴温度下制备的纤维素中空纤维膜M-1(0℃)、M-2(20℃)气体渗透通过膜的机理由原来干膜的Knudson扩散过渡到湿膜的溶解扩散,CO2取代H2成为在膜内扩散速度最快的气体.在较高的凝胶浴温度下(40℃、60℃),由于所制备的膜结构过于疏松,对几种气体没有表现出"溶解选择性".

Cellulose hollow fiber membranes（CHFMs） were prepared by a new dissolving method.The influence of coagulation bath temperature on the morphology and properties such as crystallinity degree,mechanical strength and gas permeation performance of CHFM was systematically investigated.The results showed that with the increase of coagulation bath temperaturet,he morphology of asymmetric cellulose hollow fiber membranes would become much looser,and more large finger-like pores could be found across the section.At the same time,crystallinity degree almost showed no change and mechanical strength became worse obviously.As a result gas permeation performance of dry CHFMs would increase dramatically with the coagulation bath temperature and show obvious ＂Knudson-diffusion selective ＂ mechanism.While for wet CHFMs,permeation rates for all gases would decrease sharply and interestingly for CHFMs from coagulation bath temperature of 0℃ and 20℃ carbon dioxide became the fastest gas because of the permeation mechanism had changed to ＂solution selective＂in wet CHFMs.While for CHFMs from coagulation bath temperature of 40℃ and 60℃ t,his＂solution selective＂effect cannot be found because of their much looser structure.