Abstract:

A pertraction system was constructed by flat sheet composite membrane ［poly（dimethylsiloxane）（PDMS）/polyvinylidene fluoride（PVDF）］.Phenol was chosen as model compound to study and caustic stripping solution（sodium hydroxide）was used as stripping solution.The mass transfer process and characteristics of the systems were investigated.The experiments were carried out to investigate the effects of composition and flow rate（feed and stripping solution），temperature，and thickness of selective layer on the pertraction mass transfer performance.The experimental results showed that the overall mass transfer coefficient（OMTC），Kov was independent of stripping solution flux and concentration（pH>13）.Feed-side boundary layer mass transfer coefficient was proportional to Re^0.46，and mass flux increased exponentially with increasing temperature，that is，Arrhenius relationship.OMTC was independent of initial phenol concentration（5.0—15.0 g•L^-1）.Membrane diffusive mass transfer coefficients of selective layer（thickness 4，6 and 8 μm）were 15.0×10^-7，9.9×10^-7 and 7.5×10^-7 m•s^-1 respectively（323.2 K），which were 2—4 times higher than those of homogeneous silicone rubber.Mass transfer resistance of phenol in membrane was also dominant for composite membrane system.

摘要：

以苯酚为模型污染物，以氢氧化钠溶液为萃取液，利用平板复合膜［聚二甲基硅氧烷（PDMS）/聚偏氟乙烯（PVDF）］构造渗透萃取体系，系统地研究了该体系渗透萃取含酚水溶液的传质过程与特性。探讨了料液与萃取液的浓度及流量、运行温度等操作条件及活性层厚度对渗透萃取传质性能的影响。结果表明，pH>13时，总传质系数K_ov不随萃取液流量及浓度变化而变化;苯酚的液膜传质系数kf与膜面流动Reynolds数Re^0.46呈正比，传质通量与温度符合Arrhenius方程。在苯酚初始浓度5.0～15.0 g•L^-1范围内，K_ov为定值。活性皮层厚度为4、6、8 μm的膜扩散传质系数分别为15.0×10^-7、9.9×10^-7及7.5×10^-7m•s^-1（323.2 K），较均质膜提高了2～4倍。苯酚在复合膜中的传质仍属膜阻控制的传质。