用脉冲梯度场核磁共振技术研究乙醇-水混合液在壳聚糖渗透汽化膜中的自扩散过程

On the Self-diffusion of Water-Ethanol Mixture in Chitosan Pervaporation Membrane with the Pulsed-field Gradient NMR

用脉冲梯度场核磁共振技术 (PFG -NMR)研究了水、乙醇和乙醇 -水混合液在硫酸交联的壳聚糖渗透汽化膜和未交联的壳聚糖渗透汽化膜中的自扩散过程 ,得到了乙醇和水的溶解度和自扩散系数 ,阐述了水和乙醇透过壳聚糖膜的机理 ;实验结果表明 :水和乙醇是分别由两种不同类型的扩散通道透过膜的 ;水是由亲水性的离子化通道扩散透过膜 ,而乙醇是由亲油性的高分子无定形区扩散透过膜 ;PFG -NMR方法所得到的结果与渗透汽化实验所得到的结果完全一致。

The self-diffusion of water,ethanol and water-ethanol mixtures in chitosan(CS)membranes with or without H 2 SO 4 cross-linkage was measured,using pulsed-field gradient(PFG)nuclear magnetic resonance(NMR)spectroscopy to obtain the partial solubilities and self-diffusion coefficients.An attempt was made to explain the transport properties of water and ethanol through the CS membrane.It was found that water and ethanol have separate diffusion channels through the membrane.Water diffusion is loca- lized in the hydrophilic ionic region formed by the ionized groups,whereas ethanol diffusion is localized in the hydrophobic amorphous network of the polymeric membrane.There was a good agreement between the separation factors estimated from PFG-NMR data and those obtained by pervaporation testing.