Benavente J, Vázquez M I, de Lara R
Grupo de Caracterización Electrocinética de Membranas e Interfases, Departamento de Física Aplicada I, Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga, Spain.
J Colloid Interface Sci. 2006 May 1;297(1):226-34. doi: 10.1016/j.jcis.2005.10.028. Epub 2005 Nov 17.
Changes in electrical and transport parameters for aged composite polyamide/polysulfone membrane samples (PAC) and their porous support layers (PSU) as a result of chemical treatment (immersion in 1 M HNO3 solution) at four different times (12 h < or = t < or = 72 h) have been obtained. Salt permeability, ion transport number, and membrane electrical resistance for the treated samples were determined from salt diffusion, membrane potential, and impedance spectroscopy measurements, which were carried out with the membranes in contact with NaCl solutions at different concentrations and compared with those determined for fresh and aged nontreated samples. Results show the strong effect of aging on membrane parameters, particularly the decrease in salt permeability (P(s)) and the increase in membrane electrical resistance (R(m)), while ion transport number is hardly affected by aging, chemical treatment, or treatment time. Results show how the compaction of the porous structure causes by aging (dried membrane matrix structure) can be partially reduced by HNO3 treatment, and they also allow the estimation of 24-h treatment as the optimum time (higher salt permeability and lower membrane electrical resistance), mainly for the polysulfone support layer. The use of equivalent circuits in the analysis of impedance spectroscopy data allows separate estimation of the electrical resistance associated with each sublayer of the composite PAC membrane samples. On the other hand, chemical changes in the active top layer of the PAC membrane (polyamide active layer) were obtained from XPS analysis, which show some modifications in the atomic concentration percentages of the polyamide characteristic elements as a result of acidic treatment time, which are more significant after 72-h acidic immersion.
已获得在四个不同时间（12小时≤t≤72小时）对老化的复合聚酰胺/聚砜膜样品（PAC）及其多孔支撑层（PSU）进行化学处理（浸入1M硝酸溶液）后，其电学和传输参数的变化。通过盐扩散、膜电位和阻抗谱测量确定了处理后样品的盐渗透率、离子迁移数和膜电阻，这些测量是在膜与不同浓度的氯化钠溶液接触时进行的，并与新鲜和老化的未处理样品所确定的参数进行了比较。结果表明老化对膜参数有显著影响，特别是盐渗透率（P(s)）降低和膜电阻（R(m)）增加，而离子迁移数几乎不受老化、化学处理或处理时间的影响。结果表明，老化（干燥的膜基质结构）导致的多孔结构压实可通过硝酸处理部分降低，并且还可以估计24小时处理为最佳时间（更高的盐渗透率和更低的膜电阻），主要针对聚砜支撑层。在阻抗谱数据分析中使用等效电路可以分别估计复合PAC膜样品每个子层的电阻。另一方面，通过XPS分析获得了PAC膜活性顶层（聚酰胺活性层）的化学变化，结果表明由于酸性处理时间，聚酰胺特征元素的原子浓度百分比发生了一些变化，在酸性浸泡72小时后更为显著。
