正渗透过程中水与溶质的传递现象

Water and solute transport phenomena in forward osmosis process

正渗透是一种利用渗透原理的新兴膜技术,近年来在国内外受到了广泛的关注。解析该过程中溶剂水的传递和驱动溶质的反向传递对其发展和应用至为关键。首先开展了两种膜的取向下,正渗透过程中的水通量和溶质反向摩尔通量的实验研究。当驱动溶液在膜分离层侧时,水通量更高,而溶质反向摩尔通量更低,表明水的传递对溶质的反向传递有限制作用。而后分别考察了不同的单一溶质和二元混合溶质作为驱动溶质时,水和溶质的传递现象。当单一中性溶质或电解质作为驱动溶质时,水通量和溶质反向摩尔通量均随驱动溶液浓度的升高而增大;在相同操作条件下,驱动溶质的扩散系数越小,溶质反向摩尔通量越小;中性溶质与电解质混合溶液为驱动溶液时,溶质分子之间存在耦合传递效应。

As a novel technology using the principle of osmosis, forward osmosis has drawn worldwide attentions in recent years. Understanding the simultaneous water transport and solute reverse transport in the forward osmosis processes is essential to the development and application of this emerging technology. In this study, the effects of two membrane orientations on solute reverse molar flux and water flux were investigated. The water flux in the mode of active layer facing draw solution was higher than that in the mode of active layer facing feed solution, whereas solute reverse molar flux presented a contrary result, which indicated that transport of water would restrict the reverse transport of solute. The effects of different types of solute, including one single solute and two-component mixed solutes, on solute flux and water flux were also investigated. Water flux and solute reverse molar flux increased with increasing draw solution concentration when using single neutral solute or electrolyte as solute. Under the same operation condition, the smaller the diffusion coefficient was, the lower the solute reverse molar flux was. Furthermore, the coupled transport of the solutes was observed in the mixed draw solution.