Although the time-lag method is one of the most common tools for the characterization of gas permeation membranes, it is entirely unknown in the vast area of liquid permeation membranes. The time-lag method requires a dynamic permeation test initiated by a step-change in the driving force for the species permeation, which is relatively easy for gas permeation, but not for liquid permeation. In this paper, we present preliminary trials to overcome this obstacle for liquid permeation membranes by performing a sudden change in the osmotic pressure by changing the draw solution concentration. To accomplish this, we have modified a standard forward osmosis testing system to monitor the changes in the mass of feed and draw solutions, and the conductivity of feed solution in real-time. To demonstrate the system's operation, we tested commercial, low-pressure reverse osmosis thin film composite membranes in the active-layer-facing-draw-solution orientation. We present and discuss the resulting time-dependent changes in the water flux and the reverse salt flux, and the processing of the experimental data. The shapes of time-dependent water and salt masses are similar to the pressure decay curves and pressure rise curves, respectively, in a time-lag gas permeation experiment.

尽管时滞法是表征气体渗透膜的最常用工具之一，但在液体渗透膜的广大领域中它是完全未知的。时滞方法需要通过针对物质渗透的驱动力的阶跃变化启动的动态渗透测试，这对于气体渗透而言相对容易，但对于液体渗透而言则相对容易。在本文中，我们提出了通过改变汲取溶液浓度来突然改变渗透压来克服液体渗透膜障碍的初步试验。为此，我们已经修改了标准的正向渗透测试系统，以实时监控进料和抽取溶液质量的变化以及进料溶液的电导率。为了演示系统的运行情况，我们测试了商用，活性层-面对-抽吸-溶液取向的低压反渗透薄膜复合膜。我们提出并讨论了水通量和反盐通量随时间的变化，以及实验数据的处理。在时滞气体渗透实验中，随时间变化的水和盐团的形状分别类似于压力衰减曲线和压力上升曲线。