Temperature as a factor affecting transmembrane water flux in forward osmosis: Steady-state modeling and experimental validation
Temperature as a factor affecting transmembrane water flux in forward osmosis: Steady-state modeling and experimental validation
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DOI：
10.1016/j.cej.2012.05.087
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发表时间：
2012-08
影响因子：
15.1
通讯作者：
S. You;Xiu-heng Wang;Ming Zhong;Yi-Jian Zhong;Chen Yu;N. Ren
中科院分区：
文献类型：
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作者：
S. You;Xiu-heng Wang;Ming Zhong;Yi-Jian Zhong;Chen Yu;N. Ren
正渗透是一种利用溶液渗透压自发驱动的新型膜法海水淡化技术。温度与溶液的理化性质密切相关，因此对FO工艺的跨膜水通量有显著影响。本研究的主要目的是评估FO性能对温度的依赖性。水通量的预测采用稳态模型，包括温度对渗透压的影响，边界层的流体动力学，跨膜质量和热通量过程。实验在FO模块中进行，其中氯化钠用作进料和汲取溶液。结果表明，在20-40°C范围内，水通量与本体溶液温度之间存在显著的正相关性。正如理论预测和实验验证所示，质量扩散动力学的改善，而不是溶液渗透压，占主导地位的FO性能的水跨膜通量时，温度升高。这初步认为是溶液粘度降低的结果，与界面层、支撑层和活性层极化电阻的降低相一致。随着流量的增加，由于边界层传质的改善，在所有温度下的水通量增加。热通量的大小被观察到的流量和跨膜温差呈正相关。为了更高效和节能的运行，这项研究不仅提供了一个深入了解温度对跨膜水通量的影响，但也表明了在FO过程中调节温度的战略重要性。
Forward osmosis (FO) represents a new membrane-based technology to desalinate seawater driven by osmotic pressure of solution spontaneously. Temperature is closely correlated to the solution physicochemical properties, and thus has a remarkable impact to transmembrane water flux of FO process. The primary goal of this study is to evaluate the dependence of FO performance on temperature. The water flux was predicted using steady-state models that incorporate temperature effect on osmotic pressure, hydrodynamics of boundary layer, transmembrane mass and heat flux processes. The experiments were performed in a FO module with sodium chloride serving as feed and draw solution. The results demonstrated a substantial positive correlation between water flux and bulk solution temperature in the range of 20–40°C. As indicated by both theoretical prediction and experimental validation, the improvement of mass diffusion kinetics, rather than solution osmotic pressure, dominated the FO performance in terms of water transmembrane flux when temperature was increased. This should be preliminarily a result of decrease in solution viscosity, which was consistent with the decrease in polarization resistances of boundary layer, supporting layer as well as active layer. With the increased flow rate, water flux was increased at all temperatures due to the improvement of mass transfer at boundary layer. The magnitude of heat flux was observed to positively relate to the flow rate and transmembrane temperature difference. Toward more efficient and energy-effective operation, this study not only provides an insight into the effect of temperature on transmembrane water flux, but also suggests a strategic importance of regulating temperature in FO process.