Hoek Eric M V, Elimelech Menachem
Department of Chemical and Environmental Engineering, A249 Bourns Hall, University of California, Riverside, California 92521, USA.
Environ Sci Technol. 2003 Dec 15;37(24):5581-8. doi: 10.1021/es0262636.
Results from well-controlled colloidal fouling experiments with reverse osmosis (RO) and nanofiltration (NF) membranes suggest the existence of a new source of flux decline for salt-rejecting membranes-cake-enhanced osmotic pressure. The physical mechanisms leading to this enhanced osmotic pressure are a combination of hindered back-diffusion of salt ions and altered cross-flow hydrodynamics within colloidal deposit layers, which lead to an enhanced salt concentration polarization layer. A model that accounts for both hindered diffusion of salt ions and altered hydrodynamics within colloidal deposit ("cake") layers is presented. The model successfully links permeate flux and salt rejection to cake-enhanced concentration polarization and provides new insight into the mechanisms through which salt-rejecting membranes foul. Experimental data support the model calculations and highlight the role of enhanced concentration polarization phenomena in the performance (i.e., water flux and salt rejection) of polymeric thin-film composite RO/NF membranes in environmental applications.
对反渗透（RO）和纳滤（NF）膜进行的严格控制的胶体污染实验结果表明，对于拒盐膜而言，通量下降存在一种新的原因——滤饼增强渗透压。导致这种渗透压增强的物理机制是盐离子反向扩散受阻与胶体沉积层内错流流体动力学改变的综合作用，这会导致盐浓度极化层增强。本文提出了一个模型，该模型考虑了盐离子的扩散受阻以及胶体沉积（“滤饼”）层内流体动力学的改变。该模型成功地将渗透通量和盐截留率与滤饼增强的浓度极化联系起来，并为拒盐膜的污染机制提供了新的见解。实验数据支持模型计算，并突出了增强的浓度极化现象在聚合物复合RO/NF薄膜在环境应用中的性能（即水通量和盐截留率）方面所起的作用。
