Qin Jian-Jun, Chen Sijie, Oo Maung Htun, Kekre Kiran A, Cornelissen Emile R, Ruiken Chris J
Technology and Water Quality Office, Public Utilities Board, 82 Toh Guan Road East, #C4-03, 608575 Singapore, Republic of Singapore.
Water Sci Technol. 2010;61(11):2897-904. doi: 10.2166/wst.2010.078.
Concentration polarization (CP) is an important issue in forward osmosis (FO) processes and it is believed that the coupled effect of dilutive internal CP (DICP) and concentrative external CP (CECP) limits FO flux. The objective of this study was to distinguish individual contribution of different types of DICP and CECP via modeling and to validate it by pilot studies. The influence of DICP/CECP on FO flux has been investigated in this study. The CP model presented in this work was derived from a previous study and evaluated by bench-scale FO experiments. Experiments were conducted with drinking water as the feed and NaCl/MgSO(4) as draw solutions at different concentrations and velocities. Modeling results indicated that DICP contributed to a flux reduction by 99.9% for 0.5 M NaCl as a draw solution although the flow pattern of both feed and draw solutions was turbulent. DICP could be improved via selection of the draw solution. The modeling results were well fit with the experimental data. It was concluded that the model could be used for selection of the draw solution and prediction of water flux under similar situation. A draw solution with greater diffusion coefficient or a thinner substrate of an asymmetric FO membrane resulted in a higher flux.
浓差极化（CP）是正向渗透（FO）过程中的一个重要问题，人们认为稀释性内部浓差极化（DICP）和浓缩性外部浓差极化（CECP）的耦合效应限制了FO通量。本研究的目的是通过建模区分不同类型的DICP和CECP的各自贡献，并通过中试研究进行验证。本研究考察了DICP/CECP对FO通量的影响。本工作中提出的CP模型源自先前的一项研究，并通过实验室规模的FO实验进行了评估。实验以饮用水为进料，以不同浓度和流速的NaCl/MgSO₄为汲取液进行。建模结果表明，以0.5 M NaCl作为汲取液时，尽管进料液和汲取液的流动模式均为湍流，但DICP导致通量降低了99.9%。通过选择汲取液可以改善DICP。建模结果与实验数据拟合良好。得出的结论是，该模型可用于汲取液的选择以及类似情况下水通量的预测。具有较大扩散系数的汲取液或不对称FO膜较薄的基材会导致更高的通量。
