Forward osmosis (FO) is a membrane process of water separation and purification. FO uses the osmotic pressure difference across a semipermeable membrane. The effective osmotic pressure at the membrane–solution interface on both the feed and permeate sides of the membrane is the main driving force for the generation of the water flux. The major hindrance to the permeation of the water flux is the prevalence of concentration polarization on both sides of the membrane. Concentration polarization inhibits permeate flux by increasing the osmotic pressure at the membrane active layer interface on the feed side of the membrane. This work focused on the development of a mathematical model for water flux in the FO process. Combined film theory model and diffusion transport through the membrane were utilized. The effect of internal concentration polarization and external concentration polarization on the flux was studied. Both internal and external concentration polarization were taken into consideration in both membrane orientations, i.e., active layer facing the feed solution and active layer facing the draw solution. The obtained explicit expression for water permeation flux in forward osmosis desalination process shows excellent agreement with the literature data.

正向渗透（FO）是水分离和净化的膜过程。 FO 利用半透膜上的渗透压差。膜进水侧和渗透侧的膜-溶液界面处的有效渗透压是产生水通量的主要驱动力。水通量渗透的主要障碍是膜两侧普遍存在浓差极化。浓差极化通过增加膜进料侧的膜活性层界面处的渗透压来抑制渗透通量。这项工作的重点是开发 FO 过程中水通量的数学模型。利用组合膜理论模型和通过膜的扩散传输。研究了内部浓差极化和外部浓差极化对通量的影响。在两个膜方向（即活性层面向进料溶液和活性层面向汲取溶液）中均考虑了内部和外部浓差极化。获得的正渗透海水淡化过程中水渗透通量的显式表达式与文献数据非常吻合。