Comparison of fouling behavior in forward osmosis (FO) and reverse osmosis (RO)
Comparison of fouling behavior in forward osmosis (FO) and reverse osmosis (RO)
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DOI：
10.1016/j.memsci.2010.08.036
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发表时间：
2010-12-01
影响因子：
9.5
通讯作者：
Hong, Seungkwan
中科院分区：
文献类型：
--
作者：
Lee, Sangyoup;Boo, Chanhee;Hong, Seungkwan
比较了正向渗透(FO)和反渗透(RO)过程中的结垢行为。以海藻酸盐、腐植酸和牛血清白蛋白(BSA)为模型有机污染物，选择两种不同大小的二氧化硅胶体悬浮液作为模型颗粒污染物。为了对污垢行为进行有意义的比较，在FO和RO污垢运行过程中，采用了相同的水动力操作条件(即初始渗透通量和错流速度)和进水化学成分(即pH、离子强度和钙浓度)。FO中观察到的通量衰减行为随着有机污染物的类型、胶体污染物的大小以及用于产生渗透推动力的拉伸液的类型而发生显著变化。基于这些实验数据和对FO和RO的结垢行为的系统比较，我们对FO的结垢机理提供了新的见解。在FO中，盐从牵引液到进料侧的反向扩散加剧了污垢层内滤饼强化的渗透压力。进料侧靠近膜表面的渗透压升高，导致净渗透推动力显著下降，从而使渗透通量显著下降。我们的结果进一步表明，FO和RO污垢层的结构(即厚度和致密性)有很大的不同。通过改变有机污垢运行过程中的错流速度，我们能够检验FO和RO中的污垢可逆性。随着错流速度的增加，FO中有机污染的渗透通量几乎完全恢复，而反渗透系统的渗透通量没有明显变化。结果表明，在不采用化学清洗的情况下，通过优化进料流中的流体动力学，可以有效地控制FO中的有机污染。(C)2010爱思唯尔B.V.保留所有权利。
Fouling behaviors during forward osmosis (FO) and reverse osmosis (RO) are compared. Alginate, humic acid, and bovine serum albumin (BSA) are used as model organic foulants, and two suspensions of silica colloids of different sizes are chosen as model particulate foulants. To allow meaningful comparison of fouling behavior, identical hydrodynamic operating conditions (i.e., initial permeate flux and cross-flow velocity) and feed water chemistries (i.e., pH, ionic strength, and calcium concentration) are employed during FO and RO fouling runs. The observed flux-decline behavior in FO changed dramatically with the type of organic foulant, size of colloidal foulant, and the type of the draw solution employed to generate the osmotic driving force. Based on these experimental data and the systematic comparisons of fouling behaviors of FO and RO, we provide new insights into the mechanisms governing FO fouling. In FO, reverse diffusion of salt from the draw solution to the feed side exacerbates the cake-enhanced osmotic pressure within the fouling layer. The elevated osmotic pressure near the membrane surface on the feed side leads to a substantial drop in the net osmotic driving force and, thus, significant decline of permeate flux. Our results further suggest that the structure (i.e., thickness and compactness) of the fouling layers of FO and RO is quite different. By varying the cross-flow velocity during the organic fouling runs, we were able to examine the fouling reversibility in FO and RO. The permeate flux during organic fouling in FO recovered almost completely with increasing cross-flow velocity, while no noticeable change was observed for the RO system. Our results suggest that organic fouling in FO could be controlled effectively by optimizing the hydrodynamics in the feed stream without employing chemical cleaning. (C) 2010 Elsevier B.V. All rights reserved.