Department of Civil and Environmental Engineering, University of Maryland , College Park, Maryland 20742, United States.
Department of Civil and Environmental Engineering, University of California , Berkeley, California 94720, United States.
Environ Sci Technol. 2017 Mar 21;51(6):3242-3249. doi: 10.1021/acs.est.6b05665. Epub 2017 Mar 2.
This study demonstrated the feasibility of using regenerable polyelectrolyte membranes to ultimately control the irreversible membrane fouling in a forward osmosis (FO) process. The regenerable membrane was fabricated by assembling multiple polyethylenimine (PEI) and poly(acrylic acid) (PAA) bilayers on a polydopamine-functionalized polysulfone support. The resulting membrane exhibited higher water flux and lower solute flux in FO mode (with the active layer facing feed solution) than in PRO mode (with the active layer facing draw solution) using trisodium citrate as draw solute, most likely due to the unique swelling behavior of the polyelectrolyte membrane. Membrane regeneration was conducted by first dissembling the existing PEI-PAA bilayers using strong acid and then reassembling fresh PEI-PAA bilayers on the membrane support. It was found that, after the acid treatment, the first covalently bonded PEI layer and some realigned PAA remained on the membrane support, acting as a beneficial barrier that prevented the acid-foulant mixture from penetrating into the porous support during acid treatment. The water and solute flux of the regenerated membrane was very similar to that of the original membrane regardless of alginate fouling, suggesting an ultimate solution to eliminating the irreversible membrane fouling in an FO process. With a procedure similar to the typical membrane cleaning protocol, in situ membrane regeneration is not expected to noticeably increase the membrane operational burden but can satisfactorily avoid the expensive replacement of the entire membrane module after irreversible fouling, thereby hopefully reducing the overall cost of the membrane-based water-treatment system.
本研究证明了使用可再生聚电解质膜最终控制正向渗透（FO）过程中不可逆膜污染的可行性。可再生膜是通过在多巴胺功能化聚砜基底上组装多层聚乙烯亚胺（PEI）和聚丙烯酸（PAA）双层膜制备的。与使用三偏磷酸钠作为汲取液的 PRO 模式相比，使用柠檬酸钠作为汲取液时，所得膜在 FO 模式（活性层朝向料液）下表现出更高的水通量和更低的溶质通量，这很可能是由于聚电解质膜的独特溶胀行为所致。通过首先使用强酸分解现有的 PEI-PAA 双层膜，然后在膜支撑体上重新组装新鲜的 PEI-PAA 双层膜来进行膜再生。研究发现，酸处理后，第一个共价键合的 PEI 层和一些重新排列的 PAA 仍留在膜支撑体上，起到有益的屏障作用，防止酸污染物混合物在酸处理过程中渗透到多孔支撑体中。即使存在海藻酸钠污染，再生膜的水通量和溶质通量与原始膜非常相似，这为消除 FO 过程中的不可逆膜污染提供了最终解决方案。通过类似于典型膜清洗方案的程序，原位膜再生预计不会显著增加膜的操作负担，但可以满意地避免不可逆污染后整个膜组件的昂贵更换，从而有望降低基于膜的水处理系统的总成本。
