添加HMPA对聚酰胺复合正渗透膜结构和性能的影响

Preparation and performance of TFC-FO membranes prepared on different HMPA concentrations

对于聚酰胺TFC-FO膜,可分别通过优化活性分离层和支撑层来获得理想的膜性能,而其中分离层对膜性能的影响尤其重要.因此,本文首先将六甲基磷酰胺(HMPA)作为极性非质子溶剂添加到水相溶液中进行界面聚合以制备TFC-FO膜,并进一步对添加不同浓度HMPA的聚酰胺TFC-FO膜进行结构分析和性能表征,以研究HMPA添加量对膜结构和性能的影响.结果表明,随着HMPA浓度的增加,聚酰胺的交联度呈现先升高后降低的趋势,添加质量分数2.0%时的交联度最大.同时,不同HMPA添加量对膜的微观形貌也有影响,分离层的厚度和粗糙度随着HMPA添加量的增加而增大.此外,研究还发现,膜表面的亲水性受到化学结构和表面形貌共同作用的影响.以1mol/L的NaCl溶液和去离子水分别作为汲取液和原料液,添加质量分数2.0%HMPA与未添加相比,膜通量提升约60%,且在较高水通量下膜具有较低的盐水比.

In order to improve the performance of the composite forward osmosis membrane,it mainly starts from the following two aspects,optimizing the porous support layer and changing the structure of the active separation layer,while the active separation layer plays an important role on properties of membrane.In this paper,as a polar aprotic solvent,hexamethyl phosphoramide(HMPA)was added to the aqueous solution during the interfacial polymerization process.A series of characterizations of polyamide composite forward osmosis membranes with different HMPA concentrations were performed to observe the effect of the aqueous phase additive HMPA on membrane performance.Results showed that the cross-linking degree of the polyamide increased first and then decreased with the increase of HMPA concentration,and achieved the top value at 2.0%.The morphology of the membrane surface indicated that HMPA had an effect on the surface morphology of the membrane,and the skin layer thickness and surface roughness of the membrane increased gradually.What’s more,it can be found that the hydrophilicity of the membrane surface was influenced by its chemical structure and surface morphology.The results of water flux and reverse salt flux showed that the water flux of M2(2.0%HMPA addition)increased by about 60%compared with M0(without HMPA)while with a lower salt water ratio under FO mode for 1mol/L NaCl draw solution from a de-ionized water feed solution.