新型正向渗透分离膜的制备及可回收聚电解质汲取液的研制

In recent years, forward osmosis (FO), as a novel membrane separation technique for clean water production, gains more and more attention in both academia and industry because of its atmospheric operation, high salt rejection, low tendency of membrane fouling, and etc. However, some technical problems existing in FO technology, such as low membrane flux, solute leakage, severe concentration polarization, and the difficulty of draw solution recovery, still restrict the real applications of FO technology in wastewater treatment and desalination industry. Developing suitable FO　membranes and draw solutes are still the important chanllenges in order to achieve the breakthoughs and industrilization of the FO　processes. In this research project, we will focus on these technical difficulties to carry out our research work in order to achieve high-performance forward osmosis processes. Several novel membrane fabrication techniques will be employed, including: 1) introduction of cyclodextrin, calixarene, polyhedral oligomeric silsesquioxane, etc into the monomers for interfacial polymerization in order to molecularly design the selective layer of the thin film composite membrane; (2) cross-linking modification of the one-layer polyelectrolyte membrane fabricated by layer-by-layer deposition, in order to improve its salt rejection and water flux simultaneously. In this research project, we will also develop various polyelectrolyte salts including acrylic acid salts, sulfonate salts and methyl acrylate acrylic acid salts, as draw solutes for applications in forward osmosis. They could be recovered by ultrafiltration or nanofiltration and used for next forward osmosis test. By employing those novel draw solutes, it is effective to avoid the leakage of the draw solute as well as the high energy consumption during draw solute recycling. It is highly expected that through the investigation of appropriate FO membranes and the molecular design of draw solutes, the research work in this project would make valuable contributions to the final industrialization of the FO process.

近年来，正向渗透过程作为未来的清洁水生产技术因其独特的常压操作、高截留率和低膜污染倾向等特性受到越来越多的关注。然而目前有一些技术难题，如膜通量偏低、溶质泄漏、浓差极化严重、汲取液回收难度大等，还制约着正向渗透在废水处理和海水淡化中的实际应用。要取得FO过程的突破和工业化，研发合适的FO膜和汲取液溶质仍然是其面临的重要挑战。我们拟采用的新型制模技术包括:1）在界面聚合反应的单体中引入环糊精、杯芳烃或聚倍半硅氧烷等，对致密层进行分子设计以制备薄膜复合膜；2）对层层自组装沉积的单层聚电解质膜进行交联改性，以同时提高其截盐率和膜通量。同时，我们也合成研制一系列不同分子量不同阴阳离子的有机酸盐聚电解质，作为新型汲取液溶质并通过超滤或纳滤方法在渗透过程后完全回收，以解决正向渗透过程中的泄漏问题和回收的高能耗问题。通过上述研究，我们希望可以为正向渗透膜技术的实际应用做出积极的贡献。

近些年来，正向渗透过程作为一种新型的用于未来清洁水生产的膜分离技术，因其独特的常压操作、高截留率和低膜污染倾向等特性受到学术界和工业界的越来越多的关注。然而，理想的正向渗透膜和合适的汲取溶质的匮乏，制约着正向渗透在废水处理和海水淡化工业的实际应用。薄膜复合膜由于其易制备、分离性能好、较好的温度稳定性和一定的耐酸碱性，是目前最常用的一种正向渗透膜。传统的薄膜复合膜通常由间苯二胺和均苯三甲酰氯通过界面聚合法制得，但是这种复合膜的聚酰胺选择层通常较为致密，亲水性不够，表面也比较粗糙，因此这种复合膜也面临着水通量相对较低和较高污染倾向的问题，因此有较大的提升空间。在我们的研究中，通过在水相间苯二胺单体溶液中加入一种纳米材料氧化石墨烯或者一种新型含硅的胺单体，制得两种新型的薄膜复合膜。这两种复合膜相比较于传统的未改性膜，其表现出更高的亲水性和水通量，并且具有更佳的抗污染性能。另一方面，常用的正渗透汲取溶质通常具有高的渗透压和水通量,但是可能存在严重溶质泄漏的问题。针对这个问题，我们合成了一系列的环境友好型的有机汲取溶质，不但表现出高的渗透压和水通量，并且有非常低的溶质泄漏。它们包括可再生且无毒的葡萄糖酸盐、含有不同羧基数目的羧乙基胺、四乙基五胺七羧酸钠盐、乙烯基二胺四丙羧酸盐和有机膦酸盐。通过上述合适的FO膜和汲取液的分子设计研发，相信可以为FO过程的最终突破和工业化做出一定推动作用。