成果報告書詳細
管理番号20120000001040
タイトル*平成23年度中間年報 最先端PG(Mega-ton Water System) 浸透圧発電 膜素材合成と薄膜形成法の検討 (H22~H25)
公開日2012/12/7
報告書年度2011-2011
委託先名国立大学法人東京工業大学
プロジェクト番号P09025
部署名環境部
和文要約和文要約等以下本編抜粋:
(1)膜素材合成
本研究では、浸透圧発電の発電効率を向上させるため、高い透水性と高い塩除去率の両立、十分な機械強度と耐薬品性(耐塩素性)を有する正浸透膜の開発を目指している。近年、逆浸透膜素材として既に確立されているポリアミド複合膜の正浸透膜への応用が検討されている。しかしこのような既存システムでは、塩除去率は十分であるものの、透水量が低いという問題がある。
英文要約The aim of our project is to develop high-performance forward osmosis (FO) membrane materials suitable for pressure retarded osmosis. High water flux and high salt rejection are required for the materials to improve the power conversion efficiency. Recently, polyamide reverse osmosis (RO) membranes have been substituted to FO membranes; however, this system has suffered from the limited water flux because of internal concentration polarization (ICP). This may be caused by the composite membrane structure, in which the rejected salts incorporate and stay within the supporting layers. In this work, a very thin single membrane system composed of a wholly aromatic polymer material without supporting layers is targeted. Wholly aromatic polymers such as aromatic polyamides and polybenzimidazoles are selected, due to their high mechanical strength, facility of introducing the hydrophilic groups, and feasibility of cross-linking. High water flux is expected by a single ultrathin membrane with hydrophilic groups dispersed in the entire region. It is essential to investigate and optimize the polymer structures including chemicals, functionality of hydrophilic groups, cross-linked network, to satisfy the requirements for FO membranes. Our group succeeded in synthesizing totally 35 kinds of aromatic polymers with different composition of hydrophilic groups. Indeed, 26 kinds of aromatic polyamides could be synthesized by polycondensation of diamines and carboxylic dichlorides. In addition, 9 kinds of polybenzimidazoles were successfully synthesized by polycondensation of tetraamines and dicarboxylic acids in the presence of polyphosphonic acid. In the case of aromatic polyamide membranes, the water permeability (A value) shows in the range of 2-12 x 10-7 ms-1MPa-1, almost being independent on the content of hydrophilic groups, although there is no water flux without hydrophilic groups. Similar tendency has been observed in the case of polybenzimidazole membranes, except for the fact that the one without hydrophilic groups still showed water permeability. We also found the clear relationship in polybenzimidazole membranes between their density and water permeability, that is, water permeability increases with decreasing the density of membranes. These results prompt us to further investigate the less dense polymer membranes to achieve high water permeability. As a next target, the cross-linked wholly aromatic polymer membranes would be developed with maintaining the amorphous nature to reduce the density and to create the pathways for water flux.
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