“压力-浓度”双驱动扩散渗析过程的传质行为研究

Traditional diffusion dialysis is a spontaneous membrane separation process driven by concentration gradient, and acid or alkali could be separated and recovered from acid/salt or alkali/salt mixed solution by it. Moreover, it is energy-efficient and environmentally friendly. But, its further development has been limited by some disadvantages, such as low membrane flux, serious water osmosis phenomenon and so on. Based on the concentration difference as the main mass transfer force, this project will add a pressure difference as the assistant mass transfer force, to build a new “Pressure-Concentration” double-driven diffusion dialysis process. It will study on the applying pressure field intensity, membrane structure and ion characteristics, to make the relevance between membrane structure and ion characteristics, the pressure field intensity and the diffusion dialysis performance. And on the premise of high selectivity and low energy consumption, the occurring mechanism, that membrane flux generates a qualitative breakthrough and water osmosis phenomenon is restrained, will be elucidated. It will combine molecule (ion) diffusion theory and non-equilibrium thermodynamics theory to reveal the ion mass transfer mechanism under the synergistic effect of pressure field and concentration field. Mathematical model will be established to calculate and predict the diffusion dialysis performance.. The achievement of this project can break through the trade-off effect of membrane flux and selectivity, and promote the technological developments, application and extension of diffusion dialysis. Also, it will provide guidance and reference for other membrane separation processes, such as pervaporation, electrodialysis and so on, and lay some science and technology bases for acidic and alkalescent wastewater and feed.

传统扩散渗析以浓度差作为传质推动力，可以从酸/盐、碱/盐混合液中分离回收酸或碱，具有节能环保的特点，但存在膜通量低、水渗透现象严重等缺陷，限制了其进一步发展。本项目拟在以浓度差为主要推动力的基础上，增加压力差作为辅助推动力，构建“压力-浓度”双驱动新型扩散渗析过程。通过变化压力场强度、传质离子特性和离子膜结构，关联膜结构性能和离子特性—压力场强度—扩散渗析性能三者关系，阐明在保持选择性和低能耗的前提下，提升膜通量和抑制水渗透的发生机制；将分子（离子）扩散理论与非平衡热力学理论结合起来，揭示压力场和浓度场协同作用下的离子传质机理，建立数学模型以计算和预测扩散渗析性能。. 本项目的成功实施可突破传统膜通量-选择性之间的博弈效应，有力地推动扩散渗析技术的科技进步与应用推广，也可为其它膜分离技术，如渗透汽化、电渗析等提供有价值的思路，为各种酸碱废液和料液的分离奠定科学与技术基础。

传统的扩散渗析过程存在膜通量低、水渗透现象严重等局限性，限制了其进一步发展。本项目针对这些局限性，设计与构建了“压力-浓度”双驱动新型扩散渗析过程。项目执行期间，顺利地构建了“压力-浓度”双驱动扩散渗析的静态装置和动态装置；通过相转化法制备了多孔溴化聚苯醚阴膜和多孔聚酰亚胺阴膜，部分溴化聚苯醚多孔阴膜的酸/盐分离因子最高可达235.11；通过“压力-浓度”双驱动扩散渗析实验，得到“膜结构性能和离子特性-压力场强度-扩散渗析性能”三者之间的关系，结果显示压力场强度为0.08Mpa时，氢离子和亚铁离子的渗析系数增加4倍；基于非平衡热力学理论，建立了“压力-浓度”双驱动扩散渗析传质模型，揭示了压力场和浓度场协同作用下的离子传质机理，可以计算和预测“压力-浓度”双驱动扩散渗析过程的性能。.本项目的成功实施可突破传统膜通量-选择性之间的博弈效应，有力地推动扩散渗析技术的科技进步与应用推广，也可为其它膜分离技术，如渗透汽化、电渗析等提供有价值的思路，为各种酸碱废液和料液的分离奠定科学与技术基础。