离子膜和脱气膜耦合强化技术在高盐氨氮废水中的资源化应用研究

To solve the disadvantages of high chemical consumption, high pollution and low resource use efficiency in ammonia-nitrogen containing high salinity wastewater treatment, a process intensification of dense and microporous membrane will be proposed to achieve resource recycling in this kind of wastewater. Ion exchange membranes will be introduced in the degas membrane process for ammonia-nitrogen recycling. By taking advantage of the water dissociation in bipolar membranes, the produced proton and hydroxyl ions can be respectively applied as the supplied chemicals for ammonia dissociation and sorption. As a consequence, a chemical-free ammonia recycling technology can be obtained. Meantime, several novel cell configurations with bipolar membrane and mono-valent selective ion exchange membranes will be designed. These novel configurations are expected to realize one-step conversion of mix salts into high purity monoprotic and diprotic acids. The add-value of the salt resources in wastewater thus can be increased. Moreover, fouling in the membranes will be investigated. The tolerant concentrations of membranes against metal ions and organic matters will be evaluated. Possible mechanism for membrane fouling will be elucidated and the corresponding strategies to alleviate fouling will be proposed. Finally, the basic ion transfer principles in the membrane under a high salinity circumstance will be investigated to give some references for high saline specialized membranes design. Successful conduction of this project is expected to expand the examples of membrane process intensification in chemical engineering field, and to give some references for other cleaner production process. This project is also expected to lay some basis for green and environmental benign production in chemical industry.

针对氨氮高盐废水治理过程中化学品消耗高、污染大、资源利用率低的缺点，本项目拟通过致密膜-微孔膜集成强化实现氨氮资源和盐资源的综合化利用。通过把离子膜引入脱气膜氨回收过程，借用双极膜水解离产生的氢离子和氢氧根离子分别用于脱气膜氨氮吸收和解吸过程中的化学品供应源，现实无化学品添加的氨氮回收绿色新工艺。同时，通过双极膜和一二价离子选择性膜的创新膜池设计，有望实现混盐一步转化得到较高纯度的一元酸和二元酸，提升盐资源的附加值。此外，项目还将关注膜污染研究，获取双极膜和一二价离子选择性膜对金属离子和有机物的耐受情况，阐述膜污染发生机制，并提出相应的防治措施。最后，本项目还将揭示高盐条件下离子在膜内的传递规律，为高盐专用膜的研发提供理论支撑。本课题的顺利实施有望补充化学工程中膜过程强化的应用案例，对其他清洁生产过程研究也具有一定的借鉴意义，为我国化学工业的环境化和绿色化奠定科学与技术基础。

针对氨氮高盐废水治理过程中化学品消耗高、污染大、资源利用率低的缺点，本项目建立起一套双极膜-脱气膜耦合系统，借用双极膜水解离产生的氢离子和氢氧根离子分别用于脱气膜氨氮吸收和解吸过程中的化学品供应源，可实现在不消化酸碱化学试剂的条件下，从废水中选择性的提取氨氮。实验结果表明，当标准化电流密度在0.29mAcm-2(mg/min)-1时，脱氨最低能耗为63.59kJ/mol。针对高浓度氨氮(5000mg/L)废水，通过循环操作模式，对高浓度氨氮十个批次的提取效率都达到了99%，远高于“连续进料-连续出料”操作模式所获得的65.2%的提取率，且废水中的氨氮浓度低于10mg/L，同时获得139.07g/L的(NH4)2SO4作为副产品。但由于同离子迁移和浓差扩散，会导致酸室中氢离子从酸室泄露到盐室，导致提氨效率下降。同时，搭建起双极膜+一二价离子交换膜的新型膜池构型，实现了混盐一步转化得到较高纯度的一元酸和二元酸。实验发现制备无机酸的纯度随电流密度增加而显著下降。在电流密度10mA/cm2时，一元酸纯度92.3%-92.5%之间；而电流密度50mA/cm2时，一元酸浓度下降至65.1%-81.95%之间，推测主要是由于一二价离子交换膜的选择性由电流密度的增大而降低，且随着电解质浓度的下降而降低。另外，针对含盐废水"零排放"对盐浓缩过程中的"浓差渗漏"和"电渗漏"导致的水分子渗透现象，开发出“多级梯度电渗析浓缩”工艺。采用“多级-多段”电渗析梯度浓缩，可降低每一段浓淡室盐浓度比，有利于缓解电渗析过程中“水迁移”现象和提高电流效率，可将NaCl从3.5wt%分别浓缩到20.6wt%以上，能耗仅为12.37kWh/t。随着电渗析级数的增加，单个NaCl离子在电渗析迁移过程中所携带的水分子数量随电渗析级数的增加是逐步减少的。相关研究工作在AICHE Journal、Chemical Engineering Science、Journal of Membrane Science等期刊上发表论文12篇，申请发明专利5项。项目的顺利实施证明脱气膜和离子膜集成过程具有很好优越性，不仅实现高含盐废水的减排，还能对废水中氨氮等有价值资源进行回收利用，对其他清洁生产过程研究也具有一定的借鉴意义。