Collaborative Research: Electrodialysis/Reverse Osmosis - Development of an Improved Method to Concentrate Dissolved Organic Matter from Seawater

摘要海洋溶解有机质（DOM）库的巨大规模和动态性使其成为全球元素旋回研究的重要焦点。这些研究的动机是DOM循环对全球变暖和海洋生产力等过程的直接和间接影响。在过去的三十年中，对不同大小的馏分和化学提取物的大量组成研究大大增加了我们对海洋DOM起源和循环的理解。然而，海洋DOM的很大一部分在组成上仍未被表征。海洋DOM研究的一个主要障碍是从海水中分离出足够的量来分析这种高度稀释和化学复杂的材料。在这个项目中，乔治亚理工学院和堪萨斯州立大学的研究人员将开发、测试并应用一种将反渗透（RO）与电渗析（ED）相结合的工艺，从海水中浓缩并实际回收大量基本未改变的DOM。反渗透方法已被证明可以从淡水中回收相当一部分（90%）的DOM，并且几乎没有物理或化学变化。不幸的是，由于反渗透膜将无机盐与DOM共同浓缩，所以DOM样品在盐水中被反渗透浓缩的程度非常有限。反渗透过程中的盐积累导致溶液在处理过程中需要非常高的压力来克服渗透力，并形成污染膜的无机沉淀物。为了从盐水中获得与RO处理淡水时相同的高DOM回收率，需要一种独立的去除无机盐的方法。电渗析，一种从水溶液中去除无机盐的成熟方法，就是这样一种方法。共同研究人员的初步实验表明，ED可以显著降低天然水体中的盐浓度，而DOM的损失很少或没有损失。因此，提议的工艺将使用ED来降低盐浓度，以便RO技术可以用于回收DOM。一系列实验室实验将采用人工和天然海水溶液来评估和优化RO/ED耦合过程。在本研究的最后阶段，将联合技术应用于海水样品。pi已经拥有两个实验室规模的ED系统和一个能够处理大量水（数百升）的便携式RO单元，这为NSF的这项工作节省了大量成本。更广泛的影响：这项工作的预期结果是一种环境研究的有利工具，远远优于目前回收海洋DOM的最佳技术（即超滤）。涉及从天然水源（河流、湖泊、海水）中回收复杂有机分子的研究将因可在现场部署的预浓缩方法而大大便利。就更广泛的教育影响而言，这项调查将使pi能够培训和指导各种各样的学生和研究人员，包括一些少数民族和妇女。

ABSTRACTOCE-0425624The large size and dynamics of the ocean dissolved organic matter (DOM) pool have made it an important focus of many studies of global elemental cycles. These studies are motivated by the direct and indirect influences of DOM cycling on processes such as global warming and marine productivity. Over the last three decades, numerous compositional studies of various size fractions and chemical extracts have significantly increased our understanding of the origin and cycling of marine DOM. A large fraction of marine DOM, however, still remains compositionally uncharacterized. A major obstacle in the study of marine DOM has been isolating from seawater sufficient quantities for analysis of this highly dilute and chemically complex material. In this project researchers at the Georgia Institute of Technology and Kansas State University will develop, test, and apply a process using reverse osmosis (RO) in combination with electrodialysis (ED) for the concentration and practical retrieval of significant quantities of essentially unaltered DOM from seawater. RO methods have been shown to recover a significant fraction (90%) of DOM from fresh waters with little physical or chemical alteration. Unfortunately, the extent to which a DOM sample can be concentrated by RO in saline waters is very limited because RO membranes co-concentrate inorganic salts with DOM. Salt accumulation during RO leads to solutions requiring very high pressures during processing to overcome osmotic forces and to formation of membrane-fouling inorganic precipitates. To achieve the same high DOM recoveries from saline waters that are achieved when RO is used to process fresh waters, an independent method for removal of inorganic salts is required. Electrodialysis, a well-established process for removal of inorganic salts from aqueous solutions, is such a method. Preliminary experiments by the co-investigators indicate that ED can significantly reduce salt concentrations in natural waters with little or no loss of DOM. Thus, the proposed process will use ED to reduce the salt concentrations, so that RO techniques can be used to recover DOM.A series of laboratory experiments using artificial and natural seawater solutions will be used to evaluate and optimize the coupled RO/ED process. During the final stage of this research, the combined technique will be applied to seawater samples. The PIs already have two laboratory-scale ED systems and a portable RO unit capable of processing large volumes of water (hundreds of liters), which represents a significant cost savings to NSF for this work.Broader Impacts: The expected result from this work is an enabling tool for environmental research that is far superior to the best current techniques (i.e., ultrafiltration) for recovery of marine DOM. Research involving the recovery of complex organic molecules in natural water sources (rivers, lakes, seawater) will be greatly facilitated by a field-deployable method for pre-concentration. In terms of broader educational impacts, this investigation will allow the PIs to train and mentor a diverse group of students and researchers, including several minorities and women.