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

海洋溶解有机质(DOM)池的巨大规模和动力学特征使其成为全球元素循环研究的重要焦点。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。在过去的三十年里，对不同大小的组分和化学提取物的大量成分研究极大地增加了我们对海洋DOM的起源和循环的了解。然而，海洋DOM的很大一部分仍未确定其组成。研究海洋DOM的一个主要障碍是从海水中分离出足够数量的DOM来分析这种高度稀释和化学复杂的材料。在这个项目中，佐治亚理工学院和堪萨斯州立大学的研究人员将开发、测试和应用反渗透(RO)和电渗析(ED)相结合的工艺，从海水中浓缩和实际回收大量基本上未改变的DOM。反渗透方法已被证明在几乎不发生物理或化学变化的情况下从淡水中回收相当一部分(90%)的DOM。不幸的是，由于反渗透膜与DOM共浓缩无机盐，DOM样品在盐水中被RO浓缩的程度非常有限。反渗透过程中盐分的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，并形成膜污染的无机沉淀物。为了从咸水中获得与使用反渗透技术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。电渗析是从水溶液中去除无机盐的一种公认的方法，就是这样一种方法。合作研究人员的初步实验表明，ED可以显著降低天然水中的盐分浓度，而DOM几乎没有损失。因此，建议的工艺将使用ED来降低盐分浓度，从而可以使用反渗透技术来回收DOM。一系列使用人工和自然海水溶液的实验室实验将被用来评估和优化耦合的RO/ED工艺。在这项研究的最后阶段，联合技术将应用于海水样本。PIS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，这意味着NSF在这项工作中节省了大量成本。广泛影响：这项工作的预期结果是一个使环境研究得以实现的工具，远远优于目前最好的回收海洋DOM的技术(即超滤)。可现场部署的预浓缩方法将极大地促进在天然水源(河流、湖泊、海水)中回收复杂有机分子的研究。在更广泛的教育影响方面，这项调查将使私人投资机构能够培训和指导不同的学生和研究人员群体，包括几个少数民族和妇女。

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.