Department of Geological Science, The University of Texas at Austin , Austin, Texas 78712, United States.
Environ Sci Technol. 2017 Oct 17;51(20):11799-11808. doi: 10.1021/acs.est.7b02318. Epub 2017 Sep 26.
Salinity is an increasingly prescient issue in reactive transport, from low salinity water flooding to fracking brine leakage. Of primary concern is the effect of salinity on surface chemistry. Transport and batch experiments show a strong coupling of salinity and acidity through chemical interactions at the mineral-liquid interface. This coupling is ascribed to the combined effects of ionic strength on electrostatic behavior of the interface and competitive sorption between protons and other cations for binding sites on the surface. The effect of these mechanisms is well studied in batch settings and readily describes observed behavior. In contrast, the transport literature is sparse, primarily applied to synthetic materials, and offers only qualitative agreement with observations. To address, this gap in knowledge, we conduct a suite of column flood experiments through silica sand, systematically varying salinity and acidity conditions. Experiments are compared to a reactive transport model incorporating the proposed coupling mechanisms. The results highlight the difficulty in applying such models to realistic media under both basic and acidic conditions with a single set of parameters. The analysis and experimental results show the observed error is the result of electrostatic assumptions within the surface chemistry model and provide a strong constraint on further model development.
盐度是反应迁移中一个日益重要的问题，无论是低盐度水驱还是压裂盐水泄漏。主要关注的是盐度对表面化学的影响。传输和批量实验表明，通过矿物-液体界面的化学相互作用，盐度和酸度之间存在强烈的耦合。这种耦合归因于离子强度对界面静电行为的综合影响，以及质子和其他阳离子在表面结合位点上的竞争吸附。这些机制的影响在批量设置中得到了很好的研究，并很好地描述了观察到的行为。相比之下，传输文献很少，主要应用于合成材料，并且仅与观察结果定性一致。为了解决这一知识差距，我们通过硅胶砂进行了一系列的柱驱实验，系统地改变盐度和酸度条件。实验结果与包含所提出的耦合机制的反应迁移模型进行了比较。结果突出表明，在基本和酸性条件下，使用单一组参数将此类模型应用于实际介质具有一定的难度。分析和实验结果表明，观察到的误差是表面化学模型中静电假设的结果，并为进一步的模型开发提供了强有力的约束。
