Experimental Verification of a Chlorine-37 Minimum in Concentration Polarization Layer Profiles as Predicted by a Hyperfiltration Model

超滤模型预测的浓度极化层剖面中氯 37 最小值的实验验证

• 批准号: 0001054
• 负责人: Steven Fritz
• 金额: $ 15.19万
• 依托单位: Purdue Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-01 至 2003-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0001054&HistoricalAwards=false
• 关键词: Experimental; Verification; Chlorine; 37; Minimum

Fritz - 0001054Hyperfiltration (a.k.a. "reverse osmosis") occurs when solution advects through permselective material like clays. Isotopes of solutes are advected toward the membrane of the same velocity; however, they diffuse back into the high-pressure reservoir of different rates owing to differences of individual isotope's aqueous diffusion coefficients. For a two-isotope solute like NaCl, the developed hyperfiltration model predicts that signfiicant fractionation (5 per mil relative to SMOC) should occur in pore water of arenaceous and/or carbonate material adjacent to the upgradient side of a clay lens or shale.The easiest way to test the model is to experimentally investigate its most specific prediction: the d37Cl minimum. This aspect of the model is easily testable because solution fluxes of 10-5 to 10-7 cm.sec-1 are easy to replicate in a laboratory. Calculations show that the position of the d37Cl minimum occurs at about 10 of the length of the developed concentration polarization layer (as measured outward from the membrane's high-pressure interface). The predicted magnitude of the d37Cl minimum can attain -5 per mil for a clay membrane of moderate (20%) ideality. The unique aspect of this project is in situ sampling of solutions directly from a CPL. Until now, this has neither been done nor even considered. The proposed experiments will yield show unequivocally that a minimum does (or does not) exist. Should the experiments fail to confirm the theory, then hyperfiltration plays no meaningful role in fractionation of solute isotopes in aqueous systems. If, however, the experimental data support the model, then isotope geochemists may have to reevaluate interpretations of their solute isotope data if their groundwater samples flowed through membrane-functioning units.

Fritz -0001054超滤（又名当溶液平流通过选择性渗透材料如粘土时，发生反渗透（“反渗透”）。 溶质的同位素以相同的速度向膜平流;然而，由于单个同位素的水扩散系数的差异，它们扩散回到不同速率的高压储层中。 对于像NaCl这样的双同位素溶质，开发的超滤模型预测，显着分馏（5每密耳相对于SMOC）应发生在砂质和/或碳酸盐材料的孔隙水邻近的粘土透镜或shale.The最简单的方法来测试该模型是实验研究其最具体的预测：d37 Cl最小。 该模型的这一方面很容易检验，因为10-5至10-7 cm·sec-1的溶液通量很容易在实验室中复制。 计算表明，d37 Cl最小值的位置发生在约10的开发浓度极化层的长度（从膜的高压界面向外测量）。 对于中等（20%）理想的粘土膜，d37 Cl最小值的预测值可以达到-5/mil。 该项目的独特之处在于直接从CPL现场采样解决方案。到目前为止，这一点尚未完成，甚至尚未考虑过。 所提出的实验将明确地表明，最小值确实存在（或不存在）。 如果实验不能证实这一理论，那么超滤在水体系中溶质同位素的分馏中就没有意义了。 然而，如果实验数据支持该模型，那么同位素地球化学家可能不得不重新评估他们的溶质同位素数据的解释，如果他们的地下水样品流过膜功能单元。