Ramsburg C Andrew, Pennell Kurt D, Kibbey Tohren C G, Hayes Kim F
Department of Civil and Environmental Engineering, University of Michigan, 181 EWRE, 1351 Beal Avenue, Ann Arbor, Michigan 48109-2125, USA.
Environ Sci Technol. 2003 Sep 15;37(18):4246-53. doi: 10.1021/es0210291.
A novel surfactant-enhanced aquifer remediation technology, density-modified displacement (DMD), has been developed to minimize risk of dense non-aqueous-phase liquid (DNAPL) downward migration during displacement floods. The DMD method is designed to be implemented using horizontal flushing schemes, with in situ DNAPL density conversion accomplished by the introduction of a partitioning alcohol (e.g., 1-butanol) in a predisplacement flood (preflood). Subsequent NAPL displacement and recovery is achieved by flushing with a low-interfacial-tension (low-IFT) surfactant solution. The efficiency of the DMD method may be enhanced for heavier DNAPLs, such as trichloroethene (TCE), by increasing alcohol delivery and the extent of partitioning during the preflood. The objective of this study was to evaluate the use of a macroemulsion, consisting of 4.7% (vol) Tween 80 + 1.3% (vol) Span 80 + 15% (vol) 1-butanol to achieve efficient in situ density conversion of TCE (relative to that obtained with use of an aqueous preflood solution) prior to low-IFT displacement and recovery from a two-dimensional aquifer cell. The cell was configured to represent a heterogeneous unconfined aquifer system with an overall NAPL saturation between 2% and 3%. After flooding with approximately 1.2 pore volumes of the macroemulsion, a low-IFT solution consisting of 10% (vol) Aerosol MA + 6% (vol) 1-butanol + 15 g/L NaCl + 1 g/L CaCl2 was introduced to displace and recover NAPL. Visual observations and quantitative measurements of effluent fluids demonstrated that in situ density conversion and displacement of TCE-NAPL was successful, with effluent NAPL densities ranging from 0.97 to 0.99 g/mL. For the experimental system employed herein, 93% recovery of the introduced TCE mass was realized after flushing with a combined 2.4 pore volumes of the density conversion and low-IFT solutions. These results demonstrate the increased efficiency of the DMD method when surfactant-based emulsions are used to enhance 1-butanol delivery and partitioning behavior.
一种新型的表面活性剂强化含水层修复技术——密度改性驱替法（DMD）已被开发出来，以最大限度地降低在驱替过程中致密非水相液体（DNAPL）向下迁移的风险。DMD方法设计为采用水平冲洗方案实施，通过在预冲洗（预充水）过程中引入一种分配醇（如1-丁醇）来实现原位DNAPL密度转换。随后，通过用低界面张力（低IFT）表面活性剂溶液冲洗来实现NAPL的驱替和回收。对于较重的DNAPL，如三氯乙烯（TCE），通过增加预充水过程中醇的注入量和分配程度，可以提高DMD方法的效率。本研究的目的是评估一种由4.7%（体积）吐温80 + 1.3%（体积）司盘80 + 15%（体积）1-丁醇组成的宏观乳液，在从二维含水层单元进行低IFT驱替和回收之前，实现TCE的高效原位密度转换（相对于使用含水预充水溶液获得的转换效率）。该单元被配置为代表一个非均质无压含水层系统，总体NAPL饱和度在2%至3%之间。在用大约1.2孔隙体积的宏观乳液进行充水后，引入一种由10%（体积）气溶胶MA + 6%（体积）1-丁醇 + 15 g/L氯化钠 + 1 g/L氯化钙组成的低IFT溶液来驱替和回收NAPL。对流出液的目视观察和定量测量表明，TCE-NAPL的原位密度转换和驱替是成功的，流出液NAPL密度范围为0.97至0.99 g/mL。对于本文所采用的实验系统，在用密度转换溶液和低IFT溶液共2.4孔隙体积进行冲洗后，实现了引入TCE质量的93%的回收。这些结果表明，当使用基于表面活性剂的乳液来提高1-丁醇的输送和分配行为时，DMD方法的效率得到了提高。
