Suchomel Eric J, Ramsburg C Andrew, Pennell Kurt D
School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0512, USA.
J Contam Hydrol. 2007 Dec 7;94(3-4):195-214. doi: 10.1016/j.jconhyd.2007.05.011. Epub 2007 Jun 12.
The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.
通过批量实验和含水层单元实验相结合的方式，评估了两种可生物降解表面活性剂——聚氧乙烯（20）山梨醇酐单油酸酯（吐温80）和二己基磺基琥珀酸钠（气溶胶MA）从非均质多孔介质中回收代表性的致密非水相液体（DNAPL）——三氯乙烯（TCE）的能力。含有3.3%气溶胶MA、8%异丙醇和6 g/l氯化钙的水溶液产生的重量增溶比（WSR）为1.21 g TCE/g表面活性剂，相应的液-液界面张力（IFT）为0.19 dyn/cm。用大约两个孔隙体积的AMA配方冲洗含有TCE-DNAPL源区的含水层单元，导致TCE-DNAPL大量（>30%）迁移。然而，当水相流速足以将可移动的TCE-DNAPL驱向出水井时，TCE的质量回收率达到了81%。吐温80的水溶液表现出更大的溶解TCE的能力（WSR = 1.74 g TCE/g表面活性剂），并且IFT的降低明显较小（10.4 dyn/cm）。这些数据与用于从增溶能力估算IFT值的公认经验相关性相矛盾，并表明T80具有形成浓缩TCE乳液的独特能力。用小于2.5个孔隙体积的4% T80溶液冲洗含水层单元，TCE质量回收率在66%至85%之间，当总截留数超过2×10⁻⁵时，仅发生轻微的TCE-DNAPL迁移（<5%）。这些发现证明了吐温80和气溶胶MA溶液从非均质DNAPL源区有效回收TCE的能力，以及总截留数作为设计参数在先验预测用低IFT溶液冲洗时DNAPL迁移和堤岸角形成方面的实用性。鉴于它们在低浓度下刺激微生物还原脱氯的潜力，这些表面活性剂非常适合用于补救行动计划，该计划包括积极的大量去除，随后进行强化生物修复以处理氯化溶剂源区。
