Liang Chenju, Lee I-Ling
Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Rd., Taichung City 402, Taiwan.
J Contam Hydrol. 2008 Sep 10;100(3-4):91-100. doi: 10.1016/j.jconhyd.2008.05.012. Epub 2008 Jun 11.
In situ chemical oxidation (ISCO) is considered a reliable technology to treat groundwater contaminated with high concentrations of organic contaminants. An ISCO oxidant, persulfate anion (S(2)O(8)(2-)) can be activated by ferrous ion (Fe(2+)) to generate sulfate radicals (E(o)=2.6 V), which are capable of destroying trichloroethylene (TCE). The property of polarity inhibits S(2)O(8)(2-) or sulfate radical (SO(4)(-)) from effectively oxidizing separate phase TCE, a dense non-aqueous phase liquid (DNAPL). Thus the oxidation primarily takes place in the aqueous phase where TCE is dissolved. A bench column study was conducted to demonstrate a conceptual remediation method by flushing either S(2)O(8)(2-) or Fe(2+) through a soil column, where the TCE DNAPL was present, and passing the dissolved mixture through either a Fe(2+) or S(2)O(8)(2-) fluid sparging curtain. Also, the effect of a solubility enhancing chemical, hydroxypropyl-beta-cyclodextrin (HPCD), was tested to evaluate its ability to increase the aqueous TCE concentration. Both flushing arrangements may result in similar TCE degradation efficiencies of 35% to 42% estimated by the ratio of TCE degraded/(TCE degraded+TCE remained in effluent) and degradation byproduct chloride generation rates of 4.9 to 7.6 mg Cl(-) per soil column pore volume. The addition of HPCD did greatly increase the aqueous TCE concentration. However, the TCE degradation efficiency decreased because the TCE degradation was a lower percentage of the relatively greater amount of dissolved TCE by HPCD. This conceptual treatment may serve as a reference for potential on-site application.
原位化学氧化（ISCO）被认为是一种处理受高浓度有机污染物污染的地下水的可靠技术。一种ISCO氧化剂，过硫酸根阴离子（S₂O₈²⁻）可被亚铁离子（Fe²⁺）活化以产生硫酸根自由基（Eₒ = 2.6 V），其能够破坏三氯乙烯（TCE）。极性特性抑制S₂O₈²⁻或硫酸根自由基（SO₄⁻）有效氧化单独相态的TCE，即一种致密非水相液体（DNAPL）。因此，氧化主要发生在TCE溶解的水相中。进行了一项实验室柱实验，以演示一种概念性修复方法，即通过土壤柱冲洗S₂O₈²⁻或Fe²⁺，土壤柱中存在TCE DNAPL，然后使溶解的混合物通过Fe²⁺或S₂O₈²⁻流体喷射帷幕。此外，测试了一种增溶化学物质羟丙基-β-环糊精（HPCD）的效果，以评估其提高水相TCE浓度的能力。两种冲洗方案可能导致相似的TCE降解效率，通过TCE降解量/（TCE降解量+流出物中残留的TCE量）的比率估算为35%至42%，以及降解副产物氯化物的生成速率为每土壤柱孔隙体积4.9至7.6 mg Cl⁻。添加HPCD确实大大提高了水相TCE浓度。然而，TCE降解效率降低，因为在相对大量由HPCD增溶的TCE中，TCE降解所占百分比更低。这种概念性处理方法可为潜在的现场应用提供参考。
