In Situ Remediation of DNAPLs by coupling cosolvent flushing and hydrogen peroxide: contribution of reductive reactions on contaminant transformation

在2014年发布的一份报告中，加拿大议会预算官员估计，尽管在补救工作上投资了20年，加拿大仍有超过2.2万个联邦危险废物填埋场，需要额外支付49亿美元的补救费用。报告还指出，密集的非水相液体(DNAPL)，如氯化溶剂和多氯联苯，是这些地点最普遍的污染物。然而，到目前为止，DNAPLS的修复一直是具有挑战性的，因为这些化合物往往位于表面以下很远的地方，很少溶于水，而且相对顽固。因此，我们的研究计划旨在开发一种创新的方法，以加快DNAPLS的去除并降低补救成本。 这项拟议的研究调查了一种将共溶剂冲洗与基于过氧化氢(H_2O_2)的修复相结合的技术的效率和实用性。过去，尽管这两种技术被单独用于DNAPLS的修复，但将它们合并为单一处理技术的想法很少受到关注，因为通常认为它们是不相容的(即，过氧化氢产生的氧化剂不会氧化污染物，而是与助溶剂反应)。然而，我们的动力学模型建立在仔细回顾有机和自由基化学文献的基础上，表明在助溶剂/H_2O_2联合体系中，DNAPL可以通过意想不到的还原转化过程有效地去除。特别是，该模型表明，这些转化过程可能是由一系列自由基链反应启动的，而这些反应的重要性在过去被忽视了。因此，我们建议进行实验室实验，以检验情况是否属实，如果是这样，则寻找方法使组合技术更有效和更强大地适用于现场应用。这项研究的结果将是一种能够有效去除DNAPL的创新技术，这将减少补救成本和人类对DNAPL的暴露。

In a report released in 2014, the Parliamentary Budget Officer of Canada estimated that, despite two decades of investment in remediation efforts, Canada still has over 22,000 federal hazardous waste sites that will require an additional $4.9 billion of remediation cost. The report also indicated that Dense Non-Aqueous Phase Liquids (DNAPLs), such as chlorinated solvents and polychlorinated biphenyls, were among the most prevalent contaminants at those sites. To date, however, the remediation of DNAPLs has been challenging because these compounds are often located far below the surface, sparingly soluble in water, and relatively recalcitrant. Thus, our research program aims to develop an innovative approach that can expedite DNAPLs removal and reduce remediation cost. The proposed research investigates the efficiency and practicality of a technology that combines cosolvent flushing with hydrogen peroxide (H2O2)-based remediation. In the past, although these two technologies have been used separately for DNAPLs remediation, the idea of combining them into a single treatment technology has received little attention as it was often assumed that they are incompatible (i.e., the oxidant produced from H2O2 will not oxidize the contaminants but will react with the cosolvent instead). However, our kinetics model, built based on a careful review of organic and radical chemistry literature, suggested that in a combined cosolvent/H2O2 system DNAPLs could be effectively removed through unexpected reductive transformation processes. In particular, the model indicated that these transformation processes could be initiated by a series of radical chain reactions whose importance were overlooked in the past. Thus, we propose laboratory experiments to examine whether this is truly the case, and if so, to find ways to make the combined technology more effective and robust for field application. The outcome of this research will be an innovative technology capable of effectively removing DNAPLs, which would reduce remediation cost and human exposure to DNAPLs.