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，尽管在补救工作方面进行了20年的投资，但加拿大仍有22，000多个联邦危险废物场地，需要额外的49亿加元补救费用。报告还指出，氯化溶剂和多氯联苯等高密度非水相液体是这些场址最普遍的污染物。然而，迄今为止，DNAPL的修复一直具有挑战性，因为这些化合物通常位于远低于表面，微溶于水，并且相对不溶于水。因此，我们的研究计划旨在开发一种创新的方法，可以加快DNAPLs的去除和降低修复成本。 拟议的研究调查的效率和实用性的技术相结合的助溶剂冲洗过氧化氢（H2 O2）为基础的修复。在过去，尽管这两种技术已经分别用于DNAPL修复，但是将它们组合成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，由H2 O2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，建立在有机和自由基化学文献的仔细审查的基础上，建议在一个组合的共溶剂/H2 O2系统DNAPLs可以有效地去除通过意想不到的还原转化过程。特别是，该模型表明，这些转化过程可以启动一系列的自由基链反应，其重要性被忽视，在过去。因此，我们提出了实验室实验来检查是否真的是这样，如果是这样，找到方法，使组合技术更有效，更强大的现场应用。这项研究的成果将是一种能够有效去除DNAPLs的创新技术，这将降低修复成本和人类对DNAPLs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.