A new in situ fracturing-enhanced oxidative remediation for various low-permeability phenanthrene-contaminated soils: Oxidation effectiveness and kinetics of potassium permanganate.

A new in situ fracturing-enhanced oxidative remediation approach was recommended in this study to achieve rapid and efficient remediation of low-permeability contaminated sites. The objective of this study was to evaluate the effects of permeability and potassium permanganate (KMnO) concentration on the oxidation effectiveness and kinetics of KMnO in phenanthrene (PHE)-contaminated soil through rigid-wall hydraulic conductivity tests and a series of laboratory experiments. The results indicate that for various low-permeability contaminated soils, there was a critical KMnO concentration to significantly reduce the remediation time and a critical Darcy velocity to meet remediation goals. A systematic research method was proposed to obtain the optimal design parameters. Furthermore, based on an equivalent batch test system, the reaction of KMnO migrating in the soil matrix between two adjacent parallel fracture layers followed piecewise first-order kinetics regardless of soil type. The piecewise judgment condition was a KMnO concentration ratio of exudate to infiltrate of ∼0.65. KMnO oxidation significantly reduced the ecotoxicity of various PHE-contaminated soils but had little effect on other physicochemical properties. Meanwhile, possible degradation pathways of PHE were proposed. Overall, this study provides important engineering and theoretical guidance for the widespread application of the new fracturing-enhanced oxidative remediation method.