To elucidate pore-scale mechanisms governing the coupled process of multiphase flow,chemical reactions,and phase transformations during the oxidation remediation of dense non-aqueous phase liquids(DNAPLs),we conducted 48microfluidic experiments to investigate the trichloroethylene(TCE)oxidation by potassium permanganate(KMnO4).The results show that when KMnO4 concentration exceeded 3g/L,the manganese dioxide(MnO2)solid products during TCE oxidation formed a"solid wall",which hindered the contact between MnO4-and TCE.Under such conditions,the residual TCE oxidation proceeded only via the slow penetration of KMnO4 solution through the MnO2 wall,where limited MnO4-was converted to Mn2+.As Mn2+diffused out of the MnO2 wall,it was re-oxidized to MnO2 solid phase,creating a negative feedback loop and significantly reducing remediation efficiency.At KMnO4 concentrations below 3g/L,the MnO2 solid products were able to attach to the channel surfaces,permitting continuous reaction between MnO4-and TCE,thereby resulting in a higher remediation efficiency.The introduction of phosphate significantly suppressed the formation of MnO2 solid products and improved remediation efficiency,with an optimal KMnO4 concentration for TCE remediation determined to be 1～2g/L.
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