Optimization and analysis of a slow-release permanganate gel for groundwater remediation in porous and low-permeability media

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Dense nonaqueous phase liquids (DNAPLs) like trichloroethylene (TCE) serve as the most common form of groundwater pollution in the world. Potassium permanganate (KMnO4) is a strong oxidant that can quickly destroy DNAPLs into innocuous products. Slow-release permanganate gel (SRPG), a mixture of colloidal silica (CS) and KMnO4, has been recently developed as novel treatment option for dilute and large plumes of DNAPLs in groundwater. The objective of this study was to characterize and optimize gelling and release properties of a SRPG solution in saturated porous media. It was hypothesized that CS and KMnO4 content of the SRPG constrain gelation and release duration. Batch and column tests showed that gelation could be delayed through manipulation of the KMnO4 content. In column tests, silica content had little effect on the gelation lag stage and release rate but influenced duration of permanganate release. Flow tank tests comparing Bindzil 1440 (B-40) SRPGs with pure KMnO4 solutions under varying media conditions demonstrated that the presence of CS enhanced lateral spread and prolonged release duration of the oxidant.