PNNL

Abstract

Injectable slow-release permanganate gel (ISRPG), formed by mixing KMnO4 solution with fumed silica powder, may have a potential application in remediating chlorinated solvent plumes in groundwater. A series of batch, column, and flow cell experiments has been completed to test the gel behavior under a variety of conditions. The experiments have provided information on ISRPG rheology, permanganate (MnO_4^-) release dynamics and distribution, and trichloroethene (TCE) degradation by ISRPG-released oxidant. The gel possesses remarkable shear thinning characteristics, resulting in a relative low viscosity during mixing, and facilitating its subsurface injection and distribution. Batch tests revealed that MnO_4^-was diffused out from ISRPG into water while the gel did not dissolve or disperse into water but maintained its initial shape. Column experiments showed that MnO_4^- release from ISRPG lasted considerably longer than the release from aqueous solution. TCE degradation by ISRPG-released MnO_4^- was much more effective than that when MnO_4^- was delivered using aqueous solution injection. In two-dimensional flow cell experiments, it was demonstrated that ISRPG slowly released a long-lasting low concentration MnO_4^- plume sufficient for remediation and sustainable in an aquifer for a long period of time.