title: Permanganate diffusion and reaction in sedimentary rocks.
abstract: In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate.
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, United States.
authors.forename: Qiuyuan
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, United States. Electronic address: dongh@miamioh.edu.
authors.forename: Hailiang
authors.initials: H
authors.lastname: Dong
authors.affiliation: CB&I, Inc., 17 Princess Road, Lawrenceville, NJ 08648, United States.
authors.forename: Rachael M
authors.initials: RM
authors.lastname: Towne
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, United States.
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Fischer
authors.affiliation: CB&I, Inc., 17 Princess Road, Lawrenceville, NJ 08648, United States.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Schaefer
mesh_terms: D011232:Chemical Precipitation; D004058:Diffusion; D052918:Environmental Restoration and Remediation / Q000592:standards*; D019015:Geologic Sediments / Q000737:chemistry*; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry*; D009515:New Jersey; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D006843:Hydrocarbons, Chlorinated; D017895:Manganese Compounds; D010087:Oxides; D014874:Water Pollutants, Chemical; C048856:permanganic acid; D008345:Manganese
keywords: Diffusion; Permanganate; Remediation; Rock matrix