Per‐ and polyfluoroalkyl substances (PFAS) are a class of stable compounds widely used in diverse applications. These emerging contaminants have unique properties due to carbon–fluorine (C–F) bonds, which are some of the strongest bonds in chemistry. High energy is required to break C–F bonds, which results in this class of compounds being recalcitrant to many degradation processes. Many technologies studied that have shown treatment effectiveness for PFAS cannot be implemented in situ. Chemical oxidation is a demonstrated remediation technology for in situ treatment of a wide range of organic environmental contaminants. An overview of relevant literature is presented, summarizing the use of single or combined reagent chemical oxidation processes that offer insight into oxidation–reduction chemistries potentially capable of PFAS degradation. Based on the observations and results of these studies, bench‐scale treatability tests were designed and performed to establish optimal conditions for the formation of specific free radical species, including superoxide and sulfate radicals, via various combinations of oxidants, catalysts, pH buffers, and heat to assess PFAS treatment by chemical oxidants. The study also suggests the possible abiotic transformations of some PFAS when chemical oxidation is or was used for treatment of primary organic contaminants (e.g., petroleum or chlorinated organic compounds) at a site. The bench‐scale tests utilized field‐collected samples from a firefighter training area. Much of the available data related to chemical oxidation of PFAS has only been reported for one or both of the two more commonly discussed PFAS (perfluorooctane sulfonic acid and/or perfluorooctanoic acid). In contrast, this treatability study evaluates oxidation of a diverse list of PFAS analytes. The results of this study and published literature conclude that heat‐activated persulfate is the oxidation method with the best degradation of PFAS. Limited reduction of reported PFAS concentrations in this study was observed in many oxidation reactors; however, unknown mass of PFAS (such as precursors of perfluoroalkyl acids) that cannot be identified in a field collected sample complicated quantification of how much oxidative destruction of PFAS actually occurred.

The mining of coal most often leads to the development of Acid Rock Drainage (ARD) because during peat accumulation anoxic and reducing conditions establish and an availability of sulphate and reducible iron, even at low concentration, leads to the formation of iron sulphides (mostly pyrite). Once exposed oxidation and acid generation occurs, which may mobilize trace metals from the coals. The combination of acid and metals can seep into water ways where it can effectively sterilize many km of stream, and deposit substantial quantities of iron oxy-hydroxides. Frequently waste rock and coal washery tailings are stored where they provide suitable habitat for bacteria that accelerate the oxidation of pyrite and the production of acid. Aberdare East colliery is a former underground mine located in Cessnock, New South Wales, Australia. Coal washery tailings from the mine are impounded in a series of overlapping stacked cells in a small catchment. Relatively clean water enters the south eastern extent of the tailings and moves to the northwest down the hydrological gradient, and exit the north western batter slope into the a small creek. During flow through the tailings salinity, metal content, redox potential, and temperature all increase; solution pH decreases. Investigations indicate that the impoundment contains 109,445 m 3 of water, 337,793 m 3 saturated fines, 720,113 m 3 of unsaturated fines, and 184,568 m 3 of clay capping. Treatment rates indicate that the water requires 5.123kg/m 3 of Bauxsol™ Acid B Extra™ C5T5 blend (561 t) and that a further 24,000 t of Bauxsol™ ViroMine™ is required to prevent further acidity at the site being generated. This compares favourably with lime of 0.951 kg/m 3 for the water (104 t) and 32,750 t to prevent further acid production from the tailings. Additional benefits from the Bauxsol™ based treatments are lowered sludge volumes during water treatment, increased chemical stability of the residues and therefore greatly reduced disposal costs, a decreased susceptibility to dissolution of the ANC from the soil/tailings profile that reduces the possibility of having to reapply after 5 or 10 years and, consequently, a reduced safety margin for the Bauxsol™ application is required.

Although known to be one of the most effective oxidants for treatment of organic contaminants, catalyzed hydrogen peroxide (CHP) is typically not used for soil mixing applications because of health and safety concerns related to vapor generation and very rapid rates of reaction in open excavations. In likely the first large‐scale in situ CHP soil mixing application, an enhanced CHP, modified Fenton's reagent (MFR), was applied during soil mixing at the Kearsarge Metallurgical Superfund Site in New Hampshire. An innovative rotating dual‐axis blender (DAB) technology was used to safely mix the MFR into low‐plasticity silt and clay soils to remediate residual 1,1,1‐trichloroethane (111TCA); 1,1‐dichloroethene (11DCE); and 1,4‐dioxane (14D). It was expected that the aggressive treatment approach using relatively “greener” hydrogen peroxide (HP) chemistry would effectively treat Site contaminants without significant byproduct impacts to groundwater or the adjacent pond. The remediation program was designed to treat approximately 3,000 cubic yards of residual source area soil in situ by aggressively mixing MFR into the soils. The subsurface interval treated was from 7 to 15 feet below ground surface. To accurately track the soil mixing process and MFR addition, the Site was divided into 109 10‐foot square treatment cells that were precisely located, dosed, and mixed using the DAB equipped with an on‐board GPS system. The use of stabilizing agents along with careful calculation of the peroxide dose helped to ensure vapor‐free conditions in the vicinity of the soil mixing operation. Real‐time sampling and monitoring were critical in identifying any posttreatment exceedences of the cleanup goals. This allowed retreatment and supplemental testing to occur without impacting the soil mixing/in situ chemical oxidation (ISCO) schedule. Posttreatment 24‐hr soil samples were collected from 56 random locations after ensuring that the HP had been completely consumed. The posttreatment test results showed that 111TCA and 11DCE concentrations were reduced to nondetect (ND) or below the cleanup goals of 150 μg/kg for 111TCA and 60 μg/kg for 11DCE. Supplemental posttreatment soil samples, collected six months after treatment, showed 100 percent compliance with the soil treatment goals. Groundwater samples collected one year after the MFR soil mixing treatment program showed either ND or low concentrations for 111TCA, 11DCE, and 14D. Successful stabilization and site restoration was performed after overcoming considerable challenges associated with loss of soil structure, high liquid content, and reduced bearing capacity of the blended soils.