Carbon injection to support in-situ smoldering remediation

Per- and polyfluoroalkyl substances (PFAS) are a group of anthropogenic contaminants that are receiving increasing concern due to their associated negative health effects. The properties of PFAS result in their persistence and stability, which present challenges for remediation. Activated carbon is currently the most widely used method for PFAS treatment since carbon microparticle injection can be used for in-situ treatment; however, this method does not result in PFAS destruction. Thermal treatment is a promising posttreatment method that can be used with activated carbon as long as sufficient PFAS-destroying temperatures are achieved (>900 degrees C). A promising in-situ thermal treatment technology is Self-Sustaining Treatment for Active Remediation (STAR), which uses smoldering combustion to destroy organic contaminants embedded within a porous matrix. This study investigates carbon injection to support STAR for the treatment of PFAS. Four solutions were used (1) 17% colloidal activated carbon (CAC); (2) 23% CAC; (3) 17% powdered activated carbon (PAC); and, (4) 23% PAC. Smoldering temperatures greater than the required PFAS destruction temperature were reached if 50 g carbon/kg sand was achieved for injection and soil-mixing delivery methods. Moreover, emulsified vegetable oil (EVO) was a successful secondary surrogate fuel to enhance smoldering temperatures when supplied at a quantity less than or equal to carbon microparticles. These findings present the necessary intermediate laboratory work to evaluate methods that will achieve PFAS treatment through STAR when applied in the field.