In-place regeneration of SVE-loaded GAC using Fenton's reagents

The feasibility of Fenton's reaction as an in-place chemical regeneration process for granular activated carbon (GAC) was studied. Methods were investigated for enhancing the rate of Fenton-dependent regeneration of halogenated VOC-loaded GAC. The target organic compounds (methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, trichloroethylene (TCE), and tetrachloroethylene (PCE)) were analyzed by GC-ECD according to a modified version of EPA method 551.1. For each of the compounds tested, the rate of disappearance of the adsorbed contaminant was approximately proportional to its adsorbed concentration. All compounds exhibited pseudo first-order kinetics through much of their observed range. However, the observed pseudo first-order reaction rate constant for TCE was 0.045/hr, or less than one-third that of methylene chloride. The observed reaction rate constants were strongly correlated to contaminant solubility. The most soluble, methylene chloride, was 89% degraded during a 14-hr regeneration period. In the field trials, the halogenated organics (predominantly TCE and PCE) sorbed out of a gas-phase soil vapor extraction stream onto the GAC in a packed bed. Upon saturation, the GAC was regenerated (analogous to the laboratory trials) using Fenton's reagents in an aqueous-stream capable of expanding the bed in an up-flow mode. Preliminary results at the field site using the Fenton treatment indicated that at least 80% TCE destruction is achieved during a 6-hr regeneration period. Preliminary results indicated that H₂O₂ usage in the field is higher than expected from the laboratory trials. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).