Iron Optimization for Fenton-Driven Oxidation of MTBE-Spent Granular Activated Carbon

Fenton-driven chemical oxidation of methyl <i>tert</i>-butyl ether (MTBE)-spent granular activated carbon (GAC) was accomplished through the addition of iron (Fe) and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) (15.9 g/L; pH 3). The Fe concentration in GAC was incrementally varied (1020−25 660 mg/kg) by the addition of increasing concentrations of Fe solution (FeSO<sub>4</sub>·7H<sub>2</sub>O). MTBE degradation in Fe-amended GAC increased by an order of magnitude over Fe-unamended GAC and H<sub>2</sub>O<sub>2</sub> reaction was predominantly (99%) attributed to GAC-bound Fe within the porous structure of the GAC. Imaging and microanalysis of GAC particles indicated limited penetration of Fe into GAC. The optimal Fe concentration was 6710 mg/kg (1020 mg/kg background; 5690 mg/kg amended Fe) and resulted in the greatest MTBE removal and maximum Fe loading oxidation efficiency (MTBE oxidized (μg)/Fe loaded to GAC(mg/Kg)). At lower Fe concentrations, the H<sub>2</sub>O<sub>2</sub> reaction was Fe limited. At higher Fe concentrations, the H<sub>2</sub>O<sub>2</sub> reaction was not entirely Fe limited, and reductions in GAC surface area, GAC pore volume, MTBE adsorption, and Fe loading oxidation efficiency were measured. Results are consistent with nonuniform distribution of Fe, pore blockage in H<sub>2</sub>O<sub>2</sub> transport, unavailable Fe, and limitations in H<sub>2</sub>O<sub>2</sub> diffusive transport, and emphasize the importance of optimal Fe loading.