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Activated carbon (AC) is widely used for removing organic contaminants; however, its finite adsorption capacity may limit the long-term use. Oxidation regeneration of saturated AC is one of the effective measures to recover the adsorptive capacity of AC, even though the deterioration of AC during the regeneration is common. In this study, advanced oxidation process (Fenton combined persulfate system, Fe2+/H2O2/S2O82–) was used to regenerate the saturated AC, the mechanisms of AC deterioration were evaluated, and the interactions of oxidants, contaminants, and AC during the adsorption/regeneration processes were investigated. The results indicate that the oxidants mainly functions on the AC surface, resulting in the deterioration of AC along with the destruction of the sorbed contaminant (e.g., trichloroethylene in this study). Deterioration of AC exposed fresh carbon to the surface, however, such emergence of the fresh carbon to the AC surface does not seem to increase the AC adsorption capacity. Iron precipitation on the surface of AC was also observed during the adsorption/regeneration process, however, it can be partially removed from the surface of AC along with the carbon deterioration.

Activated carbon (AC) is widely used in the removal of organic contaminants; however, its long-term use is impeded by the limited adsorption capacity. Regeneration of AC by using advanced oxidation has been in practice, especially for Fe2+/H2O2process and Fe2+/S2O82−process, however, both of them have limitations in the regeneration of AC. This work attempted the combination of Fe2+/H2O2and Fe2+/S2O82−(Fe2+/H2O2/S2O82−) to effectively regenerate AC and recover its activity through exposing fresh carbon on its surface. Trichloroethylene (TCE) was selected as the target contaminant in this study. Fe2+, H2O2, and S2O82−were the variables to optimize for AC’s regeneration. Based on the variation of variables obtained from Fe2+/H2O2process and Fe2+/S2O82−process, the response surface methodology (RSM) was applied to have the optimum ratio of variables for the regeneration of AC of Fe2+/H2O2/S2O82−process. Results from RSM show that the Fe2+/H2O2/S2O82−process achieved a molar ratio of TCE/Fe2+/H2O2/S2O82−at 1/9.00/56.63/76.25. The iron loss was measured at 2.84%, while the TCE removal efficiency reached 98.63%. The average regeneration rate of AC through the optimized Fe2+/H2O2/S2O82− process was 26.28%, with minimum iron precipitation.

Co-oxidation of trivalent chromium (Cr(III)) to hexavalent chromium (Cr(VI)) during ozonation of organic pollutants represents a common problem facing the implementation of in situ chemical oxidation (ISCO) for environmental remediation. A laboratory study was conducted by using groundwater and saturated soil samples from a field site in Sacramento, California, to determine optimal O3dosage to achieve satisfactory remediation of MTBE while minimizing co-oxidation of Cr(III) to Cr(VI). Total oxidant demand was determined (28.33mg O3L−1) and used as the benchmark to establish a range of ozone dosages for the study. Concentration changes in MTBE and chromium were monitored at O3dosages less than and greater than the benchmark. The results indicate that MTBE is preferentially oxidized by ozone at and below the indicated benchmark dosage prior to the oxidation of Cr(III) to Cr(VI). The resultant O3dosage of 28.33mgL−1was applied in the field implementation, verifying that the O3can be applied in a controlled manner to remediate MTBE while minimizing the formation of Cr(VI).