Application of in situ chemical oxidation to remediate sulfolane-contaminated groundwater: batch and pilot-scale studies

To investigate the feasibility and effectiveness of applying in situ chemical oxidation (ISCO) on the remediation of sulfolane-contaminated groundwater, batch and pilot-scale studies were conducted in this study. The kinetics of sulfolane oxidation by Fenton and Fenton-like processes and optimal operational conditions were evaluated. The major control factors in the ISCO study included H2O2 concentrations, ratio of H2O2 to ferrous iron (mol/mol), molar ratios of oxidant to sulfolane, and catalyst effect. Results show that the Fenton reaction could obtain a complete sulfolane oxidation with the following operational conditions: 3% of H2O2, molar ratio of H2O2 to ferrous iron = 1:0.5, and initial sulfolane concentration = 72 mg/L. The calculated pseudo-first-order decay rate constants (k') were 1.32 x 10(-1) and 6.69 x 10(-2) min(-1) for sulfolane degradation under Fenton and Fenton-like oxidation reaction processes with 3% of H2O2 concentration, respectively. However, the sequential Fenton-like operational pattern could be an alternate option to obtain a complete sulfolane removal efficiency. Results from the soil oxidant demand test show that approximately 25%-35% of supplied H2O2 (3%) was consumed by soil organic matter, and thus, higher oxidant concentration would be required for field application. Sulfolane oxidation would result in sulfuric acid production, which caused the decrease in solution pH, and this would be beneficial to Fenton reaction. A sulfolane-contaminated groundwater site was selected for the pilot-scale study and Fenton oxidation process was applied for sulfolane degradation. Approximately, 600 L of H 2 0 2 solution (5%) [molar ratio of [H2O2]:[Fe2+] = 1:0.5] was injected into the injection well (IW) to oxidize sulfolane in situ. Up to 97% and 88% of sulfolane could be removed (initial sulfolane concentration = 68 mg/L) in the IW and a downgradient monitor well (located 5 m downgradient of the IW). Results from the batch and pilot-scale studies demonstrate that the Fenton reaction could be an applicable remedial option to oxidize sulfolane and cleanup sulfolane-contaminated groundwater.

Automated summary

The study investigated the feasibility and effectiveness of in situ chemical oxidation (ISCO) for remediating sulfolane-contaminated groundwater through batch and pilot-scale studies. The results showed that the Fenton reaction could achieve complete sulfolane oxidation under specific operational conditions.