DNAPL TCE Oxidation with Permanganate: Influence of the Phase Transfer Catalyst Pentyltriphenylphosphonium

Abstract

Dense nonaqueous phase (DNAPL) trichloroethylene (TCE) degradation by potassium permanganate (KMnO4) was investigated in the presence of the cationic surfactant pentyltriphenylphosphonium (PTPP) bromide, acting as a phase transfer catalyst. Series of batch tests were performed in 5.0-mL conical vials containing Milli-Q water and 1.0 mM DNAPL TCE with initial permanganate concentrations ([MnO4−]0) of 1.0, 2.0, 3.0, and 5.0 mM, adding PTPP (0, 10, and 20 mol% of permanganate, respectively). Chloride ion (Cl−) and MnO4− in water samples were analyzed to observe MnO4− consumption and TCE degradation over the elapsed time (0 to 90 min). The calculated values of pseudo first-order rate constants for MnO4− consumption indicated that the rate of MnO4− depletion increased with higher mole percent PTPP. At experimental conditions of 1.0 and 2.0 mM [MnO4−]0, analyses of Cl− concentration showed that higher mole percent of PTPP induced greater Cl− release, indicating faster TCE oxidation. On the other hand, for 3.0 and 5.0 mM [MnO4−]0, the concentration of Cl− was lower with the presence of PTPP. This result indicated that MnO4− had migrated further into the inner space of DNAPL, and consequently, the Cl− took a longer time to diffuse from DNAPL to an aqueous phase.