Date of this Version
Published in Journal of Hazardous Materials 268 (March 15, 2014), pp. 177–184; doi: 10.1016/j.jhazmat.2014.01.007
Treating dense non-aqueous phase liquids (DNAPLs) embedded in low permeability zones (LPZs) is aparticularly challenging issue for injection-based remedial treatments. Our objective was to improve thesweeping efficiency of permanganate (MnO4−) into LPZs to treat high concentrations of TCE. This wasaccomplished by conducting transport experiments that quantified the penetration of various perman-ganate flooding solutions into a LPZ that was spiked with non-aqueous phase14C-TCE. The treatments weevaluated included permanganate paired with: (i) a shear-thinning polymer (xanthan); (ii) stabilizationaids that minimized MnO2rind formation and (iii) a phase-transfer catalyst. In addition, we quantifiedthe ability of these flooding solutions to improve TCE destruction under batch conditions by develop-ing miniature LPZ cylinders that were spiked with14C-TCE. Transport experiments showed that MnO4−alone was inefficient in penetrating the LPZ and reacting with non-aqueous phase TCE, due to a distinctand large MnO2rind that inhibited the TCE from further oxidant contact. By including xanthan withMnO4−, the sweeping efficiency increased (90%) but rind formation was still evident. By including thestabilization aid, sodium hexametaphosphate (SHMP) with xanthan, permanganate penetrated 100% ofthe LPZ, no rind was observed, and the percentage of TCE oxidized increased. Batch experiments usingLPZ cylinders allowed longer contact times between the flooding solutions and the DNAPL and resultsshowed that SHMP + MnO4−improved TCE destruction by ∼16% over MnO4−alone (56.5% vs. 40.1%).These results support combining permanganate with SHMP or SHMP and xanthan as a means of treatinghigh concentrations of TCE in low permeable zones.
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