Enhanced thermal desorption of chlorinated hydrocarbons by nanoscale zero-valent iron: the effect of in situ dechlorination.

Thermal desorption provides an efficient solution to remediate soil contaminated with chlorinated organic pollutants. However, enhanced desorption efficiency is desired to facilitate easier and less costly remediation. Hence, nanoscale zero-valent iron (nZVI) was combined with thermal desorption to remove trichloroethene (TCE) and trichlorobenzene (TCB) from soil in a laboratory-scale study. The addition of nZVI greatly improved the desorption efficiency, especially at low temperature with 99.6% of TCE and 98.8% of TCB removed at 300 °C for 2 h. Characterization results revealed that the addition of nZVI loosened the structure of soil, preventing the soil from agglomerating during the thermal treatment. Besides, the analyses of dechlorination intermediates and the variation of Fe species proved the in situ dechlorination effect of nZVI and the redox cycle of Fe was revealed. Moreover, the influences of nZVI dosage and treatment time on thermal treatment were assessed. This study not only offers new perspectives for contaminated soil remediation, but also provides mechanistic insights into the dechlorination effect of nZVI in the thermal desorption.