Removal of PCDD/Fs from contaminated sediment and released effluent gas by charcoal in a proposed cost-effective thermal treatment process

• A low-cost heat treatment method for removing PCDD/Fs from solids has been proposed.
• The charcoal was recycled, enabling its use as both a thermal source and adsorbent.
• A moist sediment was used as an adsorbent for the removal of tar compounds.
• PCDD/Fs in the treated sediment and effluent gas complied with the emission limit.
• PCDD/Fs were easily released from sediment with increasing air superficial velocity.

A novel cost-effective thermal treatment technology has been proposed for the removal of PCDD/Fs from contaminated sediment and released effluent gas using charcoal as both an adsorbent and a thermal source. When a reactor was used for thermal treatment, the PCDD/Fs removal efficiency exceeded 98% from the sediment at the three different air superficial velocities employed in this study. The total PCDD/F international toxic equivalent (I-TEQ) contents, both in the treated sediments and effluent gas, were below the Japanese emission standard limit. Analysis of the PCDD/F contents in different fractions showed that large quantities of PCDDs but not PCDFs were evaporated from the sediment and adsorbed in the moist sediment column. This difference was attributed to the formation of PCDDs from pentachlorophenol (PCP) during the cooling process following the thermal treatment process in the reactor. This proposed thermal process provides a promising alternative to the conventional methods.