Dehalogenation is effective in removing halogens from hazardous organic compounds such as dioxins, furans, PCBs, and chlorinated pesticides; rendering them non-toxic. APEG will dehalogenate aliphatic compounds if the mixture reacts longer and at temperatures significantly higher than for aromatics. This technology usually costs less than incineration.
Treatability tests should be conducted before the final selection of the APEG technology. Operating factors such as quantity of reagents, temperature, and treatment time should be defined. Treated soil may contain residual reagents and treatment by-products that should be removed by washing the soil with water. The soil should also be neutralized by lowering the pH before final disposal.
Specific safety aspects must be considered. Treatment of certain chlorinated aliphatics in high concentrations with APEG may produce potentially explosive compounds (e.g., chloroacetylenes) or cause a fire hazard.
The BCD process (Figure 11.15.12) embodies the following steps: mixing the chemicals with the contaminated matrix (such as excavated soil or sediment or liquids, containing these toxic compounds), and heating the mixture at 320-340°C for 1-3 hr. The off-gases are treated before releasing to the atmosphere. The treated receptor remains are nonhazardous, and can be either disposed of according to standard methods, or further processed to separate components for reuse.
Was this article helpful?