Bk. Gullett et al., THERMAL-TREATMENT OF 1,2,3,4-TETRACHLORODIBENZO-P-DIOXIN BY REACTION WITH CA-BASED SORBENTS AT 23-300 DEGREES-C, Environmental science & technology, 31(7), 1997, pp. 1855-1862
The fate of combustion-generated polychlorinated dibenzo-p-dioxins (PC
DDs) and polychlorinated dibenzofurans (PCDFs) captured in sorbent-bas
ed, air pollution control devices remains uncertain. This process was
simulated by passing vapor-phase 1,2,3,4-tetrachlorinated dibenzo-p-di
oxin (TCDD) to a fixed-bed reactor laden with, typically, 1 g of calci
um (Ca)-based sorbent The sorbent bed, reactor rinsate, evaporation ch
amber, and gas impingers were analyzed separately to balance and accou
nt for the TCDD input. Tests at 160-300 degrees C demonstrated 50 to 1
00% conversion of TCDD to higher molecular weight, chlorinated product
s with both aromatic and aliphatic components. The unlikeliness of con
ventional semivolatile GC/MS analyses to detect these higher molecular
weight products may offer an alternative explanation for research stu
dies citing destruction or volatilization of chlorinated organics in t
he presence of Ca-based sorbents. The applicability of this reaction t
o other halogenated organics, such as polychlorinated biphenyls, may p
rovide a method for contaminated soil treatment. More extensive experi
mental and analytical work is necessary to fully understand the reacti
on mechansim, the full range and stability of potential reaction produ
cts, and the ecological and human health implications. Alteration of t
he structural symmetry and size of the TCDD molecule (and related halo
genated organics) will likely cause significant reductions in toxicity
.