Temperature-dependent partitioning of 1,4-dioxane between atmospheric emissions and landfill leachate at waste...

Highly reactive lime powder (HRLP) containing diethylene glycol (DEG) as a hydration retarder is widely used in bag-filter air pollution control units at municipal solid waste incineration (MSWI) facilities in Japan. Under the acidic, elevated-temperature conditions of the bag-filter (∼170 °C, H₂SO₄/HCl atmosphere), residual DEG undergoes acid-catalyzed cyclodehydration to produce 1,4-dioxane, a Group 2B carcinogen fully miscible with water and persistent in the environment. Using laboratory-simulated bag-filter conditions, this study quantifies both pathways for 1,4-dioxane from DEG-containing HRLP: the atmospheric gas-phase pathway and the solid-phase retention pathway with implications for landfill leachate contamination. Laboratory-prepared HRLP with systematically varied DEG content (0-4 v/v%) and drying temperature (150-350 °C) was analyzed for gas-phase 1,4-dioxane (headspace GC/MS/MS) and solid-phase 1,4-dioxane retained in the HRLP residue (DCM-extraction GC/MS/MS). Gas-phase concentrations increased with DEG content and decreased with drying temperature (maximum 58.6 mg m^-3 at 4 v/v% DEG, 150 °C). Solid-phase retention showed the opposite temperature dependence, with leachate-equivalent concentrations reaching 38.3 mg L^-1 at 4 v/v% DEG and 350 °C. These opposing trends imply a cross-media trade-off: operating changes that suppress one pathway may enhance the other. As a proof of concept for source reduction, CO₂-spray carbonation of quicklime achieved a BET surface area of 28.4 m² g^-1 without organic additives. The present bench-scale results are not designed for regulatory compliance assessment but provide a quantitative basis for evaluating the environmental significance of DEG-containing HRLP.