Accelerated solvent extraction of dioxins sequestered in activated carbon: A response surface methodology-based optimization

Activated carbon (AC) is an effective sorbent for sequestering dioxin-like compounds, thereby reducing their bioavailability. Consequently, AC amendment is a promising tool for remediating dioxin-polluted soils, but tracking remediation results requires quantification of the dioxins sequestered within ACs. Standard methods for quantifying dioxins in soils are often unable to extract dioxins from AC, so the present study addresses this gap by optimizing an accelerated solvent extraction (ASE) method. The incipient wetness method, based on AC pore volume, was found effective for preparing reproducible, homogeneous, and strong dioxin-AC complexes to test extraction processes, and was validated using ¹⁴C-2378-TCDD. Preliminary extractions were conducted with AC-sequestered 2378-TCDD, and identified AC surface area, extraction temperature, and solvent system composition as key independent variables. Extraction trials using ASE were performed according to the Box-Behnken response surface methodology, and the resulting data were statistically analyzed to understand the interaction of these variables and model extraction efficiency. This model, derived using 2378-TCDD in AC, was also effective for predicting the extraction efficiencies for all 17 of the most toxic dioxin/furan congeners from three AC materials with specific surface areas from 100 to 1100 m²/g. The optimized extraction methodology achieved an average extraction efficiency of 70–90% for dioxin congeners, depending on the surface area of the AC. This study improves the quantification of dioxins in carbonaceous materials, shows that extraction temperatures above 200 °C are required for higher efficiencies, and paves the way for more reliable assessment and remediation of dioxin-like compounds.