Insight into degradation mechanism of PCBs from thermal desorption off-gas over iron-based catalysts

Iron-based catalysts were developed to achieve the hydrodechlorination (HDC)/oxidation of polychlorinated biphenyls (PCBs) from thermal desorption off-gas, and Fe3O4/γ-Al2O3 showed higher dechlorination efficiency than Fe2O3/γ-Al2O3. The optimal Fe loading resulted in 95.5% degradation 76.9% toxicity reduction gaseous PCBs, exhibited excellent stability during a 60-h test. gas chromatography–mass spectrometry analysis intermediate products indicated presence two competitive pathways, namely, oxidation with as catalyst. During first stage (reductive dechlorination), reductive activity iron-based was effectively enhanced water, which confirmed by density functional theory (DFT) calculations. removal chlorine atoms found order meta > para ortho. second (oxidation), hydroxyl superoxide anion radicals attack PCBs on surface Fe3O4/γ-Al2O3. This study provides an insight into HDC mechanism over catalysts.