Hydrothermal decomposition of PCDDs/PCDFs in MSWI fly ash

In order to reduce the toxicity of Municipal Solid Waste Incinerator fly ash containing PCDDs and PCDFs, fly ash was hydrothermally treated. Under hydrothermal conditions, concentration of PCDDs and PCDFs decreased due to dechlorination reaction. This reaction occurred more effectively with high temperature and alkaline ingredients with/without methanol in solvent. PCDDs/PCDFs decomposed almost completely and the toxicity of treated ash decreased to 0.03 ng-TEQ/g at 573 K in 20 min with the solvent of 1 N NaOH solution containing 10 vol% methanol. Estimated activation energy for the decomposition reaction, assuming that the whole of PCDDs/PCDFs was one chemical species, was about 13 kcal/mol.