Detoxifying PCDD/Fs and heavy metals in fly ash from medical waste incinerators with a DCdouble arc plasma torch

Medical waste incinerator （MWI） fly ash is regarded as a highly toxic waste because it contains high concentrations of heavy metals anddioxins, including polychlorinateddibenzo-p-dioxins （PCDDs） and polychlorinateddibenzofurans （PCDFs）. Therefore fly ash from MWI must be appropriately treated before beingdischarged into the environment. A melting process based on adirect current thermal plasma torch has beendeveloped to convert MWI fly ash into harmless slag. The leaching characteristics of heavy metals in fly ash and vitrified slag were investigated using the toxicity characteristic leaching procedure, while the content of PCDD/Fs in the fly ashes and slags was measured using method 1613 of the US EPA. The experimental results show that thedecomposition rate of PCDD/Fs is over 99% in toxic equivalent quantity value and the leaching of heavy metals in the slag significantlydecreases after the plasma melting process. The produced slag has a compact and homogeneous microstructure withdensity of up to2.8 g/cm3 .