Abstract
ABSTRACTOur previous study demonstrated flotation to be effective in removing carbonaceous matter and dioxins from fresh fly ash in medical waste incinerators (MWIs). However, flotation of weathered fly ash seems to be difficult because of the oxidation of the ash surface and the presence of hydrophilic unburned carbon. Three types of surfactants namely nonionic Tween 80, anionic sodium dodecyl sulfate (SDS) and cationic CTAB were employed at different doses to improve flotation performance. Results indicated that Tween 80 exhibited superior decarburization performance compared with SDS and CTAB. The effect of surfactants on dioxin removal was found to correspond to the carbon removal from MWI fly ash. The optimal removal yields (90.6% of carbonaceous matter and 88.6% of dioxins) were obtained when 5% (w/w) Tween 80 was added. However, an excessive dose might cause the dissolution of dioxins.
Highlights
Medical waste is regarded as hazardous waste in China because it contains infectious, traumatic, pathological, chemical, and pharmaceutical wastes
Incineration produces a large amount of medical waste incinerator (MWI) fly ash, which is dust-like particles and has high content of chlorine, dioxin and heavy metal
Apart from Unburned carbon (UC), another type of carbonaceous matter in MWI fly ash is derived from powder activated carbon (PAC) injected into incineration systems as an adsorbent to remove gaseous phase toxic dioxins from the combustion chamber of the flue gas after a series of filtration treatment before dioxins were emitted to the atmosphere
Summary
Medical waste is regarded as hazardous waste in China because it contains infectious, traumatic, pathological, chemical, and pharmaceutical wastes. Incineration produces a large amount of medical waste incinerator (MWI) fly ash, which is dust-like particles and has high content of chlorine, dioxin and heavy metal. To some extent a reduction of the toxicity of dioxins has been realized (Hu et al, 2015; Weidemann et al, 2015; Wang et al, 2016a; Wang et al, 2016b; Mao et al, 2017) Most of these techniques may be not suitable for HSWI fly ash treatment due to its special characteristics (Wei et al, 2017a). This special type of ash contained with high carbon and dioxin content should be treated with suitable methods
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