Chlorine source is indispensable for polychlorinated dibenzo-p-dioxin and furan(PCDD/F)formation during municipal solid waste(MSW)incineration.Inorganic chlorine compounds were employed in this study to investigate their effects on PCDD/F formationthrough heterogeneous synthesis on fly ash surfaces.A fly ash sample obtained from a fluidized bed incinerator was sieved to differentsize fractions which served as the PCDD/F formation sources.The capability of different metal chlorides which facilitate the formationof PCDDs/Fs was found to follow the trends:Na177μm and 104-125μm wereused in the experiments.However,the capability of NaCl,MgCl2 and KCl did not seem much different from each other,whereas CaCl2and AlCl3 were much more active in PCDD/F formation.NaCl and MgCl2 were relatively effective to produce more PCDDs,while KCl,AlCl3 and CaCl2 generated more PCDFs during heterogeneous reactions occurring on fly ash.2,3,7,8-TCDF was the most significantcontributor to the toxicity of the PCDDs/Fs formed from inorganic chlorine sources.Decreasing the sizes of fly ash particles led to moreactive formation of PCDDs/Fs when NaCl was used as inorganic chlorine in the experiment.The highest PCDDs/Fs produced fromparticles with size<37μm,while the lowest PCDDs/Fs produced from particles with size>177μm.The toxicity generally increasedwith decreasing size of the fly ash particles.The formation of PCDDs was mainly facilitated by the two size fractions,104-125μm and<37μm,while the formation of PCDFs was favored by the two other size fractions,>177μm and 53-104μm.
LU Sheng-yongYAN Jian-huaLI Xiao-dongNi Ming-jiangCEN Ke-faDAI Hui-fen
The mechanochemical treatment of fly ash generated from a medical waste incinerator was subjected to grinding for 2 hr at 400 r/min in a planetary ball mill.The treated fly ash was characterized by a suite of analytical methods including High Resolution Gas Chromatograph/High Resolution Mass Spectrometer,Mastersizer 2000 Particle Size Analyzer,QUADRASORBTM SI Surface Area Analyzer,Scanning Electron Microscopy and X-ray diffraction.Results showed that abatement effciency of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans(PCDDs/Fs) in terms of total concentration averagely amount to 76%which was relatively higher than that of I-TEQ concentration averagely amount to 56%;the most concentration of toxic congeners as well as isomers of PCDDs/Fs decreased after mechanochemical treatment.The treated fly ash was characterized by a more homogeneous distribution of concaves as well as the significant decreasing in overall particle size and great enlargement in surface area.The major crystallization phases or intensities were considerably changed by mechanochemical treatment,of which a new phase containing chlorine formed may be a possible factor suggesting chlorination reaction occurring on the crystalline surface.
Zheng PengQiong DingYangzhao SunChen JiangXinhua GaoJianhua Yan
