Removal of Organohalogen Compounds and Recovery of Heavy Metals from Municipal Solid Waste Incineration Fly Ash by Column Flotation

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The authors have set up a column flotation equipment and developed the technique of column flotation to remove organohalogen compounds and recover heavy metals from MSWI fly ash by separating the organohalogen compounds-enriched unburned carbon (UC) from MSWI fly ash. The effects of influential factors on the UC removal efficiency have been studied in detail. UC and organohalogen compounds removal experiments under different column flotation conditions were carried out, which provides an important reference for setting up the optimum column flotation condition for organohalogen compounds removal from MSWI fly ash. The main results are summarized as follows :1) The physical and chemical influential factors : gas flow rate, sparger surface area, pH, collector and collect assistant, UC particle size have important effects on the removal efficiencies of UC and organohalogen compounds from MSWI fly ash.2) By investigating the effects of many physical and chemical influence factors on the removal efficiencies of UC and organohalogen compounds, the authors obtained the optimum flotation conditions : adding the surfactant mixture (HLB=13.5, Concentration in kerosene=3.0 Vol.%) of polyoxyethylene (20) sorbitan mono-oleate and sorbitan mono-oleate into the kerosene to make kerosene mixture, then adding 4.0ml/L-slurry kerosene mixture into the slurry ; MIBC=53.3μl/L in the slurry, pH=5.9 ; using 4# porous plate sparger, gas flow rate : 0.0534m/s; twice flotation, first time 30 minutes, second time 40 minutes (condition D).3) Under the optimum flotation condition, 64.0% of UC and 41.9% of PCDD/Fs, 40.8% of coplanar PCBs and 44.1% of PCBs were removed from MSWI fly ash.4) Most of other metals are left in the residue part, except that the transference ratios of Na, K, Ca and Zn to solution are high.