The Simulating Study Of Dioxins Inhibition Technology By Titanium-based Compounds In The Process Of Municipal Solid Waste Incineration

Recently,due to the advantages of high-temperature detoxification,significant volume and mass reduction,the municipal solid waste incineration has been booming and widely applied in developed regions of China facing the increasingly serious problem of City waste.However,the construction and operation of municipal solid waste incinerators?MSWIs?has caused widespread public concern because of potential secondary pollution emitted from the facilities,especially related to the environmental toxicities and adverse health effects of the polychlorinated dibenzo-p-dioxins and dibenzofurans?PCDD/Fs?and chlorobenzenes?CBz?.In this study,chlorobenzene degradation activities of titanium-based metal oxide produced and the mechanisms involved were studied,and the prevention of PCDD/Fs formation form chlorobenzene by the materials during the simulated thermal process of waste incineration was investigated.The methods used and the main results are described below:1.Three different morphological titania catalysts were prepared by solvothermal,co-precipitation and sol-hydrothermal methods.The materials were characterized by using X-ray diffraction?XRD?,X-ray energy dispersive spectroscopy?EDX?and field emission scanning electron microscope?FE-SEM?.The catalytic activity of titania catalysts towards pentachlorobenzene?PeCB?degradation was evaluated at 300 ?,350 ? and 400 ?,respectively.The results showed that the activity order was: TiO₂ prepared by co-precipitation method > TiO₂ prepared by sol-hydrothermal method > TiO₂ prepared by solvothermal method.The degradation efficiency of PeCB reached up to 99.83% over titania catalysts prepared by co-precipitation method,at 350 ? for 60 min.The degradation products were determined by gas chromatograph-mass spectroscopy?GC-MS?.The detection of tetrachlorobenzene?TeCB?,trichlorobenzene?TrCB?and dichlorobenzene?DCB?as the degradation products,indicated the occurrence of successive reductive hydrodechlorination reactions during the degradation of PeCB over the titania catalysts.And the major hydrodechlorination pathway was deduced to be :PeCB?1,2,4,5/1,2,3,5/1,2,3,4-TeCB?1,2,4/1,2,3-TrCB?DCB.2.Ti-Ca composite oxide materials were synthesized by coprecipitation.The precursor of the composite material at different time?5 min,10 min,20 min,30 min,60 min,3 h and 4 h?was characterized by XRD,XPS,SEM,exploring the formation process of material.And the effects of precipitator and calcinated temperature on the crystal of composite material were investigated.The results suggested that urea-NH₃·H₂O,as a precipitator,could facilitate more Ca²⁺ to precipitate the surface of TiO₂,resulting in the larger material size.Furthermore,the TiO₂ material obtained under the 500 ? calcinated temperature had a better anatase crystal.3.A series of Ti-Ca composite materials containing various mass ratio?Ti:Ca = 1:?,? = 0,0.1,0.2,0.5,0.8,1?were synthesized by using the precipitator of ureaNH₃·H₂O at 500 ?.And then the prevention of PCDD/Fs formation from 1 mg PCP over Ti-Ca composite materials and blank reaction systems during the simulated thermal process of waste incineration were evaluated.The results indicated that TiCa_0.5O_x composite material obtained the outstanding performance in increasing the inhibited efficiency and reducing TEQ of formed PCDD/Fs from PCP.