| Waste incineration fly ash,which usually contains the organic pollutant such as heavy metal,dioxin and furan,is one of the main secondary pollutants in the process of municipal solid waste incineration.In order to provide theoretical guidance for security treatment and resource utilization,the pollution characteristics and leaching kinetics of heavy metals in waste incineration fly ash has been studied in this article.1.Based on the life of waste incineration fly ash in Guangxi and Chongqin,and the The typical physical and Medical treatment of waste incineration fly ash in Liaoning,the physical and chemical characteristics of waste incineration fly ash has been detailedly reported in this article,using different modern testing and measurement technology,such as SEM,XRD,LPSA,XRF,EDS,FT-IR and so on.It was shown that the specific surface areas of three kinds of fly ash samples were small,with inconspicuous vesicular structure.The particle size with 20 mesh sieve showed normal distribution or partial normal distribution.Thereinto,the average particle size of waste incineration fly ash in Chongqin was the smallest(D[4,3]= 55.72pm),on the contrary,the average particle size of waste incineration fly ash in Guangxi was the bigger(D[4,3]= 141.9?m).In addition,the elements of waste incineration fly ash contained C,O,Al,Si,K,Ca,Fe and Si in Guangxi,Ca,Na,O,Cl,K,Fe and Si in Chongqin,C,O,Ca,S,Cl,Na and Al in Liaoning.Some heavy mental,such as Cu,Mn,Pb,Zn and Cr were included as well,and the Zn content was the highest.Three kinds of MS W fly ashes had the same type of crystals,including SiO2,CaSO4 and aluminosilicate.Meanwhile,some soluble salt crystals,such as NaCl and KCl,and amorphousness were also included in these waste incineration fly ash.2.The speciation of heavy metals,heavy-metal content and heavy-metal leaching toxicity under various size fractions of Guangxi,Chongqing and Liaoning solid waste incineration fly ash are studied.The results showed that:All 5 kinds of heavy metals in Guangxi waste incineration fly ash are mainly in the form of waste incineration.Among the samples of Liaoning,Zn is mainly in the form of Acetic acid extractable and less in the form of waste incineration;Cr?Mn?Cu and Pb are mainly in the form of Acetic acid extractable,but much more than Guangxi.Among the samples of Chongqng,Cr is mainly in the form of waste incineration.Zn,Cu and Cd are mainly in the form of Acetic acid extractable.Pb is only in the form of Acetic acid extractable and Restore extractable,and Mn could be mainly in the form of restore extractable.Those heavy metal elements in Guangxi and Chongqing waste incineration fly ash all have shown a tendency to the concentration of small particles.The heavy metal Zn?Pb?Cu and Cr in Liaoning fly ash have shown a tendency to the concentration of small particles.With the decrease of particle size,the leaching of heavy metals tended to increase.Leaching toxicity in various size fractions of fly ash are not exceeded in Guangxi,while those of Zn,Pb and Cd in Chongqing and Zn,Pb in Liaoning are seriously overweight,which show that these fly ash is typical hazardous waste.3.This paper described the evaporation and volatile changes of leaching toxicity of heavy metals in Chongqing waste incineration fly ash during the heat treatment process at different heating temperature condition The results showed that:the volatile of heavy metals Pb,Cd,Zn,Cu in fly ash had greater impact and Mn,Cr were less affected.With the increase of heat treatment temperature,the leaching toxicity of heavy metals in fly ash reducted,the amount of Zn,Pb,Cd leaching which original fly ash exceed standard,became not exceeding after the heat treatment temperature resepctively reached 600 degrees,800 degrees and 1100 degrees.4.This paper studied the leaching process of heavy metal Pb,Zn in waste incineration fly ash under acidic condition.Kinetic model for this leaching process was established through constant temperature method.The results showed that sphere controlled by internal diffusion model was appropriate for the leaching process of Pb,Zn.The relation of leaching rate and time for the process of Pb was 1-3(1-X)2/3+2X=0.7137exp(-839.96T)/t with approximately 6.983kJ/mol apparent activation energy under experimental conditions;and the relation of leaching rate and time for the process of Zn was 1-3(1-X)2/3+2X=18.25exp(-2385.25T)/t with approximately 19.831kJ/mol apparent activation energy under experimental conditions;SEM tests showed that most of MSWI fly ash particles maintained spherical or similar microstructure during the reaction,though the surface of MSWI fly ash particles had dissolution at different level,which provided microscopic scales of evidence for sphere controlled by internal diffusion model. |
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