| With the development of economy,the acceleration of urbanization and the adjustment of residents’consumption structure,the disposal of municipal solid waste(MSW)has become an important issue in urban construction.At the same time,due to the increase of urban population density and the shortage of land resources,the incineration method has gradually become one of the main methods to deal with MSW,as its proportion in the disposal of municipal solid waste increases year by year.However,the MSW incineration fly ash contains heavy metals,chlorine salts,dioxins and other toxic components,which belong to hazardous waste and need to be disposed innocently.At present,the main treatment methods are:curing and stabilization,separation and extraction,heat treatment and so on.This paper will be introduced to the ultrasonic treatment in the disposal of MSW incineration fly ash(MIFA),as ultrasonic treatment effect on leaching behavior of heavy metals in fly ash,heavy metals before and after the disposal of fly ash,environmental risk assessment,and the study on adsorption performance of fly ash after ultrasonic treatment,experimental basis for fly ash utilization can be provided.The basic physical properties of fly ash from waste incineration were analyzed to provide reference for subsequent experimental research.The main elements are C,O,Al,Si,Cl,Ca,Fe,etc.The main components are silicon dioxide,calcium sulfate,calcium carbonate,ferric oxide and sodium chloride,etc.Using the single factor experiment method,ultrasound study of heavy metals in MIFA,the factors influencing the effect and the stability mechanism are explored.the results show that the leaching concentration of heavy metals in fly ash after ultrasonic treatment reduced to some extent,in addition to the Cd and other heavy metals are below the MSW landfill pollution control standards,Cd drop rate reached 77%,the influence extent of influence factors from the high to low respectively:the species of additives;dosage of additive;ultrasonic power;ultrasonic processing time.According to XRD analysis,katoite stone and other silicon aluminate substances are produced in the MIFA after ultrasonic treatment,which has certain effect on reducing the leaching concentration of heavy metals in the MIFA.In order to understand the mechanism of ultrasonic treatment of heavy metals in MIFA,improved BCR continuous extraction experiment was used to investigate to the shape variation of heavy metals in MIFA before and after ultrasonic treatment,and the results show that the heavy metal in MIFA can be stabled by transferring the acid dissolvable state into reducibility state after the ultrasonic treatment,there are some stable effects for heavy metal,but certain activity of heavy metals,environmental risk in treated MIFA are still existed.In order to further understand the resource utilization prospect of the MIFA after ultrasonic treatment,the adsorption performance of the MIFA after ultrasonic treatment was studied.The results showed that the fly ash after ultrasonic treatment had better adsorption effect on all heavy metals,including Cu and Pb.Moreover,the specific surface area of the treated samples increased from 1.9110m~2/g to 6.5301m~2/g,and the average pore volume also increased from 14.8773 cm~3/g to 16.1599 cm~3/g,a good adsorption potential can be shown.To sum up,the ultrasonic treatment in alkaline environment can realize the harmless disposal of heavy metals in MIFA.After the treatment of ultrasonic the leaching concentration of heavy metal are reduced to some extent.After ultrasonic treatment of MIFA katoite stone and other types of zeolite materials such as silicon aluminate are produced.The specific surface area,average pore diameter of treated MIFA are increased.There are better adsorption performance,and resource-oriented utilization potential as adsorbent. |
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