Treatment On Pb,Ni Drived From Municipal Soild Waste Incineration Fly Ash By BES-electrodialysis Coupling System

Municipal solid waste incineration(MSWI)fly ash is classified as hazardous waste because it contains a lot of soluble salts and toxic and harmful heavy metals.Based on the analysis of the physical and chemical properties of fly ash,the orthogonal experiments,with liquid-solid ratio,voltage and initial pH as variables,were designed to treat the fly ash by BES-electrodialysis coupling system.The results were as follows:(1)The main particle size distribution of fly ash is 9.20～14.49 μm(65.75%),and the total amount of Pb and Ni are 622 mg/kg and 39.6 mg/kg respectively,in which Pb almost existed in reducible,while Ni mainly existed in residual and reducible forms,followed by acid extractable and oxidizable fraction.(2)With the increase of substrate concentration,the output voltage and maximum power density of MFC increased at first and then decreased.When the concentration of landfill leachate was chosen at 3841 mg/L,the maximum output voltage was 450 mV,the maximum power density was 1007mW/m3,the coulomb efficiency was 10.57%,the internal resistance wass 86.87 Ω,and the removal rates of COD and ammonia nitrogen were 85.91%and 97.43%,respectively.(3)During treatment on fly ash treated by BES-electrodialysis coupling system,the concentration of Pb at the reactor decreased,while the Pb concentration at anolyte and catholyte increasing,and 60%～85%of Pb was migrated to the anodic side,indicating that Pb formed negative complexes mainly.The concentration of Ni at reactor slightly varied with respect to time,while the concentration at anolyte and catholyte increasing slowly,and 50%～70%Ni was migrated to the cathodic side under electric field,indicating that Ni formed positive complexes.(4)After treatment,the highest removal rates of Pb and Ni in fly ash were 49.81%and 69.03%.The total amount of Pb and Ni in fly ash were higher than that in raw ash,and the leaching toxicity decreased to 1.187～5.236 mgL-1.The residual fraction and acid extraction fraction increased,while the oxidizable fraction and reducible fraction decreased.Combined with XRD and SEM analysis,the dissolution of soluble salts in fly ash caused the total amount of heavy metals in fly ash increased and leaching toxicity decreased significantly.(5)Through multi-factor analysis and marginal mean analysis of 9 groups of experiments,it could be found that the order of influence on Pb removal rate was liquid-solid ratio>pH>external power supply;for Ni removal rate,the order was external power>liquid-solid ratio>pH.The removal efficiency of Pb was the best when the liquid-solid ratio is 10,the external power supply is 3 times,and pH=2,while the removal effect of Ni is the best when the liquid-solid ratio was 20,the external power supply was 3 times and the pH is 4.9 groups of experiments and the best conditions of the experimental group also showed a higher removal effect.Figure 21 table 18 reference 125...