Preparation Of Cementitious Materials From Municipal Solid Waste Incineration Bottom Ash And Environmental Safety Assessment

The global production of domestic waste is increasing day by day.The incineration of domestic waste has the characteristics of significant volume reduction and the ability to use the thermal energy generated by incineration to generate electricity.It is the mainstream treatment method of domestic waste.However,the treatment of municipal solid waste incineration bottom ash(MSWI-BA)produced by incineration has problems such as waste of resources and environmental safety.Therefore,resource utilization and harmless treatment of bottom ash is an ideal research direction.Firstly,the basic physicochemical properties and heavy metal leaching characteristics of MSWI-BA were studied.The main chemical composition of bottom ash is calcium oxide,silica and alumina,and the activity of volcanic ash is weak.The leaching concentrations of heavy metals Cd,Cu and Pb in MSWI-BA have exceeded the requirements of GB16889-2008 ’ Control Standard for Domestic Waste Landfill Sites ’,but they are far lower than GB5085.3-2007 ’ Hazardous Waste Identification Standard Leaching Toxicity Standard ’,which belongs to general solid waste.In this paper,the effect of mechanical activation and chemical activator on the bottom ash was explored.Considering various factors,the results of single factor experiment were as follows : mechanical activation 90 min,active calcium oxide addition 6 %,liquid water glass addition 8 %,the effect was the best.In the multi-factor influence experiment,the central composite design(CCD)test was used to analyze the strength of the mortar test block with MSWI-BA10 % by multivariate nonlinear regression analysis,and the 28 d compressive strength model of the mortar test block was obtained.The samples were analyzed and it was found that the mortar test block with bottom ash can produce more C-S-H gel and C-A-H gel,which are attached to the surface and inside of the cementitious material,so that the strength of the mortar test block is higher than that of pure cement.Finally,the heavy metal leaching performance of the mortar test block prepared by the cementitious material was analyzed.It was found that this method had a curing effect on the eight heavy metals of Pb,Cr,Cd,Cu,Ni,Zn,Mn and As.Among them,the curing rate of Ni by the mortar test block reached 100 %,and the curing rate of heavy metals of Cd,Cu,Ni,and Zn reached more than 50 %.The solidification of heavy metals by cement is the coexistence of adsorption,cementation encapsulation,and precipitation.The mortar test block prepared by the cementitious material meets the requirements of GB30760-2014 " Technical Specification for Co-processing Solid Waste in Cement Kilns," and can replace some cement as a cementitious material.