Experimental Study On Solidification Of Heavy Metal In Tailings Using Slag Cementing Materials

In this thesis,the blast furnace slag(BFS)was taken as raw material,and a new type of tailings cementing material was prepared with the desulfurization ash,limestone and alkaline activator as additive.Using slag cementing materials to solidify tailings,the unconfined compressive strength,the leachability of heavy metal and the BCR(community bureau of reference)sequential extraction were measured.Main achievements were listed as follows:1.The basic properties study of BFS indicates that BFS is a kind of vitreous material be mainly composed of Si O2?Ca O?Mg O?Al2O3,it can hydrate and harden after adding activators due to good potential activity.Analyzing of compressive strength values of mortar specimens after 3?7and28 days by orthogonal test shows the optimal mixture ratio is 77:17:4.5:1.5 among slag?desulfurization ash?limestone and activator.2.According to the optimal mixture ratio,slag cementing materials were prepared to solidify tailings.After curing,the compressive strength of nine groups of specimens with different incorporations and concentrations of slurry were higher than the requirement of solidified body landfill.The compressive strength of the tailings consolidated body is higher as the curing age,slurry concentration and incorporation increases.3.The heavy metals leaching tests of tailings consolidation body found that the leaching concentration of six metallic elements Pb,Cd,Cr,Cu,Ni and Zn were lower than solid waste leaching toxic standards,and with the curing period extended leaching concentrations were reduced to varying degrees.Therefore,the slag cementitious materials were useful for the curing tailings Pb,Cd,Cr,Cu,Ni and Zn.To analyze the leaching concentration of Pb,we found that the leaching concentration of Pb decreased with slurry concentration increasing.Preliminary analysis indicates that mechanism of heavy metal leaching,tailings slag cementitious material by curing a certain extent,can reduce the toxicity of heavy metals leaching.4.Using an improved method of BCR to analyze the metal speciation of tailings consolidation Pb.The results showed that,with the increase of age,the effectiveness and mobility of Pb reducing.Regarding to samples of the same age,the greater slurry concentration and incorporation,the stronger stability.