水泥、粉煤灰及生石灰固化/稳定处理铅锌废渣

Solidification/stabilization treatment of Pb and Zn in tailing waste using cement,fly ash and quick lime

以铅锌废渣为研究对象,采用水泥、粉煤灰为固化剂,生石灰为稳定剂,对废渣进行固化/稳定化处理,并通过TCLP和Tessier连续提取法对固化/稳定化效果进行分析和评价.结果表明,单独添加水泥或水泥、粉煤灰混合固化处理废渣时,重金属铅TCLP浸出浓度显著减少,但达不到安全填埋要求;当稳定剂生石灰添加量为4%(废渣),固化剂废渣比为0.4∶1(粉煤灰与水泥比为1∶9)时,固化/稳定化效果最佳.此时,固化体中重金属Pb、Zn的浸出浓度分别为0.16 mg·L-1、0.243 mg·L-1,符合安全填埋要求.经过固化/稳定化处理后,降低了废渣中的重金属Pb、Zn交换态比例,有效地限制了重金属的迁移.XRD和SEM分析表明,废渣固化/稳定化后形成的Ca(OH)2、水化硅酸钙凝胶(C—S—H)及钙矾石等物质将重金属离子包容起来,形成稳定的固化体.

In the present work,the stabilization/solidification using cement and fly ash as curing agent and quick lime as amendment was used to immobilize the Pb and Zn waste residues. The efficiency of the process was evaluated through leaching tests and Tessier sequential extraction procedure. The results showed that when using cement alone or cement,and fly ash combination although Pb concentration in TCLP leachate reduced significantly, but still doesn＇ t meet the requirements of the safe landfill. For stabillization/solidificution（ S/S） of the waste residues,the optimum conditions are as follow： the ratio of curing agent to waste residues was 0. 4 ∶ 1（ fly ash ∶cement 1 ∶ 9）,and quick lime to waste residues 4%,respectively. Under these conditions,the leaching concentrations of Pb,Zn from solidified body were 0. 16 mg·L- 1,0. 243 mg·L- 1,respectively,The results met the requirements of the safe landfill. Meanwhile,the exchangeable proportion of Pb,Zn in the waste residues were obviously declined,which implied that the migration of Pb,Zn in waste residues was confined by S/S treatment. XRD and SEM analysis revealed that Ca（ OH）2,hydrate calcium silicate（ C—S—H） and ettringite were formed after solidification /stabilization which encapsulated heavy metals and formed a solidified body.