DTCR协同水泥固化/稳定化重金属污染底泥的研究

Stabilization/solidification of heavy metals contaminated sediment using cement and DTCR as binder materials

采用二硫代氨基甲酸盐(DTCR)为添加剂协同水泥固化/稳定化重金属污染底泥,以抗压强度和颗粒固化体(粒径9.5mm)浸出毒性为指标确定水泥和DTCR的最优配比.通过酸雨条件(pH 3)下对颗粒固化体和整个固化体的浸出试验来评价固化/稳定化的效果.利用X射线衍射仪(XRD)和环境扫描电镜(ESEM)分析了固化/稳定化机理.结果表明,固化/稳定化的最优配比为水泥掺入量为50%(干底泥),DTCR掺入量为2%(干底泥).其固化体7d抗压强度为1.03MPa,颗粒固化体中重金属Cu,Zn,Pb,Cd的浸出浓度分别为0.105,4.65,0.232,0.123mg/L,能够达到安全填埋要求.酸雨条件下(pH 3)对颗粒固化体和整个固化体浸出研究表明,水泥、DTCR固化/稳定化底泥效果更好;XRD和ESEM分析表明,固化/稳定化的机理主要是水泥在水化反应时,能够形成水化产物Ca(OH)2、水化硅酸钙(C-S-H)和钙矾石(AFt),将重金属废物包容,并逐步硬化形成具有一定强度的水泥固化体.

Cement-based solidification/stabilization（S/S） with DTCR（dithiocarbamate） as an additive was used to solidify and stabilize sediment containing heavy metals.The optimum ratios of cement and DTCR were determined by testing the compressive strength of the whole solidified body and leaching toxicity of granular solidified body（particle size 9.5mm）.And the effect of S/S was assessed though the leaching toxicity test of granular solidified body and whole solidified body in the acidic environment（pH 3）.The mechanism of S/S was analyzed by X-ray diffraction（XRD） and envrionmental scanning electron microscope（ESEM）.The optimal proportion of cement and DTCR was 50% and 2%（w/w,dry basis）,respectively.Under optimum conditions,the 7d compressive strength of the solidified body was up to 1.03 MPa and leaching concentrations of Cu,Zn,Pb and Cd in granular solidified body were 0.105,4.65,0.232,0.123 mg/L,respectively,which could meet the requirements of the security landfill.The leaching effect in the acidic environment（pH 3） demonstrated that cement-based S/S added DTCR was better than cement-based S/S only.XRD and ESEM analysis revealed that Ca（OH）2,Hydrate Calcium Silicate（C-S-H） and Ettringite（AFt） as hydration products would be formed in hydration reaction which wrapped up heavy metals and form a solidified body with certain strength.