水泥固化淤泥中重金属扩散的试验研究

摘要

对不同重金属和水泥添加量的淤泥进行了固化处理,主要通过一维动态浸出试验获得固化淤泥中重金属的扩散系数,由压汞试验分析固化淤泥的微观孔隙结构,并从微观分析重金属扩散特性.试验结果表明,通过氯离子的扩散试验求得的固化淤泥的表观弯曲因子,随着水泥掺量的增加而降低.随着水泥掺量的增加,固化淤泥主要孔隙直径由0.1~1μm变为0.01~0.1μm.当干土中铅离子的初始质量分数为2%、4%时,固化淤泥中铅离子表观扩散系数变化范围为10-16~10-14 m2/s数量级,其随着水泥掺量的增加而降低,随铅离子初始浓度的增大而增大.增加水泥掺量后,含铅固化淤泥主要孔隙直径由0.1~1μm变为0.01~0.1μm,表明水化产物对铅离子的物理包裹吸附作用不容忽视.当干土中铅的初始质量分数为2%时,含铅、氯离子的固化淤泥孔隙结构相似,而铅离子表观扩散系数比氯离子小4~6个数量级,表明水泥对铅离子的化学稳定作用也至关重要,固化淤泥对铅离子的阻滞系数随水泥掺量的增加而增大.固化淤泥中铜离子的表观扩散系数比铅离子小4~6个数量级,而含铜固化淤泥孔隙直径以0.1~1μm为主,增加水泥掺量不能有效降低其孔径大小.因此,铜与水泥熟料反应形成沉淀,降低铜离子的扩散能力,同时也抑制了水化产物的生成.%In this study ordinary portland cement was used to modify. The effects of initial heavy metal and cement contents on the diffusion and leaching behavior of heavy metals,permeability of cement-treated DM were investigated. Moreover,the microstructures of cement-treated DM was studied by using MIP. The main conclusions of the study were as follows:the apparent tortuosity factor of Cl-1 decreased with increasing cement content. Based on MIP test results,the range of main pore diameter of cement-treated DM decreased from 0.1-1 μm to 0.01-0.1 μm with increasing cement content. For an initial Pb2+content of 2%and 4%,the apparent diffusion coefficient of Pb2+ranges from 10-16 to 10-14 m2/s. It decreased with increasing cement content,but increased with increasing Pb2+content. The range of main pore diameter of cement-treated DM decreased from 0.1-1 μm to 0.01-0.1 μm with increasing cement content. Thus,the physical encapsulation of Pb2+inside the solidified matrix is one of the key mechanisms to immobilize Pb2+. The apparent diffusion coefficient of Pb2+was 4 to 6 orders of magnitude smaller than that of Cl-1,which indicated that the chemical stabilization of Pb2+ inside the solidified matrix is also a crucial factor. It was found that the retardation factor increased with increasing cement content. The apparent diffusion coefficient of Cu 2+was 4 to 6 orders of magnitude smaller than that of Pb2+. The main pore diameter of cement-treated DM spiked with Cu2+did not reduce significantly with increasing cement content,which ranged from 0.1 to 1μm. Moreover,copper silicate was detected in the XRD analysis,which indicated that copper reacted with cement clinker leading to a reduction of cement hydrates as well as a decree in the apparent diffusion coefficient.