氧化镁碱激发矿粉-膨润土-土竖向屏障材料阻隔铅污染物的化学渗透膜效应

Experimental study on chemico-osmotic membrane behaviors of reactive MgO-activated slag-bentonite backfill in vertical cutoff walls exposed to Pb-laden groundwater

采用活性氧化镁激发粒化高炉矿粉(GGBS)制备氧化镁激发矿粉-膨润土-土(MSBS)竖向阻隔屏障材料。通过一维土柱化学渗透试验,研究了硝酸铅(Pb(NO_(3))_(2))污染液浓度对MSBS阻隔屏障材料的阻隔性能参数包括化学渗透膜效率系数、有效扩散系数和阻滞因子的影响规律,对比分析了MSBS、土-膨润土(SB)和膨润土防水毯(GCL)竖向屏障材料的阻隔性能参数的差异特征。结果表明:MSBS屏障材料在Pb(NO_(3))_(2)污染液中表现出明显的化学渗透膜效应,其化学渗透膜效率系数随着Pb(NO_(3))_(2)污染液浓度增加迅速减小。MSBS阻隔屏障材料Pb^(2+)的有效扩散系数随Pb(NO_(3))_(2)污染液浓度增大略有增加,但变化幅度明显低于SB屏障材料。MSBS的阻滞因子受Pb^(2+)浓度影响不显著,而SB竖向阻隔屏障对于Pb^(2+)的阻滞因子则随其浓度增加而显著降低。

The reactive magnesia(MgO)is used as an alkali activator to activate granulated blast furnace slag(GGBS)to prepare alkali activated slag-bentonite-soil vertical barrier(MSBS)material.The chemico-osmotic memberane behavior test using lead nitrate Pb(NO_(3))_(2) solutions with different concentrations as testing liquids is conducted on the MSBS specimen,and the effects of Pb(NO_(3))_(2) concentration on the Pb^(2+) containment performance including chemico-osmotic efficiency coefficient,effective diffusion coefficient and retardation factor are evaluated.Comparative assessment of performance is made between the MSBS material in this study and other engineered barrier materials including soil-bentonite(SB)vertical cutoff wall backfill and geosynthetic clay liner(GCL)reported in previously published studies.The results show that the MSBS backfill has noticeable chemical-osmotic membrane behavior,and the chemico-osmotic efficiency coefficient decreases rapidly with the increasing Pb^(2+) concentration.The effective diffusion coefficient of Pb^(2+) in the MSBS increases slightly with the increasing Pb^(2+) concentration,and its change magnitude is significantly lower than that for the SB backfill materials.The retardation factor for Pb^(2+) in the MSBS backfill remains practically constant with the increasing Pb^(2+) concentration,whereas it decreases significantly with the increasing Pb^(2+) concentration for the SB backfill materials.