海泡石对污染土壤中铅的钝化效果

Immobilization of Pb in Contaminated Soil by Sepiolite

为了探讨不同方法改性后的海泡石对铅污染土壤的修复效果,以天然海泡石(Sep)为研究材料,对其进行巯基乙酸改性(Q-Sep)、热改性(R-Sep)、热处理+FeSO4改性(F-Sep),观察改性海泡石表面微观形态与结构,并分别添加1%、3%、6%、9%、15%天然海泡石和改性海泡石进行土培试验,采用二乙三胺五乙酸(DTPA)浸提法以及BCR连续提取法对土壤有效态铅和铅形态进行分析,探究不同添加量海泡石对铅污染土壤的钝化效果,为改性海泡石应用于土壤钝化修复提供理论依据。结果表明:经FeSO4、巯基乙酸和热处理改性后的海泡石比表面积比天然海泡石显著增大,其中F-Sep的比表面积最大。F-Sep和R-Sep的孔容也与Sep有显著差异。当Q-Sep、R-Sep和F-Sep的添加量≥3%时,土壤pH值与对照组相比有显著提高,添加量≥6%时,土壤CEC较对照组有显著提高。添加4种海泡石的土壤与对照组相比酸提取态铅含量有显著减少,添加F-Sep、Q-Sep和R-Sep的土壤酸提取态铅减少率分别为19.95%-57.74%、44.31%-71.51%和32.93%-64.56%,土壤酸提取态铅含量、可还原态铅含量与残渣态铅含量呈极显著负相关(r=0.937,P=0.000和r=0.618,P=0.001),表明酸提取态铅和可还原态铅主要是向残渣态转化。添加海泡石显著降低了土壤有效态铅含量,土壤有效态铅含量与土壤pH值、土壤CEC呈显著负相关关系(r=0.887,P=0.000和r=0.596,P=0.002),与酸提取态铅和可还原态铅呈显著正相关关系(r=0.949,P=0.000和r=0.506,P=0.008)。添加15%Q-Sep材料后的土壤有效态铅含量降幅最大,达到39.68%。3种改性海泡石材料对土壤中铅的钝化效果均优于天然海泡石,其中Q-Sep对土壤铅的钝化效果最佳。

In order to explore the effect of different methods of modified sepiolite on Pb-contaminated soil,in this study,The sepiolite was modified with thioglycolic acid(Q-Sep),thermally modified(R-Sep)and FeSO4(F-Sep),and the surface morphology and structure of the modified sepiolite were observed.Natural sepiolite and modified sepiolite were added to the tested soil for soil culture test with mass fractions of 1%,3%,6%,9%,and 15%,respectively.The available Pb and Pb speciation in soil was analyzed by extraction with diethyltriamine pentaacetic acid(DTPA)and BCR continuous extraction method.Investigating the passivation effect of different added amount of sepiolite on Pb-contaminated soil can provide a theoretical basis for the application of modified sepiolite in soil passivation.The results showed that the specific surface area of sepiolite after modifying treatment was significantly larger than that of natural sepiolite.Among them,the specific surface area ofF-Sep was the largest,and the pore volume of F-Sep and R-Sep was also significantly different from that of Sep.When the addition amount of Q-Sep,R-Sep and F-Sep was≥3%,the soil pH value was significantly improved compared with the control group.When the addition amount was≥6%,the soil CEC was significantly higher than that of the control group.Compared with the control group,the soil extracted with four kinds of sepiolite had a significant decrease in the content of Pb extracted from acid,and the reduction rate of Pb extracted from soil by adding F-Sep,Q-Sep and R-Sep was 19.95% 57.74%,44.31% 71.51% and 32.93% 64.56%,the soil acid extracted Pb and the reducible Pb were significantly negatively correlated with the residual Pb content(r=0.937,P=0.000;r=0.618,P=0.001).Acid extracted Pb and reducible Pb was mainly converted to residue state.The addition of sepiolite significantly reduced the soil effective Pb content,the soil effective Pb content and soil pH value and soil CEC showed a significant negative correlation(r=0.887,P=0.000;r=0.596,P=0.002),and acid extraction of Pb and reversible Pb showed a significant positive correlation(r=0.949,P=0.000;r=0.506,P=0.008).After adding 15% Q-Sep materials,the soil effective Pb content decreased the most,reaching 39.68%.The passivation effect of 3 modified sepiolite materials on Pb in soil is better than that of natural sepiolite,among which Q-Sep has the best passivation effect on soil Pb.