石灰干化污泥对土壤重金属稳定化处理的效果

以采自湖南省嘉禾县重金属复合污染土壤为研究对象,采用城市污水处理石灰干化污泥作为稳定剂,对污染土壤进行稳定化处理,并采用TCLP和BCR连续提取法对稳定化效果进行分析和评价。研究结果表明,单独使用石灰干化污泥,TCLP浸出浓度随着干化污泥质量分数的增加而显著减少,干化污泥的质量分数为40%时,稳定化率最大为Zn-98.92%、Cd-99.06%、Pb-96.84%;但是干化污泥的高pH值导致稳定后土壤中As的浸出增加。为了恢复植物生长功能,经过亚铁盐和磷酸调节pH后,石灰干化污泥稳定过的土壤pH有效降低,同时亚铁盐和磷酸有利于促进Pb和Zn的稳定效果;但是对Cd的稳定有负面影响;另外,亚铁盐的加入同时可以减少As的浸出浓度。经处理后土壤中重金属形态由不稳定态转为稳定态,使重金属的浸出浓度明显降低,减少了土壤重金属的浸出毒性。该研究结果表明,石灰干化污泥可以作为资源回收利用,应用于重金属污染土壤的修复中,并能改善稳定后土壤适宜植物生长的理化性质。

Effect of lime-stabilized sludge on stabilization of heavy metals in soil

Stabilization of heavy metals in contaminated soil from Jiahe Country, Hunan Province by using lime-stabilized sewage sludge(LSS) as amendment was investigated in this study, and the effectiveness was evaluated by TCLP and modified BCR sequential extraction procedure. The results of TCLP indicated that the concentrations of heavy metals in TCLP leachate reduced significantly with the increase of the mass percentage of the LSS and the leaching reduction rates were as high as 98.92% for Zn, 96.84% for Pb, 99.06% for Cd at 40% of LSS addition. However, the concentration of As in the leachate increased after stabilized because of high pH value. After adjusted by ferrous salt and phosphoric acid in order to recover soil plantation function, the pH value of stabilized soil decreased effectively, in the meantime, promoting the stabilization effectiveness of As. The BCR test revealed that, compared with the contaminated soil, exchangeable proportion of Zn, Pb, Cd in the stabilized soil and the soils adjusted by ferrous salt and phosphoric declined obviously, which implied that the migration of Pb, Cd and Zn in contaminated soil would be confined.The results demonstrate that municipal LSS can be reused in the stabilization of heavy metal contaminated soils and that physical and chemical properties of LLS-stabilized soil are improved for plantation.