磷基及铁基钝化剂对Pb、Cd、As复合污染土壤的修复效果及其工艺条件优化

Remediation effects of phosphorus and ferric amendments on the soil complexly contaminated by Pb,Cd and As and the process optimization

通过DTPA和Na HCO3浸提方法评价磷基、铁基钝化剂对Pb、Cd、As复合污染土壤的钝化修复效果。结果表明,磷基钝化剂中磷酸二氢钙对有效态Pb、Cd固定效果较好,35 d后其去除率分别为61%、38%;铁基钝化剂中以硫酸高铁对有效态As固定效果最好,28d后其去除率达74.6%。工艺条件优化结果表明,随磷酸二氢钙用量增加,土壤中有效态Pb、Cd含量明显下降;随硫酸高铁用量增加,对有效态As的固定效果明显增加,当硫酸高铁添加量为土壤中As总物质的量的3.06倍时,28 d后土壤中有效态As的去除率高达74.5%。土壤水分含量在最大田间持水量的60%~80%时,对有效态Pb固定影响不大,但均略高于最大田间持水量30%~50%时的Pb去除率;土壤水分含量在最大田间持水量的60%~80%时,有效态Cd固定效果较好。当磷酸二氢钙用量为土壤中Pb、Cd总物质的量的10倍,土壤水分含量为最大田间持水量的60%时,21 d后有效态Pb、Cd去除率分别达到93%和39%。铁基与磷基钝化剂复配可以同时固定土壤中的Pb、Cd、As。当Fe3＋与PO3-4物质的量的比为7.2∶1时,7 d后土壤有效态Pb、Cd、As去除率分别为99%、41%、69%。

The paper is aimed at an investigation on the immobilization of Pb,Cd and As in the contaminated soil by using the phosphorus and ferric amendments and the process optimization.We have evaluated the effects of the phosphorus and ferric amendments on immobilization of Pb,Cd and As in contaminated soil by DTPA and NaH CO3 extractable methods. The experimental tests we have done prove that the monocalcium phosphate（ Ca（ H2PO4）2） can effectively immobilize the available Pb and Cd in the contaminated soils by a percentage of 61% and 38% after 35 d,respectively. Ferric sulfate（ Fe2（ SO4）3） could decrease the available As by 74. 6% after 28 d. The results of the optimized application condition of Ca（ H2PO4）2and Fe2（ SO4）3indicate that：（ 1） The concentrations of the available Pb and Cd can obviously be reduced with the increased dosage of Ca（ H2PO4）2.However,no serious effect tends to be made on the available Pb immobilization on the condition when the water content in the soil is at a range of 60%-80% of the maximum field water capacity,although available Pb immobilization efficiency at 60%-80% of the maximum field water capacity is higher than that at 30%-50%of the maximum field water capacity. The effective removal of available Cd can be found when at 60%-80% of the maximum field water capacity. And the removal efficiency of available Pb and Cd would also like to reach 93% and 39% after 21 d on the condition when the molar ratio of Ca（ H2PO4）2to Pb and Cd is equal to 10： 1 and the water content in the soil reaches 60% of the maximum field water capacity.（ 2） The immobilization effect of the available As can be noticeably raised with the increased dosage of Fe2（ SO4）3. For example,when the molar ratio between Fe2（ SO4）3and As is made equal to 1： 3. 06,the removal rate of available As can be made to go up to 74. 5% from the contaminated soil after 28 d. Moreover,the mixture of Ca（ H2PO4）2and Fe2（ SO4）3can immobilize Pb,Cd and As simultaneously. When the molar ratio of Fe3 ＋to PO3-4is equal to 7. 2： 1,the removal efficiency of the available Pb,Cd and As can be made up to 99%,41% and 69% after 7 d,respectively. Thus,the results of our research shall be able to provide a technical support for the remediation of the soils complexly contaminated by heavy metals.