自制硫系稳定剂对重金属六价铬污染土壤的稳定化效果及长期稳定性研究

Study on the Stabilization and Long-term Effect of Chromium Contaminated Soil Using Homemade Reagent KTWDJ-1

  • 摘要: 为验证自制硫系稳定剂(KTWDJ-1)修复Cr6+污染土壤的可应用性,以某铬盐厂污染场地为依托进行了稳定化试验,同时与多硫化钙(CPS)、硫化钠(Na2S)进行对比。总结了硫系稳定剂对Cr6+污染土壤的化学还原稳定化修复效果。结果表明:KTWDJ-1对Cr6+还原效果最佳,当KTWDJ-1的投加比例为3%时,Cr6+浸出浓度从128.5mg/L减少至0.05mg/L,还原效率高达99.96%,然而相同条件下,CPS和Na2S对Cr6+的还原效率分别为99.04%和85.52%。随着硫化物添加比例的增加,浸出Cr6+浓度持续下降。硫化物稳定化后的土壤中Cr的铁锰氧化态显著增加,可交换态含量的变化是Cr浸出浓度变化的主要原因。此外,三种硫系稳定剂,KTWDJ-1显示了相对较好的长期稳定性,经过酸性水反复沥滤状态下仍能保持稳定的浸出浓度。最后,探究KTWDJ-1的工程最优参数,稳定化过程中,土壤含水率需控制在30%左右,土壤pH调节至9左右,养护时间保证5d以上,污染土壤Cr6+的稳定化效果能达到最佳。

     

    Abstract: To verify the applicability of homemade sulfide-based stabilizers( KTWDJ-1) in remediation of Cr6+ contaminated soil,stabilization tests were carried out based on the contaminated site of a chromate factory,and compared with calcium polysulfide( CPS) and sodium sulfide( Na2S). The effect of sulfide-based stabilizers on reduction and stabilization of Cr6+ contaminated soil was summarized. The results showed that KTWDJ-1 had the best effect on Cr6+ reduction. When the proportion of KTWDJ-1 was 3%,the Cr6+ leaching concentration was reduced from 128. 5 mg/L to 0. 05 mg/L,and the reduction efficiency was as high as 99. 96%. However,under the same conditions,the reduction efficiency of CPS and Na2S to Cr6+ was 99. 04% and 85. 52%,respectively. As the proportion of sulfide-based stabilizers addition increased,the concentration Cr6+ leaching continued to decrease.The fraction change of iron and manganese oxides increased significantly in soil stabilized by KTWDJ-1,and the change of exchangeable content of Cr in soil stabilized by sulfide-based stabilizers was the main reason for the change of Cr leaching concentration. In addition,three sulfide-based stabilizers,KTWDJ-1 showed relatively good long-term stability,after repeated leaching of acid water could still maintain a stable and low leaching concentration. Finally,the engineering optimal parameters of KTWDJ-1 were explored. In the stabilization process,the water content of soil should be controlled at about 30%,the p H of soil adjusted to about 9,and the curing time is guaranteed for more than 5 days. The stabilization effect of contaminated soil Cr6+ would reach the best.

     

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