Research on the Effect of Chemical Reduction-Stabilization Combined Remediation of Cr-contaminated Soil
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摘要: 六价铬是国际公认的47种最危险废物之一，研究铬污染土壤的修复效果对污染场地风险管控具有重要的现实意义。本文以济南市某典型铬污染场地土壤作为研究对象，提出了"化学还原+固化稳定"的修复治理思路，针对修复剂类型、投加比、反应时间、还原效率、修复成本和环境效应等因素，确定了该修复工艺的最佳条件，并对污染土壤的修复效果进行评价。结果表明土壤中Cr（Ⅵ）的最佳修复条件为：以氯化亚铁作为化学还原剂，其投加比为5倍的理论投料比，还原时间为2天；以钙镁磷肥作为稳定剂，其投加比为10%（换算成钙镁磷肥与总铬的质量比为72：1）。采用以上条件修复铬污染土壤，总铬的生物可利用系数由0.4398降低至0.0017，修复后的土壤Cr（Ⅵ）含量介于0.315~0.501mg/kg，Cr（Ⅵ）被还原率大于99.5%。该结果可为土壤修复和决策提供依据。Abstract:
BACKGROUNDCr(Ⅵ) is one of the 47 internationally recognized most dangerous wastes. Study on the remedy of Cr-contaminated soil is of great significance for risk control of contaminated soil. OBJECTIVESTo build a reliable method for Cr-contaminated soil, and to screen the optimal remediation conditions. To propose a chemical reduction-stabilization combined method for remediation of Cr(Ⅵ) contaminated soil and screen the remediation conditions including choice of reductant, soil/liquid ratio and stabilizer. METHODSSoil from a typical chromium contaminated site in Jinan is used as the research object, and the idea of 'chemical reduction + solidification stability' is suggested, which is aimed at the types of repair agent, dosage ratio, reaction time, reduction efficiency, repair cost and environmental effect. The optimal conditions for the repair process were determined and the remediation effects of contaminated soil were evaluated. RESULTSThe results demonstrated that the optimal parameter for Cr(Ⅵ) treatment was using ferrous chloride as the reductant and treating for 2 days, controlling the addition amount of the reductant at 5 times of its stoichiometric need. Calcium magnesium phosphate was used as the stabilizer and its addition amount was controlled as 10%. After remediation, the bioavailable efficients of Cr in the soil reduced from 0.4398 to 0.0017. The results showed that contents of Cr(Ⅵ) in the treated soil were 0.315-0.501mg/kg, and 99.5% of Cr(Ⅵ) was reduced. CONCLUSIONSThe remedied soil satisfies the risk screen number for residual land. This result could provide reference and theoretical basis for soil remediation and decision-making. -
Key words:
- chemical reduction /
- stabilization /
- Cr(Ⅵ) /
- soil remediation /
- combined method
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表 1 最佳还原剂的筛选
Table 1. Screen of optimal reductant
还原剂 还原剂市场价格 理论还原(1x)条件下Cr(Ⅵ)被还原率 最佳投加条件下Cr(Ⅵ)被还原率 反应副产物及环境风险 氯化亚铁 400元/吨 89%~94% >99.5% Fe(OH)3沉淀，环境风险较小 硫化钠 6600元/吨 45%~80% >99.5% 单质硫及硫化氢气体，环境风险较大 亚硫酸钠 2400元/吨 -15%~20% 21% 易溶的SO42-，环境风险一般 
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