FeSO4稳定铬污染土的铬赋存形态及浸出特性研究

Chromium speciation and leaching behaviors of hexavalent chromium contaminated soil stabilized by FeSO4

采用硫酸亚铁(FeSO4)对Cr(Ⅵ)污染土进行稳定化处理。研究了Fe(Ⅱ)/Cr(Ⅵ)摩尔比和养护龄期对污染土稳定过程中的铬赋存形态及浸出特性的影响规律。结果表明:随着Fe(Ⅱ)/Cr(Ⅵ)摩尔比和养护龄期的增加,Cr(Ⅵ)和总Cr的浸出浓度降低,稳定土中Cr(Ⅵ)的含量降低,当摩尔比为3时,Cr(Ⅵ)和总Cr的浸出浓度均低于我国《危险废弃物鉴别标准浸出毒性鉴别》(GB/T50853―2007)的限值;当摩尔比为10时,稳定土中Cr(Ⅵ)的含量低于我国《土壤环境质量标准》(GB15618―2008)中工业和商业用地的限值(30 mg/kg);当摩尔比为20时,低于居住用地限值(5 mg/kg)。形态提取试验结果表明:FeSO4改变稳定土中铬的赋存形态,可促使铬从弱酸态向可还原态和可氧化态转化,而对残渣态的铬影响不大。Cr(Ⅵ)的浸出浓度与稳定土中的Cr(Ⅵ)含量均存在指数函数关系,且浸出试验不能全面、客观地评价铬污染土稳定效果。

Ferrous sulfate(FeSO4)was used to stabilize chromium-contaminated soils. Leaching test, alkaline digestion test and sequential extractions test were conducted to investigate the variation of chromium speciation and leaching properties of FeSO4 treated chromium-contaminated soils along with Fe(Ⅱ)/Cr(Ⅵ) molar ratio and curing time. Results showed that the leaching concentration(hexavalent chromium and total chromium) and hexavalent chromium content of the soil were decreased significantly with Fe(Ⅱ)/Cr(Ⅵ) molar ratio and curing time. When Fe(Ⅱ)/Cr(Ⅵ) molar ratio was 3, the Cr(Ⅵ) and total Cr leaching concentrations were lower than the identification standards for hazardous wastes: identification for extraction toxicity(GB/T5085.3-2007) of China. Furthermore, When Fe(Ⅱ)/Cr(Ⅵ) molar ratio was 10, the amount of Cr(Ⅵ) in soil was below the threshold allowed by Environmental quality standards for soils(GB15618-2008) for industrial and commercial reuse of China(Cr(Ⅵ)<30 mg/kg). And the civil reuse of soil(Cr(Ⅵ)<5 mg/kg) was only achieved with Fe(Ⅱ)/Cr(Ⅵ) molar ratio of 20. Sequential extraction procedures revealed that majority of acid soluble fraction of chromium was converted to reducible fraction with FeSO4 stabilized. The leaching concentration of Cr(Ⅵ) increased as exponential function with the amount of Cr(Ⅵ) increases in soil. The leaching test(TCLP, SPLP) could not reliably evaluate the stability effect of chromium.