Cr(Ⅵ)污染土壤的热解还原无害化处理

Study on the detoxification of Cr(Ⅵ)-contaminated soil by pyrolysis

提出了用热解还原法对含铬土壤进行无害化处理的新技术，研究了热解温度、热解时间及土壤有机质对铬无害化处理的影响，分析了热解前后土壤中铬的元素形态的变化，同时还探讨了热解还原过程中Cr（Ⅵ）的无害化机制。结果表明，土壤中的有机质在热解还原过程中产生的挥发分对Cr（Ⅵ）的无害化起核心作用；在200～600℃范围内，Cr（Ⅵ）的还原量随着热解温度升高而增大，500．0℃最适合于经济有效地实现Cr（Ⅵ）的热解还原处理；Cr（Ⅵ）的热解还原过程较快。铬的形态分析结果表明，热解后可交换态和碳酸盐结合态铬量大大降低，大部分铬转化成了活性低的残渣态，极大地降低了铬的危害。

The detoxification of Cr（Ⅵ）-contaminated soil by pyrolysis technology was reported. The effect of temperature, treatment time, and soil organic matter on the detoxification of Cr（Ⅵ ） in the process of the pyrolysis was investigated. The speciation of chromium in soil before and after the treatment was performed which indicated that chromium in the soil after pyrolysis was quite stable and much less reactive. The mechanism of Cr（ Ⅵ ） econtamination was discussed. The results showed that the gaseous components, which released from the soil organic matter during the pyrolysis, played a predominant role in the Cr（ Ⅵ ） reduction. The reduction amount of Cr（Ⅵ ） was in creased with increasing of the temperature in the range of 200- 600 ℃, 500.0 ℃ was optimal to efficiently and economically detoxify Cr（Ⅵ ）-contaminated soil by pyrolysis. The detoxification rate of Cr（Ⅵ） by pyrolysis was fast and could be completed in less than 10 minutes when the treatment temperature was kept at ≥300℃.