柠檬酸土柱淋洗法去除污染土壤中Cr的研究

Column Leaching of Chromium from a Contaminated Soil Using Citric Acid

为降低铬渣污染场地土壤中高含量铬向其周围农田、水体迁移的风险,我国急需修复铬渣污染土壤的关键技术和数据支撑。采用柠檬酸进行模拟土柱间歇式淋洗的方法,研究滤液中总Cr含量和pH值的变化规律,分析了淋洗前后不同深度土壤中重金属形态的变化,并对淋洗后土壤中C(rⅥ)含量随深度变化的迁移规律进行了研究。结果表明,间歇淋洗方式造成滤液中总Cr含量和pH值跳跃式变化,提高了去除率。淋洗后土壤pH值从11.9降至8.8,土壤C(rⅥ)从土柱顶部向底部强烈迁移。当淋洗量达到5.4个孔隙体积(水土比为2.88)时,土壤总Cr去除率为29.3%,且土壤中主要污染物C(rⅥ)的去除率达到50.8%。柠檬酸淋洗能有效去除酸可提取态部分Cr,降低原场地污染土壤的环境风险,柠檬酸间歇淋洗法可作为修复高污染铬渣场地土壤的初步措施。

In order to reduce the chromium transfer risk from chromium residue contaminated site to the surrounding farmland and water, the relevant technologies and data support for contaminated site cleanup are urgently needed in China. In this paper, simulated soil column in- termittent leaching experiment using citric acid was conducted to study the change of chromium concentration and pH value in the leachate. And the chemical forms of chromium and Cr（ VI ） content in contaminated soil with depth were determined after leaching. The results showed total Cr concentration and pH in leachate had a jump change in the intermittent leaching and increased the removal rate of chromi- um. The soil pH value changed from 11.9 to 8.8, and soil Cr（ VI ） had strong migration from the top to the bottom of soil column during leaching. When leaching volume achieved approximately five pore volumes （water-soil ratio was 2.88 ）, the total Cr and Cr（ VI ） removal rates of the soil were 29.3% and 50.8%, respectively. Citric acid leaching could effectively remove the chromium bound to the acid ex- tractable fraction and reduced the environmental risk of the chromium residue contaminated site. Thus, it is feasible that applying the citric acid intermittent leaching method as the preliminary measure to remediate the polluted soil with high level of chromium.