Soil Washing Experimental Study Of The Soils Contaminatetd By Chromium In Qingdao Hongxing Chemical Plant

In our country, groundwater, surface water and soil were severely polluted bychromium residue, and ecological environment and human health were also threatenedimmensely. Remediation chromium residue contaminated site was one of thedesiderated case of our country because the high contamination concentration and theeasily diffusion. The difficulty of the remediation technology was that the topsoil of thesite is sticky, small particle size and severely polluted. Soil washing can thoroughlyremove contaminants from contaminated soils with low cost, and it’s easily to controlthe remedial process, so it is suitable for the remediation topsoil.According to the pollution property of topsoil, research of a combined ex-situremediation technology was conducted in exchangeable and acid-soluble fractionationchromium-contaminated soils, and the feasibility of the technology was validated. Then,the technology of third counter-current washing was advanced.The main results of research were shown as follows:The different washing solutions had no significant difference in the removal rate oftotal Cr. but they had different removal efficiency in different fractionations ofchromium. The main fraction of Cr removed by deionized water was exchangeable andweak acid extracted fraction, while EDTA-Na2could extract Cr with exchangeable andweak acid extracted fraction as well as reducible Cr fraction; besides the first twofractions above, citric acid could also extract oxidizable Cr fraction; however, Na2SO4showed removal ability on all fractions. Due to exchangeable and acid-solublefractionation was the main fractionation of chromium in chromium-contaminated soil,and in view of economy, the best washing solution was water. The optimal stirring timeof water washing was40minutes and the suitable ratio of liquid to solid was30:1.