Remediation Of Heavy Metals Contaminated Soil By Washing With Citric Acid And Polyepoxysuccinic Acid

In many soil remediation methods,soil washing is considered to be one of the most time-efficient,cost-effective,and permanent techniques to remove heavy metal from the soil.In this paper,an efficient compound agent was prepared for the remediation of heavy metal contaminated soil,which provided experimental and theoretical basis for the practical application of compound agent in remediation of heavy metal contaminated soil.In this study,citric acid,ferric nitrate and polyepoxysuccinic acid were used as research agents.The effects of concentration,liquid-solid ratio and washing time on the washing efficiency and washing mechanism of single and compound agents were studied.And the effects of washing on soil physical and chemical properties were analyzed.The main conclusions are as follows:(1)When the optimum ratio of citric acid and polyepoxysuccinic acid was 7:3,the optimum concentration of citric acid and polyepoxysuccinic acid was 0.5 mol/L and0.05 mol/L,the liquid-solid ratio was 15,and the washing time was 240 min,the removal rates of Cu,Zn,Pb and Cd were 86.06%,74.55%,67.88%,and 91.63%,respectively.Compared with single agents,it has better washing effect.(2)The kinetic of Cu,Zn,Pb and Cd removal by compound agents was analyzed,regard of different times.The results showed that: double constant equation and Elovich equation were the most suitable equation to descripte Cu,Zn,Pb and Cd desorption process.Indicating a non-homogeneous diffusion process.(3)The soil physical and chemical properties and heavy metal forms before and after washing were analyzed.Compared with single agents,the p H value of soil washed by citric acid and polyepoxysuccinic acid had little change,and the effect of citric acid and polyepoxysuccinic acid on soil was mild.The results of X-ray spectrum and Fourier transform infrared spectrum showed that citric acid and polyepoxysuccinic acid washing had little effect on the soil.The contents of exchangeable Cu,Zn,Pb and Cd decreased significantly after being washed with citric acid and polyepoxysuccinic acid,and the contents of reducible,oxidizable and residual Cu,Zn,Pb and Cd also decreased.Therefore,the washing with citric acid and polyepoxysuccinic acid significantly reduced the potential ecological risk of heavy metals in the soil.