Research On Solidification/Stabilization Treatment And Security Of Soil Contaminated By Typical Heavy Metals

The solidification/stabilization technology is a common method for the treatment of heavy metal from soil,which has the advantages of short remediation period,low price,flexible construction,strong applicability and so on.Among many solidification/stabilization technologies,chemical passivation technology and high temperature solidification technology have the advantages of economy,high speed and safety,which were considered to be the most promising solidification/stabilization technologies.In this paper,the effect of different particle size and concentration of hydroxyapatite（HAP）on the passivation performance of heavy metals,and the adsorption and desorption properties of micron hydroxyapatite（m HAP）and nanometer hydroxyapatite（n HAP）to Cu²⁺and Zn²⁺were investigated.In addition,the curing effect of coal gangue on the treatment of heavy metals under different conditions,and effects of material ratio,sintering temperature and other factors on the solidification effect of Cu²⁺and Zn²⁺in soil were also explored.The content of this paper included the following two aspects.（1）The contaminated soil from an environmental pollution accident in Jiangsu Province was used as the raw material.The n HAP and m HAP were used to study the adsorption and desorption performance of heavy metals.The results showed that the soil improved by n HAP lost the characteristics of nano-materials due to the clustering effect,and the improvement of soil adsorption performance was lower than that of m HAP improved soil,and the improvement of anti-desorption ability was also lower than that of m HAP.Compared with the adsorption process of Cu²⁺and Zn²⁺on m HAP（or n HAP）improved soil,the adsorption affinity of Cu²⁺is better than that of Zn²⁺.At the same time,p H of soil and the coexistence of low molecular organic acids will affect the soil immobilization process of heavy metal ions.（2）Taking the coal gangue as the main raw material,the high temperature solidification results of simulated soil contaminated by heavy metal and actual contaminated soil were discussed,respectively.And the best solidification conditions of heavy metals were determined.The results show that the experimental results of simulated soil are consistent with those of real soil.As for Cu²⁺,the order of the influence of relevant factors on the leaching toxicity is listed as material ratio>sintering temperature>heating rate>holding time.As for Zn²⁺,the order is material ratio>sintering temperature>holding time>heating rate.After high-temperature solidification,the leaching toxicity of Cu²⁺was reduced by more than95%and maintained near 1.2 mg/L.Since Zn was volatile at high temperature,the leaching toxicity of Zn²⁺was reduced by more than 98%and maintained near 0.9 mg/L after the treatment.Based on these result,the composition of coal gangue is changed by adding diatomite,Si O₂ and Al₂O₃,respectively,to study the influence of leaching toxicity.The result showed that the leaching toxicity is reduced to Cu≤0.750 mg/L and Zn≤4.5 mg/L,which were lower than half the lethality of zebrafish in 48 h.