Research On Influence Factors And Migration Characteristics Of KMP For Stabilization Of Soils Soils Contaminated With Lead,Zinc And Cadmium

The remediation of high concentration heavy metals contaminated industrial sites is currently an emergent concern in geoenvironmental engineering practice.As a widely used remediation technology,Stabilization/solidification(S/S)involves mixing binders and contaminated soils to reduce the mobility of heavy metals and enhance the strength of the soils by both physical and chemical means.At present,the most widely used traditional cement-based materials are difficult to meet the stabilization and solidification requirements of high concentration heavy metal contaminated soil.With the financial support of National High Technology Research and Development Program(2013AA06A206),National Natural Science Foundation(41330641),and Outstanding Youth Foundation of Jiangsu Province(BK2012022),the key process parameters,low temperature influence characteristics and heavy metal migration characteristics using soil column test of KMP S/S contaminated soil were studied in this thesis,also included the numerical simulation of the soil column test.Conclusions obtained are as followed:(1)Through the toxicity characteristic leaching procedure test,unconfined compressive strength test and determination of the effective phosphorus content of solidified soil,studied the leaching characteristics and strength characteristics of KMP solidified soil.The results showed that the leaching toxicity was the lowest and the strength was the highest,and the effective phosphorus content in the solidified soil was the highest in KMP soil using acidizing method No.1.With the increase of initial moisture content,the strength of stabilized soil decreases gradually,the strength is less than 150 kPa when the initial moisture content reaches 35%;The concentration of heavy metals in the cured soil firstly decreased and then increased with the increase of water content,and the leaching toxicity was the lowest when the initial water content was 25%(for water-cement ratio 4.17).(2)By changing the dosage of KMP,increasing MgO content and adding low alkaline cement,to solve the problem of low strength of KMP solidified soil under high moisture content were improved.The results show that under the same conditions,the soil strength of adding mixture of KMP and alkaline cement is the highest,and the leaching toxicity can meet the requirements;However,the pH value of KMP+MgO solidified soil is too high,and leaching toxicity is higher,too.(3)The low temperature influence test results show that:With the decrease of curing temperature,the leaching concentration of heavy metals Pb,Zn and Cd increased slightly,its ability to stabilize heavy metals is hardly affected by low temperature,while the leaching toxicity of cement soil was significantly affected by low temperature With the decline of curing temperature,the strength of cement or KMP stabilized soil all decreased.(4)Results showed that the saturated hydraulic conductivity of S/S soil is 4.65×10-9 m/s.Combined with the soil column diffusion model test and numerical simulation,the effective diffusion coefficient of the lead,zinc and cadmium in the KMP soil were calculated.The De of Pb,Zn and Cd are 1.5×10-13 m2/s,7.4× 10-13 m2/s,1.6×10-12 m2/s respectively.The Kp of Pb,Zn and Cd are 7690 mL/g,3150 mL/g,1640 mL/g respectively.(5)Through numerical simulation,the long-term safety characteristics of the solidification and stabilization remediation of Baiyin pollution site were studied.The simulation results show that when the flow rate was 0.05 m/s and 1.46 m/s,the concentration of heavy metals Pb,Zn and Cd in water decreased with time,and in one year the concentration of heavy metals in water was far lower than the standard limit.When the flow rate of groundwater was 1.5 m/d,the concentrations of Pb,Zn and Cd were all far lower than the standard limit.