Study On In-situ Remediation Of Lead-Contaminated Soil Through Combination Of Leaching And Adsorption

The development of industry and agriculture was lead to occurrence of numerous heavy metals contaminated soil,which pose a serious crisis to human and environmental health.Based on high efficiency of heavy metal enrichment capacity in aquatic system,ion exchange resin has been widely used in remediation of heavy metal contamination in water environment system.And the chemical leaching method is widely used in soil restoration of heavy metal contaminated soil due to its low cost,high efficiency and simple operation.In this study,the inorganic zirconium phosphate-organic ion exchange adsorption resin composite materials was used as functional repair agent and combined with NH₄NO₃ eluent to build a new method to rapid in situ remediation of lead contaminated soil,where the repair agent,soil,and eluent fully contact so that promote the migration of Pb from soil to eluent and repair agent as well as complete remediation.First,the main influencing factors of the removal rate in the in-situ remediation process were analyzed,the repair conditions were optimized,and the in-situ remediation behavior under optimized conditions was examined.The results showed that the type of eluent,the dosage of composite resin,the ratio of liquid to soil,and time have a great influence on the removal rate of Pb in soil.With the different eluent,the removal rate of Pb is between 3.63%and 78.48%.With increasement of dosage of composite functional resin,the removal rate of Pb increased from 13.49%to 69.35%.With increase of ratio of liquid to soil from 1:3 to 20:3,the removal rate of Pb reached from 11.40%to 67.1%.And with period of treatment increased to 30 days,the remove rate of Pb increased to 72.56%.The results show that highest removal rate was reached to 67.1%on condition of 0.1mol/L ammonium nitrate solution as eluent,1:1 of liquid to soil,10%of soil quality of dosage of composite resin and one day oscillation in constant temperature.At the same time,the stability of the regenerative recycle of composite functional resin was also studied.With 5 times of cyclic utilization,the removal rate of Pb is between 61.7%and58.3%,the adsorption capacity of composite functional resin was still stable.Further,the migration path and distribution of Pb was investigated during process of in-situ remediation,and change of lead form in soil as well as the biological availability of Pb in soil were also analyzing before and after remediation.As the results show,a large proportion of Pb was adsorbed by remadiation agent through dynamic adsorption process,and it was also supported by SEM and EDS.Besides,the content of different form of Pb were all decreased where the 88.5%decreased for exchangeable,71.9%decreased for carbonate bounded form,65.3%decreased for Fe-Mn oxides bound from,7.8%decrease for organic form,28.7%decrease for residual form,and decreased with prolong of time.Pb could affects plant growth and development,where the root and leaves become shorted,the dry matter accumulation was decreased,and the germination rate of pakchoi seed was inhibited and decreased from 95.8%to 79.2%.