Remediation Of Chelating Agents And Surfactants On Copper And Lead Ontaminated Lou Soil

In recent years, the contamination ancident of heavy metals in the environment happenedfrequently. Ministry of Environmental Protection has reviewed and approved the "12thFive-hazardous waste pollution prevention planning", which said that the environmentalprotection special action in2012is to strengthen the heavy metal pollution prevention, andcurb resolutely the occurrence of heavy metal contamination. With the development ofChina’s industry, especially the emission of heavy metals enterprise was increasing, resultedin increasing pressure on the environment. There are physical, chemical and biologicalmethods to remediate the heavy metal contaminated soil, physical method costs higher,chemical remediation is easy to produce secondary pollution to the environment,bioremediation required longer time, so the combination of physical repair and chemicalrepair,that is soil washing technologies have come into being. The soil washing remediationtechniques was critical to the choice of the eluent, chelating agents and surfactant are widelyused with a strong chelating complexation, solubilization characteristics. It was found that theeffects of surfactant treatment in heavy metal contaminated soil is good, especially after theaddition of EDTA is even more significant. In this paper, Cu and Pb was choose torepresentative, using batch tests and column leaching methods, choosing the chelating agentEDTA and citric acid （CIT） and the anionic surfactant sodium dodecyl sulfate （SDS） and thebiosurfactant rhamnolipid （RL2）, to research the desorption effect and desorption kineticcharacteristics of Cu and Pb in lou soil, as well as the best leaching conditions, to select theoptimal chelating agent/surfactant concentration ratio, and compared the leaching of heavymetals before and after morphological variation, and provide a scientific basis for heavy metalpollution of the calcareous soil.（1）The kinetics of leaching Cu and Pb in contaminated Lou soil using different eluensshowed that the Cu and Pb leaching were slow process with the two kinds of chelating agentstreatment, it was about240minutes to reach leaching equilibrium. while the Cu and Pbleaching was rapid process with two surfactants treatment, and it was about60minutes toreach leaching equilibrium. The leaching amount of Cu followed the trend of EDTA> CIT>RL2> SDS, the leaching amount of Pb followed the trend of EDTA> CIT> SDS> RL2.The EDTA leaching of Cu and Pb in the contaminated Lou soil was the best among the four kindsof leaching agents; The two constant rate and pseudo-second-order equations were well fit theexperimental data. The parameters b of the two-constant equation model could be used todescribe the leaching rate.（2）The equilibrium research of leaching Cu and Pb in contaminated Lou soil usingdifferent eluents showed that the optimal conditions of EDTA and CIT solutions are the ratioof water to soil20:1, solution concentration0.01mol·L^-1, pH7and the solution ionic strength;RL2solution is concentration0.02mol·L^-1, pH8, the solution ionic strength;SDS should notbe used as leaching agent, because it’s easy to precipitate with Ca²+in the Lou soil. Theresults of the cumulative leaching indicated that EDTA、CIT and RL2can effective removedCu in contaminated Lou soil as well as EDTA was effective to the removal of Pb fromcontaminated soil.（3）The results of leaching Cu and Pb in contaminated Lou soil by chelating agent andRL2complexed showed that the concentration of RL2was100CMC,it has stimulative effectfor two kinds of chelating agent leaching Cu, and the concentration of RL2was200CMC, theleaching of Cu was inhibited. When the concentration of RL2was100CMC, it hasstimulative effect for the leaching of Pb with EDTA, and when the concentration of RL2in200CMC, the leaching of Pb with EDTA were inhibited; the mixde RL2and CIT leaching Pbhad little effect on leaching.（4）The results of column leaching Cu and Pb in contaminated Lou soil showed the effectof column leaching Cu and Pb was much better in1mL min^-1flow rate,.With the cumulativevolume increased, the cumulative leaching amount of Cu and Pb was increased gradually, thecumulative leaching amount of Cu and Pb followed the trend of EDTA> CIT> RL2.Theremoval of Cu and Pb by EDTA and CIT was most obviously in the early stages ofleaching,and the cumulative leaching amount of Cu and Pb by EDTA reach the peakpoints,which is15.00mg·kg^-1and71.36mg·kg-1respectively, the cumulative leaching amountof Cu by CIT is15.27mg kg^-1. The fractionation results showed that after EDTA andEDTA-RL2leaching, every fraction of Cu and Pb were reduced obviously; CIT, RL2, and themixed of CIT and RL2solution leaching can effectively remove the exchangeable fraction,adsorption states and organic heavy metal, and greatly reduce the heavy metal risk inenvironmental, and also showed that CIT and RL2have large potential to remendiation heavymetal contamination soil.