Washing Remediation Of Pb(Ⅱ) Contaminated Soil And Its Forecast Evaluation Model

With the rapid development of urbanization and the implementation ofindustrial structure adjustment policy, the situation of the heavy metal pollution ofthe land in China has been very serious. Meanwhile, the resulted environment andhealth risk, and loss of economy is immeasurable. What’s more, a lot of the heavymetal polluted sits need to be repaired immediately. In this paper, we took Pb²⁺contaminated soil for example and studied the removal mechanisms and effect lawsof Pb²⁺under the action of oscillation leaching and column leaching, proposing thetwo-stage leaching repair technique of the Pb²⁺contaminated clay soil, establishingthe adsorption-desorption-migration dynamics model of Pb in the contaminated soilunder the action of leaching, building a fuzzy mathematical model for polluted siterecovery evaluation. The main work is as follows:（1） Studying on the effect and influence laws of the oscillating leaching ofdifferent burden contaminated soil with different eluents, proposing theoptimal eluent and controlled conditions. Oscillating leaching of Pb²⁺contaminated soil under the different burdens（50、150、200mg/kg）with pure water,1MHCl,0.1M tartaric acid,0.05MNa2EDTA,0.01M rhamnolipid and theircombinations separately. The effect of time, pH, liquid to solid ratio, concentration,temperature and organic matter content on leaching characteristics was studied.（2） Studying the characteristics of column leaching of Pb²⁺polluted soil,developing a set of leach remediation device for contaminated soil. Washing ofPb²⁺contaminated soil with0.05MNa2EDTA through self-made soil leachingcolumn, the effect mechanism of soil pollution time, void ratio, flow rate of eluent,location of injection point and repeated leaching was studied.（3） Proposing modification leaching method of contaminated clay,studying the solutions of recycling and handling of eluent. Since the effect ofleaching is poor in dealing with Pb contaminated clay and the reutilization value ofthe treated soil is very low, the clay was modified by addition of sand, the leaching effect could be increased by nearly20%and the strength of the clay after leachingcould be significantly increased. When the addition amount of sand was about30%,the C and φ of modified clay would reach the max. Using organic sulfur TMT todeal with the waste eluent, the removal rate of Pb²⁺would be higher than85%whenthe pH of the eluent was9, the reaction time was10min and the addition amount ofthe TMT was1time（mol ratio）(Pb²⁺～2/3TMT).（4） Establishing the environmental prediction model for adsorption-desorption-migration dynamic process of Pb²⁺contaminated soil. Throughstudying of Pb²⁺adsorption isotherms and desorption kinetics, the dynamic releaseand transmission process model of Pb²⁺was established through combination ofsoil water seepage equation, solute transport equation and Pb²⁺desorption kineticsequation. Besides, the model was numerically solved and used in simulating thedynamic release and transmission process of Pb²⁺in contaminated soil, the validityof the model has been proved by instances.（5） Building remediation effect evaluation system and model for Pbcontaminated sites. Through the fuzzy mathematical principle, establishing acomprehensive evaluation index system, which reflects the hierarchy and fuzzycharacteristics of contaminated site remediation effect evaluation, overcoming thesidedness of single or few indicators in the evaluation of contaminated site andimproving the accuracy and efficiency of the evaluation results.