Study On Washing Effect Of Heavy Metal Contaminated Soil With Ultrasound And EDTA Washing Process After Acid-dipping

Soil heavy metal pollution has become an important factor of a global shortageof land resources. In recent years, the environmental pollution caused by improperelectrical and electronic waste dismantling, and population health hazard issue graduallycaused the researchers’ interest.China is becoming the electronic waste disassemblycenters in the world.At present, there are many kinds of ways, fix the soil heavy metalpollution, including leaching, solidification/stabilization, phytoremediation,biodegradation, thermal desorption and gas stripping technology.The leaching technologybecause of its fast speed, can thoroughly remove heavy metals in the soil, by the wideattention of scholars at home and abroad to study.From the point of technology utilization,mainly for Europe and the United States using existing elution battery recycling, type ofslag and metallurgical field.Electronic waste disposal site is a special kind of site types,and the contaminated sites are mainly concentrated in China, India and other developingcountries.Due to the special pollution source, the combination of heavy metals and soilforms, existing elution technology parameters is not necessarily suitable for electronicwaste disposal site contaminated soil, therefore, it is necessary to carry out to electronicwaste disposal sites contaminated soil elution parameters of exploration research.Through this study mainly through indoor simulation test, analysis of ultrasonic,acidification of elution parameters, such as electronic pickling sites contaminated soil Cd,Cu, Pb, and the influence of zinc elution efficiency.Put forward for the elution of Chinaelectronic waste disposal site soil bioremediation technology parameters, provide areference for this type of site restoration.The experimental results showed that:1. The electronic waste disposal activities lead to Cd, Cu and Pb pollution ofdismantling site soil,which are the main pollutants. Major pollutants of Cd, Cu and Pbhas spread to nearby rivers and farmland, rice. Content of Cd and Pb in vegetables andother agricultural products surrounding the repositories exceeds national food limitedstandard of heavy metals.Consuming the highest percentage of heavy metals, edibleagricultural products accounted for86.6%~99.8%, and agricultural product consumptionis the main way to threaten exposure population health.From the point of element intake,edible agricultural products dose of As, Cu and Pb11.0,4.63, and26.89times of USEPArecommends RfD values respectively, the biggest threat to the health of exposed workers.2. The ultrasound as an auxiliary means of EDTA elution, which can effectivelyimprove the removal efficiency of heavy metals.Let stand, oscillation and ultrasonictreatment, ultrasonic on the removal rate of Cd, Cu, Pb, Zn is best,34.89%,48.09%, 59.29%and48.09%respectively.Let stand, quiet place-stirring and ultrasonic-stirringafter three treatment, ultrasonic-stirring treatment of Cd, Cu, Pb and zinc removal rate ishighest,74.67%,26.24%,90.24%and40.66%respectively.3. The best ultrasonic ultrasonic time is2~3h, the best ultrasonic power is80%~100%.Difference is that the ultrasound after elution, Cd, Cu, Pb and zinc can berespectively in180,120,150,120minutes when the maximum removal rate of36.87%,56.24%,56.68%and56.24%respectively.Cd, Cu, Pb, zinc are maximum removal ratewhen power is more than80%,38.11%,57.94%,56.33%and59.70%respectively, but inthe power set to80%and80%two power changes in heavy metal removal rate is not big,so considering the cost problem, can choose to power by80%.4. The acidification time in12h, the removal rate of Cd, Cu, Pb and zinc reach ahigher level.Cd after leaching of heavy metals content close to the soil environmentquality grade A standards for land use in the exhibition, after more than12hours afteracidification of soil sample achieves exhibition for soil environmental quality grade Bstandard (HJ350-2007).5. After acidification pretreatment, can significantly reduce the soil can also squareone heavy metal content, EDTA elution can further improve the elution efficiency ofheavy metal contaminated soil.Acidification-EDTA elution process of soil Cd, Cu, Pb,and the elution efficiency of zinc were64.5%,40.2%,74.8%,40.2%, content were1.16,1.16,1.16,81.77mg/kg, achieves the B grade standards for land use in the exhibition, Cdto the exhibition land soil environmental quality grade A standard.Compared with EDTAelution process, this process of soil Cd, Cu, Pb, and the elution efficiency of zincincreased by30.16%,11.28%,24.24%and11.28%respectively.After acidificationtreatment, the pollution in the soil can also square one Cd, Cu, Pb and zinc content by0.91,27.22,532.70,27.22mg/kg reduce to0.33,8.49,37.25,8.49mg/kg, was reducedby63.82%,68.80%,93.01%,74.84%, acidification treatment on soil heavy metal acidextract state, and oxidation state, residual state.Acidification treatment also significantlylower the pH, improves the oxidation reduction potential.This paper conduct research of the elution effect to the contaminated pickling sitessoil of Longtang town Qingyuan city, Guangdong province,through the combinedultrasonic-EDTA and acidification pretreatment-EDTA put forward the elutionreference parameters of ultrasonic and acidification treatment, providing theory basis forindustrial field soil heavy metal contaminated sites elution provide scientific.