New Biodegradable Chelator GLDA Leaching Restoration Of Heavy Metal Contaminated Soil

With the development of China's industrialization rapidness,soil heavy metal pollution problem is increasingly serious,caused widespread attention at home and abroad.In situ leaching of soil remediation technologies because of its simple application,repair of high efficiency,the advantages of low cost,has great application potential.In view of the existing spray lotion biodegradability is poor and can't efficient elution to repair the problem of heavy metal pollution of soil,based on the green environmental protection biodegradable chelator GLDA to drench lotion,with heavy metal Cu,zinc,Pb,Cd to target the pollutant,using static batch test and onedimensional soil column simulation experiment,the elution repair effect and the mechanism of leaching process is analyzed and drench lotion dosage,PH,organic matter content,interfering ions,leaching velocity,the influence of such factors as particle diameter,obtained the optimum leaching conditions.The main research results are as follows: Volatile leaching experiment results show that:1.Static batch experiment results:?1?GLDA elution effectPb,Cd,Cu and Zn in the p H = 4,and the molar ratio of heavy metal chelating agent for GLDA: M = 3:1,the elution effect respectively medium sand removal rate of Cd?93%?> Cu?86%?> Pb?78%?> zinc?71%?,fine sand Cd?95%?> Cu?90%?> Pb?83%?> zinc?81%?.?2?Effect of p H on the elution effectAcid under the condition of four kinds of heavy metals of elution effect is best,followed by the neutral and alkaline.When lack of chelating agent usage,p H of a smaller effect on Pb when the dosage of chelating agent enough,p H has a significant influence on Pb removal effect.Influenced by the p H of Cu,alkaline conditions in addition to the effect is obviously lower than that of neutral and acidic conditions,the Cd show a very good place to effect regardless of the p H,smaller influence on zinc removal effect.?3?Effect of particle size on the elution effectSize has certain influence on removal efficiency,size large to remove effect is better than that of small particle size effect.?4?The organic matter content on the elution effectsThe higher organic matter content,the lower removal rate.Organic matter content of Cd and Pb in soil has a great influence on removal efficiency,and for Cu and zinc organic matter on final removal effect.?5?The target ion of elution effectsNon-target ions of iron,calcium,magnesium has a certain influence on spray lotion GLDA to remove heavy metals,four kinds of influence of heavy metals as Pb > Cu > Zn > Cd.Performance of Fe2 + minimal impact on the target metals,Mg2 +,Ca2 + effect.?6?Before and after the elution morp Hological analysisGLDA main efficient elution is water soluble,soluble state,the state is combined with carbonate,zinc state due to the residue content is higher than other heavy metals,so the leaching out the lowest efficiency.In medium sand and fine sand,four kinds of heavy metal leaching out and 100% water soluble state residue removal rate 0%,GLDA to the size of the removal of heavy metals in different form and different forms of heavy metals before leaching proportion of the total accounted for roughly the same size.?7?Mechanism analysisAffect the removal efficiency is the main mechanism of the influence of p H on the protonation effect,when the p H value increased less protons,acidification.Another important factor is the integration of GLDA and metal forming Lg KML stability constant and stable K value,the greater the combined with chelating agent generated by the more stable chelate,the less easily replaced by other metal.2.Leaching experiment results:?1?Elution velocity effectWhen p H = 11 removal effect is stable,eluent of four kinds of heavy metal removal rate as the Pb?99.95%?,Cd?99.94%?,Cu?99.95%?,zinc?99.96%?,p H influence on the precipitation of Pb,the other three kinds of heavy metals in the p H = 9,10,11,12 had no obvious difference,when precipitation after the removal of heavy metal leaching lotion can be used again.?2?The dosage of eluentWith the increase of leaching liquid volume,heavy metal leaching first to improve quickly,then change is very small.Amount of chelating agent leacheate achieves GLDA: when M = 3:1 leaching effect is stable,the same as the static test results.?3?Particle size effecLeaching of heavy metals in fine sand effects are better than the medium sand,showing the same as the static test results.3.The leaching liquid recycling the result:?1?The PH effectsWhen pH = 11 removal effect is stable,eluent of four kinds of heavy metal removal rate as the Pb?99.95%?,Cd?99.94%?,Cu?99.95%?,zinc?99.96%?,p H influence on the precipitation of Pb,the other three kinds of heavy metals in the p H = 9,10,11,12 had no obvious difference,when precipitation after the removal of heavy metal leaching lotion can be used again.?2?The dosage of Na₂SWhen the dosage of Na2 S 2.5 tendency,precipitation to remove heavy metal to achieve the best effect,the dosage of Na2 S and overall quality of molar ratio of heavy metals as Na₂S: M = 3:1.Sequence of four kinds of heavy metal removal capacity for Cd > zinc > Pb > Cu were more than 99%.