Study On Removal Of Heavy Metals From Soil By Biodegradable Chelator GLDA

With the development of human society,the problem of soil heavy metal pollution is becoming more and more serious,and it directly causes great harm to animals,plants and human beings.The remediation technologies for metal-contaminated soils include chemical,physica,or biological techniques.Phytoextraction and soil washing are effectively useful for remediate contaminated soils..In this study,the treatment effect of chemical leaching and co-planting on contaminated soil was studied by the method of plot experiment and long-term follow-up was conducted.The leaching effect of biodegradable chelator GLDA(glutamic acid,N,N-iminodiacetic acid,L-glutamic acid,N,N-diacetic acid)on 14 contaminated soils(pollution soil collected from Guangzhou baiyun,Shaoguan qujiangzhanru,Hunan Lengshuijiang,Hunan Cuijiaqiao,Shaoguan Yingde,Huizhou Gongzhuang,Ganzhou Wukuang and Fo gang,Dabaoshan,Zhuzhou Zuoquan,Changsha Beishanoutang,Changsha Beishanronghe,Shaoguan tielong,Lechang)the elution effect;The optimum conditions of leaching were studied.The leaching efficiency of different salt and GLDA was preliminarily explored.The main research results are as follows:(1)Sweet corn JZY is suitable for planting on Cd and cadmium-contaminated soil,but it is not suitable to use in combination with leaching agent on Pb and Pb contaminated soil.(2)Compared with 2017,the content of heavy metals in soil under different treatments decreased to different degrees in 2018.Compared with the control treatment,the content of Cd and Pb in the soil treated with ferric chloride leaching and deep lime fixation decreased the most,and the content of heavy metals in the control and fallowing treatment was higher than that in other treatments,indicating that the leaching agent added in the soil at the early stage played a certain follow-up role in reducing the absorption of heavy metals in the soil by plant co-planting system.The highest phytoextraction of Cd and Pb were gained by co-planting Sedum alfredii,which were up to 24.1 mg/m~2with 35.36 mg/m~2;The biomass of Sedum alfredii was the lowest when mixed additive(MC)was added.The soil after MC leaching inhibited the growth of Sedum alfredii.(3)The adding of citric acid,to adjust GLDA to acidity,could greatly improved the leaching efficiency of GLDA,especially for heavy metal Pb.The leaching effect of mixed GLDA and citric acid on Pb was better than the sum of GLDA and citric acid respectively.The leaching time was 120min,the concentration of eluent was 10mmol/L,and p H=4 was the optimal leaching condition.(4)After soil was eluted by GLDA with p H=4 and concentration of 10mmol/L for120min,the total amount and available state content of heavy metals in soil were significantly lower;Soil p H value changes little,soil residual sodium can be washed with water.(5)When sodium citrate,sodium hexametaphosphate,ferric chloride and potassium chloride were mixed with GLDA,the leaching rate of Cd was higher than that of GLDA.The leaching rate of Pb was improved by adding sodium hexametaphosphate and ferric chloride.After the four salts were mixed with GLDA,the leaching rates of Cd and Pb were less than the sum of their respective leaching rates.