The Study Of Soil Washing In Heavy Metals Contaminated Soil And Engineering Application

Because the previous researches were based on some non-biodegradable eluents,which existed ecological risk to remove contaminant from heavy metals contaminated soil,in the paper that the green and biodegradable chelators were named Polyaspartic acid(PASP),Polyepoxysuccinic acid(PESA),and Iminodisuccinic acid(IDS),they were maken a choose as the washing eluents for soil washing remediation of the heavy metals contaminated soil.The batch washing experiments’ s results showed that the PASP,PESA,and IDS could significantly improve the washing effect that the heavy metals removal from the heavy metals contaminated soils.For the heavy metals contaminated soil of the total content of 2990.36 mg/kg,when PASP,PESA,and IDS were choosed that the concentration is 150 mmol/L,respectively,the results that the total heavy metals removal of 19.19%,9.70%,and 13.11%,respectively.As for the Pb contaminated soil,the 20.65% was removed by using 8.8mmol/L IDS solution.The heavy metals were extracted from the contaminated soil,including some relevant factors,such as the the pH value of eluent,concentration of the eluent,temperature,contacting time,and the ratio of washing solution to the sample.To determine the effect factors of PASP,PESA,and IDS on heavy metals in different fractons,the BCR sequential extractions were carried out on the soils before and after washing.The results showed that the heavy metals fractions of different heavy metals in soils were different,which directly affected the washing effect.The order of the extraction efficiency for different fractions was acid-soluble fraction>reducible Fe-Mn oxides and hydroxide fraction>oxidizable organic mater bound fraction>redidual fraction.By comparing the different washing time,the results showed that the fractions of heavy metals could be transformed into each other in the soil during the washing process.According to the optimized washing conditions in the laboratory,the washing equipment was used to carry out the demonstration project of the Pb contaminated soil.When the concertration of IDS was 4.4 mmol/L,and the pH vaule of IDS was 6.00,the concertration of the heavy metal(Pb)was tested by self-test and the Shanghai Academy of Environmental Sciences Environmental Testing Laboratory(the third testing organization),the results showed that the concertration of the heavy metal(Pb)was 100 mg/kg and 64.6 mg/kg.which were lower than the standard concertration of heavy metal(Pb)(《Soil environmental quality Risk control standard for soil contamination of development land(GB36600-2018)》),and the cost of soil washing remediation techniquesfor heavy metal contaminated soil was 1375.76 yuan.