富里酸-纳米零价铁复合物对土壤中铅的钝化

PASSIVATION OF LEAD IN SOIL BY FULVIC ACID-NANO-ZERO-VALENT IRON COMPLEX

为了降低土壤中重金属铅的生物活性,将从富硒土壤中提取的富里酸(FA)和传统方法制得的纳米零价铁(NZVI)复合,制得不同FA质量比的复合物,探讨其对土壤铅污染的钝化效应。以SEM、FTIR以及XRD对复合物进行表征;通过土壤培养试验,研究各复合物在不同投加量及反应时间下对土壤中铅的DTPA有效态的影响,并以Tessier五步连续提取法比较形态变化规律,探讨其钝化效果。结果表明:FA与NZVI合成了不同质量比的复合物;在相同投加量下,土壤中铅的二乙基三胺五乙酸(DTPA)有效态随着复合物中FA质量分数提高而减小;以FA质量分数10%的复合物投加土壤质量的2%(20.0 g/kg)进行土壤培育,第10天时土壤中铅的DTPA有效态降低83.01%;加入复合物后,土壤中铅明显从可交换态和碳酸盐结合态向铁锰氧化物结合态和残留态转化,有机结合态含量基本不变,这种变化在添加FA质量占1%的复合物时尤为显著,使得可交换态和碳酸盐结合态分别降低了50.61%和66.90%。基于不同的形态表征方法,土壤铅活性形态均呈下降趋势,表明所制备的复合物对土壤铅具有一定的钝化效应,但其机制有别,表现出的钝化规律具有差异性。

In order to reduce the biological activity of heavy metals in soil,composites were made using fulvic acid(FA)extracted from selenium-enriched soil and nano-zero-valent iron(NZVI)prepared by conventional methods with different FA mass ratios.The composites were characterized by SEM,FTIR and XRD.Trough soil cultivation experiments,the effect of each compound on the occurrence of DTPA with lead added externally in soil under different dosages and reaction times were studied,and analyzed the morphological changes with Tessier method to discuss its passivation consequent.The results showed that FA and NZVI formed composites successfully with different FA mass ratios;under the same dosage,the effective state of DTPA of lead in the soil decreased with the increase of the FA mass ratio in the composites;when the composites with 10%FA mass was added to the soil in 2%(20.0 g/kg),the DTPA effective state of lead in the soil was reduced by 83.01%on the 10 th day;after adding the composites,the lead in the soil transformed significantly from the exchangeable state and the carbonate combined state to Fe-Mn oxide combined state and the residual state,and the organic bound state was unchanged basically.These changes were especially significant when the compound with 1%FA mass was added,making the exchangeable state and the carbonate bound state reduced respectively by 50.61%and 66.90%.Therefore,based on different morphological characterization methods,the active forms of soil lead showed a downward trend,indicating that the prepared composite had a certain passivation effect on soil lead,but the mechanism was different,and the passivation laws shown were different.