Purpose

The palygorskite-coated nanoscale zero-valent iron (PAL-nZVI) was synthesized and used in the remediation of Cd-contaminated soils. The function of PAL-nZVI on fraction of Cd in soils, the growth, Cd translocation, and accumulation in corn (Zea mays L.) were investigated using a pot experiment.

Materials and methods

Cd-contaminated soils were amended with palygorskite, nanoscale zero-valent iron (nZVI), and PAL-nZVI (with varying mass ratios between PAL and nZVI) and with no amendment as control. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the changes in both the surface and the structure of stabilizers. CaCl₂-extractable and toxicity characteristic leaching procedure (TCLP)-extractable Cd were measured in order to estimate the bioavailability and the stabilization efficiency. The Community Bureau of Reference (BCR) sequential extraction method was applied to evaluate the speciation change of Cd in soils stabilized by nZVI, PAL, and PAL-nZVI with different coating mass ratios of PAL to nZVI. The Cd accumulation in root and shoot fresh weight was measured to assess the stabilization efficiency.

Results and discussion

SEM and XRD indicated that nZVI particles were distributed uniformly and well fixed on the surface of palygorskite. After adding PAL-nZVI, the pH value of soil increased by 1 pH unit; CaCl₂-extractable Cd decreased from 2.24 to 0.95 mg/kg; the residual Cd increased by 23.06% after 30-day incubation. The fresh weight of corn reached 43.02 g/plant, and the Cd contents in roots and shoots achieved minimum values of 1.50 and 0.73 mg/kg, respectively, when applying PAL-nZVI composite with a coating mass ratio of 2:1.

Conclusions

The application of PAL-nZVI decreased the bioavailability and mobility of Cd in soils effectively. The stabilization showed a better effect when applying PAL-nZVI in Cd-contaminated soils than applying nZVI alone. Hence, it was a feasible and potential material that could be applied to amend the Cd-contaminated soil effectively, which would have a high and valuable utilization in field applications.

中文翻译：

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凹凸棒石包覆的纳米零价铁对污染土壤中镉的稳定作用

目的

合成了坡缕石包覆的纳米零价铁（PAL-nZVI），并将其用于修复受Cd污染的土壤。PAL-的nZVI对土壤镉分数的功能，生长，镉易位，并且积累在玉米（玉蜀黍L.）使用盆栽试验进行了研究。

材料和方法

用坡缕石，纳米级零价铁（nZVI）和PAL-nZVI（PAL和nZVI之间的质量比变化）修改了Cd污染的土壤，但未作对照。扫描电子显微镜（SEM）和X射线衍射（XRD）用于表征稳定剂表面和结构的变化。氯化钙₂为了估计生物利用度和稳定效率，对可萃取和毒性特征浸出程序（TCLP）可萃取镉进行了测定。应用社区参考局（BCR）顺序提取方法，以不同的PAL与nZVI的质量比对nZVI，PAL和PAL-nZVI稳定的土壤中镉的形态变化进行评估。测量根和枝条鲜重中Cd的积累，以评估稳定效率。

结果和讨论

扫描电镜和X射线衍射表明，nZVI颗粒均匀分布并固定在坡缕石表面。加入PAL-nZVI后，土壤的pH值增加1个pH单位。CaCl ₂萃取镉从2.24降至0.95 mg / kg; 孵育30天后，残留的Cd增加了23.06％。当使用涂层质量比为2：1的PAL-nZVI复合材料时，玉米的鲜重达到43.02 g /株，根和枝条中的Cd含量分别达到1.50和0.73 mg / kg的最小值。

结论

PAL-nZVI的使用有效降低了土壤中Cd的生物利用度和迁移率。在Cd污染的土壤中施用PAL-nZVI比单独施用nZVI具有更好的稳定性。因此，这是一种可行且潜在的材料，可用于有效地修正受Cd污染的土壤，这将在野外应用中具有很高的价值。