Purpose

Lead (Pb(II)) can be accumulated in soil and transferred to humans via the food chain. Therefore, it is essential to improve Pb(II) immobilization during soil remediation.

Materials and methods

Nanosized zero-valent iron (nZVI) from green tea extract (tea polyphenols, TPs) was successfully synthesized as an additive reductant. Further, the nZVI was supported on montmorillonite (Mont), resulting in a GT-nZVI@Mont composite characterized by multiple techniques, including Zeta potential, SEM, TEM, XRD, and XPS. Moreover, the transport experiments and the toxicity characteristic leaching procedure (TCLP) were conducted to identify the optimum conditions (i.e., GT-nZVI@Mont dosage, Pb(II) concentration, and pH) for the remediation.

Results and discussion

The experimental results showed that the enhanced transportability of GT-nZVI@Mont was about 40% more than that of GT-nZVI. Meanwhile, Pb(II) immobilization was increased at various pH values (especially under anoxic conditions). The Pb(II) immobilization capacity of GT-nZVI@Mont was 900.8 mg∙g^-1 (per unit of Fe content), which was significantly higher than 530.1 mg∙g^-1 per unit of Fe content in GT-nZVI. Such enhancement could be ascribed to the synergistic effects of the wrapped TP around the Fe⁰ core and the Mont interlayer support, capable of protecting the Fe⁰ surface from further oxidation. When GT-nZVI@Mont reacted with the Pb(II) in soil, TPs’ unwrapped coverage increased the reaction sites of Fe⁰ cores for Pb(II) reduction and adsorption.

Conclusions

GT-nZVI@Mont with sufficient transportability provided efficient in situ remediation of Pb(II) in contaminated soil at a wide pH range.

中文翻译：

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通过茶提取物绿色合成的纳米级蒙山负载的Fe 0，用于增强土壤中Pb（II）的运输和原位修复

目的

铅（Pb（II））可以积累在土壤中，并通过食物链转移给人类。因此，在土壤修复过程中提高Pb（II）的固定性至关重要。

材料和方法

从绿茶提取物（茶多酚，TPs）中成功地合成了纳米级零价铁（nZVI）作为添加剂还原剂。此外，将nZVI负载在蒙脱石（Mont）上，得到了具有多种技术特征的GT-nZVI @ Mont复合材料，包括Zeta电位，SEM，TEM，XRD和XPS。此外，进行了运输实验和毒性特征浸出程序（TCLP），以确定用于修复的最佳条件（即GT-nZVI @ Mont剂量，Pb（II）浓度和pH）。

结果和讨论

实验结果表明，GT-nZVI @ Mont的增强的可运输性比GT-nZVI增强了约40％。同时，在各种pH值下（特别是在缺氧条件下），Pb（II）的固定化都增加了。GT-nZVI @ Mont的Pb（II）固定容量为900.8 mg∙g ^-1（每单位Fe含量），明显高于GT-nZVI @ Mont的每单位Fe含量530.1 mg∙g ^-1。这种增强可以归因于围绕Fe ⁰核和Mont中间层支持物包裹的TP的协同效应，能够保护Fe ⁰表面免受进一步的氧化。当GT-nZVI @ Mont与土壤中的Pb（II）反应时，TPs的未包被覆盖增加了Fe ⁰的反应位点 Pb（II）还原和吸附的核心。

结论

GT-nZVI @ Mont具有足够的可运输性，可以在很宽的pH范围内对污染土壤中的Pb（II）进行有效的原位修复。