To optimize carbon-based nanoscale-zero-valent iron (nZVI) material and remove hexavalent chromium [Cr(VI)] more effectively, activated low rank coals (ALRCs) and FeCl2 were used to prepare “activated low rank coals/nanoscale-zero-valent iron” (ALRCs/nZVI) composites by carbothermal reduction. The prepared ALRCs/nZVI was characterized by XRD, SEM, BET and XPS. Then the removal characteristics of Cr(VI) from solution by ALRCs/nZVI were studied. The results show that the BET specific surface area of ALRCs/nZVI is as high as 2908 m2 g−1. The nZVI microspheres are successfully loaded onto the surface of ALRCs with a diameter of about 500 nm. The low pH and high temperature is beneficial to the removal of Cr(VI) by ALRCs/nZVI. The adsorption of Cr(VI) by ALRCs/nZVI follows the Freundlich model and the pseudo-second-order kinetic model. Electrostatic attraction, reduction, and surface precipitation are main mechanisms for Cr(VI) removal. The maximum Cr(VI) removal amount fitted by Langmuir model was 159.7–196.5 mg g−1 which is higher than that of most reported carbon-based nZVI composites. The innovations of this work include (1) using low rank coal as raw material to reduce the cost, (2) the material pre-activation process improves the adsorption capacity of production, and (3) reduction and loading of nanoscale-zero-valent iron using carbothermal method (easy operation, high safety, strong combination of zero-valent iron and substrate, easy to large-scale application and continuous production, etc.). Activated low rank coals/nanoscale-zero-valent iron (ALRCs/nZVI) composites were prepared by carbothermal reduction. The ALRCs/nZVI has a very high specific surface area and exhibits high Cr(VI) removal performance. The XPS analysis showed that almost all adsorbed Cr(VI) was reduced to Cr(III). Activated low rank coals/nanoscale-zero-valent iron (ALRCs/nZVI) composites were prepared by carbothermal reduction. The ALRCs/nZVI has a very high specific surface area and exhibits high Cr(VI) removal performance. The XPS analysis showed that almost all adsorbed Cr(VI) was reduced to Cr(III).

中文翻译：

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新型 ALRCs/nZVI 复合材料的制备及其从水中去除 Cr(VI)

为了优化碳基纳米零价铁 (nZVI) 材料并更有效地去除六价铬 [Cr(VI)]，使用活性低阶煤 (ALRCs) 和 FeCl2 制备“活性低阶煤/纳米零价铁”。 -价铁”（ALRCs/nZVI）复合材料通过碳热还原。制备的 ALRCs/nZVI 通过 XRD、SEM、BET 和 XPS 进行表征。然后研究了ALRCs/nZVI从溶液中去除Cr(VI)的特性。结果表明，ALRCs/nZVI 的 BET 比表面积高达 2908 m2 g-1。nZVI 微球成功加载到直径约 500 nm 的 ALRC 表面。低 pH 值和高温有利于 ALRCs/nZVI 去除 Cr(VI)。ALRCs/nZVI 对 Cr(VI) 的吸附遵循 Freundlich 模型和准二级动力学模型。静电吸引、还原和表面沉淀是去除 Cr(VI) 的主要机制。Langmuir 模型拟合的最大 Cr(VI) 去除量为 159.7-196.5 mg g-1，高于大多数报道的碳基 nZVI 复合材料。本工作的创新点包括（1）以低阶煤为原料降低成本；（2）材料预活化工艺提高了生产吸附能力；（3）纳米零价的还原和负载用碳热法制铁（操作简单、安全性高、零价铁与底物结合性强、易于大规模应用和连续生产等）。通过碳热还原制备了活性低阶煤/纳米零价铁 (ALRCs/nZVI) 复合材料。ALRCs/nZVI 具有非常高的比表面积并表现出高 Cr(VI) 去除性能。XPS 分析表明，几乎所有吸附的 Cr(VI) 都被还原为 Cr(III)。通过碳热还原制备了活性低阶煤/纳米零价铁 (ALRCs/nZVI) 复合材料。ALRCs/nZVI 具有非常高的比表面积并表现出高 Cr(VI) 去除性能。XPS 分析表明，几乎所有吸附的 Cr(VI) 都被还原为 Cr(III)。