Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, China.
Sci Rep. 2020 Jul 22;10(1):12137. doi: 10.1038/s41598-020-69244-z.
This study fabricated novel heteroaggregates of montmorillonite (Mt) microparticles with nanoscale zero-valent iron (nZVI) (Mt-nZVI) and examined the removal of Cr(VI) by the Mt-nZVI through batch experiments. Spherical nZVI particles were synthesized by the liquid phase reduction method, which were then attached on the flat Mt surfaces in monolayer. The fabricated Mt-nZVI had similar removal efficiency for Cr(VI) compared to the monodispersed nZVI particles, but was much greater than that of nZVI aggregates. The removal efficiency of Mt-nZVI increased with decreasing its dosage and increasing initial Cr(VI) concentration, whereas had insignificant change with solution pH. The removal of Cr(VI) by Mt-nZVI was well described by the pseudo second-order kinetics and the Langmuir equilibrium model. The removal was spontaneous and exothermic, which was mainly due to chemsorption rather than intra-particle diffusion according to calculation of change in free energy and enthalpy and Weber-Morris model simulations. X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the adsorption was likely due to reduction of Cr(VI) to Cr(III) by Fe(0) and co-precipitation in the form of oxide-hydroxide of Fe(III) and Cr(III). The fabricated Mt-nZVI showed the promise for in-situ soil remediation due to both high removal efficiency and great mobility in porous media.
本研究通过批量实验制备了新型蒙脱石（Mt）微粒与纳米零价铁（nZVI）的杂化聚集体（Mt-nZVI），并考察了 Mt-nZVI 对 Cr(VI)的去除效果。采用液相还原法合成了球形 nZVI 颗粒，然后单层附着在平坦的 Mt 表面上。与单分散 nZVI 颗粒相比，制备的 Mt-nZVI 对 Cr(VI)具有相似的去除效率，但远高于 nZVI 聚集体。Mt-nZVI 的去除效率随其用量的减少和初始 Cr(VI)浓度的增加而增加，而随溶液 pH 值的变化不大。Mt-nZVI 对 Cr(VI)的去除符合准二级动力学和 Langmuir 平衡模型。去除是自发的和放热的，这主要是由于化学吸附而不是颗粒内扩散，根据自由能和焓的变化计算和 Weber-Morris 模型模拟。X 射线衍射和 X 射线光电子能谱分析表明，吸附可能是由于 Fe(0)将 Cr(VI)还原为 Cr(III)，以及 Fe(III)和 Cr(III)以氧化物-氢氧化物的形式共沉淀。由于去除效率高和在多孔介质中迁移能力强，制备的 Mt-nZVI 有望用于原位土壤修复。
