Removal of hexavalent chromium from aqueous solution by fabricating novel heteroaggregates of montmorillonite microparticles with nanoscale zero-valent iron

Yaru Yin,Tiantian Li,Chongyang Shen,Xiaoyuan Bi

doi:10.1038/s41598-020-69244-z

Yaru Yin, Tiantian Li + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-69244-z

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Journal: Scientific Reports	Publication Date: Jul 22, 2020
Citations: 28	License type: open-access

Affiliation: China Agricultural University

Abstract

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.

Highlights

This study fabricated novel heteroaggregates of montmorillonite (Mt) microparticles with nanoscale zero-valent iron (Mt-nZVI) and examined the removal of Cr(VI) by the Mt-nZVI through batch experiments
We have developed a novel method for fabrication of heteroaggregates of Mt with nZVI particles
The nZVI particles were first synthesized via liquid phase reduction method and attached on Mt surfaces in a monolayer

Summary

Introduction

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 attached on the flat Mt surfaces in monolayer. The fabricated Mt-nZVI showed the promise for in-situ soil remediation due to both high removal efficiency and great mobility in porous media. The aggregation reduces specific surface areas of the nZVI, which can significantly decrease its reactivity and efficiency for treatment of contaminants[4]. It should be noted that adding functional groups or coating of these additives on nZVI particles masks the particle surfaces, which may decrease the efficiency of nZVI for contaminant treatment compared to bare monodispersed nZVI p articles[10,11]. Our fabricated Mt-nZVI will have great promise to be used for in-situ remediation of soil contaminants if it has great efficiency for contaminant removal in water. To the best of the authors’ knowledge, our study was the first to develop a method for fabricating the nano-micro structure by decorating spherical nanoparticles on flat microparticle surfaces in a monolayer

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