Mechanistic insight into Cr(VI) retention by Si-containing ferrihydrite

IF 6.9 Q1 Environmental Science Journal of environmental sciences Pub Date : 2023-06-03 DOI:10.1016/j.jes.2023.05.040
Ying Hu , Qiang Xue , Honghan Chen , Huaming Guo , Kenneth C. Carroll , Song Wang
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引用次数: 2

Abstract

Hexavalent chromium [Cr(VI)] causes serious harm to the environment due to its high toxicity, solubility, and mobility. Ferrihydrites (Fh) are the main adsorbent and trapping agent of Cr(VI) in soils and aquifers, and they usually coexist with silicate (Si), forming Si-containing ferrihydrite (Si-Fh) mixtures. However, the mechanism of Cr(VI) retention by Si-Fh mixtures is poorly understood. In this study, the behaviors and mechanisms of Cr(VI) adsorption onto Si-Fh with different Si/Fe molar ratios was investigated. Transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and other techniques were used to characterize Si-Fh and Cr(VI)-loading of Si-Fh. The results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios, but Cr(VI) adsorption on Si-Fh decreases with increasing Si/Fe ratios. This is because with an increase in Si/Fe molar ratio, the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and Cr(VI) increases. However, the complexation of Cr(VI) is enhanced due to the increase in adsorbed hydroxyl (A-OH-) on Si-Fh with increasing Si/Fe molar ratio, which partly counteracts the effect of the electrostatic repulsion. Overall, the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with Si-Fh. Density functional theory calculation further supports this observation, showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio.

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含硅水合铁对Cr(VI)截留的机理研究
六价铬[Cr(VI)]具有较高的毒性、溶解性和流动性,对环境造成严重危害。水铁矿(Fh)是土壤和含水层中Cr(VI)的主要吸附剂和捕集剂,它们通常与硅酸盐(Si)共存,形成含硅水铁矿(Si-Fh)混合物。然而,人们对Si-Fh混合物保留Cr(VI)的机理知之甚少。在本研究中,研究了不同Si/Fe摩尔比的Si-Fh对Cr(VI)的吸附行为和机理。利用透射电子显微镜、傅立叶变换红外光谱、X射线衍射、X射线光电子能谱等技术对Si Fh和Cr(VI)负载Si Fh进行了表征。结果表明,Si-Fh的比表面积随着Si/Fe比的增加而逐渐增加,但Cr(VI)在Si-Fh上的吸附量随着Si/Fe比的增加逐渐减小。这是因为随着Si/Fe摩尔比的增加,Si-Fh的零电荷点逐渐降低,并且Si-Fh和Cr(VI)之间的静电排斥增加。然而,随着Si/Fe摩尔比的增加,Si-Fh上吸附的羟基(A-OH-)增加,Cr(VI)的络合作用增强,这部分抵消了静电排斥的影响。总的来说,静电排斥的增加对吸附的影响比与Si-Fh的额外络合更大。密度泛函理论计算进一步支持了这一观察结果,表明键合原子的电子变化和内球形配合物的反应能随着Si/Fe比的增加而增加。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of environmental sciences
Journal of environmental sciences Environmental Science (General)
CiteScore
12.80
自引率
0.00%
发文量
0
审稿时长
17 days
期刊介绍: Journal of Environmental Sciences is an international peer-reviewed journal established in 1989. It is sponsored by the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, and it is jointly published by Elsevier and Science Press. It aims to foster interdisciplinary communication and promote understanding of significant environmental issues. The journal seeks to publish significant and novel research on the fate and behaviour of emerging contaminants, human impact on the environment, human exposure to environmental contaminants and their health effects, and environmental remediation and management. Original research articles, critical reviews, highlights, and perspectives of high quality are published both in print and online.
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