Local structure of Cu2+ in Cu-doped hexagonal turbostratic birnessite and Cu2+ stability under acid treatment

doi:10.1016/j.chemgeo.2017.06.040

	Local structure of Cu2+ in Cu-doped hexagonal turbostratic birnessite and Cu2+ stability under acid treatment
	Zheng, LR; Ginder-Vogel, M; Tan, WF; Yin, H; Zheng LR(郑黎荣); Wang, MX; Qin, ZJ; Xiang, QJ; Liu, F; Feng, XH
刊名	CHEMICAL GEOLOGY
	2017
卷号	466 页码:512-523
关键词	Birnessite Cu2+ X-ray absorption spectroscopy Acid dissolution Stability
ISSN号	0009-2541
DOI	10.1016/j.chemgeo.2017.06.040
文献子类	Article
英文摘要	Geochemical behaviors of heavy metal contaminants, such as Cu2+, are strongly controlled by natural birnessite-like minerals in both marine and terrestrial environments. However, the mechanisms of the interaction of Cu2+ with birnessite are not fully understood yet. In the present study, Cu2+ was coprecipitated with Mn2+ to produce hexagonal turbostratic birnessite, which is analogous to natural birnessite. The obtained Cu-doped birnessite was characterized by powder X-ray diffraction, field-emission scanning electron microscopy, and X-ray absorption spectroscopy (XANES + EXAFS). The stability of Cu(II) in the birnessite structure was investigated by acid treatment. Increasing the dopant content reduces the mineral crystallinity in the [001] direction and the unit cell parameter b from the hexagonal layers. It also shortens the bond length of Mn-O in the [MnO6] unit and the edge-sharing Mn-Mn distance in the layers, and increases the average oxidation state (AOS) of Mn and the specific surface area. Analysis of Cu K-edge XANES and EXAFS data indicates that, only a small part of Cu(II) is inserted into the birnessite layers, while most of it is adsorbed on the vacancies. When the Cu/Mn molar ratio is increased from 0.08 to 0.23, an increasing part of Cu(II) is present as polynuclear clusters on the birnessite edge sites in the pH range of similar to 3.3-5.3. Reaction with H2SO4 solution is found to easily dissolve the polynuclear Cu clusters and the highly distorted Cu octahedra in innersphere complexes on the birnessite-water interface, with similar to 53% of the Cu2+ released into the solution. On the other hand, the reaction with HCl solution leads to reductive dissolution of the mineral matrix, the release of Mn2+ into solutions, the decrease in the first MneO and edge-sharing MneMn distances and Mn AOS, in addition to the release of Cu2+. The release rate of Cu2+ is much faster than that of Ni2+ in Ni-doped birnessites, owing to the lower stability of distorted [CuO6] octahedron upon proton attack. These results indicate the formation of multinuclear Cu complexes on birnessite surfaces under the investigated conditions. The results also suggest the lower stability of Cu2+ in these minerals and thus higher potential toxicity in acidic conditions, in comparison with other metal pollutants, such as Ni2+. This study provides new insights into the interaction mechanisms between Cu2+ and birnessite-like minerals, and help to clarify the structural stability and geochemical behaviors of Cu2+ associated with birnessite-like minerals in natural environments.
电子版国际标准刊号	1878-5999
WOS关键词	X-RAY-DIFFRACTION ; CRYSTAL-STRUCTURE DETERMINATIONS ; ABSORPTION FINE-STRUCTURE ; MANGANESE HYDROUS OXIDES ; METAL SORBED BIRNESSITE ; NA-RICH BIRNESSITE ; EXAFS SPECTROSCOPY ; SURFACE COMPLEXATION ; XANES SPECTROSCOPY ; HEAVY-METALS
WOS研究方向	Geochemistry & Geophysics
语种	英语
WOS记录号	WOS:000407861200040
内容类型	期刊论文
源URL	[http://ir.ihep.ac.cn/handle/311005/285254]
专题	高能物理研究所_多学科研究中心
作者单位	中国科学院高能物理研究所
推荐引用方式 GB/T 7714	Zheng, LR,Ginder-Vogel, M,Tan, WF,et al. Local structure of Cu2+ in Cu-doped hexagonal turbostratic birnessite and Cu2+ stability under acid treatment[J]. CHEMICAL GEOLOGY,2017,466:512-523.
APA	Zheng, LR.,Ginder-Vogel, M.,Tan, WF.,Yin, H.,郑黎荣.,...&Koopal, LK.(2017).Local structure of Cu2+ in Cu-doped hexagonal turbostratic birnessite and Cu2+ stability under acid treatment.CHEMICAL GEOLOGY,466,512-523.
MLA	Zheng, LR,et al."Local structure of Cu2+ in Cu-doped hexagonal turbostratic birnessite and Cu2+ stability under acid treatment".CHEMICAL GEOLOGY 466(2017):512-523.