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Crystalline/Amorphous Blend Identification from Cobalt Adsorption by Layered Double Hydroxides

by Lin Chi 1,2,3, Zheng Wang 1,2,3, Yuan Sun 1,2,3, Shuang Lu 1,2,3,* and Yan Yao 4
1
School of Civil Engineering, Harbin Institute of Technology, Harbin 150001, China
2
Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
3
Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology, Harbin Institute of Technology, Harbin 150090, China
4
China Building Materials Academy, Beijing 100024, China
*
Author to whom correspondence should be addressed.
Materials 2018, 11(9), 1706; https://doi.org/10.3390/ma11091706
Received: 16 August 2018 / Revised: 4 September 2018 / Accepted: 11 September 2018 / Published: 13 September 2018
(This article belongs to the Section Structure Analysis and Characterization)
In this study, the adsorption behavior of CaAl-Cl layered double hydroxide (CaAl-Cl-LDH) with a controlled pH value (pH = 6) on Co(II) ions ([Co] = 8 mM) is investigated. The comprehensively accepted mechanism of cobalt adsorption on LDH is considered to be co-precipitation, and the final adsorbed products are normally crystalline Co-LDH. One unanticipated finding is that crystalline/amorphous blends are found in the X-ray diffraction (XRD) pattern of Co-adsorbed LDH. To shed light on the adsorption products and the mechanisms in the adsorption process of Co(II) in an aqueous solution by CaAl-Cl-LDH, a series of testing methods including Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM), High-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) are applied to clarify the interaction between cobalt and CaAl-Cl-LDH. According to the comprehensive analysis, the formation of the crystalline/amorphous blends corresponds to two adsorption mechanisms. The crystalline phases are identified as Co6Al2CO3(OH)16·4H2O, which is attributed to the co-precipitation process occurring in the interaction between Co(II) and CaAl-Cl-LDH. The formation of the amorphous phases is due to surface complexation on amorphous Al(OH)3 hydrolyzed from CaAl-Cl-LDH. View Full-Text
Keywords: CaAl-Cl-LDH; cobalt; amorphous Al(OH)3 CaAl-Cl-LDH; cobalt; amorphous Al(OH)3
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MDPI and ACS Style

Chi, L.; Wang, Z.; Sun, Y.; Lu, S.; Yao, Y. Crystalline/Amorphous Blend Identification from Cobalt Adsorption by Layered Double Hydroxides. Materials 2018, 11, 1706.

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