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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
School of Civil Engineering, Harbin Institute of Technology, Harbin 150001, China
Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
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
China Building Materials Academy, Beijing 100024, China
Author to whom correspondence should be addressed.
Materials 2018, 11(9), 1706;
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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