Chi Lin, Wang Zheng, Sun Yuan, Lu Shuang, Yao Yan
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.
Materials (Basel). 2018 Sep 13;11(9):1706. doi: 10.3390/ma11091706.
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)·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.
在本研究中，研究了在pH值可控（pH = 6）条件下，CaAl-Cl层状双氢氧化物（CaAl-Cl-LDH）对Co(II)离子（[Co] = 8 mM）的吸附行为。普遍认为钴在LDH上的吸附机制是共沉淀，最终的吸附产物通常是结晶态的Co-LDH。一个意外发现是，在Co吸附的LDH的X射线衍射（XRD）图谱中发现了结晶/非晶混合相。为了阐明CaAl-Cl-LDH在水溶液中吸附Co(II)的吸附产物及吸附过程中的机制，应用了一系列测试方法，包括傅里叶变换红外光谱（FT-IR）、扫描电子显微镜（SEM）、高分辨率透射电子显微镜（HR-TEM）、X射线光电子能谱（XPS）和电感耦合等离子体（ICP），以阐明钴与CaAl-Cl-LDH之间的相互作用。综合分析表明，结晶/非晶混合相的形成对应两种吸附机制。结晶相被鉴定为Co₆Al₂CO₃(OH)·4H₂O，这归因于Co(II)与CaAl-Cl-LDH相互作用过程中发生的共沉淀过程。非晶相的形成是由于CaAl-Cl-LDH水解产生的非晶态Al(OH)₃上的表面络合作用。
