Zhang Qiongyuan, Wang Yanping, Han Jilong, Liu Haining, Zhang Huifang, Wu Zhijian, Zhang Siyuan, Han Wenjie, Ye Xiushen
Key Laboratory of Green and Highly-end Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008, China.
University of Chinese Academy of Sciences, 19 A Yuquan Road, Shijingshan District, Beijing 100049, China.
Langmuir. 2024 Aug 20;40(33):17430-17443. doi: 10.1021/acs.langmuir.4c01602. Epub 2024 Aug 7.
Layered double hydroxides (LDHs) have garnered significant attention from researchers in the field of adsorption due to their unique laminated structures and ion exchange properties. LDHs with various anion intercalation showed different adsorption effects on adsorbing ions, but the corresponding adsorption mechanisms are ambiguous. In this study, three types of NiAl-LDHs were synthesized, utilizing NO, CO, or Cl as the interlayer anions. Batch tests were conducted to study their adsorption performances for Br. Among them, the LDH with a NO intercalation layer exhibited the highest adsorption capacity for Br, reaching up to 1.40 mmol g. The adsorption kinetics, mechanism, and renewability of these NiAl-LDHs were systematically compared. As a result, the type of Br adsorption by all three materials was single molecular layer chemisorption. Moreover, the thermodynamic results of adsorption suggested that the adsorption of Br was a spontaneous exothermic process. X-ray photoelectron spectroscopy, X-ray diffraction, and point of zero charge analysis collectively indicated that the adsorption of Br by LDHs primarily occurred through interlayer ion exchange and electrostatic interactions. Structural characterizations of the adsorbents revealed that Br entered the interlayers of the three LDHs, causing varying degrees of reduction in the interlayer spacing. Density functional theory calculations indicated that the interlayer binding energy of LDH with NO intercalation was the lowest, thereby making it more susceptible NO to be exchanged with Br. Finally, the stability of the NiAl-LDHs was studied. The NiAl-LDHs retains a high removal efficiency of Br even after 5 cycles of adsorption and desorption.
层状双氢氧化物（LDHs）因其独特的层状结构和离子交换性能而在吸附领域受到了研究人员的广泛关注。具有不同阴离子插层的LDHs对吸附离子表现出不同的吸附效果，但其相应的吸附机制尚不明确。在本研究中，合成了三种类型的NiAl-LDHs，分别以NO、CO或Cl作为层间阴离子。进行了批量试验以研究它们对Br的吸附性能。其中，具有NO插层的LDH对Br的吸附容量最高，可达1.40 mmol g。系统地比较了这些NiAl-LDHs的吸附动力学、机制和可再生性。结果表明，所有三种材料对Br的吸附类型均为单分子层化学吸附。此外，吸附的热力学结果表明，Br的吸附是一个自发的放热过程。X射线光电子能谱、X射线衍射和零电荷点分析共同表明，LDHs对Br的吸附主要通过层间离子交换和静电相互作用发生。吸附剂的结构表征表明，Br进入了三种LDH的层间，导致层间距不同程度地减小。密度泛函理论计算表明，具有NO插层的LDH的层间结合能最低，因此更容易与Br进行交换。最后，研究了NiAl-LDHs的稳定性。即使经过5次吸附和解吸循环，NiAl-LDHs对Br仍保持较高的去除效率。
