Scholarlink

<p>To achieve selective leaching of ion adsorption rare earth, it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements. In this study, we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions. The results revealed that the adsorption of Dy and Al, as well as the desorption of K, followed the Langmuir model. The maximum ion-exchangeable capacity of Dy was higher (9.39&#xa0;mmol·kg<sup>−1</sup>) than that of Al (6.30&#xa0;mmol·kg<sup>−1</sup>). The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were 2.0 and 2.6. The analysis of X-ray absorption fine structure (XAFS) and density functional theory (DFT) revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds. Dy was adsorbed as [Dy(H<sub>2</sub>O)<sub>10</sub>]<sup>3+</sup>, and Al was adsorbed as [Al(OH)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sup>+</sup>. In particular, the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite. Based on the above insights, the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances (6.04&#xa0;Å for Dy and 3.69&#xa0;Å for Al) and lower adsorption energies (− 223.72&#xa0;kJ·mol<sup>−1</sup> for Dy and − 268.33&#xa0;kJ·mol<sup>−1</sup> for Al). The maximum ion-exchangeable capacity is related to the change of the surface electrical properties of kaolinite. The zeta potential was increased to − 7.3&#xa0;mV as the protonation resulted from aluminum adsorption, while Dy adsorption had a minor effect, maintaining a value of − 17.5&#xa0;mV.</p> Graphical abstract <p></p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Adsorption of rare earth elements and aluminum on the surface of kaolinite: insights from sequential chemical extractions, XAFS, and DFT

  • 期刊论文

  • 发表日期：

    2025年2月21日

查看全文
  • Jia-Xin Pan,
  • Long-Sheng Zhao,
  • Zheng Li,
  • Zong-Yu Feng,
  • De-Peng Liu,
  • Jun Chen,
  • Xiao-Wei Huang

摘要

To achieve selective leaching of ion adsorption rare earth, it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements. In this study, we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions. The results revealed that the adsorption of Dy and Al, as well as the desorption of K, followed the Langmuir model. The maximum ion-exchangeable capacity of Dy was higher (9.39 mmol·kg−1) than that of Al (6.30 mmol·kg−1). The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were 2.0 and 2.6. The analysis of X-ray absorption fine structure (XAFS) and density functional theory (DFT) revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds. Dy was adsorbed as [Dy(H2O)10]3+, and Al was adsorbed as [Al(OH)2(H2O)4]+. In particular, the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite. Based on the above insights, the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances (6.04 Å for Dy and 3.69 Å for Al) and lower adsorption energies (− 223.72 kJ·mol−1 for Dy and − 268.33 kJ·mol−1 for Al). The maximum ion-exchangeable capacity is related to the change of the surface electrical properties of kaolinite. The zeta potential was increased to − 7.3 mV as the protonation resulted from aluminum adsorption, while Dy adsorption had a minor effect, maintaining a value of − 17.5 mV.

Graphical abstract