Effect of pressure treatment on the specific surface area in kaolin group minerals

Soyeon Kwon, Huijeong Hwang, Yongjae Lee

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Abstract

Pressure can tailor the properties of a material by changing its atomistic arrangements and/or crystal morphology. We have investigated the changes in the adsorption properties of kaolin group minerals as a function of pressure treatment in the gigapascal range. External pressures have been applied using a large volume press (LVP) to kaolinite (Al2Si2O5(OH)4) and halloysite (H4Al2O9Si2·2H2O), which represent natural 2D layered and 1D nanowire structures, respectively. Powdered samples have been compressed up to 3 GPa in 1 GPa steps at room temperature and recovered by up to ca. 0.35 g from each pressure step. Brunauer–Emmett–Teller (BET) measurements were conducted using N2 gas to measure the specific surface area, pore size distribution, and pore volume of the pressure-treated samples. As the treatment pressure increased, kaolinite showed an increase in the adsorption behavior from nonpores to mesopores, whereas halloysite responded in an opposite manner to show a decrease in its adsorption capability. We discuss the contrasting effects of pressure-treatment on the two morphologically distinct kaolin group minerals based on field-emission scanning electron microscope (FE-SEM) images measured on each recovered material. We observed that the layers in kaolinite separate into smaller units upon increasing pressure treatment, whereas the tubes in halloysite become flattened, which led to the contrasting changes in surface area. Further study is in progress to compare this effect to when water is used as the pressure-transmitting medium.

Original languageEnglish
Article number528
JournalCrystals
Volume9
Issue number10
DOIs
Publication statusPublished - 2019 Oct

Bibliographical note

Funding Information:
Author Contributions: S.K. conducted the experiments and data analysis with the help from H.H. Y.L. designed Author Contributions: S.K. conducted the experiments and data analysis with the help from H.H. Y.L. designed the research, provided supervision to the project, and worked on the manuscript with all authors. the research, provided supervision to the project, and worked on the manuscript with all authors. Funding: This research was funded by the Leader Researcher program (NRF-2018R1A3B1052042) of the Korean Ministry of Science and ICT. We also thank the partial supports by NRF-2016K1A4A3914691 and NRF-20N1R7RF-12A0127BR2010A426B8280 g0r4a6n8t8s.g rants.

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Inorganic Chemistry

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