Understanding the Mechanism for Adsorption of Pb(II) Ions by Cu-BTC Metal-Organic Frameworks

Joanna N Weyrich; John R Mason; Ekaterina A Bazilevskaya; Hongwei Yang

doi:10.3390/molecules28145443

Understanding the Mechanism for Adsorption of Pb(II) Ions by Cu-BTC Metal-Organic Frameworks

Molecules. 2023 Jul 16;28(14):5443. doi: 10.3390/molecules28145443.

Authors

Joanna N Weyrich¹, John R Mason², Ekaterina A Bazilevskaya³, Hongwei Yang¹

Affiliations

¹ Department of Chemistry, Widener University, One University Place, Chester, PA 19013, USA.
² Department of Chemistry and Biochemistry, University of Delaware, 102 Brown Laboratory, Newark, DE 19716, USA.
³ Department of Ecosystem Science and Management, The Pennsylvania State University, 409 Agricultural Sciences and Industries Building, University Park, PA 16802, USA.

Abstract

With the growing population, industrialization, and agriculture, water contamination not only affects people but entire ecosystems. Metal-organic frameworks (MOFs), because of their large surface area and porosity, show great potential as adsorbents for removing pollutants, such as heavy metals, from contaminated water. The current research aims at examining copper (II) benzene-1,3,5-tricarboxylate (Cu-BTC) MOFs and understanding the mechanism for their adsorption of Pb(II) from aqueous solution. The Cu-BTC samples were characterized using FTIR and XRD, and their surface area and porosity were determined based on N₂ adsorption isotherms. The concentration of Pb(II) in the solutions was measured using atomic absorption spectroscopy (AAS). Both kinetic and equilibrium adsorption data were collected and then analyzed using numerical models. The analyses led to the findings that the limiting steps in the adsorption of Pb(II) on Cu-BTC are (a) pore diffusion of Pb(II) and (b) the availability of the active sites on Cu-BTC MOFs. It was further revealed that the former step is more dominant in the adsorption of Pb(II) when the lead concentration is low. The latter step, which is directly proportional to the surface areas of the MOFs, affects the adsorption to a greater extent when the lead concentration is high. The results also show that adsorption of Pb(II) ions on Cu-BTC is mainly a multi-layer heterogeneous process.

Keywords: Cu-BTC; Pb(II); adsorption; heavy metal ions; metal–organic frameworks.

Grants and funding

Part of J.N.W.’s work was financially supported by Widener University as a participant of the Undergraduate Research and Creative Activities (SURCA) program. H.Y. acknowledges the support from the Materials Research Facilities Network (MRFN) Faculty Fellow Program through the Materials Research Science and Engineering Center (MRSEC) supported by the National Science Foundation under grant DMR-2011839.