Efficient removal of radionuclides U(VI) by rod-like metal organic framework (MOF-5) nanomaterials

August 28, 2018, Science China Press
Credit: CC0 Public Domain

As the radionuclide 235U(VI) is inevitably released into the natural environment, its potential toxicity and irreversibility have made it a major pollution problem in nuclear energy production. A recent study revealed that a rod-like metal-organic framework (MOF-5) nanomaterial was used as a high-efficiency adsorbent for sorption of U(VI), indicating that MOF-5 can be used for rapid and efficient removal of radionuclides.

The paper, reported in Science Bulletin, is titled "Synthesis of novel rod-like metal-organic framework (MOF-5) nanomaterial for efficient removal of U(VI): batch experiments and spectroscopy study." The authors synthesized a rod-like (MOF-5) nanomaterial via solvothermal method, and used it for effective sorption of U(VI) in an aqueous solution. The batch experimental results showed that the dominant interaction mechanism was the inner sphere surface complexation and electrostatic interaction. The maximum sorption capacity of U(VI) on MOF-5 was 237.0 mg/g at pH = 5.0 and T = 298 K, and the sorption equilibrium was reached within five minutes. The thermodynamic parameters indicated that the removal of U(VI) on MOF-5 was a spontaneous and endothermic process. Additionally, the FT-IR and XPS analyses implied that the high sorption capacity of U(VI) on MOF-5 was mainly due to its abundant oxygen-containing functional groups (i.e., C-O and C=O).

Metal-organic frameworks (MOFs) are a class of crystalline porous materials consisting of metal nodes (i.e., metal ions or clusters) and organic linkers connected via coordination bonds. MOFs are among the most widely investigated materials of the 21st century, owing to their structural tailorability, controlled porosity, and high crystallinity. Widely used for the construction of MOFs include Fe(III), Cu(II), Ca(II), Al(III), Mg(II), Zn(II), Cd(II), Co(II), Zr(IV), Ln(III), and Ti(III), which can adopt various coordination geometries, such as trigonal bipyramidal, pyramidal, square, tetrahedral and octahedral. Strategies for preparing MOFs can be divided into two categories: (I) direct non-aqueous or aqueous synthesis and (II) mixed non-aqueous or aqueous synthesis. Widely used synthesis methods include solvothermal, hydrothermal, mechano-chemical, layer-by-layer growth, ultrasonic, electrochemical, microwave and high-throughput synthesis.

Since the discovery of MOFs in 1995, they have been applied in the fields of sorption, gas storage, separation, catalysis, sensing and biomedicine. Recently, many kinds of MOF-based materials (e.g. SCU-100 and UiO-66-AO) have been successfully synthesized and shown rapid U(VI) removal (within 10 min) than other contaminants. Until now, about 20 MOF materials have been applied to sequester U(VI). However, few articles have addressed the study of MOF-5 material for U(VI) removal, especially the interaction mechanism.

In this study, a solvothermal method was successfully used to synthesize a MOF-5 sample and to remove U(VI) from radioactive wastewater. The morphologies and microstructures of MOF-5 were characterized by SEM, TEM, FT-IR, XRD and XPS. The batch experiments were performed as a function of contact time, U(VI) concentration, temperature, pH and ionic strength. Furthermore, the interaction mechanism between U(VI) and MOF-5 was evaluated from the experimental results and spectroscopy characterization. This paper highlighted the application of MOF-5 as a superior candidate for U(VI) enrichment, which provided a new material for removing radionuclides from aqueous solutions and alleviating the environmental pollution pressure.

Explore further: Modular construction—on a molecular scale

More information: Yihan Wu et al, Synthesis of rod-like metal-organic framework (MOF-5) nanomaterial for efficient removal of U(VI): batch experiments and spectroscopy study, Science Bulletin (2018). DOI: 10.1016/j.scib.2018.05.021

Related Stories

Modular construction—on a molecular scale

June 13, 2016

Modular constructions from cages (proteins), hubs (metal ions), and struts (organic linkers) allows the rational design of porous scaffolds. The inherent chemical and structural diversity of these building blocks leads to ...

Solutions to water challenges reside at the interface

July 17, 2018

In response to rising water scarcity, leading Argonne National Laboratory researcher Seth Darling describes the most advanced research innovations that could address global clean water accessibility. His comprehensive paper ...

Toward designing/controlling flexibility of MOFs

December 27, 2017

Porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) have been extensively studied for their diversified and designable/tailorable framework and pore structures. Compared with conventional porous materials, ...

Blending liquid MOFs produces new glass materials

August 3, 2018

Metal-organic frameworks (MOFs) are a class of crystalline materials with a structure of inorganic nodes connected by organic ligands. There are currently more than 60,000 known MOFs, and they are being investigated as promising ...

Recommended for you

After a reset, Сuriosity is operating normally

February 23, 2019

NASA's Curiosity rover is busy making new discoveries on Mars. The rover has been climbing Mount Sharp since 2014 and recently reached a clay region that may offer new clues about the ancient Martian environment's potential ...

Study: With Twitter, race of the messenger matters

February 23, 2019

When NFL player Colin Kaepernick took a knee during the national anthem to protest police brutality and racial injustice, the ensuing debate took traditional and social media by storm. University of Kansas researchers have ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.