Detection and Selective Sorption of Copper Ions by a COF-Modified Melamine Sponge

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Melamine sponges are widely used but lack specific adsorption capabilities for heavy metals.
• Developing efficient and selective adsorbents for copper removal is crucial for environmental remediation.

Purpose of the Study:

• To functionalize melamine sponges with covalent organic frameworks (COFs) for enhanced copper ion adsorption.
• To evaluate the adsorption capacity, selectivity, and mechanism of COF-functionalized melamine sponges for copper removal.

Main Methods:

• Surface modification of melamine sponges with phosphazene units and subsequent COF formation using 4,4' bipyridine.
• Adsorption experiments using copper cations in aqueous solutions with varying metal ion concentrations.
• Characterization using X-Ray Fluorescence (XRF), X-Ray Photoelectron Spectroscopy (XPS), and Electron Paramagnetic Resonance (EPR).

Main Results:

• The COF-functionalized melamine sponge exhibited a high copper sorption capacity of 293 μg cm⁻², nearly nine times greater than the pristine sponge.
• Demonstrated preferential adsorption of copper ions over nickel, iron, and calcium cations, indicating high selectivity.
• EPR studies revealed distinct copper coordination sites on the modified sponge, with a trigonal bipyramidal geometry favored in the presence of competing metal ions.

Conclusions:

• COF-functionalized melamine sponges are effective and selective adsorbents for removing divalent copper cations from aqueous solutions.
• The enhanced adsorption capacity and selectivity make these materials promising for water treatment applications.
• The study provides insights into the coordination behavior of copper on the functionalized adsorbent surface.