A novel ionic liquid-entrapped MIL-101(Cr) framework with enhanced removal efficiency towards phosphate from aqueous...

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Phosphate pollution from aqueous solutions and eutrophic water poses environmental challenges.
• Developing efficient adsorbent materials for adsorptive dephosphorization (ADP) is crucial for water treatment.
• Existing adsorbents often require optimization for enhanced phosphate removal capacity and stability.

Purpose of the Study:

• To synthesize and characterize novel adsorbents by entrapping 1-butyl-3-methylimidazoliumbromide ionic liquid ([C4mem]+[Br]-) within the MIL-101(Cr) framework.
• To evaluate the adsorptive dephosphorization performance of the synthesized [C4mem]+[Br]-@MIL-101(Cr) materials.
• To investigate the influence of ionic liquid content and environmental conditions on phosphate adsorption.

Main Methods:

• A ship-in-a-bottle approach was used to synthesize [C4mem]+[Br]-@MIL-101(Cr) adsorbents with varying ionic liquid (IL) loadings.
• Material characterization was performed to confirm the successful incorporation and interaction of IL within the MIL-101(Cr) framework.
• Batch adsorption experiments were conducted to assess phosphate removal efficiency, capacity, and the effect of coexisting anions.
• Continuous fixed-bed adsorption experiments were performed using polyvinyl alcohol (PVA)-mixed adsorbent pellets.

Main Results:

• The optimized C4mem@MIL-101 adsorbent, with approximately 7% IL-based N content, exhibited a high phosphate adsorption capacity of around 200 mg/g.
• The incorporation of [C4mem]+[Br]- enhanced the stability of MIL-101(Cr) and provided additional adsorption sites.
• Phosphate adsorption was most effective in acidic media, with phosphate ions captured via electrostatic attraction, hydrogen bonds, and chemical interactions.
• Coexisting anions were found to diminish phosphate adsorption due to competition for adsorption sites.
• Polyvinyl alcohol (PVA)-mixed C4mem@MIL-101 pellets demonstrated efficient phosphate removal in continuous flow systems, purifying 25 L of water with 1 mg/L phosphate concentration per gram of adsorbent.

Conclusions:

• The novel [C4mem]+[Br]-@MIL-101(Cr) composite material demonstrates significant potential for highly efficient adsorptive dephosphorization of phosphate from aqueous solutions.
• The enhanced stability and adsorption capacity make these materials promising for practical water treatment applications.
• Further research into optimizing IL loading and exploring regeneration strategies could enhance their long-term applicability.