Enhanced Phosphorus Locking by Novel Lanthanum/Aluminum-Hydroxide Composite: Implications for Eutrophication Control

Area of Science:

• Environmental Science
• Materials Science
• Water Treatment

Background:

• Lanthanum (La)-based materials are effective for phosphorus (P) removal in water.
• Improving phosphate (PO4) adsorption capacity and La efficiency remains a challenge.

Purpose of the Study:

• To develop a La/Al-hydroxide composite (LAH) for enhanced P adsorption.
• To investigate the adsorption mechanisms and performance of LAH.

Main Methods:

• Coprecipitation of La and Al to form LAH.
• Phosphate adsorption experiments at different pH values.
• P K-edge and La LIII-edge X-ray absorption spectroscopy.

Main Results:

• LAH exhibited significantly higher PO4 adsorption capacities (76.3 mg P g-1 at pH 4.0, 45.3 mg P g-1 at pH 8.5) compared to commercial La-modified bentonite.
• PO4 preferentially bonded with Al at pH 4.0 and La at pH 8.5.
• Adsorption involved inner sphere bidentate-binuclear complexes and surface oxygen defects on La sites.

Conclusions:

• The synergistic effect of La and Al in LAH enhances PO4 adsorption.
• Multiple mechanisms including electrostatic interaction, ligand exchange, and oxygen defects contribute to adsorption.
• LAH presents a promising material for eutrophication mitigation.