Enhanced fluoride removal behaviour and mechanism by dicalcium phosphate from aqueous solution

Area of Science:

• Materials Science
• Environmental Chemistry
• Water Treatment

Background:

• Fluoride contamination in water poses significant health risks.
• Development of efficient and cost-effective adsorbents for fluoride removal is crucial.
• Calcium phosphates are promising materials for water remediation.

Purpose of the Study:

• To synthesize dicalcium phosphate (DCP) using ethylenediaminetetraacetic acid (EDTA) as a calcium chelating agent.
• To evaluate the fluoride ion removal efficiency of the synthesized DCP.
• To investigate the adsorption mechanism and performance characteristics.

Main Methods:

• Dicalcium phosphate synthesis utilizing EDTA.
• X-ray diffraction (XRD) for phase analysis.
• Batch adsorption experiments for fluoride removal.
• Langmuir isotherm and pseudo-second-order kinetic modeling.
• Analysis of pH range and interfering anions.

Main Results:

• The synthesized DCP primarily existed in the monetite phase.
• The adsorbent exhibited a high maximum adsorption capacity of 66.72 mg/g for fluoride, exceeding previously reported calcium phosphates.
• Effective fluoride removal was observed across a wide pH range (3-10).
• Adsorption kinetics followed the pseudo-second-order model, indicating chemical adsorption.
• Co-existing anions showed negligible interference.

Conclusions:

• The EDTA-synthesized DCP is a highly efficient adsorbent for fluoride removal from aqueous solutions.
• Chemical reaction, dissolution-precipitation, electronic interaction, and ion exchange are key mechanisms driving fluoride adsorption.
• This material shows potential for practical application in water treatment due to its broad applicability and high capacity.