Fe–Ce Bimetallic MOFs for Water Environment Remediation: Efficient Removal of Fluoride and Phosphate

TL;DR

A new bimetallic MOF material is developed to efficiently remove fluoride and phosphate from water, showing strong performance and potential for environmental remediation.

Contribution

The study introduces Fe–Ce bimetallic MOFs with rice-grain-like morphology for simultaneous and efficient removal of fluoride and phosphate from water.

Findings

Fe–Ce-MOFs achieved maximum adsorption capacities of 183.82 mg g−1 for fluoride and 110.74 mg g−1 for phosphate.

The adsorbent maintained high removal efficiencies (85.17% for fluoride and 47.34% for phosphate) after three regeneration cycles.

Fluoride removal was dominated by electrostatic attraction and ion exchange, while phosphate removal involved inner-sphere complex formation.

Abstract

Fe–Ce-MOFs with a rice-grain-like morphology were successfully obtained via hydrothermal synthesis, where ferric chloride (FeCl3) and cerium nitrate [Ce(NO3)3] served as the metal precursors and terephthalic acid (PTA) acted as the organic coordinating ligand. The effects of the Fe:Ce molar ratio, (Fe/Ce):PTA ratio, reaction duration, and synthesis temperature on adsorption performance of the Fe–Ce-MOFs were systematically studied. A comprehensive evaluation was conducted on the removal of fluoride and phosphate ions from aqueous solution. Under optimized conditions, the maximum adsorption capacities of Fe–Ce-MOFs for fluoride and phosphate reached 183.82 mg g−1 and 110.74 mg g−1, respectively. Adsorption data correlated strongly with the Langmuir isotherm, were best represented by the pseudo-second-order kinetic model, and were identified as a spontaneous and endothermic reaction. After three regeneration cycles, the adsorbent still maintained high removal efficiencies for fluoride (85.17%) and phosphate (47.34%) removal. In practical wastewater treatment, removal efficiencies of 92.04% for fluoride and 93.87% for phosphate were achieved. Mechanistic studies revealed that fluoride removal was dominated by electrostatic attraction and hydroxyl–fluoride ion exchange, whereas phosphate removal was attributed to the generation of inner-sphere complexes involving PO43− and Fe/Ce active sites. This study not only elucidates the synergistic mechanism of fluoride and phosphate elimination by Fe–Ce-MOFs but also provides theoretical guidance and application prospects for the development of highly efficient and stable bimetallic MOF-based adsorbents for environmental remediation.

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