Efficient recovery of phosphate by La-MOFs: An excellent adsorption performance and mechanism

Lanthanum-type metal-organic frameworks (La-MOFs) can be used to mitigate phosphate pollution in wastewater. Herein, La-MOFs was gained via the solvothermal method and its phosphate removal property was examined under various conditions, like variable initial phosphate concentration, solution pH, and co-existing ions. The material morphology, element composition, and crystal morphology of the La-MOFs was characterized using XRD, SEM, FTIR, and XPS. The phosphate removal mechanism was investigated by combining thermodynamic and kinetic analyses. The La-MOFs exhibited superior adsorption capability for surplus phosphate in water, and also had a high selectivity for phosphate in the complexed environment with some co-existing ions. Maximum adsorption was obtained at pH 4. The sorption procedure of La-MOFs aligned more with the Langmuir and pseudo-second order kinetic models, demonstrating monomolecular-layer-controlled chemisorption. And the maximum sorption capacity was 73.69 ​mg ​g−1. Electrostatic interactions and ligand exchange, which enabled the development of an La–O–P inner-sphere complexation, were identified as the primary mechanisms of phosphate removal. This research provides insights into the optimal conditions and mechanism of phosphate adsorption by La-MOFs.